Single shaking/ vibrating Z axis motor
Hello, I just wanted to post to ask if anyone knows a few things about the motors on the z axis. I haven't yet calibrated the printer as i noticed a jarring problem at the outset: the left axis motor seems to raise and then lower again by about 1mm continuously when asked to go in any direction. It also does not get as hot when the device is powered on, yet it does have torque when turned on. I have checked that the wires are set into the connector properly, yet I don't have the knowledge as of yet to tell if the wiring is loose in the motor (although having opened the four screws and taken a peek, it doesn't seem to be the case). Since I have had some experience with nema motors, I know it is risky business to disassemble it further without prior knowledge and would very much like to avoid doing so if possible.
The effect on the z axis is that it can still move up and down, yet one half of the carriage "drags" , causing it to skew (and be in a constant state of skew) as it fights the other motor.
If this is a busted motor, which nema motor can I order as replacement? even within the nema 17 category, the specs vary enough and i'm not sure which are relevant to achieve correct correlation between the 2 z axis motors.
Any help would be appreciated, this one has me stumped .
EDIT: Checked the motor when plugged into the other axis slot and the extruder slot. Doesn't work in either one, does the same thing.
Re: Single shaking/ vibrating Z axis motor
Shea
Check that the cable is not trapped anywhere, especially where the motor is mounted if you have the wire outlet placed towards the frame.
You may find that one of the wires is broken.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Single shaking/ vibrating Z axis motor
Thanks for the reply, Peter. Having checked the wires, the only difference i see between the 2 z axis motors is that the cable on the blue cord has a very small abrasion that doesn't compromise the wire casing (that is, only a small shaving of the casing is missing, and the wire is still fully encased by it.) Is something that small capable of interfering with the connection?
Note: I just recalled something that i went through at the beginning of the assembly process. When i first opened the case containing the motors, one of the z axis motors (which may be this one, I'm not sure now) had its drive shaft 1/2 way out of the motor casing, so I pushed it back into it. I didn't think anything more of it at the time, but i don't know if these particular nema motors are different from the ones i have had experience with using the cupcake cnc from a few years back.
Thanks for helping me sort though this.
Shea
Edit: Also, i noticed if i manually move one, it also moves the other, yet both directions i can turn the faulty one lead the other z axis downward, if i try to turn the functioning z axis motor, the faulty one does the same vibration at a slower pace.
Re: Single shaking/ vibrating Z axis motor
Reseating wires into the connector for the z axis solved the problem temporarily, yet as soon as i hooked both motors back up to the printer together, the problem resumed. The left motor stalls/ vibrates instead of turning.
Still trying to figure it out, yet i can't understand where the finicky nature of this motor is coming from.
Re: Single shaking/ vibrating Z axis motor
Shea
I still think this is a cable issue. You may want to contact support - use "Live Chat" on the shop pages and give them a link to this thread.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Single shaking/ vibrating Z axis motor
Peter is right, a power issue and possibly a cable issue. At first, Common cause. Maybe check the tightness of your main power connections to the RAMBO board. If a motor try swapping some around and see if the problem moves. Ie swap your Z axis motors around. They should be driven equally. Swap the Z axis motors around on the RAMBO board. And see if the problem moves. If it moves, you have a faulty stepper motor. Check the connectors to it first, ie are the pins fully located and not bent over.
Sorry late at night here. I see you have tried some suggestions and fault finding techniques in the past.
Nigel
Life is keeping interested and excited by knowledge and new things.
Re: Single shaking/ vibrating Z axis motor
Thanks everyone, i recently looked at the connector pin and realized that the black cable was twisted maybe 20% to the right, and removing it and re-aligning it solved the problem. It's amazing how finicky the wire was. It really has to be in there 110% to connect to the board. Thanks for all the help everyone 
Re: Single shaking/ vibrating Z axis motor
So shea.l a bent pin 🙂 A cable fault as pjr said in the first place 🙂 And I pointed out about also in the end.
My comment above "Check the connectors to it first, ie are the pins fully located and not bent over."
Nigel
Life is keeping interested and excited by knowledge and new things.
Re: Single shaking/ vibrating Z axis motor
Sorry, I took that to mean a broken/ torn cable at the motor end 😳 . Thanks for all the help though guys :D.