Single pulsing stepper

I'm hoping someone can help me or point me in the right direction. I posted this in a different section and it was suggested that you all might be better able to help. I just built a Prusa Mendel variant and I'm having a problem with the extruder stepper motor. On the first day it ran acceptably and with a little calibration work I got it to print a nice calibration cube. The print would only work halfway and everything would stop. The printer stopped accepting commands from Pronterface and the only way I could reestablish communication was to disconnect the USB cable then reconnect. Today, my second day of working with the printer, the extruder stepper motor will not turn. It makes a thump-thump-thump noise as it jiggles back and forth, almost looks like half a step. All the other steppers are moving correctly. If I unplug the USB cable, the extruder stepper keeps thumping. The only way to stop it is to remove power.

I am using a RAMPS 1.4 board and an Arduino Mega. Also using Sprinter. But I don't think the firmware is the problem. I ran the RAMPS14 test sketch and all the steppers move back and forth except for the extruder one (still thumping). I've adjusted the pot but it only gets stronger or weaker. I've swapped pololu drivers and the extruder is still thumping. I've swapped the extruder stepper with the x-axis stepper and the x-axis stepper thumps. I moved the driver and the stepper to the E1 position and it still thumps. When turn the pot on the x-axis driver I can get the x-axis stepper to stutter a little, but not to the same extent as the stepper on the E0 or E1 and when I dial it back, it returns to normal.

So I believe the RAMPS or the Arduino might be faulty. I'm leaning toward the Arduino since the RAMPS is a pretty simple board with no microprocessor. Plus the previous problem where Pronterface would lose communication with the printer. Has anyone come up against this type of problem or have an idea how I can narrow it down further? I would really appreciate it. I was so excited to get this working and on the second day I am dead in the water.

I posted a video: [vimeo.com]

First I adjust the E0 trimmer to show how the vibration changes but doesn't stop stuttering. The E0 stepper is on the table, you can barely see the gear shimmy back and forth, but you can hear it knocking on the table. Then I turn the X trimmer to show how I can somewhat create the same problem on the X stepper.

Edited 1 time(s). Last edit at 07/06/2013 03:25PM by NightOwl.

Have a very similar problem with all of my motors. Anyone know whats wrong?

If it thumps when not driven then the current is set too high and the driver is going into thermal shutdown, cutting the power and then restarting when it has cooled.

If it is quiet when not driven and just vibrates on the spot when driven, then only one coil has power. Either a duff output on the driver, or a bad connection to the motor.

USB disconnects can be caused by a bad ground connection to the PSU.

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[www.hydraraptor.blogspot.com]

Thanks for the suggestions. I don't think it is the wiring between the motor and the plug because I can move the stepper plug from E0 to X and it works fine. I can move the pololu driver module from E0 to X also and the stepper connected to X works fine.

To add confusion, if I put a driver module on E1 and connect a stepper to E1, I get the same thumping vibration.

I used a soldering iron to reflow all the connections on the RAMPS but nothing changed. Your suggestion makes me think I should check continuity between the pololu driver socket and the E1 pins.

If that checks out, could it be a bad bootloader on the Mega? Someone suggested that I try reburning the Mega.

did you try doing a continuity check with a multi meter, you might have a bad ramps board.

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[mike-mack.blogspot.com]

Thank you for all the help. I had tried everything including deleting the Mega driver and re-installing. Tonight, I finally figured out what the problem was. It was a Windows or Java update. I'm not sure why it would be the case, but in desperation I used System Restore to roll my computer back to before I started playing with this printer. I noticed that two Windows updates and a Java update had occurred during this time. After it was done, I re-installed all the software including the Mega driver and the printer worked fine. I'm going to let the computer update each part separately and keep testing in between. Maybe it was just a glitch during the process or something is wrong with one of the updates.