Thanks to great ideas from you all, I’ve got a real solid clue in the continuing saga of my haunted Printrbot Simple!!
It prints normally up to 67mm wide (in X), but starts slanting at 68.2mm getting worse at 69.5mm.
This matches the diagonal prints working! And 80mm box at 45 degrees is 57mm in X, under the magic 67mm limit. Pretty neat.
Btw it doesn’t matter what the steps/mm are set to, it’s the physical size. I tried some nice even numbers like 144s/mm - results same as 139.5.
Just printed two “proof” tests using four 20mm squares arranged at the bounds of a 60mm square and bounds of a 70mm square. The 60 has vertical walls but 70 slants.
I’m going to try 68mm bounds with offset x=5 and x=25 tomorrow to see if there is more slant on one side of the bed.
Could a linear bearing cause this? What should I look for, push or poke? They seemed smooth without the bed attached.
And thanks for all the help.
Home your machine. Then, take a sharpie or a crayon and place a witness mark (http://growingupregular.blogspot.com/2006/08/witness-marks.html) on the various rotating parts before the print, and compare after each successive failing prints. The drift in the witness mark positions might provide a clue.
When you home again, you should be able to back out the drift on misaligned parts so that a set of marks are back to their original position.
I need to test this on my simple.
This might clarify why some smaller objects I print are fine but larger objects slant. I was thinking about testing a printed linear bearing too see if that would make any difference or maybe the two rods are not 100% alligned and cause pressure around 68mm.
BTW, is the simple the one where the fishing line is wrapped around a bobbin? As you reach the extremes of travel, do the lines continue to wind evenly?
I’d guess that it’s some sort of interaction between sustained fully accelerated moves and something slipping. Most likely the “belt” on the “pulley”.
On my simple, long moves would cause the line to slip. Tighten 'em.
Also pay attention to HOW the line wraps on the motor. Mine would be fine at one point, but the wraps “travel” across the tubing, and would bind at one end. You have to account for the travel, otherwise tightening will just make it worse.
BTW: I highly doubt the problem involves your linear bearings. Just keep the rods clean and lightly lubricated.
@Joseph_Chiu he has those strings so tight. I saw he was using a tuning peg to insure it is tight.
As I said, I have the same problem when I print near the extremes. If you want a quick debug method use a small cube and place it near the +x stop or near x=0. If my understanding of the problem is correct one of those all cause slant, the other won’t.
@Carlton_Dodd Line is wrapping nicely from end to end, 4 wraps. @Joseph_Chiu Have witness mark (a cut) on inner shaft to tubing - it stays solid. Haven’t figured a way to mark black rubber tubing to line position.
Hard to believe it would slip considering with near 20 kg tension on the string. The string is tensioned enough to make its outer surface even with tubing outer surface. Plucking give an A above middle C. Todays test with offsets in X could show if it’s acceleration or friction at a location.
Guess I can try the sanding drums again. They did slip on the shaft so have to solve that
@Camerin_hahn Agree. Hoping to do that test later this evening after work.
Best of luck, I think I will be getting a different printer and scraping this our for delta parts.
I have found my effective print area to be 90x85x110. The quality is fine, but the space is not adequate.
@Camerin_hahn I would be interested in seeing a post on what can be done with the Simple’s parts. Mine was only meant to hold me over until I get my RigidBot, so it may be repurposed at that point.
I dont plan on doing this now, but at minimum the motors and driver board are usable.the linear bearings should be able to be reuseed. My thoughts are new hotend, new extruder, reuses x/z/e motors and printer board for now. the wood will be trashed, along with the rods.
@Camerin_hahn why a new hot end? Plenty of self builds specifically use the Printrbot hot end because it’s reliable and affordable.
@Jeff_Keenan : He ( @Alan_McNeil ) replied a bit ago that he is using 4 wraps, and the string is moving smoothly.
