Another Taz 5 out of round question

General LulzBot TAZ
1

I have a puzzling out of round problem. I’m currently printing mating herringbone gears and noticed that one axis is pretty significantly larger then it’s perpendicular axis. This troubled me because I did quite a bit of calibration to get my prints as accurate as possible.

So out of round tells me that something is loose or that one of the axis steps are off. The puzzling part of this problem comes from the fact that the large/small axis are both 45 degrees off from the x/y axis on the printer. They are parallel with the infill direction of the print.

This tells me that either the x or y motion command is being sent to the printer before the other, causing an offset due to mistimed x/y motion. I could very easily be overthinking this. Please let me know of anything that could cause a 45 degree oval…

I’m at work at the moment, so I can’t attach any information about the print. I have only tried using Cura, but was planning on seeing if Slic3r had the same problem when I get home this evening.

The measurements of the printed gear are as follows. I’m not sure which is the x axis and which is the y axis because it’s a circle and I didn’t know there was a problem until I pulled the part off the printer and put it in the enclosure.

X and Y axis outer diameter: 57.63mm and 57.60mm
45 degrees off from X and Y axis (parallel to the infill axis): 57.14mm and 57.97mm

I got my Taz 5 for Christmas and have been tinkering ever since. I have the OpenRail X and Y axis mod installed, the Taz 6 extruder (version 2.1), the improved extruder mount, anti-z-wobble thingies, and I think that’s all so far. I printed these gears at between 30 and 50mm/s in all the speed settings in Cura. Everything looks beautiful, there’s just this weird oval-ness at 45 degrees.

Tonight I’m going to try to print these gears from Slic3r. Then I’m going to try to print the same gear multiple times, but rotate it 45 degrees each time to make sure it’s not a problem in my model. Then possibly try printing the same gear in multiple places on the build plate to see if that changes anything. Not sure what else to try.

2

Interestingly enough, I may have just figured it out. I printed dozens of calibration cubes while working on all the mods and fine tuning the x/y steps. Looking at those cubes it appears that my x and y axis are not perfectly perpendicular. The cubes align next to each other perfectly with the z axis up, but if I flip them on their sides there is a slight gap between a cube with the x axis up and a cube with the y axis up. Withe either x/x or y/y up they align perfectly.

So my calibration cubes looking at them from top down appear to be parallelograms instead of squares. I’m not sure exactly how I’m going to be able to fix such a tiny angle offset between my x and y axis, but at least I have a place to start now.

3

Well I got home and wouldn’t you know it, not nearly perpendicular. Shored things up and ran another set of gears to test. The new gear has measurements across the board of between 57.65 and 57.73 mm. Not perfect, but acceptable for what I’m working on. Hopefully I don’t have to re-calibrate the x/y steps.

So another puzzle solved. Hopefully this helps someone else who may have this problem sometime in the future.