This entails that his magnetic measuring probe must move up and down through the bore of the magnet that is cooled to 4.2 Kelvin. He uses an interesting anti cryostat device inserted down the bore of the large magnet. And inside this his probe rotates, and is moved up and down axially through the bore of the magnet to map the magnetic field. The purpose of the anti cryostat is to keep the measuring probe at room temperature when it is inserted in the super cold bore of the magnet.
The problem we were asked to solve was a failure of a plastic part at the end of the magnetic measuring probe that couples to the rotational motor. During the test run this part somehow got warm, and the small set screws holding the coupling to the probe collapsed the probe end. There are very small instrumentation wires that pass through the center of the coupling and the probe end that really don 't like to get twisted around.
The part that had failed had some semi-complex geometry so the way they were manufactured was by the 3D printer or FDM process. This was fine for previous tests and the parts performed well. On this particular test there was a heating problem that caused the FDM parts to soften and fail. The first step was to make the probe end out of something a little more durable. We had a good sample and a drawing so I gave the job to one of the new technicians to fabricate. We chose PEEK for the probe end material. This is a tough strong high performance plastic that has a wide operational temperature and excellent machinability.
While the probe end was being fabricated I had another discussion with the scientist and we decided that the failure was most likely from eddy current heating of the metal bearing spacer that happens to ride on the probe end. With this realization we decided to try to eliminate as much metal from this particular area as possible.
One of the parts that needed to be made of some non metallic material was a small helical shaft coupling. This type of coupling is used because of its zero backlash ability. The magnetic measurements are correlated to the probes position inside the magnet with rotary and linear encoders so a map of the field can be determined for that particular magnet configuration.
This is just the kind of job many machinists love to do. A tricky job with a minimum of detailed constraints, and the freedom to do the job anyway you can. The only thing that machinists generally don't like is the time constraint. When I was learning this stuff I would have liked to sink my teeth into a job like this every day of the week. In fact, I have never done this type of operation before. Sure, I've cut lots of helices and all manner of threads, but I never had to make a coupling like this. Honestly I really wanted to do this one myself but now its more important for me to allow other folks to have the experience and successes in the trade.
Part of the tooling we needed was a special holder to fit in the toolpost of the lathe. I made a quick hand sketch and gave the job to the other new technician I'm looking after. If this was going to work we would do it as a team. The tool block was needed to hold the hand piece of a Foredom tool.
We shot some video of the operation which I will put up on my YouTube channel in the next couple of days.
Thanks for looking.