Hi All, and happy Holidays!
Having a Weis VM25-D, I lurk about this forum often as the two mills are (except for a few details) virtually identical particularly for this discussion. I too, wish to add a Z-Axis motor, but I would also like to add
plunge milling to eliminate Quill deflection. So, I am writing to this sub-forum for thoughts and ideas. In fact, I hope it might be a Project with members' input.
With all gearmotors, the problem becomes the hand wheel is useless as you are fighting the gear reduction whose added effort to spin the hand wheel is proportional to the ratio of motor shaft RPM/gearset output RPM. Not entirely impossible to use the handwheel (unless the gear reduction is worm and wheel), but sure is way too much effort, especially fighting head weight when moving up.
In my humble view and with no ill will to Priest Tools, their Power Lift kit seems cheesy. The control plate looks like something I made as a kid, PWM would have been a nice addition, but I get it - it is a "Power Lift" only device, no need for speed control. The gear motor appears to be a run-of-the-mill unit available anywhere:
https://rex-engineering.com/wp-content/uploads/2018/05/EX-BLDC.pdf. In fact, if you want to roll your own, my guess any surplus outlet like
surpluscenter.com will have a comparable replacement. In any event from several reviews, the Priest gearmotor seems to be running on fumes just for its sole purpose: quick Up/Down. If my first link is correct as to the motor, it has 240 in/lbs (or lbs/in for the scientifically minded). Perhaps Priest can correct or confirm that torque spec? In any event it seems from reviews and videos of their product, it is running on the hairy edge. More motor or higher motor speed and more gear reduction is needed just to go up and down.
I would like to add this feature. But I also want to plunge mill into mild steel. Since this is homebrew and limited by experience and funds, motor/gearhead will not be the limiting case here, rather the rigidity and integrity of the mill. Will the column flex, leadscrew break, etc... I think that will be empirically found - you know when you are driving your mill too hard. So, now it gets down to the motor/gearbox...
- As stated previously, I personally would like to use the hand wheel as well as the power feed. Now we are talking either a BIG motor and small ratio gearbox ($$$), still with a difficult hand wheel turn.
- A moderate, higher speed motor with more gearing. Perhaps the hand wheel will need two men and a boy to turn.
- A high torque motor with a worm/wheel combination. In this event, there is no turning the hand wheel.
Of all the options, I like #3 with a clutch for engagement and disengagement. Gives me the force which I need to penetrate my work and allows me to use my handwheel. Of course, the clutch is the hard part
. I think dog clutches are entirely too complicated and I invite those who have made such clutches to toss in their thoughts for maybe I am completely wrong.
To me, a homebrew, cam-actuated is perhaps the easiest. But you need to dead-nuts on the lobe of the cam (for disengagement and release) and the Neutral detent has to be in command of Neutral, but not so stiff that it takes much effort to move the lever. Tolerances are important here. It could be a catastrophe for the lever to engage accidentally or in a panic, the operator cannot find neutral. Has anyone experience with lever-operated eccentrics/cams with detents?
I was thinking a bevel gear on the leadscrew and one on the shaft of the gearmotor. The gearmotor could either be pivoted or laterally slid for disengagement, though I expect lateral is best from perspective of positive engagement. The movement of the gear, if by cam could be engaged by spring action and disengaged by cam (not fail-safe) or engaged by solenoid and disengaged by spring (safer but bulkier).
Thoughts from this forum are very much welcome.
John