Design World – August 2019

Preparing to switch

54 August 2019 http://www.makepartsfast.com DESIGN WORLD
DESIGN WORLD http://www.makepartsfast.com August 2019 55

The 45-degree rule: angles below 45 degrees require support structures to ensure

stability of the part during production.

| Courtesy of Proto Labs

Overview of how Velo3d enables additive manufacturing without support structures.

| Courtesy of VELO3D

Industrial metal parts manufactured with support-free AM overcome many of the

traditional barriers of the past.

| Courtesy of VELO3D

Finally, there’s just the sheer level of complexity of

AM technology, particularly when it involves metals.

Rey Chu, Co-founder of Phoenix, Analysis, and

Design Technologies (PADT) says: “There are no

guarantees of successful outcomes when printing

with metals. There are so many variables coming

together from the alloy, the machine architecture,

the process parameters—they all compound into

widespread complexity. Because of the nature of

machine dependency, try getting the same result

by printing the same part on a different machine

requires significant effort in process development,

validation and control ....it’s all hard.”

Is it possible to avoid or reduce this complexity?

Is full up redesign required for most parts? In fact,

lots of parts can be converted to AM now. They

haven’t been in the past because they didn’t fit

the rules of DfAM so they were being fabricated

another way. Parts like impellers, heat exchangers,

blisks, and volutes are excellent examples that

have traditionally been manufactured outside of

AM because of their geometries—low overhangs,

large inner diameters, untenable aspect ratios, and

complicated internal channels that make post-

processing difficult or even impossible.

However recent developments in AM technology—

most notably support-free manufacturing—are

challenging the traditional mindset, providing high

levels of quality control, and overcoming previous

barriers such as those in the part-geometries above.

A little more about the implications of “support

free” here: In AM, a self-supporting angle describes

the feature’s angle relative to the build plate. The

lower the angle, the less likely it is to support itself.

Each material will perform slightly differently,

but the general rule of thumb has been to avoid

designing a self-supporting feature that is less than

45 degrees. As you can see in the picture below, as

the angle decreases, the feature’s downward-facing

surface becomes rougher and eventually the part

will fail if the angle is reduced too far.

Support-free AM overcomes what were

previously thought of as written-in-stone laws of

physics, allowing you to accelerate your move to

3D printing without having to adhere to all the old

rules of DfAM.

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