Positioning a Board on a Fixture
Continuing our series of posts where we take a look at the data we have gathered in the course of machining over five hundred fixtures for customers using our custom drilling service, here we are looking at where test probes are located. This tells us about how folks have positioned their boards on the fixture.
Our guidance is that boards should be positioned as far to the front as possible, because this minimises any tilting of the board as the fixture closes. With more sophisticated parallel-motion fixtures this is not a concern, but with low-cost hinged fixtures, the further one can stay from the hinge the better.
For each of our fixtures we have a suggested "probable area" located towards the front of the probe plate, which also takes account of keep-out regions around brackets and screws. This is shows as a light grey region on the checkplots produced by our drilling service.
The image below aggregates over eleven thousand holes we have drilled for test probes in over three hundred MF300 (6" x 7") fixtures, our most popular size.
The vast majority of the locations are within the suggested probable area, concentrated towards the front and center, which is good to see.
There are a small number towards the rear of the fixture where people have either pushed their luck with test probes, or perhaps these are holes that are going to be used for other functions such as mounting items on or below the probe plate.
There is evidence of reluctance to use the area south of the origin. It is actually fine to use this area provided one avoids the origin itself. On the probe plate and pressure plate the origin is actually a physical hole that we use for alignment when drilling, and customers can use if they are drilling the plates themselves.
Overall it appears that folks are positioning their boards in the best position on the fixture. We have also analysed the data from MF500 and MF700 fixtures and the picture is very similar. Well done!