The E-beam gun has 4 pockets, they are driven by a bevel geared shaft on one side of the e- beam gun. One turn of this shaft indexes the crucible one position. Initially I was going to use a ferrofluidic feedthrough and a miter gear set to drive the crucible with a motor on the exterior of the chamber. This would really limit the positioning of the e-beam gun to one of just a couple position where there are existing 1" holes in the base plate. Another option would be to drive it with a motor internally but to do this would be pretty expensive. Vacuum rated motors are pretty rare and when you do find them, expensive. I have an octal baseplate feedthrough and only need a couple of the pins for the e-beam sweep magnets so installing something internal would be ideal.

So I made my own internal electrically driven stepper drive indexer. I have had this little stepper motor kicking around for some time, I pulled it out of a wrecked drone camera, it has a 100:1 harmonic gearbox on it. This ought to have enough torque to drive the indexer, there really is no load on it.

I found I had a small section of KF-40 line with a 1/4" VCR fitting on it, the motor was small enough to fit down the center. I scrounged up an old KF-40 Octal feedthough and a small ferrofluidic feedthrough I had lying around. The feedthrough was tig welded to a bored KF-40 flange and I made a couple stainless standoffs from 1/4" rod scrap to mount to the two screws that hold the stepper to the gearbox. These were tigged into place as well.

I ordered a couple split clamp style couplings from ebay, a 5-6mm for the motor to feed though and a 6mm-1/4" to drive the gun shaft. I have found it is just not worth the trouble to make my own couplings, they are difficult to get concentric and straight. I did have to shorten the internal coupling down to get enough room to fit everything in the can.

Typically vacuum fittings and seal do not expect to see internal pressure. When they do they need something to support the outside of the o-ring. I did had one KF-40 seal with that, the other seal is some sort of hard white plastic material, it should be hard enough to withstand the internal pressure without blowing out... I hope!

Teflon insulated wires were soldered to the motor terminals and to the octal base pine. If I am going to have a leak anywhere, it will be the base pins, they are hollow with holes in the ends so I hope I got a good seal. A couple KF clamps and a VCR plug on it and it should be good to go. I still need to figure out how to mount it internally, I want to make a saddle to clamp the feedthrough section in place but the Y axis servo drive died in my CNC mill and I need to find another used one.