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Author Topic: Unique X-axis shifting - only once per print  (Read 447 times)

NeoModulus

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Unique X-axis shifting - only once per print
« on: January 29, 2014, 07:28:14 AM »
I've got an interesting problem.  About 2 out of 3 prints, only 1 time, the printer shifts its print about 1-2mm in the Xish direction (perhaps slightly in the y?), then continues to print the rest of the object as though this was the new position.  It is as if the plate shifted, once, then stayed in the new position for the rest of the print. I've checked the plate and secured it, but it doesn't seem to be moving.

It is peculiar because it only happens once in the print, probably on about layer 40-50 (about 5mm up from the base of the print), then it doesn't do it for the rest of the print...and it doesn't always happen (only about 2/3 of prints).  It will continue to print perfect for the rest of the print, even if it is quite large, at the new position.

I am thinking it may be my X-cable rubbing the stepper motor drivers at that particular elevation and I'm working on printing an X-cable holder/organizer.  Any other ideas anyone? 

Thanks in advance,
Brando

fiya

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Re: Unique X-axis shifting - only once per print
« Reply #1 on: January 29, 2014, 05:20:44 PM »
I've had this happen a few times for different reasons.

My spool fell off a cabinet mid print and the filament jerked the machine around.
The glass plate moved during a print, tape came loose and I wasn't using binder clips.
I was video editing on the same PC that was running my print. A long time-lapse stalled the PC and print for a few seconds then restarted a bit off.
And finally, an easy to fix over extrusion issue caused the nozzle to scrape the print and made the x cable skip.

All of the prints finished, but they had a shift where the interruption took place.

Luxxi

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Re: Unique X-axis shifting - only once per print
« Reply #2 on: March 09, 2014, 10:34:45 AM »
I'm having the same issue since 2 weeks on the y-axis of my V2 duo. About 1 out of 4 prints fails.

The synchromesh tension seems to be fine, the rods are lubricated with PTFE-spray, the bed does not hit anything, the glass plate is firmly secured with at least 4 clips.
Vref for all stepper drivers is 620-640mV just as they were set when shipped.
The problem seems to be independent of the speed settings. It skips a step for speeds from 100%-180%
When I print the same object with the same gcode and settings again it usually prints fine, so the problem shouldn't be slicing-related.
As the problem appeared only 2 weeks ago and as it pinted just fine before I guess it could be an issue of wear and tear? (linear bearings, stepper motor, stepper controller...?)
What service life can be expected for the stepper motors?

Any ideas?

whosawhatsis

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Re: Unique X-axis shifting - only once per print
« Reply #3 on: March 09, 2014, 11:03:21 PM »
From the picture, it looks like you might be over-extruding slightly, which can cause plastic to build up and then catch on the nozzle, causing a skip. You might also try slowing down the print (especially the travel moves which are the fastest and thus where this type of skipping usually takes place) and see if that makes a difference.

Luxxi

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Re: Unique X-axis shifting - only once per print
« Reply #4 on: March 10, 2014, 11:56:57 PM »
Thanks Rich,
that makes perfect sense. As the tolerances for the filament are very variable, even for those of the same supplier, this could be the solution.
I'll try to reduce the extrusion to see if it makes the difference.
I'll keep you posted

NeoModulus

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Re: Unique X-axis shifting - only once per print
« Reply #5 on: March 13, 2014, 03:14:35 AM »
I've just realized one of my problems is that my power supply seems to be flicking off if tapped very slightly on the front face. One small tap and it turns off, another and it turns on.

I double checked all the connections to it from the power source and going to the controller board and everything is solid and there is no on/off behavior when handling the wires, only the front of the power supply (the flat face facing the front of the bukobot).

The motion of the printer may be causing the required tap and a transient loss of power from the power supply, hence the little misalignment. I've also noticed some complete print failures and it may be behind those too.


Rich,
 Do you know where I can buy another PS? I don't imagine they are too much..

TIA,
-brando


I may open this one up as a new thread if I don't hear back, plus its only tangentially related here.

whosawhatsis

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Re: Unique X-axis shifting - only once per print
« Reply #6 on: March 15, 2014, 12:08:58 AM »
Sounds like the power supply is defective. Send me an email at rich@deezmaker.com to arrange a replacement.

 

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