I am seeking for assistance with an issue I’m experiencing with my mpcnc. One of the motors, the Y1 motor, is not functioning properly. The motor is jumping rhythmically and the intensity of the jumping changes depending on how I move the Y-axis.
I have uploaded two videos demonstrating the issue. The problem starts shortly after I power the motors through Repetier-Host. Initially, everything seems fine, but after about one to two minutes, a faint clicking sound begins. As soon as this clicking starts, it gets progressively louder when I move the motors, as seen in the videos. The Y1 motor then starts jumping, which prevents me from using the CNC for milling.
I use a Rambo 1.4 and nema 17 motors
[Edit:] Change links
I would appreciate any advice or suggestions on what might be causing this problem and how to fix it. Have I missed something in configuration?
Either: make up a new wire and run it from that stepper to the controller.
Or swap that stepper with another and see if the problem stays (wire problem) or moves (stepper problem)
It’s not impossible that it’s the stepper but it’s far less likely.
I had similar issues, but a bit less subtle. It turned out to be a poor connection where the stepper motor wire connected to a 6-pin extension cable. It looked fully seated at first glance, but unplugging and re-seating the connection solved the problem
I have tested the cables, and they all look very good and seem to be working fine.
I swapped Y1 and Y2 so that I could directly test if the error then jumps to Y2. It did.
Then I swapped the cables between Y1 and Y2 in the control box and found that Y1 in the Rambo Board always causes the problem. Can i do anything or is the Board destoyed?
Hey, here is my setup. In another thread, I mentioned that I now have time to measure.
Here is my setup:
1. I exchanged male connector 1 with male connector 2.
• Result: Stepper Y1 works fine and stepper Y2 is now the one that wiggles.
• Conclusion: This means the outer cables are fine.
2. I exchanged female connector 1 with female connector 2.
• Result: Stepper Y1 works fine and stepper Y2 is now the one that wiggles.
• Conclusion: This means the inner cables are fine?
Based on this, I think the Y1 driver might be damaged.
What can I measure or test? Is there something I could be missing?
Let’s start with this. At the rambo board, measure the Dupont connectors for each stepper.
I’m going to steal a picture from a different thread, so the board shown below is a jackpot not a Rambo. But the pin numbering is good enough.
For each stepper in your setup, take these measurements and report:
Resistance measurement, pin 1 to 2: ____________
Resistance measurement, pin 3 to 4: ____________
Resistance measurement, pin 1 to 3: ____________
Resistance measurement, pin 1 to 4: ____________
Resistance measurement, pin 2 to 3: ____________
Resistance measurement, pin 2 to 4: ____________
I noticed that y1 and y2 are very low, but y2 is lower than y1, and y1 is fluctuating. I switched the y1 and y2 cables inside the machine box, and the measurements improved slightly, maybe by 100-200 kΩ. So, as you told me, it could be the wiring. I took another set of measurements directly on the steppers for y1 and y2. The 1-2 and 3-4 measurements on y1 and y2 are 1.2 ohms, and the rest are not measurable, or better said, show infinity.
Obviously, I had to rewire two or possibly all of the motors? At what point in terms of resistance (ohms) does it become critical for the motors, causing them to begin to jiggle?
My next question is, what kind of wire should I use? The wiring process was difficult. I used ÖLFLEX with a 0.5mm diameter. This is connected with a Dupont connector, not a simple plug-and-play solution. I did some research and found a LiYCY wire with a 0.34mm diameter. Should I go with a smaller diameter, or is this suitable?
Also, what is the best method for stripping the wires?
Frankly those numbers aren’t bad. Your stepper coils are 1.2 Ohms, and there’s good isolation between the coils. There’s only .3 ohms of additional resistance in the extensions, which isn’t terrible.
For the steppers that are misbehaving, can you wiggle the connectors at the extension spots while you have the meter measuring a coil? I suspect you may have an intermittent connection at the place where the extension cable plugs into the stepper cable.
Let’s understand if you have an intermittent connection before we go off and rewire anything.
It turns out that Y1, with a wiggle on the wire, has a good connection. It stays at 1.5 or 1.4. However, Y2 is now the one showing resistance between 0 and 4 ohms when the wire is wiggled directly near the first Dupont connector close to the stepper.
Edit:
I just measured again. When I disconnect the cable from the stepper motor, I’m left with only about a 10 cm long cable coming out of the stepper. When I measure and move it around, the readings are relatively constant between 1.3 and 1.2 for both motors (y1 y2). However, if I wiggle the cable directly at the stepper’s input, the readings change for both motors. I would also say, without measuring, that is also the case for X1 and X2. When I plug the Dupont connector back to the Long wire, I measure a significant difference between 0 and 4 ohms. So, what does this mean? Is it possible that the extended cable, specifically the Y2 cable, is faulty?
Edit 2:
I did some more Tests on the milling machine today and took another look at the setup. I connected everything, but the coil whine is still present in the Y1 motor, and the clicking noise eventually starts again as well. I tried wiggling the cables a bit, and the coil whine changes on Y1. All the other motors, except for Z1, are working perfectly. Z1, however, has almost completely stopped functioning since I connected everything today. It only moves in one direction and stutters intermittently. I have no idea what the issue could be.
