Taz 4.5 print quality issue

I’ve got an issue affecting my last dozen prints that I haven’t been able to figure out.

The photos will serve as the best description. It seems as if each layer, starting about 1cm off of the PEI surface, is offset 3mm or so in either direction in an alternating fashion. By that I mean that it looks like layer 41 is printed at a Y offset of 3mm and layer 42 is printed with a -3mm Y offset. Strangely this only occurs on the “lower” half of the build area – lower meaning from Y0 to around Y130.

Note that the photos depict a single part, not two. You can see how the issue is only affecting part of the print area.

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• Ensuring that the two cables running to the build surface are moving freely and not snagging
• Checking to make sure all belts and bushings are moving smoothly
• Made sure the nozzle is not clogged

My setup:

• Taz 4 with upgraded hexagon hot end
• Lulzbot Village Plastics red PLA 3mm
• Sliced with Simplify3D 3.0.2
• 0.25mm layer height / 205C temp
• “full honeycomb” infill at 70%, 15% outline overlap

I’m inclined to think that it’s not the gcode since the generated paths look as expected in a previewer. Any ideas? Anyone else experienced this before?

Thanks

Since the piece next to it looks ok, its probably not belts or pulley, but check those anyways. A loose pulley setscrew can produce strange motion.

It could be a small layer size area cooling issue as well. The part showing issues is smaller. Maybe up your cooling fan a bit?

Thanks piercet. I will check the setscrews and belts again. Note the photos shown are not two pieces but one, which makes me doubt that it is a cooling issue. If you zoom in on the photos you will see the problem affects every other layer. Very strange. This part was printed with the fan at 100% starting on layer 2.

I think you have a belt issue. Maybe it is or has a damaged tooth or two on its travel length. Or a bad stepper motor. I have seen some strange prints when the shaft is starting to break.

I suspect that you are both right about the belt being the cause. The more I think about it the more likely it seems. I’ll report back after I check tonight.

I should have asked here sooner! Great suggestions. I noticed the belt was very tight and that the set screw on the Y stepper was slipping. Loosened the belt and tightened the screw et voila.

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