CNC is damaged from collision -- FIXED


Affected Tool or Resource: CNC

Team, Group or Volunteer who usually handles this type of ISSUE or REQUEST (Please tag using the @ symbol. Start by typing @TEAM_ to find most responsible teams): @RealCarlRaymond

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Initially, the z axis wouldn’t move. After a reboot, it would stutter when you use page up and page down. Mach3 said it moved 1.5 inches, but I didn’t trust it.
@Aleasha and I didn’t run the machine after was saw this

The collet we pulled out of the router has been driven into material (see the attached picture)

I’ll have a look at it.

I had a look last night and found that the motor driver for the Z axis will need to be replaced. The collet really does look like it had a hard crash, and that may have pushed the driver over the edge. It’s out of service for the moment.

To the operator: please don’t feel too bad about it! CNC machining is accident-prone even when you’re doing everything right and paying attention. I have a permanent palm-shaped mark on my forehead for this reason.

Someone please put an Out of Order sign on it. I forgot to do that before I left.

In the past we have had the Z axis driver go bad, and on digging deeper, I have an idea why. The motor drivers have a settable current limit that you adjust for your particular need. It’s set by adding a resistor between two terminals. When I pulled it apart, I realized there’s no resistor installed at all, so all axes are operating at the maximum current of 7 amps. For the motors we have, that’s probably too much anyway, and running the driver at full current all the time shortened its life.

(Side note: the Z axis driver is more susceptible to damage because the machine spends long periods of time at an unchanging Z position. X and Y move around a lot, and the transistors in those driver get a break; it’s two transistors on and two off, alternating with every little step. For a constant Z position, it’s two on for a long time, stressing them. We had previously lost two of the five motor drivers the machine came to us with. At least one, and maybe both, were used on the Z axis. Now I know why they didn’t last.)

I never noticed there’s no current resistors before because they’re installed on the bottom of a circuit board. Often the bottom of things is not visible from above, and that was the case here. I put in resistors to limit the drivers to 5A.

That made the Z axis run better, although I didn’t test it fully because it was getting late. I’ll check it out more carefully tonight.

It may be usable, but consider it marginal, and don’t waste expensive materials on it. I wouldn’t trust it for anything important.


Thank you for finding time to look at it @RealCarlRaymond! Although I’ve not officially used the machine I sure just learned a lot about it!
In the interest of learning more, do you think that running lower amps may help the overheating issue? Or is that caused by something completely different?

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I set the current limit on the motor drivers to reduce the heat dissipation in the drivers by almost half. I’ll have to verify that the motors can still move the carriage, but I think it will be fine.

If you mean the spindle overheating, unfortunately this won’t help with that issue.

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If it helps any i have 1cm square heat sinks and thermal adhesive. Maybe it could help stop components cooking

@RealCarlRaymond Am I understanding correctly that if I want to use it on a project where I don’t care if it gets ruined I can go ahead and try it?

Any update on the CNC? The one day I was there and turned it on I couldn’t get the green power light to stay on even though both safety switches were not trigged.

I know @RealCarlRaymond ordered the replacement part. Last I heard, he was expecting it to be running again by the end of this weekend

The part arrived, and tonight we installed it. The CNC machine is running again. We didn’t give it an extensive test, but we ran a small job, and the Z axis sounds much happier now.

Thanks to @zimmer62 and @jody for the help tonight getting it installed.