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Sieg KX3 Erratic Spindle RPM

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Nicola Casali06/02/2021 19:08:25
27 forum posts
3 photos

I've been ignoring this problem for months. The reason why is because it tends to disappear after half an hour after power-up or after power cycling. But it seems to be getting worse? Today, I was massaging the real-time speed of the spindle via the Mach3 interface whilst it was drilling holes.

When I turned on the spindle today, clockwise (M3) did nothing. It would only spin anti-clockwise (M4). I power cycled everything and managed to get a clockwise spin, but the RPM was all over the place. Anti-clockwise seems to be stable. I checked the 0-10V voltage output on the break-out board with the spindle disconnected. The voltage output was erratic.

Isn't the only difference between clockwise and anti-clockwise the voltage on the direction pin? Would that imply that the spindle control board is faulty? But the 0-10V output is not stable, which would imply something is wrong with the break-out board. Or maybe both?

Has anyone got any theories about what could be going on here? I'm tempted to get a C11G off Amazon to help with the diagnosis or even solve it. I think I need it as backup, anyway.🤔

Andrew Johnston06/02/2021 19:23:02
6016 forum posts
670 photos

When I had intermittent spindle problems on my CNC mill it turned out to be two separate problems. First, there was a dry joint on one of the PCBs and two, a poor copy of an industrial connector was intermittent. The first rule of debugging is to break the system properly. So push/pull and generally flex things to see if there is any correlation with the spindle running, or not, or get it to fail permanently. Then one can trace through in a logical manner.


Edited By Andrew Johnston on 06/02/2021 19:23:32

JasonB06/02/2021 19:24:23
20474 forum posts
2269 photos
1 articles

Motor also send back a signal as to its actual speed which may be playing up.

You say it gets better after some run time could it be the time of year that Ketan has written about before causing dampness that will evaporate with motor heat.

Andrew Evans06/02/2021 21:21:33
340 forum posts
8 photos

I have had this issue too and I never really solved it and it was never serious enough to spend too much time on it. It could be a poor connection as the others have said. It could also be a computer issue or a mach3 issue. Mach3 can be glitchy occasionally. Do you have the parallel port or usb version of the kx3? I think usb is quite prone to interference. As Andrew said I think it's a matter of first reliably recreating the problem and then working through each element to isolate the fault.

Nicola Casali07/02/2021 01:31:40
27 forum posts
3 photos

I'm using a UC300ETH. I don't think it's that. Well, I hope not. (I do have a temperamental Z+ limit issue with it. But that's for another thread.) A poster in MyCNCUk talks about a circular magnet falling off from the motor, which sends back a signal. That's curious. Will have to investigate that one.

A couple of hours after power-up it seemed to stabilise. I'm leaving the machine on overnight with a little fan heater in case the temperature drops too much in my garage. We're supposed to be getting snow. I'd like to see if the spindle continues to perform correctly with a stable humidity and temperature.

It's very interesting to hear I'm not alone with this problem.👍

I've ordered a spare C11G in case I want to start flexing things to breaking point.😅

Nicola Casali07/02/2021 18:23:29
27 forum posts
3 photos

Ok, interference got me thinking. My Surface tablet is connected to the UC300ETH via ethernet. The UC300ETH connects to the BOB via the parallel port. There's a magnetic LED light attached to the headstock. I bought this off Amazon in October. That's when I started on my most recent project. I've had this spindle issue for a few months, including other glitches.

I powered on the spindle without the LED light on. Spindle ran fine. As soon as I powered on the light, the spindle starting speeding up. I also know that this light destroys my DAB radio reception. That should have been a clue.. I'll look into some ways to suppress the interference, but this won't be used with my mill for now.

I haven't yet been able to replicate the extreme behaviour I was getting with the spindle where it refused to even start. There could be other interferences, like humidity. I'll update when I find out.face 1

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