Modern Machine Shop

DEC 2018

Modern Machine Shop is focused on all aspects of metalworking technology - Providing the new product technologies; process solutions; supplier listings; business management; networking; and event information that companies need to be competitive.

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Page 43 of 115

ADDITIVE INSIGHTS MMS DECEMBER 2018 42 Understanding Industrial 3D Printing Smoothing out the Rough Edges TIMOTHY W. SIMPSON | COLUMNIST There are various viable processes to consider for surface finishing metal AM parts. Machining is not the only way to finish your metal part after additive manufacturing (AM). There are other post-processing techniques to improve the surface finish and dimensional integrity of your part. The big challenge with metal AM parts is that they are not "smooth" when they come off the build plate. Partially melted powder particles adhered to the part, stair-stepping effects of the layer-by-layer process, tessellation of the 3D solid model, and differences in up-skin and down-skin surfaces all contribute to surface roughness. Smoothing out these rough edges and surfaces also adds time and cost for post processing, but is critical for meeting specifications and tolerances, especially mechanical properties and fatigue life. As it turns out, there are a host of technologies available for finishing and post processing your AM parts. In fact, they are the same sets of technolo- gies that you might use to finish any metal part. Just like any other manufacturing process, AM parts still require tolerances to be met, mechanical properties to be strong and costs to be competitive. So, what are popular post-processing tech- nologies for AM? Media blasting with abrasive materials such as sand, grit and ceramic beads is a simple way to reduce surface roughness, but it can be labor-intensive and hard to achieve a uniform and precise finish on the entire part. Likewise, shot peening improves surface finish (see Figure 1), and it has the added benefit of improving Figure 1: Sur face roughness measurements of dif ferent stainless steel top and bot tom sur faces with dif ferent overhang angles: (a) as printed and (b) af ter shot peening. (a) (b)

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