1 (edited by the_alteran 2013-08-20 18:36:30)

Topic: another Y-axis calibration

hey guys,

I know this issue shows up a lot, but I've been racking my brains over this for the last two weeks and I can't seem to fix it. I've tried the circle calibration at least a half dozen times and rechecked the screws and belts; I even tweaked the code to see if it would fix it, but noth'n'. I figured you guys might be able to lend some insight.

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2

Re: another Y-axis calibration

Depending on how small those circles are (i'm assuming pretty small) they look halfway decent if not perfect.

Can you clarify what the problem is?

I could totally be overlooking it

3

Re: another Y-axis calibration

Its not printing true circles. its not traveling far enough in both Y directions to round out the circles.

I've been using this print from thingiverse to test the calibration thing:12259

sorry, for some reason I can't submit links

4

Re: another Y-axis calibration

Yeah. Those are crappy circles now that I relook.

Do you have a fan on your Pololu drivers? I had some problems on my y-axis because I forgot to plug in my driver cooling fan.

5

Re: another Y-axis calibration

I don't think I do just the basic SD3 setup

6

Re: another Y-axis calibration

Looks like belt slop between your y stepper and jack shaft. Tighten down on your stepper. Too much and you bend the shaft tho.

7

Re: another Y-axis calibration

i've tightened it down to where the shaft is ever so slightly bent. I still got the same issue sad

8

Re: another Y-axis calibration

Don't tighten it that much, that can be equally problematic. 
Err...Yeah. tricky advice, right.


Can you see about pointing a fan of some sort at your controller board to rule out the y-axis overheating? Another solution would be to slightly reduce the y-axis current potentiometer, but that's trickier and you'll have to pull out a voltmeter.

9

Re: another Y-axis calibration

Like Tomek says don't tighten it too much... as this actually stretches the belt slightly which gives more error. Because of the design of the belt the recessed flat spots can become elongated increasing backlash/slippage amount. Some people have switched to GT2 belts which is supposed to have better performance in these areas.

10

Re: another Y-axis calibration

the problem is consistant regardless of how long the printer has been on, so I really don't think that board temp is really an issue. Switching out the belt might work, do you know what I need?

11

Re: another Y-axis calibration

If the belts are properly tensioned then it could be that your y carriage is sticking. Grease rods and work back and forth until smooth. Also, be sure your front idlers have grease. Mine didn't. Finally, play with the long y belt tensions.

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Re: another Y-axis calibration

I've tried everything except for greasing the front idlers, I'll try that and see how that goes.

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Re: another Y-axis calibration

Are your grubs tight on the pulleys? Only on jack shaft and drive, not the idlers!

14

Re: another Y-axis calibration

actually i do have the same problem with my SD2 since the beginning.
I tried every calibration method found and still the same problem.
I also purchased a pocket scale to measure the belts tension.

Replaced Y-Axes motor, changed the stepper driver to a   SureStepr SD8825 Stepper driver with 1/32 microsteps, changed the pulleys and belts of the Y-axes carriage with HTD Synchrobelt profiles.

All this didnt change a thing.

Maybe it is the Steppermotor shaft that is not parallel with the y-axes top shaft. Because when Im tightening only two of the four steppermotor screws it gets a little bit better.

15

Re: another Y-axis calibration

Maybe it is the Steppermotor shaft that is not parallel with the y-axes top shaft. Because when Im tightening only two of the four steppermotor screws it gets a little bit better.

Was this the issue? Were you able to fix it?

16

Re: another Y-axis calibration

i think it is one of the issues i have. I tried tightening only one screw at a time and do have a better print now. I will try to eliminate the possible source of errors by mounting the motor shaft directly to the Y-axes shaft with a rigid or flexible coupling. Maybe someone else can test this too. I will do it when i have the time.

17

Re: another Y-axis calibration

After some testing last night, it looks like this same issue for me. The frame looks slightly tweaked which might be accounting for that issue.

18

Re: another Y-axis calibration

I had the same problem and my "fix" may be just coicidental.  My belt tension is actually not the same on both sides.  The right side is slightly tighter than the left and my circles seem to come out fine.  As I said, this may be coincidental.

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Re: another Y-axis calibration

I was wondering if that might be a fix...I'll have to try it.

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Re: another Y-axis calibration

Interesting trick... I have the same issue, been through the usual calibration procedures. I will try it today

21

Re: another Y-axis calibration

Success lads, we're on the right track.  I should be able to complete the calibration by the end of the week. I'll post picks when I get it dialed in.

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Re: another Y-axis calibration

the_alteran wrote:

Success lads, we're on the right track.  I should be able to complete the calibration by the end of the week. I'll post picks when I get it dialed in.

what method did you use to set the belt tension?  I'm using the money weight thingy and based on that i'm pretty even on both sides.  This fix has my interest..

23

Re: another Y-axis calibration

Shotline wrote:

I had the same problem and my "fix" may be just coicidental.  My belt tension is actually not the same on both sides.  The right side is slightly tighter than the left and my circles seem to come out fine.  As I said, this may be coincidental.

I figured this was worth a shot, and it actually worked! My circles started to look a lot better, they still are not "perfect" yet, but I'm on the right track now.  The method to this madness, that I've used, has been to tighten/loosen the one of the y-axis belts till the circle is as good as it is going to get. Then slightly tighten the belt on the y stepper motor. Print and repeat until the circles are damn near perfect (I'm still on this last step).

These are the calibrations files that I have been using.

used this till the circles were near perfect.
http://www.thingiverse.com/thing:34843

I'm currently using this one to true it up. using a nickel and a light behind it you can tell if the circle is getting better or worse.
http://www.thingiverse.com/thing:11215