Converting a PM X power feed to stepper or servo drive?

M

mcdanlj

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I have a https://www.precisionmatthews.com/shop/pf-bench-alb-310s-x/ on my PM-30MV. The limit switch cord got pinched and shorted to the mill, so I repaired that and then didn't re-install the limit switch on the mill, because it's literally never been valuable and only gotten in the way so far. But also I don't like that I can't set a specific speed, just dial it up and down by feel. And sometimes I'd like it to be able to crawl even slower.

Has anyone torn out the guts of one of these units and converted it to stepper or servo drive, keeping the clutch so that the handwheel on the other end still works?

I'd expect benefits:
  • Dialing in an actual speed
  • Displaying an actual speed
  • Could use optical limit switches with flags going through them instead of that bulky spring-loaded box to give coasting room
  • Could probably vastly reduce coasting need (especially with a servo)
  • Could go slower
  • Could be quieter with modern stepper drivers, or using a servo with encoder
Only downsides I can think of are inconvenience of doing the design to fit it in, and maybe slower top speed for rapids if using a stepper?
 
Seems like a perfect project for an Arduino- coasting effect would be essentially zero
-M
 
Oh, inertia is still a thing to account for; you can't stop it instantly. But I wouldn't think that an S or parabolic motion curve would be necessary, probably trapezoidal would be fine. And on a servo, it could stop very rapidly. On a stepper it could stop quicker if I don't worry about skipped steps, but I'd also want to look at using a trinamic driver that can sense missed steps, which might also allow it to stop itself in case of a crash.

I'd probably use ESP32 instead of Arduino because they are so cheap and easy to work with.

But I don't know what's in the case and how much room there is. I didn't see any projects like this already but wondered whether others had seen some they could point me to. ☺
 
For those of you who don't know what a ESP32 is (and I didn't until about 3 minutes ago):
www.hackster.io

An ESP32-Based Arduino Lookalike

Better known for their single-board computers, the folks at Banana Pi seem to be pretty keen on the ESP32 chip right at the moment, with a…
www.hackster.io
 
Oh, yeah. It's even cheap to get development boards that include a nice display. Here's a 1.1" display included on an under-$20 board with 16MB of flash storage:


The most common ones, like that one, are dual-processor 240Mhz, which is rather faster than an Arduino. Even powerful enough to run an emulator for the original Mac inside a chip that costs just a few dollars... See this amazing work!


So while you can use Arduino to write code for them, they are tremendously more powerful and cheaper; I see three dev boards (without monitors) for $10 on Amazon right now, and that's pretty normal. Try to get an Arduino for that!

The main benefit of the original Arduino is that the chip is really rugged and can run on 5V instead of 3.3V, which in some cases is really convenient. But they tend to cost more than the ESP32 for a lot less capability.
 
Lots of choices these days for cheap controllers. Recently got a Raspberry Pi Pico W. 2 cores, wireless and $6.
 
mcdanlj said:
Has anyone torn out the guts of one of these units and converted it to stepper or servo drive, keeping the clutch so that the handwheel on the other end still works?
Click to expand...
I opened up one of these that was giving trouble, thinking I would fix it. Instead, I threw it away.

If you could do anything useful inside there, I would love to see it. :)
 
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