Fehlmann Picomax 50 CNC conversion/refurb

[Agathon]

I have some parts from an older machine looks like PICOMAX100 that was being disposed of by a machinery dealer .
It used sevo motors and timing belts to drive the ball screws .
when I arrived the controls had been chucked in a skip , the sevos removed and the intention was to strip the rest to get rid of the 3000 K that was in the way .
I still have the sevos , the SF 32 spindle , some SF30 tooling , the roller slides , massive leadscrews ( maybe 30mm ) with ball nuts and bearings .
So true sevos when others used steppers ! - well as you say , it IS Swiss.

What a shame it was scrapped - I would have considered buying it.

I've only just started working on the old Fehlmann again after a couple of years of inactivity. My machine is a pain as it was originally only two axis. The Picomax 100 was a three axis machine that used the quill rack and pinion driven from a worm and wheel belt driven from a servo as the Z axis. It sounds like a terrible idea when one thinks about the average drilling machine rack and pinion, but being Swiss there's virually no backlash. As I mentioned earlier in this thread, the extremely clever engineer I bought the machine from had made a worm and wheel drive (the aluminium housing seen on the right hand side) to drive the pinion. However, I have found that because he used a fully throated worm wheel it has been almost impossible to remove the backlash.


I will probably end up using a ball-screw to move the quill, but I have recently reinstated the machine's original worm and wheel drive (which employs a gashed bronze worm wheel) and have backlash of about 0.01mm - not bad. I shall see how it works in practice once I have mounted the stepper motor to the original 90º cross-helix gear drive to the worm shaft. There is significant backlash in this gear, but it will be unimportant in terms of the ability of the quill to remain in position because of the worm and wheel - the backlash is constant so it can be accounted for in the software. As I say, this is almost identical to how it was originally done on the three axis machines, however, it has proved difficult to employ a belt drive to the worm shaft due to differences in the head castings - see drawings.