Strange print behavior, no Z movement during print.

Hi All,

I will start off this thread by saying that I have not finished my calibrations yet, but I don't know that the behavior I'm experiencing is a calibration issue. The issue is basically that the printer is not printing as if there is a Z axis, even though I can manually move the Z-axis through Pronterface/Repetier-Host. It looks like others have had this problem before, but my issue has the added flavor of it moving along the y-axis instead of just printing in one spot. I have attached an image to show this issue and hopefully clear up what I am saying. This was from one print with no Z-axis movement. The object should be a 20mm cube. I tried printing it with both Repetier-Host and Pronterface with the same results. I have also tried to print other objects and they appear to behave the same. I will attach my firmware and the .stl file to the next post.

Best Regards,
Toph

Edited 1 time(s). Last edit at 12/28/2013 09:17PM by tophstar.

Firmware and stl file.

i don't know about your Z problem, but the print 'appears' to move in the X and Y direction because without Z movement the nozzle will 'crash' into the filament on the bed causing the XY steppers to drop steps.

Thanks for the reply.

I just tried a dry print to see if it was the printed filament knocking the extrude around. It seems to be doing this "drift" with anything being printed. I am trying my best to calibrate the thing right now to prevent any skipped steps.

-Toph

Oh this is a Prusa Mendel i3 with Arduino 2560 Mega and Ramps 1.4.

After further work on it I do notice that the Motors slip when they get to the Endstops, but are eventually able to trigger the endstop. Is this an issue?

Hello All,

I am still experiencing this issue. Any more input would be very much appreciated. With regards to the last post, I slowed down my max motor speed and I am now able to trigger the endstops with out slippage. This issue really seams to be centered around the fact that the printer loses track of where it really is and prints in random spots.

Best Regards,
Christopher

You're dropping steps for some reason. Could be electrical if your stepper drivers do not have their current set properly. Could be mechanical if the axis is binding in some way.

To check the axis, remove the belt and see if you get free movement with no binding.

To check the driver current setting, it's a little thought. The original instruction to turn the pots all the way down (CCW) and the turn them back up 25% was just about right for me. One of my motors was running hot, but I found I could back off the driver a bit and still lose no steps.

One other thing to look at is top speed and acceleration. If your carriage it too heavy, and your acceleration is high, your steppers might not be able to stop the moment of inertia when the carriage needs to slow down or steed up along thet axis.