Design allowables for AM, Or, taking out the shame factor.
On one of my previous posts I got overwhelming responses about the fact that design engineers can’t trust the materials properties stated for Additive Manufacturing. This is of course a known secret in the AM market.
Two questions come to mind: Why? and, What can we do about it?
Here are my answers:
Why the published materials properties are not trustworthy?
Since AM is portrayed as a be-all, do-all and replace-all manufacturing method, it is hard for AM solutions providers to admit that printed materials have different properties than ones used in "traditional" manufacturing methods. My experience is that the difference is sometimes perceived as... shameful. After all, if AM is marketed as a plug-and-play replacement for any part that was design for any other manufacturing method, a difference in mechanical properties is not something one wants to show. Unfortunately, the widespread solution for this dissonance is presenting the data in creative ways that make it unusable for engineers.
What can we do about it?
Simply consider AM as just another manufacturing methods, with its own design considerations and resulting materials properties. As a mechanical engineer, I am used to have different physical properties for the SAME material when it is processed differently. Consider the example in the picture I took after a simple Google search (https://ucpcdn.thyssenkrupp.com/_legacy/UCPthyssenkruppBAMXUK/assets.files/material-data-sheets/aluminium/aluminium-6061.pdf): the SAME Aluminum 6061T6, from the same supplier, has DIFFERENT elongation at break numbers when extruded as a tube or as a profile. For an engineer, this is totally common. As part of the design process, I know the geometry I need so I pick the right number from the right table for the part's strength calculations. All I need the numbers to be is REPEATABLE (i.e. the material behaves the same each time it is used) and RELIABLE (i.e. the number represent the actual behavior of the material). If this line of thought is used for machining or casting, there is no shame in using it for AM too.
Put differently: there are no good or bad values when it comes to materials properties. There is just physics.
So let's have useable, repeatable and reliable data, which will allow using AM for applications that really need its strengths.
