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Layer displacements issues

Posted by pikelo 
Layer displacements issues
December 11, 2012 02:56PM

From a few days I'm having this issue that you can see on pictures attached. Randomly the layers get a displacement. My brother is having the same problem but his machine is 4000km far of mine. When the print fails the axis does a noise like "gggg" for a half second moreless, it get displaced layer and then go on.

Does anyone know about what could it be causing this problem? I only have this displacement on X axis and I have tried changing from Slic3r to Cura and nothing changed. I have tried installing a new Pololu and still same. Nothing seems disturbing the smooth movement of the X belt.. so weird.

For my brother the issue is same but with Y axis only.

Any help please?
open | download - DSC_0242.jpg (256.1 KB)
open | download - DSC_0251.jpg (282.1 KB)
Re: Layer displacements issues
December 12, 2012 01:41AM
You're dropping steps.
It's either
mechanical - some times the belt can rub on the outside of the idler bearing
Or electrical - stepper driver ref voltage set too low (or possibly too high)

That assumes you're printing at reasonable speeds and have normal printer electronics.
Re: Layer displacements issues
December 12, 2012 02:12PM
I am having the same issue and suspect it is electrical:
When printing a filament with a low melting point this does not occur, but will happen when I am printing at a higher temperature. Changes in electrical system may trigger it, I have had it happen 3x with the lower temp filament after the first layer right after I turned the cooling fan (from same psu) on. I suspect that my salvage psu is running minimum standards, or that the stepper motor needs to be further adjusted.

Another possible cause noted in other threads of this nature is the acceleration in the firmware.. recommendation is to tune it down to 500 and start from there.

I have not had a chance to check any of these theories in the last few days and do not expect to until thrusday night . Please keep up updated if you investigate further before that.
Re: Layer displacements issues
December 12, 2012 02:19PM
Issue solved as A said. I decreased the acceleration to 1000 mm/s^2 and also on Slic3r I also tuned down the travel speed to 100 (over this value my carriage is too heavy to can move smoothly).

Thank you to everyone!
Re: Layer displacements issues
December 12, 2012 02:53PM
Hello Pikelo

Glad you solved your issue. Power/stepper current was not an issue? I'm itching to get back at my printer. Too bad work and Christmas shopping obligations (so early i know right) are eating my printer time. Lunch is over, back to work lol.
Re: Layer displacements issues
December 12, 2012 03:02PM
Hello A, If I were you, I firstly change the acceleration values fixing it down. Then upload the firmware and turn down the pololu potenciometer and move your axis till the get power enough to do the movements smoothly. That would be a good approximation to your job. For me, the pololu power was fine and only the accel. issue was causing this problems.

Re: Layer displacements issues
December 13, 2012 01:05PM
After two printings again it failed. No idea about how to solve it. No belt problem, no pololu problem, no acceleration max problem (I decreased it on Sprinter to 1000mm/s^2)..

Any other idea? my brother is having the same issue but at the other axis..
Re: Layer displacements issues
December 13, 2012 03:46PM
Hello Pikelo

Try 500?

Re: Layer displacements issues
December 15, 2012 09:46AM
I also tried to go down to 500 and still same problem. Here I attached the last three attemps with fails. Still no idea of how to solve it even I unassembled and assembled the X axis again..
open | download - IMG_20121215_160808.jpg (530.6 KB)
Re: Layer displacements issues
December 16, 2012 06:31PM
Given that it wasn't the acceleration, here are some remaining possibilities:
1. Too much friction on the X-axis (caused by a heavy carriage, or mis-aligned bearings/bushings, or a bad combination of rods and bushings/bearings)
2. Travel speed set too high (because carriage is too heavy or friction is too high)
3. Pololu is set too high without a fan cooling it (causing it to briefly shut down before it overheats)
4. Pololu set too low (causing it not to rotate with enough torque for the speed you told the axis to move)

As you can see, the potential causes are interrelated. If you air-cool your pololus and then turn them up as high as they'll go without skipping, lighten your X-carriage, reduce friction on the X-axis rods and bearings/bushings, you'll probably find that the problem disappears.
Re: Layer displacements issues
December 16, 2012 09:32PM

Try #3, I am cooling with some fans and have not seen an issue since.

Re: Layer displacements issues
December 17, 2012 06:42AM
Agree with Pointedstick.

What hot-end are you using? - exactly, and a photo of the nozzle if possible.

Some other things to consider or at least rule out -

Do you see this problem only with parts using high infill >35% ? - if so you may be over extruding, see below.

Are you seeing the layer shift at the same point on the print? - if so you may be over-extruding and the nozzle is catching on the part at a high level of infill.

In extreme situations you can get machine resonances at periods of high-speed (tiny zig-zag line infill for example) that can also cause a shift in the printed part usually on one Axis.

Check your extrusion rates and estep number.

Rotate the printed part by 45 degrees.

Have you tried using lift (hop) on the Z axis, just lift 0.2 or 0.4mm for moves, if your machine can handle this it's a good thing to be doing.


Re: Layer displacements issues
December 27, 2012 07:29AM
Does sprinter have a jerk setting like marlin? If so, you may wish to decrease it. That will probably have more impact than decreasing the acceleration.
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