AM - Transfer to Machine, File Manipulation
- 1. Process Chain of Additive Manufacturing Transfer to AM Machine, File Manipulation, Machine setup and Build
- 9. AM Unique Capabilities Various types of nano/microstructures can be achieved by careful control of the process parameters (e.g. laser power, scan rate) for a particular material, and can vary from point to point within a structure. The ability to simultaneously control a part's nano/microstructure, mesostructure, and macrostructure simply by changing process parameters and CAD data is a capablity of AM which is unparalleled using conventional manufacturing.
- 10. AM Unique Capabilities □ When building parts in an additive manner, one always has access to the inside of the part. □ Component can be inserted and it is possible to fabricate operational mechanisms in some AM processes. Pulley-driven snake-like robot Source: Gibson.
- 11. AM Unique Capabilities The concept of functionally graded materials, or heterogeneous materials, has received considerable attention. However, manufacturing useful parts from these materials often has been problematic. Example: Turbine blade for a jet engine I. The outside of the blade must be resistant to high temperature and very stiff to prevent elongation; II. The blade root must be ductile and has high fatigue life; III. Blade interiors must have high heat conductivity so that the blades can be cooled. Apart with complex shape that requires different material properties in different regions. No single material is ideal for this range of properties. A significant issue hindering the adoption of AM’s material complexity is the lack of design and CAD tools that enable representation and reasoning with multiple materials.
- 12. Process Planning in Layered Manufacturing
- 13. There are four main planning tasks: (i) orientation optimization, (ii) (iii) (iv) support design, slicing, and tool-path/scanning-path planning. Process Planning in Layered Manufacturing
- 14. Sample STL File Advantages and Disadvantages?
- 15. STL File Advantages (iii) (i) Provides a simple method of representing 3D CAD data (ii) A de facto standard and has been used by most CAD systems and RP systems It can provide small and accurate files for data transfer for certain shapes Disadvantages (i) (ii) (iii) The STL file is many times larger than the original CAD data file The geometry flaws exist in the STL file The subsequent slicing of large STL files can take many hours
- 17. Valid vs. Invalid Tessellated Models
- 18. STL File Repair
- 20. • One of the most important additive manufacturing technologies currently available. • The first ever commercial RP systems were resin-based systems commonly called stereolithography or SLA. • The resin is a liquid photosensitive polymer that cures or hardens when exposed to ultraviolet radiation. • This technique involves the curing or solidification of a liquid photosensitive polymer through the use of the irradiation light source. • The source supplies the energy that is needed to induce a chemical reaction (curing reaction), bonding large no of small molecules and forming a highly cross-linked polymer. Stereolithography
- 21. • The UV light comes from a laser, which is controlled to scan across the surface according to the cross-section of the part that corresponds to the layer. • The laser penetrates into resin for a short distance that to the layer the corresponds thickness. • The first layer is bonded to aplatform, which is b p e l a l o c e w d the surface of container. just the resin • The platform lowers by one layer thickness and the scanning is performed for the next layer. This process continues until the part has been completed.
- 22. A part produced by stereolithography (Source: 3D Systems, Inc.).
- 23. Facts About STL • Each layer is 0.076 mm to 0.50 mm (0.003 in to 0.020 in.) thick – Thinner layers provide better resolution and more intricate shapes; but processing time is longer • Starting materials are liquid monomers • Polymerization occurs on exposure to UV light produced by laser scanning beam – Scanning speeds ~ 500 to 2500 mm/s
- 24. Part Build Time in STL Time to complete a single layer : d + vD T Ai Ti = where Ti = time to complete layer i; Ai = area of layer i; v = average scanning speed of the laser beam at the surface; D = diameter of the “spot size,” assumed circular; and Td = delay time between layers to reposition the worktable
- 25. Part Build Time in STL - continued Once the Ti values have been determined for all layers, then the build cycle time is: nl c ∑ T = Ti i=1 where Tc = STL build cycle time; and nl = number of layers used to approximate the part ▪Time to build a part ranges from one hour for small parts of simple geometry up to several dozen hours for complex parts
- 26. Numerical Problem A prototype of a tube with a square cross-section is to be fabricated using stereolithography. The outside dimension of the square = 100 mm and the inside dimension = 90 mm (wall thickness = 5 mm except at corners). The height of the tube (z-direction) = 80 mm. Layer thickness = 0.10 mm. The diameter of the laser beam (“spot size”) = 0.25 mm, and the beam is moved across the surface of the photopolymer at a velocity of 500 mm/s. Compute an estimate for the time required to build the part, if 10 s are lost each layer to lower the height of the platform that holds the part. Neglect the time for postcuring.
- 27. Numerical Problem: Solution Layer area Ai is same for all layers. 2 2 2 Ai = 100 -90 = 1900 mm . Time to complete one layer Ti is same for all layers. T 2 i = (1900 mm )/(0.25 mm)(500mm/s)+10 s = 25.2 s Number of layers nl = (80 mm)/(0.10 mm/layer) = 800 layers Tc = 800(25.2) = 20,160 s = 336.0 min = 5.6 hr
- 28. How layer by layer adhesion takes place in stereolithography? The new layer adheres to the previous one because the depth of penetration of each pulse of laser is greater than the thickness of the layer and hence over cures the prior layer. This process is repeated as many times as is necessary to recreate the entire object layer by layer. When completed, the platen is raised from the vat and the model is ready for removal of the support structure and postcuring.
- 29. Thank You