I finished building my MPCNC a few weeks ago and It’s been working awesome! I’m super impressed with it, I’m even helping a friend build another one at the moment.
I have only had this one issue though.
I’ve seen people have issues with the Z axis falling down on here before, But I’m having mine fall down mid-cut.
The Z motor is shutting down and plunging the router into my piece.
The X and Y motors keep on going, dragging my now overloaded router through the piece.
It’s only happening on this last job I have been doing, and it’s the biggest thing I have done so far.
My theory is that because it takes so long to do 1 layer, the Z axis is going into standby.
If anyone knows how to fix this, I would be forever grateful.
I don’t think the Stepper Driver should be overheating, The Z axis is doing literally nothing for a few minutes, stepping down 1mm then going back to doing nothing for ages.
The motors and drivers still use the full amount of current even if they are just holding position. But you are probably right, they are probably not overheating. You can make sure, next time you run a long-ish job, after a while just feel the drivers and you will get an idea.
Hey @finchy. I have exactly the same problem with my machine.
I just wanted to dig this post since its most relate before I open a new one.
The falling time is not predictable. It sometimes falls and sometimes doesn’t. I use cooling fans and measure the Z driver (Pololu DRV8825 High Current) temperature and it reaches 50 degrees maximum as other axies.
So couldn’t solve the issue yet. Did you catch any other clue since May?
The original problem really sounds like an overheating driver. Try reducing the current setting. Keep in mind, the current is being used even if it’s not moving. Also, if it is a drv8825, I would also suggest trying another one, swapping it out for another axis
And just to be clear, you need to set the current on every driver before using it.
My steppers are 1.5A so I set vref to 750ma according to instructions set by Pololu. Do you think this value is overrated? Also I already tried swapping drivers and no luck.
I’m another with this issue. With me it starts after a few minutes. I’m running the mini-Rambo board (from Ryan).
In my garage it’s currently almost freezing, so that should be an ideal climate. Can it be a “current” thing on the mini-Rambo. I thought it was kinda plug-and-play since I bought it here.
My MPCNC has got the same issue with the Z-Axis. I use the Arduino uno with the CNC Shield and the drv8825. After check the voltages for all 3 drivers I found out, the voltages aren’t @0.7V .
After reset all Drivers to 0,7V my MPCNC works fine.
Thankls to [Jeffeb3]
I was having a similar problem with the Z - axis always going down. I have a RAMBO board and pulled my Z axis connector from one slot on the RAMBO board to the adjacent slot which is also for the Z axis. This seems to have fixed it for me. Time will tell I suppose.
