Case Studies

RS Precision assures quality production—and consistent performance—for a global leader in energy control technologies.

Summary:

An aerospace manufacturer of fuel control valves for jet engines was having a problem finding a reliable EDM supplier to produce a ultra-precision component that had a very direct bearing on the performance and reliability of their products. They asked the dealer of the EDM machines they had purchased if they could recommend a reliable Sinker EDM supplier for these challenging and critical parts. The dealer immediately recommended RS Precision.

The Challenge:

The required part is made very small from solid carbide. It has an OD tolerance of +/-.0001” and has two side holes 180 degrees apart that are EDM’ed at 30 degrees from the sides. The part also has two top holes of very small diameter that are 20 degrees off vertical, and have a tiny separation between them of only .0008” to .0015���! In addition, the holes must have a 32 rms finish or better, must be perfectly centered to the OD and to each other, must have a perfect profile with no chips or imperfections, and must connect cleanly in the center of the 30-degree side holes. Any variations in location, surface finish and spacing result in changes in the performance of the valve.

The Solution:

Consistency was critical. Recognizing the magnitude of the challenges, an innovative fixturing system was designed and built that would allow the side holes to be EDM’ed productively, while the ultra-critical top holes required the utmost in control. The parts the customer received from the previous supplier were of very poor consistency, and only about 60% were useable—resulting in a slight compromise to their standards. In contrast, the parts RS Precision supplied were 100% useable. The customer experienced an improvement in the consistency of the performance of their valves and a reduction in the assembly and testing time. One interesting side note to this project is that as part of the process, the edges around the top holes were broken very slightly, by about .0001” to .0002”. This made it nearly impossible to reliably measure the all-important spacing between the holes.

RS Precision set up a toolmaker���s microscope with a .000050” digital micrometer, and measured this critical dimension on every part we made. We then ran the statistics on the measurements and derived the CpK for this process, which was in excess of 1.33. After surveying our operations, our customer agreed to base their acceptance for this feature on our SPC data. This allowed them to have the utmost confidence in the quality of the parts, while relieving them of the cost and time necessary to inspect this feature themselves. To date, RS Precision has delivered over 20,000 pieces with a nearly perfect quality and delivery record.