Simple Metal Layer Shifting

Troubleshooting talk for software

Simple Metal Layer Shifting

Postby kman1863 » 2016-Apr-Tue-14-Apr

Hey guys, I've been having layer shifting issues in the x axis recently, and I've tried pretty much everything I can think of. GT2 belts are tight and have no worn-out teeth, digital pots are at 50% (which is where I've been told they're supposed to be, but feel free to correct me on that), I reflashed the firmware (board is a rev F4, by the way), all parts of printer are secure, and it doesn't seem like the x endstop is phantom triggering. Still, I get either gradually slanted parts or just outright misplaced layers (again, only in the x-axis). The first seems like a stepper current issue, but I can't figure out what, and the second seems like belt skipping, but it doesn't look like that's the case. I'm totally confused. I'm using Slic3r and Repetier. Any ideas would be awesome. I've attached a couple examples of what I'm talking about. Thanks!
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Simple Metal Layer Shifting



Re: Simple Metal Layer Shifting

Postby RetireeJay » 2016-Apr-Tue-15-Apr

First, check to make sure that the toothed pulley is secured properly to the motor shaft. This is a classic problem. There is a little hex-head screw (called a "setscrew" or "grubscrew" inside the pulley that needs to be tight against the center of the "flat" on the motor shaft. It takes either a Metric or Imperial hex driver; you'll have to try out different ones until you find one that fits because different manufacturers ship them with different screws.

With power on, and after a recent move, the stepper motor should be "locked" in place. If you try to move the bed manually, it should be VERY difficult to move in either direction. If you can move it, then it's probably the setscrew.

If it's not the setscrew, then the next likely candidate is misalignment of the rods causing high friction. With the power off, you should be able to move the bed fairly easily from end to end. You'll feel a little "cogging" as the poles in the motor move past the permanent magnets. If you are ambitious, you could detach the belt and check; with the belt disconnected the bed should move EXTREMELY easily.

If these two checks don't yield any fruit, then the next thing to do is increase the motor drive current. Go up in increments of 5 or 10 percent at a time until you reach satisfactory results or the motor gets too hot to touch. (You could also check your speed setting and especially your acceleration setting; if they are way too high, they might cause skipped steps.)
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
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Re: Simple Metal Layer Shifting

Postby cacb » 2016-Apr-Sat-01-Apr

search the forum for the issue with the clamps under the bed, holding the linear bearings. They are often loose and can cause this kind of layer shifiting.
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