Visualizing the XY axis
Since I got the MK2, I've been thinking of good ways to estimate the accuracy of calibration.
I have printed as many as seven one cm side cubes. I am not very convinced by the results on that - my measuring instruments are inexpensive, and don't provide very consistent results. What if I could use the grid on the bed itself to reveal the problems ?
A few days back, I hit upon the idea of drawing the grid lines. I wrote an OpenSCAD script for this. The zip attachment contains a the script, STL model, and gcode (for PLA at 210 degrees, 0.2 mm layers sliced using Slic3r).
It takes about 10 minutes to print at default settings. I printed with red filament, then with white filament for better contrast on the heat bed. Then photographed the bed with a tripod mounted camera. The high resolution picture (24 MP in my case) captures the slightest misalignment easily. I have attached the high-res image to this post.
Clearly my XY is off by a bit. But there other interesting jumps happening at Y=105 and Y=55. I haven't been able to explain them yet.
Re: Visualizing the XY axis
But there other interesting jumps happening at Y=105 and Y=55. I haven't been able to explain them yet.
I guess loose screws in X-motor pulley. If it is loose only little bit, it causes shifts in X dependent on actual direction of drawing moves.
Re: Visualizing the XY axis
Be careful when relying on the lines printed on the bed; some of the lines on my bed are not straight when the bed is hot.
I found this out when eyeing up the frame to check it was square; a couple of lines were OK in the centre but bent forward at the ends.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Visualizing the XY axis
I guess loose screws in X-motor pulley. If it is loose only little bit, it causes shifts in X dependent on actual direction of drawing moves.
I will check this. Thanks for the hint.
Be careful when relying on the lines printed on the bed; some of the lines on my bed are not straight when the bed is hot.
I will check the lines a combination square. Just to confirm : Are you saying that the lines are straight when cold and that they bend when the bed becomes hot ? That will be interesting.
Re: Visualizing the XY axis
(Updating here after a long time.)
I was able to debug and fix the X axis "jumps" at Y=105 and Y=55. I figured the belt was going over the pulley & causing a slight X axis jump. Due to this, the head wasn't able to reach X=250 smoothly.
I trimmed a cm or so off the the X axis timing belt on the right side of the extruder - and that fixed it... The grid printed by my MK2 is now smooth & square, and without discontinuities.