Your Questions Answered
There are many methods of manufacturing, and many methods of inspection. Do the same inspection methods used in casting apply to products built by additive manufacturing with powdered metal?
A Tech Briefs reader asks our industry expert Kevin Brigden, an Applications Engineer at the U.K.-based engineering company Renishaw.
INSPECTION METHODS: ADDITIVE MANUFACTURING VS. CASTING
“When it comes to inspection for evaluating fatigue, how does a part made via additive manufacturing compare to a forged or cast one?" a Tech Briefs reader asked the 3D-printing pro.
When talking about fatigue in powdered metal and 3D printing, this is the elephant in the room, says Brigden. With materials like AlSi10Mg aluminum orTI64 titanium, the application of anticipating fatigue is somewhat more difficult.
There’s not enough data. The amount or volume of test information regarding additive manufacturing with powdered metal is nowhere near the same as it is for conventional processes such as forging and casting.
Learn about the official groups – ASTM being one of them – that are working on developing standards and frameworks where this data can be published collectively as a group. ASTM committees offer additive manufacturing guidelines on reporting data, terminology, and mechanical and material evaluation.
There may not be enough test-and-measurement information right now, but Brigden is optimistic about the maturity of additive manufacturing inspection methods:
“Over the next five to ten years, I would anticipate seeing that data coming out in spades,” says the Renishaw engineer.
INSPECTION METHODS: HOW MATURE IS SIMULATION FOR ADDITIVE MANUFACTURING
Instruments like coordinate measuring machines, X-ray imagers, and ultrasonic testers can all find defects in the finished metal component, including unintended flaws like rough surfaces, cooling deformations, or cracks.
Can those methods of manufacturing inspection be used in additive manufacturing?
A second reader question for Brigden: "How mature is the simulation of items created by additive manufacturing/3D printing vs. items created by casting?"
When you’re micro-welding at the smallest scale and then building up to a macroscale part, effectively modeling residual stresses and effects, such as surface burning, are considerably more difficult, says Brigden. While a number of companies are working on developing print simulation, the additive-manufacturing tests still have quite some way to go to be an effective tool in day-to-day use.
If you’re trying to understand design limitations of the product, and specifically trying to find fatigue on the material properties, your choices are relatively limited. For tensile properties, however, the tools are significantly better developed.
With metal powders in metal additive manufacturing, mechanical properties may vary slightly depending on the direction of the print and the orientation of the part with respect to the print. Brigden explains how most of his customers use the “worst-case scenario,” building tensile bars in a range of orientations, and finding the one that is the least befitting to what they’re after.
Simulating the print process itself is somewhat less mature at the moment, according to the Renishaw engineer. Most models use an inherent, strain-based simulation approach, which has limitations in terms of accuracy and precision. In this Tech Briefs Q&A, learn why there needs to be improvements in resolution.Read Brigden’s responses to both reader questions at TechBriefs.com.