E Axis Jitter/Whine - Faulty Stepper Driver?

Hello,

I am building a RepRapPro Mendel with a club at my school and we have just finished assembling the printer. We are on the "commissioning" step on the RepRap Wiki page for the Tricolour Mendel, and we have gotten all the axes to move smoothly, except for the E axis.

At the beginning of our tests, the E axis whined and jittered. Without the large gear on the extruder drive (mini-extruder), the small gear turned with jerky motions. With the large gear inserted into the small gear there was no movement at all, only shaking and whining. We interpreted this as being too low of a current setting, so we raised the voltage measurement on the current setting potentiometer to the maximum recommended amount of 0.6V (Referenced Page). Unfortunately, this did nothing to stop the jitter of the motor.

To see if the motor was damaged, we switched the wiring on the X and E stepper drivers so that the extruder's stepper motor would run off of the X stepper driver, and the X motor on the E driver. Under these circumstances, the extruder drive ran smoothly, but the X carriage began to shake about without moving. It was at this point that we assumed that the controller board, a Melzi, was the source of the problem.

There is nothing wrong with the board as far as we can see. All of the screw terminals are soldered on well, and the connections with the stepper motor wires are sound. The board communicates with the computer, heats up the heated bed and the heating block, and runs the X, Y, and Z axes without any faults. It would seem as if the E stepper driver on the Melzi is not functioning correctly. Is there any way that we could test this to be sure? If this is the problem how could we fix it without having to buy a new board?


I have attached a picture of the E stepper driver on the Melzi board. Below is the link to a video of the X axis hooked up to the E stepper driver, showing the jittering movement that I describe. I apologize for the bad word at the end of the video. It is a bit frustrating being so close to printing, yet having to deal with this possibly expensive problem.

Link: http://www.youtube.com/watch?v=B0i8akUpAlU

I should add that during our tests without the large gear placing a load on the motor, the motor turned in a consistent direction. The only real problem seems to be too little current being given out by the stepper drive, but the current level is set at its recommended maximum.

The wiring on the Stepper could be incorrect.

Switch pin 1 and 2 or 3 and 4.

We switched the pins, and there is no difference. The motor turns in the right direction (not smoothly though) if the extrusion speed is set high enough (500mm/minute), but there is no torque.

I do not think that low current is a problem now either, because the same jerking problem occurs from a range of 0.4 to 0.65 volts. When I tested it at 0.35V, the motor just whined, without moving about much.

Whoops, misread first post.

Edited 1 time(s). Last edit at 06/01/2013 10:23AM by foshon.

Did you ever get your problem solved? I'm having a similar problem with my extruder motor as well.
but yet it also runs fine on another axis.

I'd bet that a 6 month dead thread isn't going to get much traction, even more so when all the posts are within a day or so of each other. You probably would do better starting a new thread.

If the motor runs fine plugged into another axis, then it's not the motor. If you swap the driver boards, does it follow the board or the socket on the Ramps? If it follows the driver, then spend some time seeing if there's a bum solder joint on that driver. Also double check (or triple check) the Vref settings. If it's always the extruder socket on the Ramps, check the solder joints and connectors on that socket.

Uncle Bob, it's not a ramps set up, but a Melzi, so the drivers are all integral on the same board and can't be swapped around in the way you suggested unfortunately.

For what it's worth (more for future reference if others are searching in future, since I appreciate this is an old thread...), but my Melzi has a vaguely similar fault it seems today.
I also have just got my machine set up ready to try a first print, and the X axis has begun only moving in one direction. I've tried lots of things and can confirm the motor is fine, and that it's not the PC either, so I have to assume that my almost new Melzi has developed a fault with the driver for this axis. Odd in my (limited) experience for a motor driver to fail partially like this, I'd expect it to go completely if it's bad, but I can't see what else it could be.

A bit upsetting though as this will set me right back. I can't afford to just pay out another £50-60 for a replacement board when I have already spent so much.