A precision micro-machining company (Micron Solutions) contracted with QRP to design and build a fixture for use in a micro-plunge EDM operation. The result was the elegant, single piece, precision fixture shown above. This is a great example of 3D printing’s ability to enable unique customization, with low design and manufacture cost.
For the customer, the fixture needed to fit within a tiny vice that can only open .75” wide. The part it held was a tiny disk. The disk had to be clocked and consistently located when they removed and re-inserted it (it had some features on it to line up with). The micro-EDM process had to traverse the part to drill holes in a few spots, so anything holding it down needed to be out of the way of the machining process.
For QRP, we wanted the part to take minimal time to design to keep our costs down. We also wanted it to print with low machine and material costs. It needed to require minimal support removal effort.
The part was designed to have 3 flat surfaces oriented in orthogonally and such that their surfaces were as smooth as we could get with our M-lab Powder Bed Fusion (PBF) printer. This printer enabled us to print in a delicate clocking feature on one of those critical surfaces that was .010” thick. The two sliding surfaces were printed vertically to get them very smooth. The same is true for the 4 surfaces that interface with the vice. We planned to use 316 Stainless Steel to save cost. All inside corners included a small relief on the order of .008” diameter so that no corner radii would impede contact of the disk with the surface. The same relief was added to the inside corners that would mate against the vice. Since the length of the part wasn’t as critical, we extended the tool toward the back of the fixture so that we could keep 50° overhangs and avoid any support structure. We also added lightning holes to remove material and speed up build time. Clips were used to press the part against two of the 3 flat surfaces. They needed to account for a disk thickness range that varied by .010” and still press the part down in all conditions. This is another example of how Additive Manufacturing can reduce part count by designing-in compliant members—a practice traditionally only used on plastic parts.
We worked over the weekend and got the part into their hands within 2 business days. The disk fit into place perfectly on the first try and was used right away. This was a super fun project to work on and shows off some of Design For Additive Manufacturing (DFAM) that we specialize in here at QRP.