Mechanical Engineering Commons^™

Impact Of Extended Sintering Times On Mechanical Properties In Pa-12 Parts Produced By Powderbed Fusion Processes, Garrett Craft, Justin Nussbaum, Nathan B. Crane, J. P. Harmon

Faculty Publications

Additive Manufacturing provides many advantages in reduced lead times and increased geometric freedom compared to traditional manufacturing methods, but material properties are often reduced. This paper considers powder bed fusion of polyamide 12 (PA12, Nylon 12) produced by three different processes: laser sintering (LS), multijet fusion (MJF)/high speed sintering (HSS), and large area projection sintering (LAPS). While all utilize similar PA12 materials, they are found to differ significantly in mechanical properties especially in elongation to break. The slower heating methods (MJF/HSS and LAPS) produce large elongation at break with the LAPS process showing 10x elongation and MJF/HSS exhibiting 2.5x the …

Evaluation Of Processing Variables In Polymer Projection Sintering, Justin Nussbaum, Nathan B. Crane

Faculty Publications

Purpose – Projection sintering, a system for selectively sintering large areas of polymer powder simultaneously with a high power projector is introduced. The paper evaluates the suitability of laser sintering process parameters for projection sintering as it uses substantially lower intensities, longer exposure times, and larger areas than conventional laser sintering (LS).

Design/methodology/approach – The tradeoffs in sintering outcomes are evaluated by creating single layer components with varied exposure times and optical intensities. Some of these components were cross-sectioned and evaluated for degree of densification while the single layer thickness and the maximum tensile force was measured for the rest. …

Stress-Limiting Test Structures For Rapid Low-Cost Strength And Stiffness Assessment, Andrew Katz, Craig P. Lusk, Nathan B. Crane

Faculty Publications

Purpose: Evaluate the use of a simple printed geometry to estimate mechanical properties (elastic modulus, yield strength) with inexpensive test equipment.

Design Methodology/Approach: Test geometry is presented that enables controlled strains with manual deformation and repeatable measurement of vibrational frequencies. This is tested with multiple FDM machines to assess measurement accuracy and repeatability. Printing orientation and some printing parameters are varied to assess the measurement sensitivity.

Findings: The test methods show good correlation with manufacturer material specifications in the X-Y plane and reported elastic strain limits. It is also sensitive to printing orientation and printing parameters.

Research Limitations/Implications: Further work …