Design for AM

Question 1

What is the definition of AM?

Answer 1

The additive manufacture of end-use products or components directly from 3D Computer Aided Design (CAD) data without the need for any tooling – Hopkinson et al

Question 2

How many core types of additive processes are available?

Answer 2

5

Question 3

What are the design related major advantages of AM?

Answer 3

1. Design freedom; anything that can be modelled using 3D CAD can be manufactured
2. Geometrical complexity/optimisation
3. Personalisation/customisation
4. Multiple free-moving assemblies
5. Part consolidation (integrated fasteners, live hinges, springs etc)
6. Scalable

Question 4

What does ‘unlimited design freedom in AM’ actually mean?

Answer 4

Removal of Design for Manufacture (DfM) considerations?

Yes, the majority of conventional ones!

1. No tooling considerations required!
2. No part extraction
3. Draft angles not required
4. Re-entrant geometry achievable

New DfAM exist that are process and geometry specific.

Question 5

What is the difference between industrial/product design and engineering/component design?

Answer 5

Industrial/Product Design: Starts with ‘ill-defined’ problems – User want or need

Engineering/Component Design: Starts with ‘well-defined’ problems – PDS

Question 6

What is important when designing for AM?

Answer 6

1. 3D modelling must be of very high quality
2. DfM/DfAM considerations depending on whether we use AM or RP
3. Process selection: materials, volumes & parts, resolution & accuracy, costs

Question 7

What are the DfM/DfAM for additive processes?

Answer 7

– Minimum feature size (mm) – Part separation (mm)
– Tolerancing & accuracy
• Three dimensional
– Design for tighter tolerances – Hollow-out parts (Shelled)
– Support structures?
• Requirements, placement & removal – Powder removal?
• Enclosed volumes & conformal channels

Minimum feature size
– Process specific – check
– General rule ≈ Ø0.8mm
– Jetting & Metal processes ≈ Ø0.1 – 0.2mm – Height = one layer, typically 0.1 – 0.2 mm

Part separation
– Ensure parts do not fuse during build – Process specific & Geometry specific – General rule ≈ 0.4mm (min)

Question 8

What is important regarding tolerances?

Answer 8

Tolerancing & accuracy
– Three dimensional tolerancing
– Process specific ≈ +/- 0.2mm
– Repeatability is an issue...
– Build all ‘mating’ parts in the same build!

Design for tighter tolerances

Question 9

How can we use less material but increase integrity of product in AM processes?

Answer 9

Hollow-out solid sections (shell)
– Save material
– Decreased costs
– Increase build time

Ribbing – increase structural integrity – Use the design freedom

Question 10

How can we save up material?

Answer 10

Hollow-out solid sections (shell)

Question 11

What is the widest angle simple overhangs can support?

Answer 11

up to 60 degrees

Question 12

What is the better angle for complex shape overhangs?

Answer 12

up to 45 degrees

Question 13

What can happen with no proper supports?

Answer 13

sagging, collapse, warpage

Question 14

How do we increase build speed/reduce time?

Answer 14

By minimising z axis height (build height)

Question 15

Where are the mechanical properties weakest?

Answer 15

Along the z axis due to the different layers

Question 16

What parameters are important in the machine setup?

Answer 16

All process specific
• Temperatures
• Layer height (resolution) 
• Feed rates
• Laser power
• Scan strategies
• And on, and on...