Roughness Plate Testing
My roughness test set up using a Mitutoyo roughness tester.
At Desktop Metal, I investigated how to get different roughness for various machining processes. The company’s production series printer uses binder jet technology to print metal parts. Therefore, it is important that the base, which has parts printed on top, is consistent and stable. However, we didn’t know whether the base plate’s roughness affected the print quality. So, my goal was to understand how to control the average roughness (Ra) of a piece of stainless steel and whether it affected print quality.
Generating Roughness Patterns. Please Wait . . .
A close up of the piece I machined for testing machining processes and surface roughness.
The planned machined surfaces on top of the printer’s baseplate.
First, I took a piece of 17-4 stainless steel and machined four surfaces, two on each side. I would place the piece in a milling machine and have a fly cutter with one-bit cut knurled surfaces. I would have the cutter move at a fixed speed but changed the feed rates. The slower the feed, the more separated the knurling cuts were. Since the cuts were circular the edges of the surface had a lower Ra than the centerline. In addition to knurling, I applied various grits of sand paper using an orbital sander onto the surfaces.
What’s The Roughness?
Average roughness of a knurled surface versus how far away the sample length was from the centerline.
A close up of the print bed with a machined surface. The other half was left blank as a control surface.