Additive Manufacturing IV

Question 1

3D-Printing -Technologies

Answer 1

-3D-Printing/Powder:

• Category-Binder Jetting
• Ink-jet printing heads move across a powdered material in a scanning pattern, distributing (printing) a liquid inorganic binder & ink to “glue” the powder particles in the shape of each layer.

-3D-Printing/Photopolymer:

• Category - Material Jetting:
• Ink-jet printing heads ejects micro-droplets of molten plastic or wax material onto a stationary platform which is cured by UV light (polymer phase change inkjet or jetted photopolymer technology)

Question 2

3D-Printing Principle

Answer 2

• Ink-jet printing heads move across a powdered material in a scanning pattern ejecting droplets of an adhesive bonding material into the required cross section shape.
• Lowering the platform with the powder bed by the slice thickness after each new layer is formed at the surface.
• The unbounded powder remains loose & acts as support structure for overhanging or fragile features.
• Post-process e.g. heat treatment to strengthen the part by solidification.

Question 3

3D-Printing - Process Characteristics

Answer 3

• Layer thickness 0.1mm
• Vertical build speed 5-28mm/hr
• Prototype often porous with a slightly grainy surface.
• May lack in strength; sinter or infiltrate with a hardener (wax,glue,or metal) to increase strength.
• Parts can be sanded, drilled, tapped, painted and electroplated.
• Parts can be sanded, drilled, tapped, painted & electroplated.
• Accuracy

Question 4

3D-Printing - Materials

Answer 4

• Plastic or starch-based powders
• Ceramic-,glass-or metal-based powders (e.g. stainless steel)
• Special powders for:
• Direct metal casting; blend of foundry sand, plaster and additives.

*investment casting:
Mix of cellulose, speciality fibres & additives.

*Elastomeric properties:
Mix of cellulose, speciality fibres & additives.

Question 5

3D-Printing - Applications

Answer 5

• Concept models
• Parts for limited functional testing
• Colour models for FEA & other engineering related applications.
• Architectural & landscape models
• Colour industrial design models, especially consumer goods & packaging
• Castings

Question 6

3D-Printing - Advantages

Answer 6

• Good range of materials
• Two material method allows for a number of different binder-powder combinations and various mechanical properties.
• Quick processing time.
• No support structure required.
• Realistic, multi-coloured models, complex geometries with intricate, small, and detailed features.
• Good for secondary operations (parts can be sanded, drilled, tapped, painted & electroplated).
• Office friendly (quiet, safe, odour-free, easy to use).

Question 7

3D-Printing - Limitations

Answer 7

• Accuracy & surface finish fair
• Fragile prototypes - may require strengthening.
• Post processing is often required to strengthen the part
• Overall process time is extended by binder to set & the part to fully solidify while in the machine.

Question 8

3D-Jetted Photopolymer -Principle

Answer 8

• Ink-jet printing heads ejects micro-droplets of molten or wax material onto a stationary platform (polymer phase change inkjet or jetted photopolymer technology).
• Continuous or drop on demand (DOD) approach.
• Build & support material is ejected simultaneously via separate jets.
• Curing of the photo-polymer build material using a UV flood lamp (mounted on the ink-jet heads)

Question 9

3D-Jetted Photopolymer - Characteristics

Answer 9

• Layer thickness 16-32 (micrometres)
• Gel-like support structure can be easily removed by water jetting

-Accuracy:
*20-85 (micrometres) for features smaller than 50mm;
~200 (micrometres) larger model sizes.

*Up to 750x750x1600 DPI (x-y-z axis)

Question 10

3D-Jetted Photopolymer - Applications

Answer 10

• Concept development
• Design validation
• Form & fit analysis
• Moulding & foundry casting patterns
• Pattern for investment casting

Question 11

3D-Jetted Photopolymer - Advantages

Answer 11

• Small layer thickness eliminating the stair effect common to complicated curved surfaces.
• Quick processing time; adjustable resolution.
• Coloured printing.
• End-use parts.
• Office friendly (quiet, safe, odour-free, easy to use)
• Living hinges & joints.

Question 12

3D Jetted Photopolymer -Limitations

Answer 12

• Limited choice of materials - only polymer & waxes can be used.
• Limited opportunity to enhance properties during post processing - functional & aesthetic qualities of parts are largely determined during the printing stage.
• Support structure needed for overhangs, undercuts & fragile elements.