plastic and processing.pptx manufacturin

manufacturing process

1. Unit 4 Plastics and their Processing

2. The term ‘plastic’ is applied to all materials capable of being moulded i.e. Plasticity is the general property of all materials which can deform irreversibly without breaking. However, The meaning of word today has changed to a group of materials which, when heated, can be formed into a variety of useful articles by moulding, casting or extrusion. 1. Introduction

3. Plastic  is material consisting of any of a wide range of  synthetic  or semi-synthetic  organic compounds that are malleable and so can be  moulded  into solid objects. Plastics are the most versatile materials in our modern engineering world as they offer advantages in weight, cost, moisture, strength, chemical resistance, toughness, abrasive resistance, insulation (both thermal and electrical), appearance, formability and machinability. And hence, plastics are used in a wide range products of different scale, including paper clips and spacecraft.

4. Plastics have many uses in the medical field as well, with the introduction of polymer implants and other medical devices derived at least partially from plastic. The field of  plastic surgery  is not named for use of plastic materials, but rather the meaning of the word plasticity, with regard to the reshaping of flesh.

5. Advantages of Plastics The growth in the use of plastic is due to its beneficial properties which include: Extreme versatility and ability to be tailored to meet specific technical needs. Lighter weight than competing materials reduces fuel consumption during transportation. Good safety and hygiene properties for food packaging. Durability and longevity Resistance to chemicals, water and impact. Excellent thermal and electrical insulation properties Comparatively lesser production cost Unique ability to combine with other materials like aluminium foil, paper, adhesives Far superior aesthetic appeal. The material of choice – Human lifestyle and plastic inseparable. Intelligent features, smart materials and smart systems.

6. Disadvantages of Plastics Plastics production also involved the use of potentially harmful chemicals which are added as stabilizers or colourants . Many of these have not undergone environmental risk assessment and their impact on human health and the environment is currently uncertain. Such an example is phthalates which are used in the manufacture of PVC. PVC has in the past been used in toys for young children and there have been concerns that phthalates may be released when these toys are sucked. Risk assessment of the effects of phthalates on the environment is currently being carried out. The disposal of plastics products also contributes significantly to their environmental impact. Most plastics are non-degradable and they may take a long time to break down once they are landfilled. With more and more plastic products, particularly plastics packaging, being disposed of soon after their purchase, the landfill space required by plastics waster is a growing concern.

7. Plastic processing methods Compression moulding Transfer moulding Injection moulding Extrusion Casting Slush moulding Calendering

8. 1. Compression Moulding

9. Thermoset compound, usually preformed, is positioned in a heated mould cavity; the mould is closed with the application of heat and pressure the material flows and fills the mould cavity. Heat completes polymerization and identification the part of ejected.

10. Compression molding is a high-volume, high-pressure method suitable for molding complex, high-strength  fiberglass reinforcements. Advanced composite  thermoplastics  can also be compression molded with unidirectional tapes, woven fabrics, randomly oriented fiber mat or chopped strand. Advantages: The advantage of compression molding is its ability to mold large, fairly intricate parts. Also, it is one of the lowest cost molding methods compared with other methods such as transfer molding  and  injection molding ; moreover it wastes relatively little material, giving it an advantage when working with expensive compounds.

11. Advantages of the Compression Molding Process 1. Production rate is high as the mold cycle time is in few minutes. 2. Good surface finish with different texture and styling can be achieved. 3. High part uniformity is achieved with compression molding process. 4. Good flexibility in part design is possible. 5. Extra features like inserts, bosses and attachment can be molded in during the processing. 6. Raw material wastage is minimum. 7. Maintenance cost is low. 8. Residual stresses are absent or negligible in the molded component. 9. Twisting and shrinkage in product is reduced therefore dimensional accuracy is good.

12. Disadvantages of compression molding process 1. Due to expensive machinery and parts, the initial capital investment associated with compression molding is high. 2. The process is suitable for high production volume. It is not economical for making a small number of parts or for prototyping applications. 3. It is a labour intensive process. 4. Sometimes secondary processing (trimming, machining) of product is required after compression molding. 5. Sometimes uneven parting lines are there. 6. There is limitation on mold depth.

13. Applications: Aircraft applications range from various clips and brackets, to many different covers and access panels, to wing fences and missile components. Space applications also include various brackets, truss tube end fittings and even major load bearing structures on launch vehicles. Commercial applications center around interiors for aircraft and include structures like trays and panels, but interest is also gathering in the oil and gas industry related to ground exploration hardware. Anywhere complex shaped parts are needed, where injection molding materials do not offer enough mechanical performance, and the weight, cost and corrosion of metal shapes is a concern, we have seen success.

14. Advantages of Compression Moulding : 1. Lower cost Tooling   Because the process does not involve an Injection or Transfer cycle, the tooling has less infrastructure requirements than tools designed for other moulding methods; other than the particular features of the cavity itself that will produce the moulded parts, which clearly have to replicate the detail of the product, there is little else needed in the way of additional features. Tools can be made of aluminium or lower cost grades of steel which can save cost, although any tool must be capable of withstanding the considerable moulding pressures required.  

15. 2. Good for small production runs   The lower capital cost of manufacturing a mould tool, setting up a press and beginning to run production parts means that compression moulding is the most cost effective method of making smaller runs of parts. There is of course a breakeven point where the higher capital cost of an injection mould tool becomes viable due to the lower cost of the parts it makes, and making the correct determination of this point is a key consideration when developing the best production solution for a new product.

16. 3. No gates, sprues or runners   This form of moulding does not use gates, sprues or runners which are tooling features that materials have to pass through in other methods of production before entering the mould cavity. These consume extra material and therefore cost, and can also detract from the cosmetic requirements of a part, both of which can be considerations when deciding the most appropriate tooling method for production.  

17. 4. Good for large parts   This form of moulding is particularly suited to the production of large parts, which require significant bulk of material to manufacture. Because the material is loaded into the mould cavity directly, there is no limitation on the weight of part that can be made other than the size of press and tonnage required, whereas injection moulding presses are limited in the weight of part they can produce by the volume of the injection barrel that fills the mould.

18. Disadvantages of Compression Moulding : Greater waste of   material Compression moulding is not as precise a method of making a product as injection moulding , due to the fact that the mould cavity has to be overfilled to some degree to achieve the correct pressure to cure the part. It is also often necessary to push air out of the cavity using excess material in order to create a void-free part, which again increases wastage, whereas an injection mould is more precisely filled and the material inherently drives out the air as the cavity is filled. Waste thermoset rubber or plastic generally cannot be melted down and reused so the cost of the part must reflect this.

19. Disadvantages of Compression Moulding : Higher labour cost This production technique is fairly simple, however it requires more man power than a semi-automatic injection moulding process to run. The skill level is often proportionately higher, and for larger parts or tools, manual handling may become an issue.

20. Slower process time Because the thermal conductivity of rubber and resin is relatively poor, bringing a blank of material up to curing temperature by contact with the hot surfaces of the mould takes time for larger parts, which limits the speed at which parts can be cured and de- moulded . On the other hand, Injection moulding shoots material into the mould that is already at a temperature just below curing, therefore the extra time required to begin cure once the press closes is drastically shorter. Depending on the size of a part, a typical cycle can take around ten minutes, whereas the equivalent cycle of injection moulding would take approximately five minutes to complete. This can make a significant difference when producing parts in higher volume, when production rate and part cost become the priority.

21. 4. Not suitable for complex mould While complex parts can be made using Compression moulding , depending on the material required and the design of the product, it is generally better suited to the production of larger, simpler objects. This is because the limited flow of material within the cavity often makes the elimination of voids, air traps and parting lines difficult when trying to produce more intricate parts.

22. 5. Contamination It is much easier to produce clean, consistently coloured rubber parts by Injection or transfer moulding . However, the uncured blank of compound used in Compression moulding can pick up specks of dirt which then simply get pressed and cured into the surface of the part, which the results in poor cosmetic appearance. Despite the part being dimensionally and physically acceptable, this often leads to an increase in reject rates and waste.

23. 6. Difficult to control flash Flash  is a necessary by-product of Compression moulding due to the need to expel air during the moulding process by overfilling the mould cavity. This  flash  can also vary in thickness depending on the exact fill of each particular shot, leading to issues with variable dimensions of the part over across the split line. The  flash  has to be mechanically cut off and, again, is a thermoset material that cannot be recycled easily. The resulting parting line witness mark is often more evident than on an Injection moulded part. This may create an aesthetic problem for the customer. Generally, Compression moulded parts require more labour effort to trim and finish them, which can also increase the cost.

24. 7. Moulds can be damaged The repetitive nature of this process means that the moulds themselves can become victims of general wear and tear due to manually loaded blanks of material. Quite often, the mould is made to be run loose and is not bolted into a press. This can lead to deterioration of trim grooves and fine details, or in extreme cases, impact damage on mould faces caused by poor handling.

25. Materials used: Most fiber types can be compression molded including fiberglass, aramid , standard modulus carbon fiber and every other grade of carbon fiber. When it comes to resin, two general categories are used: thermoset , like epoxies and cyanate esters ; and thermoplastics, like Polyether ether ketone ( PEEK) and Polyetherimide ( PEI).

26. Video of compression moulding

27. 2. Transfer moulding

28. Thermoset moulding compound is fed into transfer chamber where it is then heated to plasticized; it is then fed by a plunge through sprue , runners, and gates into a closed mould where it cures; mould is opened and part ejected. Types of Products: Plugs, Sockets, Handles, Engine Casing Switches, Container etc.

29. This moulds are costlier but operation is easier & enables trouble free production of intricate parts with thin sections as mould is not directly subjected to compression force.

30. Transfer moulding

31. Transfer moulding

32. Advantages: 1) High Cavity Count  In many cases, transfer molded rubber products require few and simple pre-forms. One pre-form can fill hundreds of cavities. This is an advantage over compression molding, and can save a significant amount of time in the molding process.  This is also an advantage over injection molding since there is not a runner to fill each cavity reducing the number of cavities. 2) Design Flexibility   Transfer molding allows for sharper edges. Micro grind vents reduce the need for overflows allowing for near flash less parts, greatly reducing deflash process or allow flash limits to directly ship parts. With pot and plunger design, simplified preforms required allowing for standardization and lower cost.

33. Advantages: 3) Short production cycle Transfer molding offers shorter cycle times than compression molding and can provide more consistency, too. The process allows for tighter tolerances and more intricate parts.

34. The Disadvantages 1)  Complex molds   Since the design and mold tends to be complex, tooling can also become expensive. 2) Waste material Transfer pots typically produce higher volume waste than traditional overflows in compression tools. Transfer molding typically produces a large pad with sprues . The scraps are not reusable, since the polymers are thermosetting. 3) Mold Maintenance Inserted transfer tools require more mold maintenance than compression tools. Typically, inserts have to be taken out and reset to maintain movement over time. Cleaning the tool can be time consuming, and sometimes special equipment like dry ice blasters are used to clean the intricate transfer insert.

35. Advantages Fast setup time and lower setup costs Low maintenance cost Plastic parts with metal inserts can be made Design flexibility Dimensionally stable Uniform thickness of parts Large production rate Disadvantage: Wastage of material Production rate lower than injection molding Air can be trapped in the mold

36. Materials The material most commonly used for transfer molding is a thermoset plastics (epoxy, polyester, phenol formaldehyde, vinyl ester, silicone) This type of polymer is easy to mold and manipulate, but upon curing, hardens into a permanent form.  For simple homogeneous transfer molded parts, the part is simply made of this plastic substrate. On the other hand, resin transfer molding allows for a composite material to be made by placing a fiber within the mold and subsequently injecting the thermosetting polymer.

37. Applications This process is widely used to encapsulate items such as integrated circuits, plugs, connectors, pins, coils, and studs. It is suitable for molding with ceramic or metallic inserts which are placed in the mold cavity. When the heated polymer fills the mold it forms bonding with the insert surface. Transfer molding is also used for manufacturing radio and television cabinets and car body shells.

38. Video of Transfer moulding

39. Compression Moulding

40. Transfer Moulding Transfer Moulding Transfer Moulding Transfer Moulding

41. Compression Moulding

42. Transfer Moulding

43. 3. Injection moulding

44. Horizontal Injection moulding

45. 1. Injection ram 2. Screw 3. Hopper 4 . Barrel 5. Heaters 6. Plastic material 7. Nozzle 8. Mould 9. Final product

46. Horizontal Injection moulding

47. 1.  Granules of plastic powder (note the plastics listed above) are poured or fed into a hopper which stores it until it is needed.   2.  A heater heats up the tube and when it reaches a high temperature a screw thread starts turning.      3.  A motor turns a thread which pushes the granules along the heater section which melts then into a liquid.  The liquid is forced into a mould where it cools into the shape (in this case a DVD storage unit).   4.  The mould then opens and the unit is removed.

48. Horizontal Injection moulding

49. Horizontal Injection moulding

50. Vertical Injection moulding

51. Injection Moulding : Thermoplastic or Thermoset plasticized at control temperature inside the screw pump (a combination of screw & barrel), then forced under pressure through a nozzle into sprue , runners, gates and cavities of mould. Types of products: Spools, bobbin, bottle caps, automotive parts, gem clips, crates, buckets etc. Types of Injection moulding machine: 1. Hand injection moulding : 2. Semi-auto (Plunger type) Injection moulding : 3. Fully-auto (Screw type) Injection moulding : 4. Advanced injection moulding :

52. Tool materials Tool steel is often used. Mild steel, aluminium , nickel or epoxy are suitable only for prototype or very short production runs. Modern hard aluminium (7075 and 2024 alloys) with proper mould design, can easily make moulds capable of 100,000 or more part life with proper mould maintenance.

53. Advantages SCALABILITY Injection Molding can be the ideal process for production runs of  250-25,000+ parts. STRENGTH Injection Molded parts will generally  perform better  than the same part CNC Machined from the same material. Careful selection of the resins allow for a wide range of corrosion resistance and chemical and solvent compatibility. PRECISION Injection molds are CNC machined to high precision, high tolerances and are able to produce  thousands of identical parts  with very small tolerances and intricate details.

54. Advantages: EFFICIENCY In higher volumes, injection molding produces  significantly less waste  than other manufacturing processes. PART PRODUCTION Piece  price is significantly lower  with Injection Molding vs other processes, particularly as production quantities increase into the thousands. Disadvantages : High initial costs, not ideally suited for small runs/jobs.

55. Materials used: Injection moulding can be performed with a host of materials mainly including  metals , (for which the process is called  die-casting ),  glasses ,  elastomers , confections, and most commonly  thermoplastic  and  thermosetting  polymers.

56. Applications Injection moulding is used to create many things such as wire spools,  packaging ,  bottle caps , automotive parts and components, toys,  pocket combs , some musical instruments (and parts of them), one-piece chairs and small tables, storage containers, mechanical parts (including  gears ), and most other plastic products available today. Injection moulding is the most common modern method of manufacturing plastic parts; it is ideal for producing high volumes of the same object.

57. Advantages: The main advantage of this process is that complex shapes components having small wall thickness (5-15 mm) can be easily molded and removed from the die without damage. Parts which are made by injection molding have good dimensional tolerance. The major advantage of this technique is that the scrap produced by this is very less as compare to some other processes. Parts made by injection molding process are competing with parts made by investment casting and complex machining parts. This process is having high production rate as compare to other techniques.

58. Disadvantage: Initial cost/ setup cost of this process is very high due to design, testing and tooling of the whole equipment. Investment molding is generally limited to some special kind of materials like thermoplastic materials or some polymers only. High tooling cost i.e. the mould used is made by several processes and testing the overall cost of making a single mold is very high. For different parts different kind of molds are required.

59. Video of plastic injection moulding

60. Transfer Molding Vs Injection Molding Vs Compression Molding： Which One is Better

61. Investment The molds for both of these procedures must be constructed by a toolmaker or machinist, which is a pricey operation in and of itself. The main determinant of launch expenses, however, is the cost of the necessary equipment. The press required for a transfer mold is considerably less expensive than the injection molding machine, primarily due to the equipment’s complicated and specialized internal design. Additionally, it requires a lot more time to set up than a transfer mold machine, delaying the start of a project. The price and complexity of injection molding machines also result in much greater maintenance costs.

62. Production speed Depending on the size of the product, the injection molding production cycle might last anywhere from two seconds to two minutes. Even after removing any surplus material, such as flash or sprue, the whole production time is still substantially less than the total production time for transfer molding. Transfer molding’s main drawback is that the material must be prepared before being put into the machine, greatly lengthening the cycle time. Compression molding requires a lot more time to produce than injection molding. Additionally, compression molding requires hand trimming of the extra flesh around the pieces, which slows down the manufacturing cycle and increases labor requirements.

63. Production capability Transfer molding cannot compete with injection molding for a number of required items. Faster cycle times and relatively automated technologies make this strategy far more cost-effective over the long term for high-volume projects. High-quality items can be created using injection, compression, and transfer molding is very comparable ways. Compression molding may produce large quantities when the molding process is automated and there are short cycle periods. Transfer molding is better suited to encasements and limited quantities of straightforward molds, while injection molding is considerably better suited to bigger quantities of larger, thin-walled parts.

64. Precise molding tools Both procedures offer findings that are very reliable and with excellent accuracy. Injection molding, however, struggles to handle sharp edges and sometimes ends up smoothing off edges that were intended to be sharp.  Products shape/size and accuracy although both methods are capable of creating products with extremely complex forms, transfer molding is much less expensive than injection molding to accomplish this, mainly because complicated injection molds demand more complex and expensive injection systems to manufacture.  Regarding compression molding, this is untrue. The shape and final design of the product might be impacted by the pressure of the upper mold.

65. Amount of waste Even though injection molds occasionally produce flash and sprue waste, transfer molding often generates much more waste. This is mostly because overflow grooves, air holes, and a broader sprue are present that are absent from injection molds. This can cause significant material waste if the substance is thermosetting.

66. Cost comparison The geometry of the product determines the cost of production rather than generally favoring one method over another. It would be more expensive to employ an injection machine as opposed to a transfer machine for materials requiring a high injection pressure because a more powerful injection machine would be needed. For a larger part, the same can be true. However, the production per cycle is increased by the fact that injection machines can handle more cavities. Additionally, injection molding requires greater automation than transfer molding devices, which lowers long-term labor expenses for large-scale projects.

67. Extrusion

68. Motor

69. Plastic extrusion machine used for films

70. It is continues Process. Thermoplastic moulding compound/material is fed from a hopper to a screw pump where it is to plasticized then pumped out through the shaping orifice (die) to achieve desired cross section. Types of products: Films, Pipes, Strapping, Sheets, Multilayer films, Profiles etc.

71. Advantage -- Low Cost Extrusion moulding has a low cost relative to other moulding processes. This stems, in part, from the efficiency of the process. Most extrusion moulding uses thermoplastics, which can repeatedly undergo melting and hardening. Leftover materials, normally discarded as waste in other processes, can be reused. This lowers raw material and disposal costs. Neglecting mechanical failure or planned downtime, plastic extrusion machines operate continuously. This reduces the chances of inventory shortage and allows for 24 hours-a-day manufacturing.

72. Advantage - Flexibility Extrusion moulding provides considerable flexibility in manufacturing products with a consistent cross-section. To picture a consistent cross-section, imagine cutting straight through a block of cheese in several places. No matter which pieces you pick up, they all maintain the rectangular block shape. So long as the cross-section remains the same, extrusion moulding can produce complex shapes, such as decorative trims. With minor alteration to the process, manufacturers use extrusion moulding for plastic sheets. Variation on the extrusion process also allow for the manufacturing of products that mix plastic attributes, such as hard and soft surfaces.

73. Advantage -- Post-Extrusion Alterations The plastic remains hot when it leaves the extruder, which allows for post-extrusion manipulation. Manufacturers take advantage of this and use a variety of rollers, dies and shoes to alter the shape of the extruded plastic to fit their needs.

74. Disadvantage -- Size Variances When the hot plastic exits the extruder, it frequently expands. The expansion of the plastic at this stage of the process is called die swell. Predicting the exact degree of expansion remains problematic as it arises from different factors in the process. Due to unpredictable expansion, manufacturers must often accept significant levels of deviation from the product dimensions or tolerance. While methods exist to limit this issue, the tolerance problem largely disqualifies extrusion moulding as a method for precision parts manufacturing.

75. Disadvantage -- Product Limitations The nature of the extrusion moulding process places limits on the kinds of products it can manufacture. For example, plastic soda bottles narrow at one end to accommodate a cap, which normal extrusion moulding cannot achieve. Alternatives, such as extrusion blow moulding do provide an option for these types of products, but require investment in a different type of extrusion equipment.

76. Advantages of extrusion Low cost per part Flexibility of operation In hot extrusion, post execution alterations are easy because product is still in heated condition Continuous operation High production volumes Many types of raw materials can be used Good mixing (Compounding) Surface finish obtained is good Good mechanical properties obtained in cold extrusion

77. Disadvantages of extrusion Variations in size of product Product limitations because of only one type of cross section can be obtained at a time High initial cost setup Applications of extrusion process Electrical wires, bars and tubes are some of the items produced by hot extrusion.

78. Plastic extrusion moulded products

79. Video of plastic extrusion

80. Casting

81. Liquid resin which is generally thermoset except for acrylics is poured into a heated mould without pressure, cured, and taken from the mould. Cast thermoplastic films are produced via building up the material against a highly polished supporting surface. Types of products: Rain boots, Shoes, Hollow toys, Balls, large pipes and tubes etc.

82. Casting involves introducing a liquefied plastic into a mold and allowing it to solidify. In contrast to molding and extrusion, casting relies on atmospheric pressure to fill the mold rather than using significant force to push the plastic into the mold cavity. Some polymers have a viscosity similar to bread dough even when they are at elevated temperature so they are not candidates for the casting process. Examples of this are polymers like POM ( Polyoxymethylene ), PC ( Polycarbonate ), PP ( Polypropylene ) and many others. Casting includes a number of processes that take a monomer, powder or solvent solution and pour them into a mold. They transition from liquid to solid by either evaporation, chemical action, cooling or external heat. The final product can be removed from the mold once it solidifies.

83. Casting has several advantages: -Cost of equipment, tooling and molds are low. -The process is not complex. -Products have little or no internal stress. Casting can have some disadvantages: -The output rate is slow and has long cycle times. -Dimensional tolerances are not very good. -Moisture and air bubbles can be difficult to manage and may cause problems.

84. Materials than can be used for plastic casting Nylon Type 6 is one of the most popular and commonly used cast products. Polyurethanes are another example of cast materials we offer. Either way, the casting process is often times the preferred method providing large size stock shapes for machining parts.

85. Video of plastic casting

86. Slush moulding

87. Slush moulding is a closely related but somewhat different technique to dip moulding and is used for the production of flexible and semi-rigid mouldings where a detailed surface finish is required on the outside of the moulding . Whereas a male former or tool is used to produce a dip moulding , reproducing the tool surface on the inside of the moulding , slush moulding enables you to produce the fine detail effects on the outside of the moulding using a hollow female mould or tool, in effect, the reverse of dip moulding .

88. The mould is pre-heated then filled with liquid material to a pre-determined level, subsequently the curing process starts resulting in the desired wall thickness. The remaining liquid material is then decanted and final curing takes place, after which the tool is cooled and the finished moulding is stripped from the mould. The process requires electro-plated aluminium tools which can be expensive to produce, however our experience within the plastics industry allows us to source these tools at a very cost effective level.

89. Typical applications are toys, dolls heads, suspension covers, mannequin models ( a model of a human body used for displaying clothes in shop window ), containers, balls, large gaiters and many others. Slush molding is an excellent method of producing open, hollow objects, including rain boots, shoes, toys, dolls and automotive products, such as protective skin coatings on arm rests, head rests and crash pads.

90. Electroplated

91. Slush moulding toys

92. Introduction:   Slush Casting  is a traditional method of permanent mold casting process, where the molten metal is not allowed to completely solidify in the mold. When the desired thickness in obtained, the remaining molten metal in poured out.  Slush casting  method is an effective technique to cast hollow items like decorative pieces, components, ornaments, etc.

93. Process:  Mostly pewter is casted using the  slush casting  technique. Firstly, a pattern is made using plaster or wood. Now the pattern is placed on a cardboard or wooden board. A mold box is kept around the pattern. The unwanted space that is formed is the mold box can be eliminated by placing a board. Once the pattern is set the molding material is poured on the pattern and allowed to set with the molding aggregate. When the mold is set, the pattern is withdrawn from the mold.

94. The metal melted completely and poured into the mold which is shaped in the desired form. Rotate the mold to coat the sides. When the metal settles in the mold, remaining liquid metal is poured out of the mold. Thus, a hollow skin metal is formed inside the mold. If the cast needs to be more thicker, once again molten metal is poured into the mold and poured out. This process is repeated until the desired thickness is achieved. In some  slush castings , bronze molds are used. When the metal hardens, the mold is broken to remove the castings. The inside of each cast retains molten textures while the exterior is smooth and shiny. Bowls and vases ( container holding flowers or decoration ) are serially produced by this technique that ensures no two are ever the same.

95. Similarly, to cast metals a bowl, a new process designed to capture the beauty of Pewter (Pewter is a  grey  metal which is made by  mixing  tin and lead. Pewter was often used in former times to make  ornaments or  containers  for  eating  and drinking) and its unique characteristics. Recycled molten Pewter is swirled inside a mould to form a fine skin. The inside of each cast retains molten textures whilst the exterior is smooth and shiny. Bowls are serially produced by a technique that ensures no two are ever the same. 

96. Application:  Some casting of pewter is cast using  slush casting  method. Using pewter and other metals mainly hollow products are casted. Decorative and ornamental objects that are casted are as vase, bowls, candlesticks, lamps, statues, jewelries, animal miniatures, various collectibles, etc. Small objects and components for industry like tankard ( a large drinking cup ) handle, handles for hollow wares, etc. Advantages: Slush casting is used to produce hollow parts without the use of cores The desired thickness can be achieved by pouring our the left over molten metal A variety of elegantly designed casting can be casted for decorative and ornamental purpose. Good surface finishes & good surface details. Reusable mould & fast cooling rates.

97. Disa dvantages: Casting thickness wall can vary. Lower melting point alloys Requires manual labor. Time consuming

98.   Variety of materials can be processed using this technique, but most often polyvinyl chloride (PVC), thermoplastic polyurethane (TPU) and thermoplastic polyolefins (TPO) are employed, depending upon the final performance specification. The actual molding material may be a plastisol or a powder. 

99. Video of slush moulding

100. Calendering

101. Calendering  is a finishing process applied to textiles and plastic. During calendaring rolls of the material are passed between several pairs of heated rollers, to give a shiny surface. Extruded PVC sheeting is produced in this manner as well other plastics. Calendaring is a final process in which heat and pressure are applied to a fabric by passing it between heated rollers, imparting a flat, glossy, smooth surface . Luster ( shine ) increases when the degree of heat and pressure is increased. Calendaring is applied to fabrics in which a smooth, flat surface is desirable, such as most cotton, many linens and silks, and various man-made fabrics.

102. The molten material is fed to the calendar rolls from a Banbury mixer ( The Banbury mixer  invented by Fernley H.  Banbury . Internal batch mixers  such as  the Banbury mixer  are used for  mixing  or compounding rubber and plastics ) and two-roll mill system, or from a large extruder. The major plastic material that is calendared is PVC. Products range from wall covering and upholstery ( Upholstery  is the work of providing  furniture , especially  seats , with  padding ,  springs ,  webbing , and  fabric  or  leather  covers fabrics to reservoir linings and agricultural mulching materials ) Owing to the large separating forces developed in the calendar gap, the rolls tend to bend. This may result in undesirable thickness variations in the finished product. Compensations for roll deflections are provided by using crowned rolls having a larger diameter in the middle than at the ends or by roll bending or roll skewing.

103. Calendar installations require large initial capital investment. Film and sheet extrusion are competitive processes because the capital investment for an extruder is only a fraction of the cost of a calendar. However, the high quality and volume capabilities of calendaring lines make them far superior for many products. Calendaring in principle is similar to the hot rolling of steel into sheets. It is interesting to note that strip casting of semi-solid alloys can be modeled with the help of the hydrodynamic lubrication approximation for a power-law viscosity model, just like plastics calendaring. The process of calendaring is also used extensively in the paper industry.

104. Uses floor tile continuous flooring rainwear shower curtains table covers pressure-sensitive tape automotive and furniture upholstery wall coverings Luminous (shinning) ceilings signs and displays etc.

105. Material The best polymers for calendaring are thermoplastics. One reason for this is because they soften at a temperatures much lower than their melting temperature, giving a wide range of working temperatures. They also adhere well to the rollers, allowing them to continue through the chain well, but they don't adhere too well and get stuck on the roller. The last reason is that thermoplastic melts have a fairly low viscosity, but they are still strong enough to hold together and not run all over the place. Heat sensitive materials are also great for calendars because calendars put immense pressures on the materials to work them and therefore do not need as high of temperatures to process them limiting the chances of thermal degradation. This is why calendaring is often the method of choice for processing PVC. Due to the nature of the process the polymers must have a shear and thermal history that is consistent across the width of the sheet.

106. Advantages 1. The best quality sheets of plastic today are produced by calendars; in fact, the only process that competes with the calendar in sheet forming is  extruding . 2. The calendar also is very good at handling polymers that are heat sensitive as it causes very little  thermal degradation . 3. Another advantage to calendaring is that it is good at mixing polymers that contain high amounts of solid additives that don't get blended or fluxed in very well. This is true because compared to extrusion the calendar produces a large rate of melt for the amount of mechanical energy that is put in. Due to this companies are able to add more filler product to their plastics and save money on raw materials. 4. Calendars are very versatile machines meaning that it is very easy to change settings like the size of the roller gap.

107. Disadvantages The process is more expensive to perform which is a major deterrent for many companies. The calendaring process also is not as good at too high of gauges or too low of gauges. If the thickness is below 0.006 inches then there is a tendency for pinholes and voids to appear in the sheets. If the thickness is greater than about 0.06 inches though there is a risk of air entrapment in the sheet. Any desired thickness within that range though would turn out much better using a calendar process.

108. Video of Calendaring

109. Plastic fabricating methods Several techniques have been developed for fabrication of plastics to convert the m into useable forms. Some popular techniques of these are the following: Blow moulding Forming methods.

110. Blow moulding

111. Plastic fabricating methods 1. Blow moulding Blow molding  is a specific manufacturing process by which hollow  plastic  parts are formed and can be joined together: It is also used for forming  glass bottles  or other hollow shapes. In general, there are three main types of blow molding: extrusion blow molding, injection blow molding, and injection stretch blow molding. The blow molding process begins with melting down the plastic and forming it into a  parison  or in the case of injection and injection stretch blow moulding a preform . The parison is a tube-like piece of plastic with a hole in one end through which compressed air can pass. The parison is then clamped into a  mold  and air is blown into it. The air pressure then pushes the plastic out to match the mold. Once the plastic has cooled and hardened the mold opens up and the part is ejected. The cost of blow moulded parts is higher than that of injection – moulded parts but lower than rotational moulded parts.

112. There are three types of blow molding:  1)       Extrusion Blow Molding (EBM) EBM is organized for very high production of plastic bottles and is often integrated downstream with operations such as filling and labelling the bottles. In the extrusion blow molding process the plastic is first melted and extruded into an object called a parison , which is a hollow tube of plastic to be formed into a hollow object, as a bottle, by blow molding. The parison is then inserted into a cooled metal mold.  Air is then blown into the parison to inflate it into the desired shape.  When the plastic has cooled enough the mold is opened and the part ejected . EBM can be used to process many different kinds of plastics including HDPE ( High-density polyethylene ), PVC ( polyvinyl chloride ), PP ( Polypropylene) and PETG ( Polyethylene Terephtalate Glycol-modified ) .

113. There are two variations of this type of blow molding, continuous and intermittent extrusion.  With continuous extrusion blow molding, the parison is continuously extruded and the parts are cut off with a knife.  Intermittent extrusion blow molding is not a continuous cycle and can be useful when processing plastics that have a low melt strength, like  polycarbonate .

114. EBM processes  may be either continuous (constant extrusion of the parison ) or intermittent. Types of EBM equipment may be categorized as follows: Continuous extrusion equipment rotary wheel blow molding systems shuttle machinery Intermittent extrusion machinery reciprocating screw machinery accumulator head machinery

115. Examples of parts made by the EBM process include most polyethylene hollow products, milk bottles, shampoo bottles, automotive ducting, watering cans and hollow industrial parts such as drums.

116. 2)    Injection Blow Molding (IBM) This is a two stage process as the parison is produced in a separate operation.   First the molten plastic is injected into a heated preformed mold around a hollow mandrel blow tube or core rod. This process is similar to  injection molding .  Then a preform -mandrel assembly is placed in a larger mold cavity for blow molding.  After blow molding, the part is stripped from the core rod at an ejection station.  This method is used to produce hollow glass and plastic products in large quantities.  This is the least popular of the blow molding processes and is used to make small medical or single serve bottles.

117. 3)       Stretch Blow Molding (SBM)   This method produces a part with a biaxial (having or relating to two axes) molecular alignment.  In this process, the parison or preform is elongated mechanically in a mold and then radically expanded in a blowing process. The temperature needed to product the desirable molecular orientation is lower than in other blow molding processes with a smaller temperature range.  Thus this process is harder to control. The resulting molecular orientation yields a material with increased strength. Products can be produced with less material than if they were manufactured using simpler blow molding techniques.  Stretch blow molding is best known for producing PET bottles.

118. Advantages of blow molding include : low tool and die cost; fast production rates; ability to mold complex part; Handles can be incorporated in the design. Disadvantages of blow molding include: limited to hollow parts, low strength, to increase barrier properties multilayer parisons of different materials are used thus not recyclable. To make wide neck jars spin trimming is necessary.

119. 1. It is a revolutionary form of technology. Blow molding is said to have revolutionized the industrial sector by allowing companies to use it widely to meet consumers’ needs for plastic ware. As you can see, this plastic production method brought about a lot of production perks, such as quick manufacturing and high volume outputs, which means that we are able to produce a lot of plastic containers. 2. It can produce a variety of products. Most plastic containers on the market today that holds some forms of liquid has went through this process. In fact, the commonness of blow molding has allowed engineers to try and create a variety of applications and designs, which resulted to multiple interesting uses. Just to mention a few, the products created using this technology include fuel tanks, seat support for vehicles, flower pots and toy wheels .

120. 3. It comes with low costs. With a focus on extrusion blow molding, it uses a lower level of pressure, which means that machinery costs are low, making it easier and more cost-efficient to mold external threads or open-ended and large parts, which can be split by opening a closed molding. Moreover, the use of this technology will allow you to reduce labor costs. 4. It allows for multiple methods of production. As already implied, blow molding uses various methods to create final products. For one, extrusion blow molding works similarly as traditional glass blowing, where materials are blown through a long tube to work on the end, which can create products, such as light bulbs. As for injection blow molding, it is employed to produce receptacles in huge quantities, where melted polymers are injected into the blow mold, instead of being blown through by air. Now, this technology is continuing to develop to improve such production methods, using tweaks in design and moving towards pure automation.

121. 5. It promotes a higher level of productivity. This technology has always been moving forward with the purpose of becoming universally used with plastic production. It has allowed for a significant increase in production capabilities, allowing manufacturers to produce greater quantities in just a short period of time. Using machines that allow for 3D moldings, it has allowed for a production cycle that is much faster. 6. It offers the benefits of automation. Blow molding was taken to greater heights when the Placo X-Y machine from Japan was developed, giving rise to 3D blow molding. Basically, this is an automated production method that allows for minimal flash (excess polymer) around the material, seamless part incorporation and increased speed of production, thanks to the precise receptacle it creates.

122. Low cost Fast production rates High productivity Ability mold complex parts Cost effective High product variety Low tooling cost It can produce variable products It is a technological revolution.

123. Video of Blow moulding

124. Plastic fabricating methods Forming methods The common methods of forming or shaping plastic sheets into Useful shapes are the following: Drape forming Vacuum forming Snap back forming Pressure forming Draw forming Plug or ring forming

125. 185 Thermoforming Advantages Low machine cost Low temperature requirement Low mold cost Low pressure requirement Large parts easily formed Fast mold cycles Disadvantages High cost of raw materials (sheets) High scrap Limited part shapes Only one side of part defined by mold Inherent wall thickness variation Internal stresses common

126. Plastic fabricating methods Forming methods Drape forming It is the simplest of all methods of forming & co nsists of Draping the heated plastic sheet over the contours of a male form, followed by applying pressure & cooling.

127. Selecting the right material Certain materials are more accustomed to drape forming than others. Acrylic one of the most commonly used, although other plastics such as ABS ( Acrylonitrile butadiene styrene) , polystyrene and polycarbonate also have the necessary qualities needed for drape forming. The type of material will depend on what the  drape-formed  part will be used for. Bath panels, for example, are commonly made from polystyrene, ABS or acrylic, while polycarbonate is better accustomed to providing plastic windscreens. It’s possible to create deep draw components with the aid of drape forming. Again, this will have a bearing on the type of material used and the temperature it will need to be heated to.

128. Advantages ➺This manufacturing process makes use of plastic sheets that are higher in quality and have good durability as compared to the ones used in other methods. ➺This process is known to have a good speed when compared to other manufacturing methods i . e. once the designs are confirmed, the thermoformed parts can be ready within a month which is not possible in other methods. This speed in production, in turn enables delivery on time. ➺This process enables the manufacture of a wide range of custom-made products since it is believed to be the only method by which plastic sheets can be molded into bigger objects. This process also has a wider design scope.

129. Advantages ➺The plastic products manufactured by this process are able to meet the requirements of companies that demand highly specific dimensions for the same. Moreover, they are quite adaptive to the design needs of customers. ➺Almost all types of plastic can be used in this process, which is not the case with the other methods. ➺The costs involved in tooling and engineering are quite low, which is another great advantage over other methods as it makes this process ideal for prototype development and low-volume production.

130. Disadvantages ➺During this process, the plastic sheets that are in a pliable state can break due to excessive stretching under certain temperatures. This in turn leads to wastage and about 20% more use of plastic that results in higher process costs. ➺Due to the use of higher-quality plastic sheets, this method is costly (about 50 % more) as compared to other methods. ➺In this process, only one side of part is defined by the mold. ➺Here, the parts that include sharp bends and corners are not easy to produce and internal stresses are common. Even though thermoforming is a costly process, it is quite popular due to the production of higher-quality products in a wide range of sizes and designs.

131. Drape forming is used to manufacture forms that have a lot of shape mostly in one dimension, such as corner bath panels, shower screens or vehicle bumpers / fenders.

132. Video of Drape forming

133. Plastic fabricating methods 2 . Forming methods 2. Vacuum forming Intricate shapes are easily formed by the application of pressure or v acuum on the plastic sheet draped over the mould. The operation consists of stretching the sheet over the mould cavity to form a seal, heating it by suitable means & then drawing the air out of the space between sheet & the mould. A few typical vacuum forming examples ar e illustrated.

134. Only vacuum

135. Only vacuum is used for drawing the heated sheet into the mould.

136. Only vacuum is used for drawing the heated sheet into the mould.

137. Air pressure & vacuum

138. Heated sheet is pressed against formed mould by air pressure, forming it partially, followed by pulling the vacuum through the mould to complete the forming.

139. Core plug & air pressure are used

140. Cored plug is used to push the heated sheet into the mould, followed by applying air pressure through the plug to complete forming operation. Relief holes in the mould allow the air to escape.

141. Advantages of Vacuum Forming

142. Precision Vacuum formed products are more precise to design specifications, compared with those produced by molding together multiple parts. This is particularly important for parts required to support or fit into another object. Vacuum forming minimizes error during the production process, reducing the likelihood of recalling stock and the related costs. Cost Effective It has “comparatively low cost tooling.” Because it uses low pressures, it requires a smaller quantity of less sophisticated tools, which also means that molds can be produced from relatively inexpensive materials. A second benefit is that large parts can be produced from one sheet of plastic, reducing quantity costs. Additionally, discards from finished products can be recycled into new plastic sheets. Low start-up costs make vacuum forming attractive for small production lines or businesses.

143. Design Flexibility It enables products to realize the design aesthetics of a company or designer. This is important in a market economy dominated by company logos and branding. Vacuum forming also fulfills practical design requirements. It is a popular process of production within the packaging industry, used to produce anything from yogurt pots to the inserts in convenience food packages. Time Efficient It is often an economical choice of production. With its simple production process, less time is spent between the design and outcome of the product. Not only does this liberate time to focus on the more intricate details, but products are also introduced into the market much quicker. Additionally, sophisticated versions of vacuum forming facilitate automated production, thus generating a larger quantity of products in less time.

144. Depth The plastic pieces that you can make with vacuum forming need to be relatively shallow, as deeper pieces can warp or twist in the process. Typically vacuum forming isn't used to create deeper pieces, but when it is special precautions have to be taken to stretch the plastic beforehand to prevent warping, which adds to the cost of the manufacturing. Bubbling It also lead to distortion as the material forms bubbles. The bubbles form as a result of air pockets that get into the material while it's being stretched and molded and they can ruin the pieces produced. These bubbles form from additional moisture being absorbed into the plastic, so it's very important that if vacuum forming is the chosen manufacturing technique, the environment is strictly controlled so no added moisture messes up the process. Production Speed It cannot create as many pieces as quickly as other processes. It is relatively cheap, but the trade off is that it has to be strictly controlled and that it's also relatively slow. Additionally, the speed of the vacuum molding has to be controlled because if the piece is left to sit too long it can spider web into cracks due to the long exposure to the necessary heat.

145. Typical applications Original equipment manufacturers  (OEMs) utilize heavy gauge vacuum formed components for production quantities in the range of 250–3000 units per year. Vacuum-formed components can be used in place of complex fabricated sheet metal,  fiberglass , or  plastic injection molding . Typical industry examples besides product packaging include: fascias for outdoor  kiosks  and  automated teller machines , enclosures for medical imaging and diagnostic equipment, engine covers in a truck cab or for construction equipment, and railcar interior trim and seat components. Vacuum formers are also often used by hobbyists, for applications such as masks and remote control cars.

146. Plastics used for plastic vacuum forming Acrylonitrile Butadiene Styrene (ABS) High Impact Polystyrene (HIPS) High-density polyethylene (HDPE) Polycarbonate (PC) Polyethylene Terephtalate Glycol-modified (PETG) Polyvinylidene difluoride  (PVDF)

147. Video of Vacuum forming

148. Plastic fabricating methods 2 . Forming methods 3. Snap back forming It is also known as vacuum forming method. In this, the heated plastic sheet fitted at the top of the vacuum box is pulled to a certain depth in the cavity by pulling the vacuum. Male plug is then moved down until it reaches a predetermined position. Vacuum is then pulled through the male plug to form the plastic sheet around the contours of the plug.

149. Video of snap back forming

150. Plastic fabricating methods 2 . Forming methods Pressure forming In this, the heated plastic sheet is formed into the required shape between a pair of male & female dies. The sheet is heated until it is soft, and then both mold halves clamp together to form the part. Used with parts that do not have large draws. No vacuum and no air is used in this process.

151. Advantages excellent definition and dimensional control on both sides. complexity high tolerances

152. Pressure Forming Applications: Plastic pressure forming is an excellent alternative to injection molding or structural foam molding in many applications. A wide variety of pressure formed parts such as:       Outdoor plastic housings      Medical enclosures      Point of Purchase displays & retail items      Recreational equipment      Bezels  ( Bezel  is a term used to describe the outside frame of a computer, monitor or any other computing device)      Bases      Plus many, many more

153. Plastic fabricating methods 2 . Forming methods 5. Draw forming It is similar to the Deep Drawing for metals. In this, a heated blank of plastic sheet is placed over a die & held firmly by means of a Hold down Plate. A punch is pressed down into the die cavity to draw the material into the die & around its own body. Flange if remaining, may be trimmed ( make (something) neat or of the required size or form by cutting away irregular or unwanted parts ) separately or within the same operation.

154. Deep Draw Forming Applications Deep drawn plastic films have applications across a wide variety of industries and applications. Some examples include: Membrane switches requiring wrapped edges to protect sensitive circuitry from moisture or ESD. Automotive instrument clusters requiring complex deep draw 3D shapes with registered graphics. Packaging application requiring a registered graphics or specialized closure. 3D gaskets for electronics housing and other ESD applications. Functional deep draw plastic components where the formed shape provides a functional element.

155. Some of the cost-saving benefits of deep draw forming includes: Eliminate layers:  By utilizing the overlay on a membrane switch to provide the function of the switch  and  the ESD shielding in a single layer, you eliminate the need for an additional layer of material. Eliminate components:  Deep draw forming of 3D features within a speedometer eliminates the need for additional components to create the desired 3D appearance. Eliminate tooling:  Using deep draw thicker film with incorporated graphics allows manufacturers to produce rigid decorated parts without the need for costly injection mold tooling. Eliminate processes:  Reducing layers and components also means fewer manufacturing steps and less labor.

156. Video of draw forming

157. Plastic fabricating methods 2 . Forming methods Plug and Ring Forming It is combination of stretch and draw forming methods. In this, the heated plastic sheet is clamped over a Draw ring which forces the sheet on the form block. Finally the mould mounted at the bottom of a Ram is forced into clamped sheet to complete the forming to final shape.

158. Lamination of plastics High pressure laminating This process involves joining of layers of fibrous reinforcing material with thermosetting resin binders by application of heat & pressure both. The pressure usually ranges from 80 to 240 kg/cm 2 . The layers are generally of some fibrous material like paper, cotton fabric or mat, asbestos, glass, nylon or wood veneer. The resins commonly used are phenol, formaldehyde, urea, melamines  ( white crystalline organic base C 3 H 6 N 6  with a high melting point that is used especially in  melamine  resins ) , silicones, epoxies or their combinations.

159. Lamination of plastics High pressure laminating The process consists of preparing varnish solution from resins by dissolving them suitable solvents, followed by impregnating or coating the fibrous sheets with this varnish. These sheets are tied, then dried, trimmed to the size & heated & pressed between metal plates to form laminated sheets. Tubes are made by rolling the impregnated fibrous material around mandrels & heating till they are cured. Rods are made by rolling & heating the impregnated material inside cylindrical moulds followed by grinding to size.

160. Lamination of plastics High pressure laminating Moulded shapes are formed by cutting the impregnated sheets to required shapes & sizes, followed by heating & pressing as usual.

161. Video of High Pressure Laminating

162. Lamination of plastics 2. Low pressure laminating It is also known as Reinforced Plastic Moulding. In this, pressures of only up to 32 kg/cm 2 are applied. Mostly thermosetting resins are used in laminating, although in some cases thermoplastic resins are also used. The reinforcing materials used are glass fibres, cotton, asbestos, nylon, hemp, paper & other fibres. They are used in various forms like cloth, preforms or mat, etc. The commonly used resins are phenolics , polysters , epoxies, furnaces & silicones.

163. Lamination of plastics 2. Low pressure laminating Pigments are added to obtain different colours shades. Fillers like clay, calcium carbonate, asbestos and aluminium silicate, are used for obtaining good surface finish, better physical properties, reducing shrinkage & lowering cost.

164. Video of Low Pressure Laminating

165. Joining of Plastics Plastics can be joined by the following four methods. Some Thermoplastic Plastics like acrylics, polysters , cellelosics & few vinyls can be joined by cementing with a solvent. Another method of joining plastics is by using an adhesive. This method can be used for all plastics, & also for joining them with metals & other materials. All the plastics, except a few inflammable ones, can be joined by welding. The common welding process used for joining plastics are hot gas welding, heated tool welding, friction welding & induction heating.

166. Joining of Plastics Plastics can be joined by the following four methods. 4. Various engineering fasteners like bolts, screws, nuts & rivets can be used for fastening plastic parts together. Also, peening & press fitting, etc., can be used.

167. Video of Plastic joining by welding, adhesive and solvent