ADDITIVE MANUFACTRING TECHNIQUES MECHANICAL ENGINEERING

ADDITIVE MANUFACTRING

1. ADDITIVE MANUFACTURING Dr. K. Sri Ram Vikas Assistant Professor, Dept of Mechanical Engineering GAYATRI VIDYA PARISHAD COLLEGE FOR DEGREE AND PG COURSES (AUTONOMOUS) GAYATRI VIDYA PARISHAD COLLEGE FOR DEGREE AND PG COURSES (AUTONOMOUS) (Affiliated to Andhra University | Reaccredited by NAAC) (MBA and UG Engineering B.Tech (CE,CSE,ECE and ME) programs are Accredited by NBA)

2. Course Objectives: To understand the principles of prototyping, classification of RP processes and liquid-based RP systems 2) To understand and apply different types of solid-based RP systems. 3) To understand and apply powder-based RP systems. 4) To understand and apply various rapid tooling techniques. 5) To understand different types of data formats and to explore the applications of AM processes in various fields.

3. UNIT– I: INTRODUCTION: Prototyping fundamentals, historical development, fundamentals of rapid prototyping, advantages and limitations of rapid prototyping, commonly used terms, classification of RP process. LIQUID-BASED RAPID PROTOTYPING SYSTEMS: Stereo lithography Apparatus (SLA): models and specifications, process, working principle, photopolymers, photo polymerization, layering technology, laser and laser scanning, applications, advantages and disadvantages, case studies. Solid Ground Curing (SGC): models and specifications, process, working principle, applications, advantages and disadvantages, case studies.

4. UNIT– II: SOLID-BASED RAPID PROTOTYPING SYSTEMS: Laminated object manufacturing (LOM) - models and specifications, process, working principle, applications, advantages and disadvantages, case studies. Fused deposition modelling (FDM) - models and specifications, process, working principle, applications, advantages and disadvantages, case studies. UNIT– III: POWDER BASED RAPID PROTOTYPING SYSTEMS: Selective laser sintering (SLS): models and specifications, process, working principle, applications, advantages and disadvantages, case studies. three dimensional printing (3DP): models and specifications, process, working principle, applications, advantages and disadvantages, case studies.

5. UNIT– IV: RAPID TOOLING: Introduction to rapid tooling (RT), conventional tooling Vs RT, Need for RT. rapid tooling classification: indirect rapid tooling methods: spray metal deposition, RTV epoxy tools, Ceramic tools, investment casting, spin casting, die casting, sand casting process. Direct rapid tooling: Direct AIM, LOM Tools, and Direct Metal Tooling using 3DP.

6. UNIT– V: RAPID PROTOTYPING DATA FORMATS: STL Format, STL File Problems, consequence of building valid and invalid tessellated models, STL file Repairs: Generic Solution, other Translators, and Newly Proposed Formats. RP APPLICATIONS: Application in engineering, analysis and planning, aerospace industry, automotive industry, jewellery industry, coin industry, GIS application, RP medical and bioengineering applications: customized implants and prosthesis, forensic sciences.

7. TEXT BOOKS: 1.Rapid prototyping: Principles and Applications /Chua C.K., Leong K.F. and LIM C.S/ WorldScientific publications REFERENCES: 1. Rapid Manufacturing / D.T. Pham and S.S. Dimov /Springer 2. Wohlers Report 2000 /Terry T Wohlers/Wohlers Associates 3. Rapid Prototyping & Manufacturing / Paul F.Jacobs /ASME Press 4. Rapid Prototyping / Chua and Liou

8. Course Outcomes: At the end of the course, student will be able to CO1: Understand the principles of prototyping, classification of RP processes and liquid-based RP systems. CO2: Understand and apply different types of solid-based RP systems. CO3: Apply powder-based RP systems. CO4: Analyze and apply various rapid tooling techniques. CO5:Understand different types of data formats and explore the applications of AM processes in various fields.

9. Prototyping fundamentals An approximation of a product (or system) or its components in some form for a definite purpose in its implementation.

10. The general definition of the prototype contains three aspects of interests: (1) the implementation of the prototype; from the entire product (or system) itself to its sub-assemblies and components, (2) the form of the prototype; from a virtual prototype to a physical prototype, and (3) the degree of the approximation of the prototype; from a very rough representation to an exact replication of the product. Types of Prototypes

11. Prototypes are early versions of products or systems used for testing and validation. They help in refining ideas, improving designs, and identifying issues before full production Three Key Aspects of Prototypes Implementation Different levels: From entire product to sub-assemblies/components. Form Varied forms: From virtual to physical prototypes. Degree of Approximation Varying levels: From rough representation to exact replication.

12. Implementation of Prototypes Full Product Prototype Represents the entire product/system. Sub-Assemblies/Components Prototype Focuses on specific parts for detailed testing. Form of Prototypes Virtual Prototype Computer-generated model for simulation. Physical Prototype Tangible model with different levels of detail.

13. Degree of Approximation Rough Representation Basic, low-fidelity prototype for initial ideas. Medium Level Detailed prototype capturing essential features. Exact Replication High-fidelity prototype closely resembling the final product. Putting It Into Practice Implementation: From a car's entire assembly to testing just the engine. Form: From a computer simulation of a game to a physical mock-up of a smartphone. Degree: From a simple cardboard model of a building to a 3D-printed, detailed architectural replica.

14. Roles of the Prototypes The roles that prototypes play in the product development process are several. They include the following: Experimentation and learning (2) Testing and proofing (3) Communication and interaction (4) Synthesis and integration (5) Scheduling and markers

15. Experimentation and Learning Experimentation : Trying out new ideas and concepts in a risk-free environment. Learning : Gaining insights into what works and what needs improvement. Testing and Proofing Testing: Identifying design flaws, functionality issues, and potential improvements. Proofing: Ensuring that the product meets its intended goals and functions as expected. Communication and Interaction Communication: Clearly conveying design concepts to stakeholders and team members. Interaction: Allowing users to experience and provide feedback on the product's usability.

16. Synthesis and Integration Synthesis: Bringing together various components to form a coherent whole. Integration: Ensuring seamless interaction between different parts of the product. Scheduling and Milestones Scheduling: Estimating timeframes for different development stages based on prototype outcomes. Milestones: Using prototype progress as markers for tracking project advancement.

17. Practical Application Putting Prototypes to Work Experimentation: Trying out different car dashboard layouts before finalizing one. Testing: Identifying bugs in a mobile app prototype before coding begins. Communication: Presenting a virtual walkthrough of a building design to clients. Synthesis: Integrating user feedback to improve an e-commerce website's navigation. Scheduling: Using prototype feedback to adjust project timelines.

18. Historical development of Rapid Prototyping and related technologies

19. Parallels between geometric modelling and prototyping

20. FUNDAMENTALS OF RAPID PROTOTYPING 1. CAD/CAM Modelling: A model or component is created using Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) software. The model represents the physical part with closed surfaces that define an enclosed volume, ensuring all necessary information is provided. 2. STL File Conversion: The model is converted into an STL ( STereoLithography ) file format, which approximates surfaces with polygons. This format is used for slicing the model into cross sections for fabrication.

21. 3. Slicing and Fabrication: A computer program slices the model into cross sections. These sections are then recreated using methods like solidification of liquids or powders, or bonding thin laminations, to build a 3D model. Four Key Aspects: Rapid Prototyping development involves Input (CAD model), Method (fabrication technique), Material (substances used for fabrication), and Applications (ways the technology is used).

22. Faster Product Development: Rapid Prototyping significantly speeds up the product development cycle by allowing quick creation and testing of physical prototypes. This helps identify design flaws, functional issues, and improvements early in the process, reducing time to market. Cost Efficiency: By catching design errors early and enabling iterative testing, Rapid Prototyping reduces the risk of costly mistakes during full-scale production. This results in cost savings by avoiding expensive modifications later in the development process. ADVANTAGES OF RAPID PROTOTYPING

23. Iterative Design Improvement: Rapid Prototyping supports an iterative design approach, where multiple versions of a prototype can be quickly produced and tested. This iterative process leads to refined designs and better end products. Enhanced Communication and Collaboration: Physical prototypes are tangible and easier to understand than complex CAD models. This facilitates better communication and collaboration among design teams, stakeholders, and clients, leading to a clearer shared vision. Customization and Personalization: Rapid Prototyping allows for the creation of customized and personalized products with relative ease. This is particularly useful in industries like healthcare, where individualized medical implants or devices can be tailored to a patient's unique needs.

24. Material Limitations: Rapid Prototyping techniques often require specific materials that may not possess the exact properties of the final production material. This can lead to discrepancies in mechanical, thermal, or other material characteristics. Surface Finish and Resolution: The surface finish and resolution of rapid prototypes may not match the quality of traditional manufacturing processes. This can be a limitation when precise detailing or smooth surfaces are crucial. limitations of Rapid Prototyping

25. Size and Scaling Constraints: Some rapid prototyping methods have limitations in terms of the size of the prototype that can be produced. Scaling up a design to a full-sized product may be challenging or require specialized equipment. Cost of Equipment and Expertise: Acquiring and maintaining the necessary equipment for rapid prototyping can be expensive. Additionally, skilled personnel are required to operate the equipment effectively, adding to the overall cost. Limited Production Suitability: While rapid prototyping is excellent for creating prototypes and low-volume production runs, it may not be as cost-effective or efficient for large-scale manufacturing. Traditional methods may be more suitable for high-volume production.

26. Layering: The process of building an object layer by layer, which is a fundamental aspect of most RP techniques. Additive Manufacturing (AM): The process of creating objects by adding material layer by layer, as opposed to subtractive manufacturing. Slicing: Dividing a 3D model into thin horizontal cross-sections to guide the RP process. Build Envelope: The maximum dimensions within which an RP machine can create objects. Resolution: The level of detail or fineness in which an RP system can produce features. Commonly Used Terms in Rapid Prototyping (RP):

27. Support Structures: Temporary structures used to hold up overhanging or complex features during the RP process. Build Time: The time required to complete the layering and fabrication of a prototype. CAD (Computer-Aided Design): The use of computer software to create detailed 3D models. CAM (Computer-Aided Manufacturing): The use of computer software to control machinery in manufacturing processes. STL File: A standard file format used in RP that represents a 3D object's surface geometry using triangles.

28. Rapid Prototyping processes can be classified based on the technique used for material deposition and consolidation. Here are some common classifications: Stereolithography (SLA): Uses a UV laser to solidify liquid photopolymer resin layer by layer. Selective Laser Sintering (SLS): Utilizes a laser to fuse powdered materials (plastics, metals) layer by layer. Fused Deposition Modeling (FDM): Extrudes melted thermoplastic material to create layers. PolyJet Printing: Sprays liquid photopolymer that solidifies with UV light to create layers. Classification of Rapid Prototyping Processes:

29. Digital Light Processing (DLP): Similar to SLA but uses a digital light projector to cure entire layers at once. Binder Jetting: Layers of powder material are selectively bound together with a liquid binding agent. Laminated Object Manufacturing (LOM): Layers of adhesive-coated sheet material are bonded and cut into the desired shape. Electron Beam Melting (EBM): Uses an electron beam to melt and fuse metal powder layer by layer. Direct Metal Laser Sintering (DMLS): Similar to SLS, but specifically for metal powders. 3D Printing (3DP): Various methods that extrude or jet material to create layers.

30. Additive Manufacturing Short introduction to the technology “See the difference in the conception of the part” Conventionally designed and produced cast steel nacelle hinge bracket for an Airbus A320 (left) and optimised titanium version of the nacelle hinge bracket made by additive manufacturing technology. Commercial airplanes can have up to several hundred seat belt buckles. A standard buckle weight is around 155g in St. and 120g in Al. With AM the weight was reduced to 68 g in Ti.

31. Part manufacturing Advantage for sport shoe manufacturer is the data exchange between development and production over night. e.g. ADIDAS with the development in Germany an the production side in China. Example for medical application 3D printing can be personalised Giving back life quality

32. The assembly can be personalised and printed in one process. NASA has carried out parabolic flights that mimic microgravity to test "additive manufacturing” Many other applications for printing on-site

33. The fast packaging solution, French postal The part is scanned in the post office and a cutter is cutting the different layer on site. For her Spring/Summer 2015 collection, presented in Paris, Dutch fashion designer Iris van Herpen unveiled 3D-printed garments and accessories "grown" that explores the interplay of magnetic forces. Her inspiration of this collection came after she visited CERN, and the Large Hadron Collider

34. Chocolate printer Concrete Printer Figure Print

35. Additive Manufacturing CAD Model Preparation Build Process Post Process PART CAD Design CAD Translator File Verification Orientation Support Parameters Part Build Cleaning Support remove Post curing Material Chemical properties Physical properties

36. Easy Cutting Path Angled surfaces

37. Supports Holes

38. Down Ward Facing Surfaces

39. LIQUID-BASED RAPID PROTOTYPING SYSTEMS Starting material is a liquid About a dozen RP technologies are in this category Includes the following processes: Stereolithography (STL) Solid ground curing (SLG) Droplet deposition manufacturing

40. The laser cures the resin near surface, forming a hardening layer. Most liquid based rapid proto typing systems build parts in a vat curable resin, which cures or solidifies under the effect of exposure to laser radiation, usually in UV range. When a layer of a part is formed, it is lowered by an elevation control system to allow the next layer of resin to be similarly formed over it. This continues until the entire part is completed. The vat can then be drained out and the part is removed for further processing.

41. There are variations to this technique by the various vendors and they are dependent on the type of light or laser, method of scanning or exposure, type of liquid resin, type of elevation and optical system used.

42. Stereo lithography Stereo – three dimensions Lithography – printing Started with acrylic resins in the early 1980’s Epoxy resins are more common now Very good accuracy UV Laser cure Relatively slow speed Newer resins with improved properties

43. SLA was pioneered by Chuck Hull in the mid-1980s (see picture right). Hull founded 3D Systems to commercialize its new manufacturing process.

44. 3D Systems iPro 9000 XL Current market leaders 3D Systems Sony

45. What is Stereolithography (SLA)? A "rapid-prototyping" process which produces a physical, three dimensional object from a 3D CAD file. Fabricating a solid plastic part out of a photosensitive liquid polymer using a directed laser beam to solidify the polymer Part fabrication is accomplished as a series of layers - each layer is added onto the previous layer to gradually build the 3-D geometry

46. A structure support base is positioned on an elevator structure and immersed in a tank of liquid photosensitive monomer, with only a thin liquid film above it A UV laser locally cross-links the monomer on the thin liquid film above the structure support base The elevator plate is lowered by a small prescribed step, exposing a fresh layer of liquid monomer, and the process is repeated At the end of the job, the whole part is cured once again after excess resin and support structures are removed 5. A suitable photosensitive polymer must be very transparent to UV light in uncured liquid form and very absorbent in cured solid form, to avoid bleeding solid features into the layers underneath the current one being printed.

47. Stereolithography: (1) at the start of the process, in which the initial layer is added to the platform; and (2) after several layers have been added so that the part geometry gradually takes form.

48. 2. The building is done layer by layer, each layer being scanned by the optical scanning system and controlled by an elevation mechanism which lowers at the completion of each layer. Principle The SLA process is based on the following principles. 1. Parts are built from a photo-curable liquid resin that cures when exposed to a laser beam which scans across the surface of the resin.

49. UV curable photo polymers are resins which are formulated from photo iniators and reactive liquid monomers. Photopolymers There are many types of liquid photopolymers that can be solidified by exposure to electro-magnetic radiation, including wavelengths in the gamma rays, X-rays, UV and visible range. The vast majority of photopolymers used in the commercial RP systems are curable in the UV range.

50. Photo polymerization is polymerization initiated by a photochemical process whereby the starting point is usually the induction of energy from the radiation source. The process through which photopolymers are cured is called as photo polymerization process. It is the process of linking small molecules (monomers) into chain like larger molecules (polymers). When the chain like polymers are linked further to one another, a cross linked polymer is said to be formed. Photo polymerization

51. Layering Technology, Laser and Laser scanning Almost all RP systems use layering technology in the creation of prototype parts. The basic principle is the availability of computer software to slice a CAD model into layers and reproduce it in an output device like a laser scanning system. The layer thickness is controlled by a precision elevation mechanism. It will correspond directly to the slice thickness of the computer model and the cured thickness of the resin. The important component of the building process is the laser and its optical scanning system. The key to the strength of the SLA is its ability to rapidly direct focused radiation of appropriate power and wavelength onto the surface of the liquid photopolymers resin, forming patterns of solidified photopolymer according to the cross-sectional data generated by the computer.

52. Advantages Round the clock operation without much attention. Good user support Build volumes. From small to large size to suit the needs. Good Accuracy Good surface finish. Best among many RP technologies. Wide range of materials. For general purpose materials to specific applications.

53. Disadvantages Requires support structures Requires post processing Requires post curing

54. Models for conceptualization, packaging and presentation Prototypes for design, analysis, verification and functional testing Parts for prototype tooling and low volume production tooling Patterns for investment casting, sand casting and molding Tools for fixture and tooling design, and production tooling. Applications

55. A part produced by stereolithography (photo courtesy of 3D Systems, Inc)

56. Solid Ground Curing SGC - (Cubical) Similar to stereolithography Uses UV light Selectively hardens photosensitive polymers Cures entire process at a time Photomask Printed on glass plate UV light passes through the mask to the polymer

57. Like stereolithography, SGC works by curing a photosensitive polymer layer by layer to create a solid model based on CAD geometric data. Instead of using a scanning laser beam to cure a given layer, the entire layer is exposed to a UV source through a mask above the liquid polymer. Hardening takes 2 to 3 s for each layer

58. Figure: SGC steps for each layer: mask preparation, (2) applying liquid photopolymer layer, (3) mask positioning and exposure of layer, (4) uncured polymer removed from surface, (5) wax filling, (6) milling for flatness and thickness. Solid Ground Curing

59. Photosensitive resin is sprayed on the build platform. The machine develops a photomask (like a stencil) of the layer to be built. This photomask is printed on a glass plate above the build platform using an electrostatic process similar to that found in photocopiers. The mask is then exposed to UV light, which only passes through the transparent portions of the mask to selectively harden the shape of the current layer.

60. After the layer is cured, the machine vacuums up the excess liquid resin and sprays wax in its place to support the model during the build. The top surface is milled flat, and then the process repeats to build the next layer. When the part is complete, it must be de-waxed by immersing it in a solvent bath.

61. Schematic illustration of the solid-base-curing process. Source: After M. Burns, Automated Fabrication, Prentice Hall, 1993. Solid-Base Curing (Solid Ground Curing)

62. NO support structure is needed, the wax supports the model in all directions Volume of the production environment is as big as what we get from Stereolithography. Large parts, 500 × 500 × 350 mm (20 × 20 × 14 in), can be fabricated quickly. Dimensional accuracy is good. The model produced by SGC process is comparatively accurate in the Z-direction because the layer is milled after each light-exposure process. ADVANTAGES

63. It has got ability to build the layer by layer of 0.1 mm thickness. Very fast and decently accurate (though not as accurate as SLA). No post-cure required Milling step ensures flatness for subsequent layer Ideal technology for short production runs. ADVANTAGES

64. Shrinkage effect has been minimized due to the full cure of every layer No final curing in a special oven is needed NO support structure is needed, the wax supports the model in all directions Model structural strength/and stability are higher and the models are much less brittle. This is due to the curing process that minimized the development of internal stresses in the structure. Other benefits of this technology are

65. Any geometrical shape can be made without limitation High throughput is achieved due to the three dimensional nesting of models within the wax No hazardous odors are generated, the resin stays in liquid state for a very short time, and the uncured liquid is wiped off immediately. Thus safety is considerably higher. Other benefits of this technology are:

66. When the liquid polymer solidifies, some wax also gets entrapped in the artifact. Space requirement is also more. Relatively High Cost. High Operating costs due to system complexity Expensive equipment Expensive materials High running & maintenance cost Produces a lot of waste. Narrow range of material i.e., Photopolymers only DISADVANTAGES

67. Models for conceptualization, packaging and presentation Prototypes for design, analysis, verification and functional testing Pattern for investment casting replacing the wax pattern Masters for prototype tooling and low volume production tooling Applications

68. Sequence for each layer takes about 90 seconds Time to produce a part by SGC is claimed to be about eight times faster than other RP systems The solid cubic form created in SGC consists of solid polymer and wax The wax provides support for fragile and overhanging features of the part during fabrication Facts about SGC

69. UNIT– II: SOLID-BASED RAPID PROTOTYPING SYSTEMS: Laminated object manufacturing (LOM) - models and specifications, process, working principle, applications, advantages and disadvantages, case studies. Fused deposition modelling (FDM) - models and specifications, process, working principle, applications, advantages and disadvantages, case studies.

70. Solid physical model made by stacking layers of sheet stock, each an outline of the cross-sectional shape of a CAD model that is sliced into layers • Starting sheet stock includes paper, plastic, cellulose, metals, or Fiber-reinforced materials The sheet is usually • supplied with adhesive backing as rolls that are spooled between two reels • After cutting, excess material in the layer remains in place to support the part during building Laminated Object Manufacturing (LOM)

71. Laminated object manufacturing: 1 Foil supply. 2 Heated roller. 3 Laser beam. 4. Scanning prism. 5 Laser unit. 6 Layers. 7 Moving platform. 8 Waste.

72. LOM Examples Layer laminate manufacturing, paper lamination, gear housings (LOM)

73. Layer laminate manufacturing; paper lamination; MCOR Matrix 300 machine (left), coloured part made from paper, right (Source: MCOR Technologies)

74. Layer laminate manufacturing; plastic laminate printers; machine (left); fan wheel made by the laminate Printer Solido SD 300 pro, PVC (right) (Source: Solido )

75. G-Scale (1 : 22.5) model of a toy train steam engine; laminated object manufacturing (LOM); paper, post-processing by varnishing (Source: CP‑GmbH)

76. Wi de v ari e t y o f m a t erials : A n y m a t e r i a l i n s he e t f o r m c a n b e use d i n t h e L O M s y s t e m s . T hes e i n c lu d e a w i d e var i e t y o f o r g an i c a n d i no r g an i c m a t e ri a l s s u c h a s p ape r , p l a sti cs , m e t a l s , c o m p o s i t e s a n d c e r a m i cs . Fast build time: The laser in the LOM process does not scan the entire surface area of each cross-section, rather it only outlines its periphery. Therefore, parts with thick sections are produced just as quickly as those with thin sections, making the LOM process especially advantageous for the production of large and bulky parts High precision: The feature to feature accuracy that can be achieved with LOM machines is usually better than 0.127 mm (0.005"). Advantages

77. Support structure: There is no need for additional support structure as the part is supported by its own material that is outside the periphery of the part built. These are not removed during the LOM process and therefore automatically act as supports for its delicate or overhang features. Post-curing: The LOM process does not need to convert expensive, and in some cases toxic, liquid polymers to solid plastics or plastic powders into sintered objects. Because sheet materials are not subjected to either physical or chemical phase changes. The finished LOM parts do not experience warpage, internal residual stress, or other deformations.

78. Disadvantages of LOM The main disadvantages of using LOM are as follows: Precise power adjustment. The power of the laser need to be precisely controlled so that the laser only cuts the present layer of lamination. Fabrication of thin walls: The LOM process is not well suited for building parts with delicate thin walls, especially in the Z-direction. This is because such walls usually are not sufficiently rigid to withstand the post-processing process when the cross-hatched outer perimeter portion of the block is being removed.

79. Removal of supports: The most labour-intensive part of the LOM process is its last phase of post-processing when the part has to be separated from its support material within the rectangular block of laminated material. This is usually done with wood carving tools and can be tedious and time consuming. Integrity of prototypes: The part built by the LOM process is essentially held together by the heat sealed adhesives. The integrity of the part is therefore entirely dependent on the adhesive strength of the glue used, and as such is limited to this strength. Therefore, parts built may not be able to withstand the vigorous mechanical loading that the functional prototypes may require.

80. Applications of LOM Visualization: Many companies utilize LOM ability to produce exact dimensions of a potential product purely for visualization. LOM part's wood-like composition allows it to be painted or finished as a true replica of the product. As the LOM procedure is inexpensive several models can be created, giving sales and marketing executives opportunities to utilize these prototypes for consumer testing, marketing product introductions. Form, fit and function: LOM parts lend themselves well for design verification and performance evaluation. In low-stress environments LOM parts can withstand basic tests, giving manufacturers the opportunity to make changes as well as evaluate the aesthetic property of the prototype in its total environment.

81. Manufacturing: The LOM parts can be used as a pattern or mould for most secondary tooling techniques including investment casting, sand casting, injection moulding, silicon rubber mould, vacuum forming and spray metal moulding. Rapid tooling: Two part negative tooling is easily created with LOM systems. Since the material is solid and inexpensive, bulk complicated tools are cost effective to produce. These wood-like moulds can be used for injection of wax, polyurethane, epoxy or other low pressure and low temperature materials. Also, the tooling can be converted to aluminium or steel via the investment casting process for use in high temperature moulding processes.

82. FDM is a registered, protected trade name for a fused layer process offered by Stratasys Company, Eden Prairie, MN, USA. Fused Deposition Modeling (FDM) A FDM machine consists of a heated (app. 80 °C for ABS plastic processing) build chamber equipped with an extrusion head and a build platform. Consequently, the machine does not use a laser. The extrusion head provides the material deposition in the x‑y area according to the contour of the actual layer. It is a plotter-type device.

83. The build material is a prefabricated filament that is wound up and stored in a cartridge from which it is continuously fed to the extrusion head. The cartridge has a build-in sensor that communicates with the material management system of the machine. In the head, the material it is partly molten by an electric heating system and extruded through a nozzle that defines the string diameter that nearly equals the layer thickness. Usually, string diameters range from 0.1 mm to 0.25 mm.

84. The platform moves in z‑direction and defines the layer thickness, as the material is squeezed on the top of the partly finished part. The process needs supports. They are made by a second nozzle that extrudes another plastic support material simultaneously with the build material. The simultaneous processing of two materials indicates that the FLM process is basically capable of handling multi-material print heads. Therefore, the manufacture of multi material parts can be expected in the future.

85. After deposition, the pasty string (of the build material as well as of the support material) solidifies by heat transfer into the preceding layer and forms a solid layer. Then the platform is lowered by the amount of one layer thickness and the next layer is deposited. The process repeats until the part is completed.

86. There are a wide variety of machines that follow the principle of the FDM process. The machines range from the personal printer μPrint (starting at € 11,900; status 2011) and the almost double priced Dimension office printers to the high-end Fortus Production Systems brand, including the Fortus 900mc that offers the largest build space (914 × 610 × 914 mm) currently available.

87. There are many plastic materials available for FDM processes, including engineering materials such as ABS, PC-ABS, and specialty grades for medical modeling . Some machines are restricted to only a limited number of different materials. There is a big variety of colours available, amongst it even translucent, black, and white qualities. Because the colour is linked to the filament, it cannot be changed during the build process The Fortus 400 and 900 machines process the high temperature thermoplastic material polyphenylsulfone (PPSF/PPSU). They were the first machines on the market to handle these high performance plastics.

88. ABS (Acrylonitrile Butadiene Styrene) Polycarbonate (PC) PC-ISO Medical grade PC PC-ABS blend Polyohenylsulfone(PPSF) ABSi(Sterilizable & translucent) Investment wax FDM Nylon 12 ULTEM 9085 Materials used in FDM Process

89. Material Loading Liquification Support Generation Positional Control Extrusion Solidification Bonding Basic Principle of FDM

90. Fused deposition modeling . Epicyclic gear set assembled from monochromatic FDM parts, made from ABS plastic (left); part with support as manufactured (center); part after removal of the supports and manual polishing (right) (Source: RP-Lab, FH Aachen University of Applied Science (2), Stratasys (1 left))

91. Typical part properties resemble those of plastic injection molded parts; however, they tend to show anisotropic behavior that can be reduced by properly adjusted build parameters. The parts are either used as concept models, functional prototypes, or as (direct manufactured) final parts. FDM parts show typical surface textures that result from the extrusion process According to the layer thickness and the orientation of the part in the build chamber, these textures are more or less visible. Therefore, the positioning (orientation) in the build chamber has a big influence on the appearance of the part.

92. Post processing requires the removal of the supports, which can be done manually, or using a special washing device. Finishing requires manual skills and time; but together with artisan capabilities leads to perfect surface qualities and astonishing results. It is needless to say that intensive finishing affects the part’s accuracy.

93. Scaled wrenches Articu -Light lamp

94. a djusting the process parameters of the machine.

95. POWDER BASED RAPID PROTOTYPING SYSTEMS: Selective laser sintering (SLS): models and specifications, process, working principle, applications, advantages and disadvantages, case studies. three dimensional printing (3DP): models and specifications, process, working principle, applications, advantages and disadvantages, case studies. UNIT-3

96. •SLS was developed and patented by the University of Texas at Austin and subsequently commercialized by DTM Corporation. •Established in 1987, DTM Corporation shipped its first commercial RP machine in 1992 With the financial support from the BF Goodrich Company. •In August 2001, 3D Systems bought DTM Corporation and further enhanced its position as a world leader SELECTIVE LASER SINTERING (SLS)

97. Sinter station Pro SLS systems Sinter station HiQ series SLS

98. Specifications

99. The SLS process is based on the following two principles: Parts are built by sintering when a CO 2 laser beam hits a thin layer of powdered material. The interaction of the laser beam with the powder raises the temperature to the point of melting, resulting in particle bonding, fusing the particles to themselves and the previous layer to form a solid. 2. The building of the part is done layer by layer. Each layer of the building process contains the cross-sections of one or many parts. The next layer is then built directly on top of the sintered layer after an additional layer of powder is deposited via a roller mechanism on top of the previously formed layer Working principle

100. 1  Laser  2  Scanner system  3  Powder delivery system  4  Powder delivery piston  5  Roller  6  Fabrication piston  7  Fabrication powder bed  8  Object being fabricated (see inset)  A  Laser scanning direction  B  Sintered powder particles (brown state)  C  Laser beam  D  Laser sintering  E  Pre-placed powder bed (green state)  F   Unsintered material in previous layers

101. Sintering in SLS primarily occurs in the liquid state when the powder particles forms a micro-melt layer at the surface, resulting in a reduction in viscosity and the formation of a concave radial bridge between particles, known as necking, due to the material's response to lower its surface energy. In the case of coated powders, the purpose of the laser is to melt the surface coating which will act as a binder. Solid state sintering is also a contributing factor, though with a much reduced influence, and occurs at temperatures below the melting temperature of the material. The principal driving force behind the process is again the material's response to lower its free energy state resulting in diffusion of molecules across particles.

102. Three stages of powder sintering

103. Titanium powder produced by the Advanced Plasma Atomization Process

104. 1. SLS technology is in wide use at many industries around the world due to its ability to easily make complex geometries with little to no added manufacturing effort. 2. Its most common application is in prototype parts early in the design cycle such as for investment casting patterns, automotive hardware, and wind tunnel models. 3. SLS is also increasingly being used in limited-run manufacturing to produce end-use parts for aerospace, military, medical, pharmaceutical, and electronics hardware. 4. On a shop floor, SLS can be used for rapid manufacturing of tooling, jigs, and fixtures. 5. Because the process requires the use of a laser and other expensive, bulky equipment, it is not suited for personal or residential use; however, it has found applications in art Applications

105. The average surface roughness value of the machined surface is increased with increase in the process parameters like open circuit voltage, discharge current, duty cycle and pulse-on-time and better surface finish achieved by using AlSi10Mg SLS tool electrode

106. The scanning electron micrograph of the machined surface by three different types of tool electrodes are taken by SEM (Model: Jeol JSM-6480LV, Japan) and the surface crack density (SCD) of the machined surface are measured by pdf xchange viewer software (a) AlSi10Mg RP, (b) Copper, and (c) Graphite

107. Fabricated specimens using design of experiments

108. The biomedical application of 3D printing of bio-metals includes (a) cranial prosthesis (b) surgical guide; (c) scapula prosthesis; (d) knee prosthesis; (e) dental implants; (f) interbody fusion cage; (g) acetabular cup; and (h) hip prosthesis

109. Objects manufactured by direct SLS technology. (a) CAD design, (b) real manufactured part. (Data from P. Bertrand et al., Appl Surf Sci , 254, 989–92, 2007.)

110. Accurate geometry performed by SLS/M technology using pure zirconia powder (a: part of a turbine blade, b: walls)

111. (a) Zirconia cube with 56% density; (b) top view of open porosity.

112. Recently, Liu reported a novel slurry-based SLS using HA, silica sol, and sodium tripolyphosphate (STPP) as slurry suspension for biomedical scaffolds preparation. Sintering at 1300°C resulted in scaffolds with porosity of ~14% and compressive strength of 43 MPa. As shown in Figure , scaffolds have high resolution and dimensional accuracy, which indicated the great potential for applying this method for bone tissue engineering scaffolds manufacture. (a) Green body, (b) front view, (c) top view, and (d) back view of scaffold parts obtained by direct slurry-based SLS via a laser scan speed of 300 mm/s and laser energy of 10 W. (Data from H.C. Yen, H.H. Tang, Int J Adv Manuf Technol , 60, 1009–15, 2012.)

113. Application and Future Development SLS is an advanced AM process that is excellent for complex geometry because no support structure is needed during the process. Hence, this method has been used in many fields based on their specific requirements. It has been adopted to produce Lead zirconate Titanate (PZT) ceramics from precursor powders. The property of the part was manipulated to match the requirements of some medical ultrasonic equipment such as hydrostatic charge and voltage. Bone tissue engineering scaffolds were also prepared by SLS. Bioceramics , such as Hydroxyapatite (HA) and Tricalcium phosphate (TCP), were manufactured by SLS with high processing accuracy and biocompatibility, which is excellent for bone regeneration.

114. The density of parts is usually modest, which will cause poor mechanical strength. 2. Due to the high processing temperature, the cooling cycle is an important issue. An inappropriate cooling might cause failure of the whole part. 3. Ceramic parts in large dimension are hard to manufacture. The future development will move forward to adjust the processing parameters to overcome these drawbacks. There are three main challenges for SLS process:

115. 3D PRINTING

116. Technology invented at MIT, Part constructed with starch powder Layer of powder spread on platform 2. Ink-jet printer head deposits drops of water/glue* on part cross-section 3. Table lowered by layer thickness 4. New layer of powder deposited above previous layer 5. Repeat steps 2-4 till part is built 6. Shake powder to get part

117. *Materials used: starch, plaster-ceramic powder * Multi-colored water can be used to make arbitrary colored parts (same as ink-jet printing) 3D Printing: companies, applications Engine manifold for GM racing car, Cast after Direct Shell Production Casting [source: www.soligen.com ] 1. Z-corporation [www.zcorp.com] 2. Soligen [www.soligen.com]

118. Advantages (1) High speed . Fastest 3D printer to date. Each layer is printed in seconds, reducing the prototyping time of a hand-held part to 1 to 2 hours. (2) Versatile . Parts are currently used for the automotive, packaging, education, footwear, medical, aerospace and telecommunications industries. Parts are used in every step of the design process for communication, design review and limited functional testing. Parts can be infiltrated if necessary, offering the opportunity to produce parts with a variety of material properties to serve a range of modelling requirements.

119. Advantages (3) Simple to operate . The office compatible Zcorp system is straightforward to operate and does not require a designated technician to build a part. The system is based on the standard, off the shelf components developed for the ink-jet printer industry, resulting in a reliable and dependable 3D printer. (4) No wastage of materials . Powder that is not printed during the cycle can be reused. (5) Colour . Enables complex colour schemes in RP-ed parts from a full 24-bit palette of colours.

120. Limited functional parts. Relative to the SLS, parts built are much weaker, thereby limiting the functional testing capabilities. (2) Limited materials. The materials available are only starch and plaster-based materials, with the added option to infiltrate wax using the ZW4 Waxer. (3) Poor surface finish. Parts built by 3D printing have a relatively poorer surface finish and post-processing is frequently required. Disadvantages

121. Sports Shoe Industry Sports shoe design model created by Z Corporation system (Courtesy of Z Corporation)

122. Javelin Puts Computer Sculpting in the Artist’s Hands “Dino-head” produced by Javelin using the Z Corporation System (Courtesy of Z Corporation)

123. A 3D-printed nasopharyngeal swab for COVID-19 diagnostic testing Case Study on Stereolithography Process

124. This case study discusses the development and implementation of a 3D-printed nasopharyngeal swab as an alternative to traditional swabs used in COVID-19 testing kits. Here is a breakdown of the key points in the case study: Teams from USF Health Radiology and Northwell Health System developed a 3D-printed stopgap alternative.

125. The COVID-19 pandemic disrupted the global supply chain for critical medical supplies. Shortages included nasopharyngeal swabs used in COVID-19 testing kits. 3D printing was considered a viable solution to address these shortages. The study outlines the initial steps taken by USF Health's Division of 3D Clinical Applications to explore 3D printing a swab alternative and highlights their collaboration with Northwell Health.

126. Swabs were printed using Formlabs Form 2 and Form 3B SLA 3D-printers because -in combination with FDA cleared software, they were considered readily available with biocompatible materials and relatively affordable for local deployment. Initial prototype computer-aided design (CAD) designs used Solidworks (France), 3-matic (Belgium) or Fusion 360 (United States). Over twenty tip designs were prototyped, some early examples can be seen in Fig. 1. The goal of tip design was to maximize surface area, sample retention and comfort. Swab design and development

127. Prototypes were narrowed down by clinicians from radiology, infectious disease and otolaryngology. After several design modifications were requested and completed, a final design consisting roughly of a 150 mm in total length with a 70 mm breakpoint. The tip length is 15 mm long, with a diameter of 3.85 mm. The tip has a rounded nose for patient comfort. The neck is 1.5 mm in diameter and the shaft is 2.45 mm in diameter. The base is 1.75 mm long with a 5 mm diameter (Fig. 2). Swab design and development

128. As each 3DP swab utilizes approximately 0.76 ml of resin to print (when combined with post-processing materials and potential waste), each swab costs approximately $0.25 USD to print. “Tip C” is the current tip configuration that is in use presently. “Tip D” is an experimental swab designed for smaller nasal passages made at the request of our clinicians. Swab design and development Bench lab testing of the final swab designs was conducted to ensure the geometries picked up enough of a sample to allow for viral testing. Swab materials were incubated for up to 3 days to ensure the printer resin would not interfere with downstream viral testing. As viral transport media (VTM) is also potentially in short supply, additional testing was used utilizing in house mixing of VTM using the World Health Organization recipe.

129. Early alternate 3DP swab designs. Letter C is the current version in use

130. Computer-assisted Drawing (CAD) of NP Swab

131. Four batches of 324 3DP NP swans ready for post-processing

132. 3DP swabs are rinsed using a Form Wash for 20 min in 99% isopropyl alcohol. This washing process is performed while the swabs are still attached to the build plate. Manual washing may be possible using the Finishing Kit, however swabs would need to be removed from the platform first. Once the wash is complete, the prints are allowed to airdry for at least 30 min. Afterwards the swabs are gently scraped off the build platform. The placing of a loose rubber band around the printed swabs prior to scraping them from the platform assisted in overall organization 

133. The swabs are then suspended from the base (with the tip pointing down) in a curing rack and placed in the Form Cure for 60 °C for 30 min (Form 2) or 70 °C for 30 min (Form 3B). An example of a curing rack can be seen in Fig. The inverted suspension of the NP swabs by a rack during curing removed issues with bent necks or shafts. It is recommended that the curing rack not be overcrowded to ensure that enough airflow and UV exposure occurs for each swab. Once the curing is complete, 3DP swabs are placed in steam sterilization pouches, and prepared for sterilization. Pre-vacuum steam sterilization cycle set at 132 °C/270 °F with a 4 min sterilization phase and 30 min dry is an appropriate sterilization cycle. Additionally, swabs may be treated in Prolystica 2X Enzymatic Presoak and Cleaner prior to pouching.

134. Several differences were also noted between the Form 2 and Form 3B. Form 2 s printed at 15–16 h per batch. Form 3Bs initially printed between 26 and 36 per batch. However, firmware updates and software settings have lowered print times to 10–11 h. Form 3Bs also have greater reject rates with some swabs failing to adhere to the build platform as well as higher rates of print inconsistencies with a “jittery” effect noted

135. UNIT– IV: RAPID TOOLING: Introduction to rapid tooling (RT), conventional tooling Vs RT, Need for RT. rapid tooling classification: indirect rapid tooling methods: spray metal deposition, RTV epoxy tools, Ceramic tools, investment casting, spin casting, die casting, sand casting process. Direct rapid tooling: Direct AIM, LOM Tools, and Direct Metal Tooling using 3DP.

136. Rapid Tooling Rapid tooling (RT) and rapid prototyping (RP) is any method or technology that enables one to produce a tool or product quickly . The term rapid tooling refers to RT-driven tooling. A prototype is a 3-D model suitable for use in the preliminary testing and evaluation of a mould, die or product.

137. Rapid Tooling Rapid tooling refers to mold cavities that are either directly or indirectly fabricated using additive manufacturing techniques There are primarily used to create multiple prototypes. Additive manufacturing techniques are not economical when more than one prototype needs to build for the same component

138. Rapid Tooling The term “tooling” refers in this case to the use of AM to create production tools. The tool is therefore an impression, pattern, or mould from which a final part can be taken. There are a variety of different ways in which this can be achieved. In recent years, there has been a tendency to attempt to use AM for production of parts directly from the machine. This is the so-called Direct Digital Manufacture (DDM) and there are numerous reasons why this can be a preferable approach to production.

139. What is Rapid Prototyping? Rapid prototyping is the fast fabrication of a physical part, model or assembly using 3D computer aided design (CAD). The creation of the part, model or assembly is usually completed using additive manufacturing, or more commonly known as 3D printing. Where the design closely matches the proposed finished product it is said to be a high fidelity prototype, as opposed to a low fidelity prototype, where there is a marked difference between the prototype and the final product.

140. What is Rapid Prototyping?

141. What is Rapid Prototyping?

142. What is Rapid Prototyping? Rapid prototyping (RP) is a technology and apparatus for fabricating physical objects directly from parts created in CAD using additive layer manufacturing techniques without manufacturing process planning, tooling, or fixtures. Rapid prototyping is a group of techniques used to quickly fabricate a scale model of a physical part or assembly using three- dimensional computer aided design data. Construction of the part or assembly is usually done using 3D printing or "additive layer manufacturing" technology.

143. What is a Prototype? & why do we use a prototype? A prototype can be defined as; " The three-dimensional model or imitation of an object or a project that provides the real-time information and visualization regarding its functionality, design and the fact that how much better or worse the product or project would turn out in reality after completion " . Prototyping serves the following purpose A prototype helps to decide in the favour of a product or against it. It can help us rectify flaws even before the production starts on a large scale, to avoid any future losses. Prototyping gives us the idea about the substantial future of the project whether it would be a hit or a miss The future product can help gain investors and sponsors if the prototype turns out to be successful.

144. Rapid Prototyping Rapid prototyping encompasses an amalgamation of several techniques for making a three dimensional model of a certain product or mechanical part of an object to be manufactured, through data provided by Computer- Aided Design (CAD) after the approval of the initial design for the product or a smaller part of the product The model which is produced through this method is scalable, which means that actual values and measurements are used to make a prototype that can be extrapolated on a large scale afterward turning it into a gigantic object. Computer-aided design (CAD) data is processed further into reality for fabricating the three-dimensional model after approval from the design team.

145. How Does Rapid Prototyping Work? Rapid prototyping (RP) includes a variety of manufacturing technologies, although most utilise layered additive manufacturing. However, other technologies used for RP include high-speed machining, casting, moulding and extruding. While additive manufacturing is the most common rapid prototyping process, other more conventional processes can also be used to create prototypes. These processes include: Subtractive - whereby a block of material is carved to produce the desired shape using milling, grinding or turning. Compressive - whereby a semi-solid or liquid material is forced into the desired shape before being solidified, such as with casting, compressive sintering or moulding.

146. Those familiar with rapid prototyping may find themselves asking about the difference between rapid prototyping and rapid tooling Rapid prototyping is the group of techniques used to quickly fabricate a scale model of physical part or assembly using three dimensional computer aided design (CAD) data. Because these parts or assemblies are usually constructed using additive fabrication techniques as opposed to traditional subtract two methods the phrase has become synonymous with additive manufacturing and 3D printing. Rapid tooling uses additive manufacturing or machining processes to create not the parts directly but tooling such as molds dyes or patterns which are then used in traditional manufacturing processes to produce the final parts bridging the gap between (rapid) prototyping and production and enabling the manufacturing of end -use parts Rapid Tooling Vs Rapid Prototyping

147. Key Factors in Selecting the Tooling Method Here are some of the basic criteria that product developers and engineers should look into when choosing a tooling method. Design Stage. All product designs have room for improvement. The question is, how far would the designer go to reach what they are production-ready? The answer will help them understand if they need more time in prototyping, or they can start production. The complexity of the product. The more complex the components a product has, the longer it will take them to prototype and complete the process before production.

148. Key Factors in Selecting the Tooling Method Intended market . Another factor in choosing the tooling method is for whom the product is designed for. Each will have different tooling needs depending on its intended market. Competition . When you have the intended customer, naturally, you will have potential competition in this same market. Although the idea is unique, it is not unusual to have other people with the same idea to solve a common problem. The first to get the product to the market will emerge as the winner. Budget . The budget will determine the type of tooling you are going to use to work on a prototype. Most designers conserve their funds by going for low-cost tooling at the beginning.

149. What is conventional tooling? In manufacturing, smaller production requirements are produced using conventional tooling or also known as single operation tooling. A manufacturing process involves the use of multiple tools in the different stages the product is taking shape until the final form is produced. In conventional tooling, the cost is higher and the production time is much longer.

150. The difference between rapid tooling and conventional tooling The first difference between rapid tooling from conventional tooling is speed . This can be seen in smaller and more multifaceted geometries. If you use conventional tooling in this project, you need more manufacturing operations in order to build them. However, if these parameters fit the qualifications of rapid tooling, you can build them in one procedure. Another difference is in the cost-effectiveness . Rapid tooling has an advantage on the cost of producing complex geometries because it is more difficult to manufacture them using conventional tooling. With rapid tooling, there is also little room for human error that can happen in conventional tooling. Using the CAD model, human error is greatly reduced.

151. The difference between rapid tooling and conventional tooling In addition, rapid tooling has the ability to produce outputs with complex designs because of its ability to interpret intricate designs directly from CAD. It allows flexibility in the designs and conforming to customer’s specification. Here the conceptual designs can be improved without incurring higher costs as compared to using the conventional tooling process. All these can contribute to excellent product quality and high manufacturing operation.

152. Difference Between Rapid Tooling and Conventional Tooling Conventional tooling has a wider scope, and it all boils down to different manufacturing techniques used to create a product. The processes involve human interventions and are not automated. Rapid tooling, on the other hand, is connected to rapid prototyping and is used in creating product models and in troubleshooting existing issues. It is never used in high-volume production runs. Rapid tooling involves two types: direct and indirect. Here are the differences between rapid tooling and conventional tooling based on three criteria.

153. Speed As the name itself, rapid tooling is much faster than conventional tooling. It is particularly useful in time-sensitive small production runs, like in rapid prototyping. In this case, the demand for a quick process that allows multiple iterations of the same concept is solved by using rapid tooling. Cost Rapid tooling is more economical to use than conventional tooling because it requires less human work and time. Since it is done by computer programs and machines, it is not prone to human errors. It leads to further savings on labour and less wastage.

154. Quality The downside of using rapid tooling is durability and lifespan. These types of the tooling also affect the longevity of the products it created. However, this is not all bad since there are products that are not needed to last for a long time. Therefore, there is no need to invest in its tooling. Rapid tooling can help manufacturers produce products in a much shorter amount of time. It offers many advantages over conventional tooling. It can work as long as you have the right parameters to match the capability of the rapid tooling machine.

155. Benefits of Rapid Tooling It provides an opportunity for innovation Beca use rap i d too l ing e l i m i n a t es t h e use o f c onven t ion a l too l ing, it initiates up a new range of opportunities for improvements. Traditional prototyping takes a long time because it needs making the prototype tooling and its components to exact the tolerances. In rapid prototyping, the designers can conceive complex geometries that will be impossible to develop in conventional prototyping too.

156. Time-saving Rapid tooling is time-saving because it eliminates the need to produce moulds, patterns, and special tools that you used in conventional tooling. Because of this, rapid tooling shortened the time between the initial idea and evaluation. The resulting prototypes are accurate and readily accessible for testing the forms, features, usability, and performance. Its designers can also modify the product based on the feedback. A fast turnaround can help the company to obtain a competitive edge to bring new products into the market.

157. Cost Savings Another benefit of rapid tooling is the cost savings. The part produced in rapid tooling is synonymous with full-scale production. You can use these parts for impact and stress testing. With the results from testing, you can determine the changes needed before going into an expensive tooling process.

158. Tooling time and cost is lower when compared to the conventional tool The product brings into the current market previous than the planned time This tool is utilized for small quantity requirements including the rapid prototyping The rapid tooling facilitates different kinds of products manufactured in the large range of materials It helps to resolve the existing problems and used to develop moulds for several commercial operations This tool is an effective method to produce quality products to customers and allows the organization to produce products with huge benefits

159. Importance of Rapid Tooling The term rapid tooling is typically used to describe a process which either uses a additive manufacturing model as a pattern to create a mold Quickly or uses the additive manufacturing process directly to fabricate a tool for a limited volume of prototypes Decrease total Time: Tooling time is much shorter than a conventional tool, typically time to first articles is below 1/5 date of conventional tooling

160. Importance of Rapid Tooling Minimize the cost : tooling cost is much less than for a conventional tool cost can be below 5% of conditional tolling cost Increase the productivity Shorter tool life: Tool life is considerably less than for a conventional tool Wider tolerances: tolerances are wider than for conventional tool

161. There are many applications for rapid tooling, and these a p plic a t i ons will co n t i n u e t o grow bec a use o f t h e d e vel o pm e nt o f n e w pr o c e dur e s . Here are so m e of them: The making of molds – both metallic and non-metallic molds can be made through rapid tooling. The m aking o f c a s t i ng sh a p e s and c o r es – SLS a p plic a t i on i s the l a t e s t t e ch n ol o gy inve n t ed i n s a nd casting shapes and cores. The electrodes for EDM, making of marking stamps, production of hybrid patterns for casting, and producing splint e ring to o ls are s ome o f t he a p plic a t i o n s o f r a pid tooling. Applications of Rapid Tooling

162. Rapid tooling Classification

163. Complete tool-bolster assembly

164. DMLS tooling of core and cavity of a pressure die-cast tool.

165. A DMLS mold with integrated cooling system (left), conformal cooling channels in the DMLS mould (right).

166. CAD model of Shell Core & Cavity

167. Differences Between Direct and Indirect Rapid Tooling Tools or dies are significant in the manufacturing process. They are so important that in the global market, tooling alone has a revenue of around 60 billion dollars last year. The increase in automation like CNC machining has also paved the way for simple tools that are faster to make. When there is a demand for production, tooling usually takes longer to make. This long lead time can cause a delay in the entire production process. The solution is going for rapid tooling . To maximize the benefits of this process, you need to choose the right rapid tooling type for your part. There are two types of rapid tooling: direct and indirect . Both have their own set of pros and cons and the choice will depend on the requirements.

168. Differences Between Direct and Indirect Rapid Tooling Direct Rapid Tooling Many attempts have been made to develop a new manufacturing technique that would reduce the lead times that has been a huge obstacle in the industry in the past. One approach is called direct tooling and the best example for this would be CNC machining . With the use of CAD digital file, the direct tooling machine can chip off part from a block in a subtractive process. The newest addition to the direct tooling process is 3D printing, which is an additive process. It builds a 3D shape object by adding the materials layer by layer. Both processes are frequently used in manufacturing and took less time to produce

169. Differences Between Direct and Indirect Rapid Tooling In - Direct Rapid Tooling The second approach to rapid tooling is indirect tooling where the tool is formed using an intermediate step known as the “master” model. The master is a 3D shape which can be copied multiple times. The process may be retrogressive but it was proven effective. It ensures that the tools are strong and robust for high-volume production.

170. Differences Between Direct and Indirect Rapid Tooling Direct Rapid Tooling Faster production It involves fewer steps and resources to make You can produce multiple prototypes Flexible Less durable Prone to minor errors Not suitable for complex designs Increase in cost In-Direct Rapid Tooling It makes durable tools More cost-effective You can create hard or soft tools depending on your requirement It produces tools with less discrepancies and variations You can use it to experiment with different materials Co n s It is more time-consuming Entails additional costs It needs high quality materials to improve its durability It does not fit simple designs and is more appropriate for complex designs Pros Co n s Pros

171. Spray ARC metal deposition This technique is the most common metal deposition technique and can be divided in two main types: Gas Metal Spraying and Arc Metal Spraying. The former involves a low melting point alloy that passes through a nozzle similar to a paint sprayer. A metal wire, usually lead/tin, is melted by a conical jet of burning gas , atomized and propelled onto the substrate. The second method, also known as the Tafa process , involves a gun in which an electric arc between two wires causes them to melt. The molten material (aluminium or zinc) is then atomised by a compressed gas that sprays it. Spray metal tools can be used to mould up to 2000 parts in the exact production material. The tools are inexpensive, fast to produce, accurate and capable of handling abrasive materials.

172. RTV Tools RTV tools are an easy, relatively inexpensive and fast way to fabricate prototype or pre-production tools. RTV tools are also known as silicone rubber moulds. The fabrication of RTV moulds usually includes the following main steps 1. Producing a pattern. Any RP method can be employed. 2. Adding venting and gating to the pattern. 3. Setting-up the pattern in a mould box with a parting line provided in a plasticine. 4. Pouring silicone rubber to form one half of the mould. 5. Inverting the first half of the mould and removing the plasticine. 6. Pouring silicone rubber to produce the second half of the mould.

173. There are two types of silicone used in this process: tin- and platinum-based silicones. Tin-based silicone is generally less expensive and more durable. RTV tools can be utilised for moulding parts in wax, polyurethane and a few epoxy materials. The process is best suited for projects where form, fit, or functional testing can be done with a material which mimics the characteristics of the production material.

174. Another form of RTV moulding known as Vacuum Casting is widely used for producing accurate silicone tools for casting parts with fine details and very thin walls. The process requires initial investment in a vacuum chamber with two sections. The upper section is for mixing the resin and the lower is for casting the resin into the mould. MCP vacuum casting chamber

175. The MCP vacuum casting process includes nine steps 1. The first step is to produce a pattern using any of the available RP processes (SLA, SLS, FDM, etc.). 2. The pattern is fitted with a casting gate and set up on the parting line, and then suspended in a mould casting frame. 3. Once the two-part silicone-rubber is de-aerated and then mixed, it is poured into the mould casting frame around the pattern. 4. The mould is cured inside a heating chamber. 5. The pattern is removed from the silicone mould by cutting along the parting line.

176. 6. The urethane resin is measured, dye is added for coloured components and casting funnels placed. Then, the mould is closed and sealed. 7. The computer-controlled equipment mixes and pours the resin inside the vacuum chamber. Because this takes place in a vacuum, the mould is filled completely without leaving any air pockets or voids. 8. After casting the resin the mould is moved to the heating chamber for 2 to 4 hours to cure the urethane part. 9. After hardening, the casting is removed from the silicone mould. The gate and risers are cut off to make an exact copy of the pattern. If required the component can be painted or plated.

177. Vacuum castings are precise replicas of the patterns, dimensionally accurate without blemishes, with all profiles and textures faithfully reproduced. A variety of resins specially-formulated for vacuum casting are available on the market to offer various characteristics in hardness, toughness, flexibility and temperature resistance.

178. Epoxy Tools Epoxy tools are used to manufacture prototype parts or limited runs of production parts. Epoxy tools are used for [3D Systems, 1995]: • Moulds for prototype injection plastics; • Moulds for castings; • Compression moulds; • Reaction injection moulds.

179. The fabrication of the mould begins with the construction of a simple frame around the parting line of the RP model Sprue gates and runners can be added or cut later on, once the mould is finished. The exposed surface of the model is coated with a release agent and epoxy is poured over the model. Aluminium powder is usually added to the epoxy resin and copper hose cooling lines can also be placed at this stage to increase the thermal conductivity of the mould. Once the epoxy has cured, the assembly is inverted and the parting line block is removed, leaving the pattern embedded in the side of the tool just cast. Another frame is constructed and epoxy poured to form the other side of the tool. When the second side of the tool is cured, the two halves of the tool are separated and the pattern is removed

180. Soft-Surface® rapid tool Another approach, known as Soft-Surface® rapid tool involves machining an oversized cavity in an aluminium plate. This offset allows for the introduction of the casting material, which may be poured into the cavity after suspending the model in its desired position and orientation. Some machining is required for this method and this can increase the mould building time but the advantage is that the thermal conductivity is better than for all epoxy moulds. Soft-Surface®

181. Unfortunately, epoxy curing is an exothermic reaction and it is not always possible directly to cast epoxy around an RP model without damaging it. In this case, a silicone RTV mould is cast from the RP pattern and a silicone RTV model is made from the mould and is used as the pattern for the aluminium filled epoxy tool. A loss of accuracy occurs during this succession of reproduction steps. An alternative process is to build an RP mould as a master so that only a single silicone RTV reproduction step is needed. Because epoxy tooling requires no special skill or equipment, it is one of the cheapest techniques available. It is also one of the quickest. Several hundred parts can be moulded in almost any common casting plastic material.

182. Epoxy tools have the following limitations [3D Systems, 1995]: Limited tool life; Poor thermal transfer; Tolerance dependent on master patterns; Aluminium-filled epoxy has low tensile strength. The life of injection plastic aluminium-epoxy tools for different thermoplastic materials Approximate aluminium-epoxy tool life

183. Ceramic Tools Instead of epoxy, any plaster ceramics can also be cast around a master to produce a tool cavity. Ceramic tools can be employed in plastics processing, metal forming and metal casting. In making ceramic tools, the amount of water used has to be controlled to avoid excessive shrinkage as the material sets. Recently, attention has been focused on non-shrinking ceramics. These Calcium Silicate-based Castable (CBC) ceramics were initially developed for applications where metal spraying was not suitable.

184. The stages of producing the two halves of a CBC ceramic tool differ slightly from the epoxy mould procedure described earlier. CBC ceramics only generate a small amount of heat during curing (approximately 50°C). This allows them to be poured directly over the RP master without damaging it. The two halves of the mould must be vacuum cast to avoid air bubbles and a vibration table can help to pack the material. After about one hour, the RP pattern can be removed and the ceramic tool is cured for about 24 hours in an oven. Once the ceramic is fully cured, the back surfaces of the two mould halves are machined flat and guides are drilled to receive the ejector pins

185. Ceramics are porous materials, which is not desirable when the tool is used to mould very adhesive polymers. Various surface treatments can be carried out to reduce the porosity including the application of a dry film lubricant, a release agent, silicone, or PTFE. Ceramic tools are brittle and must be handled with care. Finely chopped fibres are often added to enhance fracture toughness and tensile strength, as well as aluminium fillers to increase the thermal conductivity. In this way, a tool can be used to produce several hundred parts and injection moulding cycle times as low as 30 seconds can be achieved.

186. The main advantage of this process, apart from the low cost of the ceramics used, is the short time needed to build a mould. Some beta-tested CBC ceramics have been reported with a curing time of a few hours, which could enable an injection tool to be made in one day after obtaining the RP model.

187. Cast Metal Tools Metal moulds are generally time-consuming and expensive to machine, but by combining RP techniques with casting techniques, some zinc or aluminium alloy moulds can be rapidly made. Investment casting: The use of RP sacrificial models for investment casting was one of the first applications of RP. Nowadays, models for investment casting can be made on almost every RP machine. They can be obtained directly without any change to the building process (LOM), by modifying the building style ( Quickcast ™), or by using a special material (SLS, FDM). Another technique is to build the ceramic shell that will be used for investment casting (3-D Printing).

188. Die-casting: Proceeding in the same way as for ceramic tooling, it is possible to fabricate a ceramic mould to cast a metal alloy mould. The ceramic mould then behaves like a die cast mould but can be used for the fabrication of one metal mould only.

189. Spin-casting: The spin-casting process consists of injecting a material through a central sprue into a mould that is rotated at high speed. Spin-casting moulds for metal parts are made of heat vulcanised silicone. The heat that is given out during the fabrication of such moulds is too high for usual RP patterns. For this reason, the fabrication of a metal part using spin-casting consists of several steps. First, an RTV rubber mould is made from the RP master. From this mould, a tin based metal alloy part is cast and is used as a model for the fabrication of a heat-vulcanised silicone mould. This final mould can produce spin-cast zinc alloys parts that have similar physical strength properties to both die cast aluminium parts and die cast zinc parts.

190. The aim when using an RP model for metal casting is to make a mould as similar as possible to the final mould so that only finishing is required. In this way, time and machining are saved compared with traditional mould making methods. Unlike the tooling methods presented previously, these metal tools have relatively good strength and thermal conductivity. This allows normal clamping forces and injection pressures during the moulding cycle. The injection moulding conditions can then be considered similar to production conditions but the life of the mould is usually limited to below a thousand parts

191. Investment Casting The investment casting process is used to cast complex and accurate parts. The process was invented by the early Egyptians and was called "lost wax". As the name indicates, wax patterns are used to define the part shape that are then melted away. It is also possible for patterns to be produced from foam, paper, polycarbonate and other RP materials which can be easily melted or vaporised. The investment casting process includes the following main steps as shown in Figure

192. 1 . Multiple patterns are produced. 2. The patterns are assembled as a group on a "tree" where they are gated to a central sprue. 3. The tree of patterns is dipped in a slurry of ceramic compounds to form a coating. Then, refractory grain is sifted onto the coated patterns to form the shell. 4. Step 3 is repeated several times to obtain the desired shell thickness (5-10 mm) and strength. 5. After the tree has set and dried, the patterns are melted away or burned out of the shell, resulting in a cavity. 6. Molten metal is poured into the shell to form the parts. 7. The ceramic shell is broken away to release the castings. 8. Finally, the castings are removed from the sprue and the gate stubs are ground off.

193. Another form of investment casting is solid flask investment casting. The latter employs solid flask moulds instead of shells. In addition, the moulds are filled while applying a vacuum differential pressure method. An automated system for solid flask investment casting manufactured by MCP is shown in Figure. Production of castings employing this system involves the following processing steps MCP Metal Part Casting System 1. A master is built using any of the available RP processes. 2. A silicone mould is produced from the master under vacuum in the MCP Vacuum Casting System. Multiple patterns are cast from the silicone mould in the same system under vacuum. 4. The patterns are gated to a central sprue to create a pattern cluster. The cluster is then placed in a flask. 5. Ceramic embedding material is poured around the pattern cluster under a vacuum in a special vacuum chamber to avoid creating bubbles.

194. 6. After the ceramic mould has set and dried, the flask is placed in a furnace to melt out the patterns. 7. The flask is next placed in the casting chamber of the MCP Metal Part Casting system. The melting chamber is designed to provide a melting pressure independent of the casting chamber. Thus, the mould is filled with metal by vacuum differential pressure. 8. The ceramic mould is broken away from the castings using a water jet. Then, the sprue and gate stubs are removed from the castings. The MCP Metal Part Casting system is manufactured in three unit sizes: MPA 150, MP A 300 and MP A 1000. The technical specifications of these three models are given in Table Technical specifications of the MCP Metal Part Casting systems

195. Sand Casting The sand casting process is often employed for the production of relatively large metal parts with low requirements for surface quality. RP techniques can be utilised to create master patterns for fabricating sand moulds. These moulds are produced by placing RP patterns in a sand box which is then filled and packed with sand to form the mould cavity. When employing RP techniques, it is much more convenient to build patterns that include compensation for the shrinkage of the castings as well as additional machining stock for the areas requiring machining after casting. The other benefits of employing RP techniques are significantly reduced lead-times and increased pattern accuracy.

196. Direct Methods for Rapid Tool Production

197. Indirect methods for tool production as described in the previous chapter necessitate a minimum of one intermediate replication process. This might result in a loss of accuracy and could increase the time for building the tool. To overcome some of the drawbacks of indirect methods, some RP apparatus manufacturers have proposed new rapid tooling methods that allow injection moulding and die-casting inserts to be built directly from 3D CAD models.

198. Direct ACES TM Injection Moulds ( AIM) Stereo lithography is used to produce epoxy inserts for injection mould tools for thermoplastic parts. Because the temperature resistance of the curable epoxy resins available at present is up to 200°C and thermoplastics are injected at temperatures as high as 300°C (572°F) specific rules apply to the production of this type of injection mould.

199. Using a 3D CAD package, the injection mould is drawn. Runners, fan gates and ejector pin clearance holes are added and the mould is shelled to a recommended thickness of 1.27mm The mould is then built using the Accurate Clear Epoxy Solid (ACES) style on a stereolithography machine. The supports are subsequently removed and the mould is polished in the direction of the draw to facilitate part release. The thermal conductivity of the stereolithography resins is about 300 times lower than that of conventional tool steels

200. To remove the maximum amount of heat from the tool and reduce the injection moulding cycle time, copper water cooling lines are added and the back of the mould is filled with a mixture made up 30% by volume of aluminium granulate and 70% of epoxy resin. The cooling of the mould is completed by blowing air on the mould faces as they separate after the injection moulding operation. The main disadvantage of Direct AIM TM (ACES TM Injection Moulds) is that the number of parts that can be obtained using this process is very dependent on the shape and size of the moulded part as well as the skills of a good operator who can sense when to stop between cycles to allow more cooling.

201. Because finishing must be done on the internal shapes of the mould, the process is slightly more difficult than for indirect methods where most of the model shapes are external. Also, draft angles of the order of 1/2 to 1 degree and the application of a release agent in each injection cycle are required to ensure proper part ejection. • Production Time: A Direct AIM mould can typically be grown and processed in 1 to 2 weeks. • Tool Life Expectancies: Less than 100 parts. Life of the tool is a function of the thermoplastic material and part complexity. Some moulds can create as few as 10 parts, while other can exceed 100. • The moulds can have a dynamic failure, but typically gradually degrade with each shot. • Accuracy: Tolerances of between 0.005-0.015 inches can be achieved.

202. LOM Tools

203. laminated tooling The concept of rapid laminated tooling is very similar inmany respects to laminated object manufacturing (LOM), the rapid prototyping process conceived and commercialised by Helysis in the late 1980s. In the LOM process each layer in the model is formed from a sheet of paper coated with a thermoplastic adhesive. The sheet is bonded to the layer below using a heated roller and then a CO 2 laser cuts the required cross-section into a layer of paper. This process is repeated, layer-upon-layer, until the object is completed.

204. However, as opposed to employing paper bonded with a thermoplastic binder, laminated tooling is most usually formed from relatively thick steel sheets that are bolted, bonded with adhesive or brazed together. The first published research, in the area of laminated tooling was undertaken in Japan by Nakagawa. His initial work focused on the manufacture of blanking dies for sheet metal components.

205. In these early trials, relatively simple shapes were produced, through a process of stacking horizontal steel sheets into which profiles had been cut using either lasers or the wire EDM process. This work eventually extended to the manufacture of deep drawing dies . International interest in rapid laminated tooling increased dramatically in the 1990s with the advent of rapid prototyping. In addition to stirring the imagination of researchers around the world, the commercialisation of the rapid prototyping process signalled the availability of the software tools to assist the manufacture of laminated dies.

206. Over the last 10 years there have been numerous research programmes the area of laminated tooling, undertaken by organisations which include MIT, Nottingham University, Bremen Institute of Applied Beam Technology, Lone Peak, the Danish Technical Institute and CRIF. However, despite the level of academic interest there has been little commercial exploitation of this process.

207. Direct Metal Tooling using 3DP.

208. The 3D Printing process developed by the MIT [Sachs et al., 1997; MIT, 1999] can be employed to build metal parts for injection moulding tooling inserts from a CAD model in a range of materials including stainless steel, tungsten and tungsten carbide. The process allows the fabrication of parts with overhangs, undercuts and internal volumes as long as there is an escape route for the unused loose powder.

209. 1. Building the part by combining powder and binder employing the 3DP TM process. 2. Sintering the printed parts in a furnace to increase their strength. 3. Infiltration of the sintered parts with low melting point alloys to produce fully dense parts. The production of metal parts includes the following steps:

210. The 3DP™ process can be easily adapted for production of parts in a variety of material systems, for example metallic/ceramic compositions with novel material Properties. Tooling inserts fabricated using the 3DP TM process (Courtesy of MIT) (a and b - injection moulding inserts with conformal cooling, c - finished metal inserts) a) c) b)

211. A cooling passage printed conformable to the tooling cavity. Fast thermal response tooling with conformal cooling passages with a cellular/truss structure behind it for thermal isolation. 3D Printing can be used to create tooling with integral cooling passages which are conformable to the moulding cavity and near to its surface. Such channels can be printed in virtually any geometry and with virtually any interconnectedness. Tools with cooling passages can be used to control the temperature accurately and yield reproducible parts with predictable properties. Fast thermal response tooling can be created by printing passages for liquids near the surface and then providing a low thermal mass back-up structure, possibly by printing a truss structure (shown below). Textures may be printed onto the cooling channels themselves to further enhance heat transfer With such tooling, the temperature of the tool can be raised before injection and then quickly dropped after injection. This results in demonstrated and significant improvements in part quality (by reduced residual stress) and increased production rate.

212. UNIT– V: RAPID PROTOTYPING DATA FORMATS: STL Format, STL File Problems, consequence of building valid and invalid tessellated models, STL file Repairs: Generic Solution, other Translators, and Newly Proposed Formats. RP APPLICATIONS: Application in engineering, analysis and planning, aerospace industry, automotive industry, jewellery industry, coin industry, GIS application, RP medical and bioengineering applications: customized implants and prosthesis, forensic sciences.