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Uneven layers issue?

Posted by Nate523 
Uneven layers issue?
March 05, 2017 01:03AM
Picture of issue:



I used to get very good even layers with this delta printer, almost perfect layers, I switched to drv8825 stepper drivers, 24V PSU, and recalibrated the whole thing, and now I get this fairyl consistent uneven layers that stick out on my prints. Never have had this before.

I suspected mechanical, checked eveything seems fine, I suspected extrusion, I checked the extrusion, seems to put out 100mm when I ask for it.

Any ideas folks? I have no idea wheere this might be happening, effector doesn't seem to wobble, at least no this much so I am lost, maybe a rod end is messed up, but like I said seems everything is pretty tight.

Edited 1 time(s). Last edit at 03/05/2017 11:53AM by Nate523.
Re: Uneven layers issue?
March 05, 2017 01:41AM
Your image is not accessible.

May be it is related to your switch to DRV8825. Those drivers (when in the default mixed decay mode) do not like motors with high impedance and low resistance. Maybe you need to switch your drivers to fast decay or add load diodes (better than adding load resistors).

Check this whether it looks like your problem.
Re: Uneven layers issue?
March 05, 2017 11:58AM
Thanks for letting me know, updated the picture source, google drive doesn't like sharing it seems...

My problem doesn't seem to be related to the link you gave me, It is smooth, my problem is if you can see in the picture, that I get an consistent uneven layer pattern at around the same amount of layers each time, I have checked and double checked, I may still be missing it, but mechanically it seems like everything is intact. I will triple check though. I did do a much slower print, because I still think it has to do something with the drv8825, and the effect was much less, but still noticeable. I am going to try first, switching from 1/32 to 1/16 with these driver motors, and then if that still doesn't do anything I will switch back to old drivers and see if it reverst back to what it was previously doing which was beautiful even layers.

I was wondering, I have a Ramps 1.4 modified to handle 24V, I wonder if 8-bit arduinos cant handle 1/32?

Edited 1 time(s). Last edit at 03/05/2017 11:59AM by Nate523.
Re: Uneven layers issue?
March 05, 2017 12:26PM
First test, changing DRV8825 to 1/16 steps, no change, same issue, next to try the Old drivers A4988.
Re: Uneven layers issue?
March 05, 2017 03:48PM
Quote
Nate523
I was wondering, I have a Ramps 1.4 modified to handle 24V, I wonder if 8-bit arduinos cant handle 1/32?
Yes, if your segments per second is set to 90 (or less) and the maximum print speed is about 70 cm/s (or less). Maybe more agressive settings can be used but I did not try them.

Edited 1 time(s). Last edit at 03/05/2017 03:49PM by hercek.
Re: Uneven layers issue?
March 05, 2017 03:52PM
Well, third test, went back to A4988 1/16 steps, still have the same issue. Like the whole printer just went to crap too because the Z-probe stopped triggering, and I can't get it to trigger now. Completely lost on the bad print problem. Check the mechanical stuff again I guess.
Re: Uneven layers issue?
March 05, 2017 04:19PM
I suspect heatbed flex.

Try turning the heatbed off as soon as the print starts.
Re: Uneven layers issue?
March 05, 2017 04:24PM
I do that every print, that made no difference unfortunately.
Re: Uneven layers issue?
March 05, 2017 08:01PM
Checked the build again, seems legit, stepper gears don't move or jiggle, they are solid, belts seem solid, effector is tight, I'm at a loss, I had this thing printing 0.1mm layer heights no problem just a week ago, great prints, no bumps or uneven layers, was perfect, now I can't even get a cube to print right, what a shame sad smiley
Re: Uneven layers issue?
March 05, 2017 08:29PM
Did another print 20 mm/s with a different ramps board, still get the same results, less mind you, but still visible consisten uneven layer issue, never had this before, really strange.
Re: Uneven layers issue?
March 06, 2017 12:41AM
Did another check on my mechanics, the only thing that I could find was my eye bolts have some minor play, kinda annoying really because I just bought them a month or so ago, must have been a cheap brand. They don't play enough to cause the amount of slop that I am seeing in the model though, so I did an entire re-calibrate, found that my printer was way off, something must have happened to eeprom while searching for the issue because I already calibrated once.

Long story short, did my calibration and the printe was coming much better, but the consisten patterns started to resemble much more of an extrusion problem, so I adjusted the extrusion until the print looked great, was down to 85% flow to get the print to be right, 100mm extrusion check didn't go so well I guess.

Did a test print at 0.1mm (left on the picture, see the transition of extrusion adjustment) layer height and 0.3mm (right on the picture) layer height.

Thanks for the suggestions and help, I was really getting frustrated because my printer was fine before I did this 24V upgrade, but now I can use the DRV8825 drivers, 12V wasn't cutting it when I tried with my previous PSU.



Edited 1 time(s). Last edit at 03/06/2017 12:42AM by Nate523.
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