Bed Dropping

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terrymcc
Posts: 21
Joined: Thu May 29, 2014 12:23 am

Bed Dropping

Post by terrymcc » Thu Oct 21, 2021 12:01 am

I am having issues with the bed dropping during a print and creating a bird nest. I have an early M2 and it was a reliable workhorse for years. No issues. A little over a year ago, I did a major upgrade to all current hardware and firmware. Not long after that, this issue started. I worked with Garrett and Jason of MG support for a couple of months. I replaced the Z motor twice, the controller board, firmware, wiring harness, and tested power supply voltages. If I disable motors, the bed drops like a rock. I also removed the drive screw and the bearings glide very smooth. I finally gave up and put it in the closet and bought an M3 ID. I have now brought it back out and am trying to get it to once again print reliably.

Jason indicated to me that the motor is marginal and if it meets any resistance, it cuts power. He says it has always been that way, but I swear that in the early days if it came up against resistance it would sit there and hammer like it does in X or Y and Z in the down direction. Does anyone else remember it that way or am I wrong. I wish I could disable this "feature". I would rather risk breaking something than keep fighting it.

I also tried slowing down the max Z speed. I can't think of anything else to try.

Are there any new developments with this issue? Any input would be much appreciated.

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ednisley
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Re: Bed Dropping

Post by ednisley » Thu Oct 21, 2021 2:15 pm

terrymcc wrote:
Thu Oct 21, 2021 12:01 am
A little over a year ago, I did a major upgrade to all current hardware and firmware. Not long after that, this issue started
Measure the winding resistance. If it's more than a few ohms, they sold you a crap replacement motor:

https://softsolder.com/2013/04/10/maker ... per-motor/
https://softsolder.com/2013/06/28/maker ... ransplant/

You can get a better motor+leadscrew from Amazon.

Verify the maximum extruder motor current is set to something similar to the other motors. The motor should be warm; if it's scary hot, then it's likely the old-old crap motor.

Reduce the maximum Z-axis speed and acceleration to 10% of whatever they are now. If the platform now works properly, increase the speed by factors of two until it stops working again, then back off by a factor of two.
it cuts power
The RAMBo controller has no way to know the motor has stalled, so there's no way it can "cut power".

This has been beaten to death over the years; searching the forum will unearth many many useful threads …

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