I’m working on using dual endstops on my MPCNC (classic version) and am using some A4988 drivers for the steppers (can’t find the link to which ones in particular). Everything is working great except for when one of the axis. One of the motors runs faster than the other (https://photos.app.goo.gl/mssq6ehavScnYpwg7) causing the axis to bind. I tried switching the drivers on each axis and found that the issue also switched axis, leading me to believe its a driver issue. The voltage on both of the drivers is .8V (https://photos.app.goo.gl/Fu9nKDCKVhPj9YWs7). I’m using the MPCNC with dual endstops software found on github (Ramps,T8,16T, LCD, DualEndstop version). Here’s the link to the steppers I’m using (https://www.amazon.com/gp/product/B07BKRWK1Q/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1).
So my question is this: what could be wrong? Is the slower stepper driver broken? How do I test to see if a stepper driver is broken?
I double checked that while swapping the drivers running each axis and the steppers worked fine with the other axis’s drivers so I doubt the microstepping pins are the issue.
Each stepper motor has it’s own stepper driver so that the machine can zero both motors independently and ensure everything is perfectly square when I start a job.
I was able to identify the driver that’s causing problems but now I’m at a loss of what to do. Is there a way to decide whether the stepper driver is broken and if it is, if it’s repairable?
I’m just guessing. That’s where I would look, even though if you used standard firmware and didn’t do any changes, it really points to a hardware problem.
In the ramps, the firmware doesn’t know anything about the drivers. It doesn’t control microstepping or the current limit.
It sounds like it is broken. I highly doubt there is a way to fix it. It is weird that it is going slower. Are you sure it isn’t just off completely and getting dragged by the good side?
You said the slowness followed the drivers, so I assume it can’t be attributed to wiring or the pulley grub screws getting loose?
From the first video this is what I suspected too.
Take off the belts on the motor acting bad and the opposite one, and put tape or something so you can see it spin. This should be conclusive as to whether its moving slow or not at all. You can also feel if it has any holding torque.
Stepper drivers are cheap. I keep extras. (Also I blow them up.) That is a fairly straightforward way to check if the driver itself is bad. Or with the belts off you can unplug and swap the drivers in their sockets and see if the problem moves.
Thank you all for the advice. I’m pretty sure it was just being slower but I’ll verify that with the belts off (as Jamie suggested) in the morning and will post a video at that time as well.
Either way, I think I’ll be getting some extra steppers just in case this happens again so I can at least test it.
Alright, I finished testing everything and this is what happened:
Without the belts, the stepper driver still worked and, oddly enough, it was somehow faster than the other stepper today. Here is the link to some videos on it: https://photos.app.goo.gl/JokFAsUyC3M7ZVqd6
Something I should mention is that I concluded that the other stepper was broken (I pulled it out of a pile of parts and I think the others are fried as well since one lit my board on fire, which I fixed). I found the stepper I used today alone in another pile. What this means is that the axis was getting dragged by only one motor like Jeff suggested.
I ordered some more drivers so once those come in I’ll be able to do an update.
The drivers came in and I ended up finding out that not only was one of the drivers acting up as I expected, but one of the cables for a stepper got disconnected, meaning it only had one phase and couldn’t work!
I guess that’s how these weird problems come up. When two small problems are happening at the same time.
Thanks for everyone’s help!