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Layered Manufacturing

Layered Manufacturing

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Layered Manufacturing

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  1. Layered Manufacturing

  2. Additive Subtractive Deformation How can we make physical form?

  3. Additive Process • Add materials bit by bit • Less material wastage • Usually need a mould • Casting

  4. Subtractive Process • Remove un-needed material from stock • Waste material • Usually need only cutting tools • Milling, Sculpting

  5. Deformation Process • Deform stock material • Less material wastage • Limited form, need many different tools • Bending, kneading • Sometimes called Net-Shape Manufacturing

  6. Layered Manufacturing • Additive process in nature • No mould required • No special tools • One machine, unlimited forms

  7. Basic process

  8. Basic process • Prepare CAD model • Slice model virtually into layers • Produce the bottom most (or top most) layer according to the layer profile • On top of (or beneath) the produced layer, add subsequent layer • Loop until completion

  9. Freedom of LM • Undercut • Hollow • Jig and fixture not required

  10. Advantage of LM • Reduce operator intervention • Easy to learn • Time and cost only related to size, not complexity

  11. Disadvantage of LM • Time and cost only related to size, not complexity • Limited choice of material • Double approximation of the form, first during polygonization and then by slicing

  12. Common use of LM • Rapid Prototyping • One-of-a-kind manufacturing • Art sculpting • Medical modelling • Architectural modelling

  13. Shape implications in LM • Overhang • Cliffs • Holes • Slicing errors

  14. Exercise

  15. Rapid prototyping process • Polygon model creation • Model verification • Pre-processing • Orienting and positioning • Support generation (optional) • Slicing • Building • Post-processing

  16. Rapid prototyping process

  17. Data input • Almost all RP systems rely on STL • A polygon model format • ASCII and Binary • With normal vectors • Implicit unit • Can be generated from all major applications • One file can contain multiple components

  18. Data Input

  19. An ASCII STL file

  20. Model verification • LM can deal with only non-manifold polygon models • Check for ‘leakage’ • Check for naked edges • Check for holes • Check for reversed facets • Check for model obscurities

  21. Model obscurities • Crossed facets • Overlapping facets • Degenerated facets

  22. Source of manifold errors

  23. LM Errors caused by bad STL • Delaminate due to double facets • Reversed normals • Ill-behaved CAD translators

  24. Verification applications • Major polygon modelling applications • RapidForm, Surfacer, GeoMagics, etc. • Specific STL applciatons • Magics • SolidViews

  25. Function of verification applications • Check and repair model errors • Rotate and section model to facilitate error correction • Merge and separate components • Move, rotate, and scale models • Checking dimensions • Advanced editing

  26. Advanced editing • Fill holes by adding facets • Add draft angle • Shelling and hollowing • Smoothing and re-sampling

  27. Pre-processing • Done by equipment specific applications • Move, rotate, and scale models • Some contain basic STL repair functions • Some contain support generation and edit functions • Slicing STL and generating equipment control code

  28. Supports

  29. Position and size of model • Machine specific, usually lower left corner as the origin • Position and size can be verify in pre-processing application • Built-specific errors (beam width, thread width, growth, etc.) compensated by application • Shrinkage, form and fit, etc. compensated by operators

  30. Building process

  31. Post-processing • Draining and rinsing • Support removal • Post-curing and heat-treating • Surface finishing