Powders are expensive and poorly utilized in AM processes. In a typical build, only 5-20% of the powder volume is fused into useful parts.
This project seeks to demonstrate a substantial reduction in material costs involved in AM part production by taking a systematic approach to quantifying results of reusing specific powders in the AM process.
High material costs are a major economic reason for continued limited application of additive manufacturing (AM) for batch production. Powders are expensive and poorly utilized in AM processes. For example, nylon powders cost between $75 and $100 per kilogram, while titanium powder is roughly twice that amount. While, in a typical AM build, only 5-20% of the powder volume is fused into useful parts. Depending on the material and machine manufacturer, it may be possible to reuse the powder up to three times, but often it is recommended that only virgin powder be used, or that reused powder be blended with virgin powder, and most of the unfused powder be discarded. Further, some manufacturers require discarding the unused powder in the feed chamber. This drives costs upwards – thus making the material in AM parts up to five times more expensive than the raw powder. This is a major factor limiting AM’s extension to batch production.
The objective of this program is to characterize materials produced from reused powders or blends of virgin and reused powders in selective laser sintering. This approach could provide a substantial reduction in material costs involved in AM part production by decreasing the amount of discarded powder. Powders investigated will include Nylon (PA 2201), Titanium (Ti-6Al-4V) and Stainless Steel (316L and 17-4PH).
Using directed energy deposition (DED) as the testing process, an apparatus for simulating thermal cycles is being produced to increase the yield of powder and reduce the burden on production equipment. Powder characterization will be performed after each reuse to measure the effect of thermal cycles on the morphology of the powder. Information on particle size and distribution will be obtained through a laser scanning system. Powder flow data will be captured through a particle flow analyzer and an angle of repose of free-flowing powder. A design of experiments (DOE) is being conducted to identify the important variables on the ultimate tensile strength of dog bone samples using tension testing. A two-level experimental matrix is being designed and executed for each material to identify the important parameters and the interactions between factors. A response curve will be generated and inverted to use the DOE characterization as a method for improving performance or compensating for variables to produce more consistent outcomes.
Other Project Participants
- Case Western Reserve University
- SCM Metals Products
- Johnson & Johnson-Depuy Synthes
- U.S. Department of Defense
- National Science Foundation
- U.S. Department of Energy
Updated: November 20, 2017