Direct metal ddiposotion dmd materialsmdmd design

Direct metal ddiposotion dmd materialsmdmd design

1. Direct Metal Deposition

2. Objectives Describe DMD and be able to compare it with conventional rapid prototyping processes Explain what is meant by “The Big Three of Manufacturing” Discuss how the DMD process is used in various industrial applications

3. Direct Metal Deposition (DMD) Form of rapid tooling- Makes parts/molds from metal powder, melted by laser to computer-aided design of part, and then solidified. Rate of solidification dependent on heat-affected zone of laser and metallurgical properties of powder. Allows production of molds/dies in end material DMD Technology Blending of five common technologies Lasers Computer-aided design (CAD) Computer-aided manufacturing (CAM) Sensors Powder metallurgy DMD Process Focuses CO2 laser beam onto flat tool-steel workpiece to create molten pool of metal Small stream powdered tool steel injected into melt pool Move laser beam back and forth (CNC control) tracing out pattern (CAD design) Solid metal part built, line by line, one layer at a time No material waste

4. Heat is generated using a focused heat source of various kinds, sufficient to melt the surface of the substrate and form a small melt pool.  Material is added to the melt pool using a focused powder stream or a wire feed system to form a raised portion of material. To create the desired geometry, the substrate is manipulated using a computer-controlled positioning system. Gas and material are fed into the path of a heat source. Material feed angle can be altered to influence the build characteristics. A feed angle of 0° benefits design and manufacturing flexibility due to the onmidirectional scanning possibilities, but requires more complex apparatus to avoid interference with the laser.

5. Manufacture: 1. There are three main heat sources used for direct metal deposition: o  Lasers are the most common, providing a focused heat source down to fractions of a millimetre. They require shielding from oxidation but do not require a vacuum.  o  Electron beam systems are less common, providing the smallest spot size and best beam definition. However, due to the high attenuation of electrons by gases, the process needs to be encapsulated in a vacuum. o  Plasma arc techniques provide opportunities for much greater deposition rates compared to laser and electron beams. The heat source is analogous to a GTAW welding system, melting the substrate with a plasma arc. With high depositions rates and relatively large spot sizes comes low precision, surface quality and feature definition.

6. 2 . The positioning system for DMD systems are what set them apart from other metallic systems. By feeding material via the heat source, the flexibility in position becomes significantly freer compared with powder bed systems. Possible benefits include: o  Flexibility in movement. Systems with 6 or more degrees of freedom have been created, even robotic arm systems have been used. o  Very large substrates can be used, meaning material can be deposited onto existing components. o  Repair applications require the flexibility offered by DMD systems.

7. DMD Creates consistent, fine microstructures that yield superior quality and tool strength Allows creation of mixture of graded metallic compositions that have never been available Provides closer tolerances Lower tooling costs Improved productivity From CAD to Steel Customer Posts CAD files Engineers download and edit CAD files Updated CAD model sliced, toolpaths created Data post-processed and embeds laser and powder commands Information downloaded to 3-axis machine DMD process Hard faces applied within argon filled box

8. DMD Materials Proven for a wide range of materials, however many do not exhibit properties close to wrought material of the same chemical composition. Development is popular with high cost materials due to the reduction in wastage compared to subtractive manufacturing. Materials such as (limitations in brackets): 1.Nickel-based super alloys (rapid cooling rates limit the extent to which precipitates can form, limiting the possible strength without post thermal treatments). 2.Titanium alloys (limited by shielding of oxidising gases). Variety of metal powders and metal matrix composite materials Tool-steel alloys Stainless steel Copper Stellite alloys Inconel Tungsten carbide Titanium diboride Fast solidification rate results in very-fine-grain part microstructure

9. Big Three of Manufacturing Speed -Faster product to market Economy -Lower tooling costs due to factors including reduction of labor and capital equipment costs Quality -Parts produced are generally .001 in. oversized -Quick clean-up and ready for use

10. Design: Component design is limited by: 1. The minimum feature size cannot be smaller that the minimum track size for the setup. This is linked to the spot size of the heat source and to the material feed rate. 2. Surface finish is limited by the minimum track size for the setup: the smaller the track size, the finer the surface finish. 3. The number of degrees of freedom in the control system.  4. Overhanging material requires supporting structures or a control system with sufficient degrees of freedom to produce the overhang perpendicular to the feed nozzle.  

11. DMD Applications Die repair and refurbishment Thermal management Creation of thermal model to locate hot spots Direct metal prototypes instead of plastic models Surface modification and coatings Aerospace and aircraft component repair

12. From Prototype to Production Time saved - deposition begins when CAD file ready First-stage tooling (create prototype ) Design change flexibility -Material added to tooling without interface boundary Suitability for complex designs -Work same without regard for size or complexity

13. Overview DMD process among most promising metalworking advances in decades Benefits directly impact manufacturers' bottom line -Reduce time to market -Die repair and refurbishment -Direct metal prototyping -Thermal management -Strength improvements -Reduce environmental waste