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Post by chiliarch on Apr 3, 2016 23:45:32 GMT
Hi Everyone Just got my printer up and moving, but I haven't been able to pass the 'X-Y Break-In' file without skipped steps and binding. Here's what's going on:
Any time the printer makes a crossing move: G1 X0 Y0 G1 X200 Y195 .. or .. G1 X200 Y0 G1 X0 Y195 at any speed over F10000, there's some degree of binding. At F12000 this is just annoying harmonics, but at F18000 it will flat out fail and skip steps.
I've gone through the forums and done the following things: 1) Trammed out the Y-axis rods so that they are parallel to within ~100microns 2) Lubed the rods with low cpe oil 3) Leveled the pulleys and sheaves on the y axes. (There was some rubbing on the screw heads of the shuttle) 4) Tried several times to square the X axis, and have ensured that the rods are in fact perfectly parallel
FWIW, this binding is present whether moving under power or by hand. By hand it's enough friction to slow (not stop) movement, and has a "zipper" feeling to it, like it might be related to the belts. I'm wondering if perhaps this is a tension related issue.
Anyone have any suggestions? Thanks in advance
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Post by scottadams on Apr 5, 2016 0:59:47 GMT
Was it binding before you put the belts on? If not, maybe it's power related - either stepper currents set in the Azteeg config or power supply not putting out enough? Belts tension could be off. Are you sure the grub screws are tightened on the stepper sprockets? I'm too inexperienced to know anything else. Best of luck.
BTW, I get the "zipper" feeling on mine, but I'm quite sure it's the stepper steps themselves like when you move a stepper by it's shaft, even when disconnected from everything.
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Rick
Junior Member
Posts: 75
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Post by Rick on Apr 5, 2016 1:37:29 GMT
I would make sure that each individual part slides smoothly on its own. I would start and check each of the individual parts. Disconnect the belts and unscrew the X-axis rods and remove. Take each of the A15 sliders and make sure that they each are absolutely free. Now take one of the X-axis rods and make sure that each side of the A1 carriage is also free to slide along the rods. Any binding that you have at this point needs to be resolved.
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Post by chiliarch on Apr 5, 2016 3:31:44 GMT
Thanks for the replies, gents.
Last night I decided to tear everything back down, just to be sure I wasn't missing something fundamental. All changes mentioned above had been done with belts on; I wanted to ensure there were no basic mechanical issues with tension off.
The Y axis was silky-smooth. So much so that I could probably put a bit of pre-load between the A15 sleds. it was running well, so I decided to leave it as is.
The X axis was less smooth. There was noticeable drag towards both ends of the stroke. I cleaned this up as best as possible, loosening the ends and rotating the rods. I'm not entirely sure whether there was a torque on one of the rods, or if one of them has a slight bow.
I then went about putting the belts back on, this time relieving some tension. In all I loosened the belts by a total of 4 teeth (2 per side). This alone seemed to make a difference. I did notice that small differences in tension between the belts made a BIG difference in square of the X-axis. Finding #1: I think it is very possible that small differences in drag on the belts pulls the X-axis in to a parallelogram, causing binding in the bushings of A1.
I also noticed that I had a considerable amount of slop in the bushings of A1. So much in fact that I could get some substantial rotation of A1 about its Z-axis (picture twisting of the carriage). I was able to replicate the binding/stuttering I was seeing by manually moving the X-axis while twisting the carriage. I'm pretty sure I caused this fault - I was probably overly aggressive in cleaning up the prints before pressing in the bushings. I corrected this be forcing apart the X-axis rods into a preload. Seemed to work more reliably than squeezing the rods together. Finding #2: Any rotational slop in A1 is liable to induce binding when the carriage is furthest from the drive pulley.
At this point things are running pretty smoothly, but I can still get the G1 X0 Y0, G1 X200 Y195 move to cause a lock-up if I command it at full speed. I suppose I may just have to live with reduced printer speeds until I can print a new copy of A1 and try tightening things up.
To that point though, has anyone arrived at a technique for keeping the rods parallel while inserting the bushings into A1? Seems anything less than perfectly parallel would result in an over-constrained system, no?
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