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Ripples on X and Y axis

Posted by jsaiko 
Ripples on X and Y axis
November 24, 2015 08:47PM
Hello,

I am new to 3d printing and am not sure I know the correct terms to find the answer to my issue via google. I printed a test object that came with the printer and noticed ripples/lines on the sides of the print. I just now printed out a calibration cube that I downloaded from thingiverse and it also has the lines as well. Can someone please guide me in the right direction as to what might be causing this?

Thank you in advance,

Jsaiko
Attachments:
open | download - cube.jpg (128.8 KB)
Re: Ripples on X and Y axis
November 24, 2015 09:24PM
It's called "Z banding". Search on that term to find causes and solutions.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Ripples on X and Y axis
November 24, 2015 09:30PM
Thank you so much!
Re: Ripples on X and Y axis
November 25, 2015 06:44PM
Hi Jsaiko, welcome to the forum smiling smiley

There's a very useful visual guide to common printing problems at the following link:

[support.3dverkstan.se]

[edit]Hmm, think I was actually thinking of this one: [www.simplify3d.com]

Regards,
James

Edited 2 time(s). Last edit at 11/25/2015 06:47PM by JamesK.
Re: Ripples on X and Y axis
November 25, 2015 06:57PM
Thanks for the guides James!

Just as a follow up, the problem appears to be bent Z axis rods. I ordered new 8mm, 2mm pitched threaded rods and will attempt to convert my kit over to them. Just not sure how I am going to be able to print the conversion parts with this Z ribbing as bad as it is. I'm confident I will be able to modify the firmware and everything else though.
Re: Ripples on X and Y axis
November 25, 2015 07:24PM
Before you make those changes, I'd try this mod:
anti z wobble thing

I spent ages to straighten the m5 rods but always some wobble remains. Even M8 aren't 100% straight. They are made to clamp things along the axis, not for precision stuff. Either get a trapezium acme threaded rod with matching ball nuts or decouple the xy movement from the z rods. It worked well for me. It also reduces z nut backlash.


--
Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]
Re: Ripples on X and Y axis
November 25, 2015 07:38PM
Thanks Imqqmi! I'll be sure to give this a go. The tolerances look like they might be a bit more forgiving with that mod.
Re: Ripples on X and Y axis
November 25, 2015 08:12PM
Some stuff from my old days using bow and arrow might be helpful here:
Build a rig with two rollers at each end to hold the rod horizontally.
The roller should be small enough so that they do not touch but still keep the rod secure so it can rotate freely.
When you now turn the rod you can see where it is bend - turn this "bulge" up and use a little pressure to bend it in the opposite way.
You always need to push a bit further than the centerline.
For areas with very small dints you can support the part left and right from the dint and then push it down to correct.
Even a badly "wobbled" arrow, like after hitting the concrete wall, could be set straight this way within a few minutes.
To get it 100% you will need a micrometer, these things with a dial and pin that we love to use for bed levelling.
Put a single layer of kapton tape over the thread, mount the micrometer on a stand and move it along the rod - where it gives you bad reading you reapeat the pushing and turning but use supports as otherwise you might mess up good areas as well.

But IMHO the best option would be free running rods.
Smooth rods that hold the moving parts in a block and the threaded rods going through the same block using spring supported nuts.
A bit of wobble is absorbed by the system, before I straightened my threaded rods a bit the bottom part of them would move around about 4mm once a print got really high.
But there was never a problem with those wobbles making it into the print.
However, I was chasing a wobble on the Y-axis for weeks until I realised it was as simple as the belt rubbing on a washer - a bit of silicone grease solved that for good.
Turned out the rubbing caused vibrations through the entire belt, go figure...
Re: Ripples on X and Y axis
November 26, 2015 12:08AM
Also a chance that it is extruder temp variation.
Re: Ripples on X and Y axis
November 27, 2015 02:58AM
@downunder35m thanks for sharing the straightening technique, I might try it out. I was wondering, when moving the micrometer, the bench should be perfectly flat, right? By roller do you mean a bearing the m5 rod fits into for example?


--
Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]
Re: Ripples on X and Y axis
November 27, 2015 01:48PM
Quote
imqqmi
@downunder35m thanks for sharing the straightening technique, I might try it out. I was wondering, when moving the micrometer, the bench should be perfectly flat, right? By roller do you mean a bearing the m5 rod fits into for example?

That would work too, any rollers that are close enough to support the rod and reasonably round, bring out the LEGO.
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