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Weird Ripple

Posted by Lzrstrm 
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Lzrstrm
Weird Ripple
March 29, 2016 03:31AM
I've noticed that my prints are starting to get a weird ripple in them throughout the whole print.



The strange thing is that it seems to only be the X-Axis because the Y looks almost fine, there's still a very small ripple but not like the X



Not sure what is causing this issue confused smiley

-My printer is a Prusa I3 Migbot
-Printing at a .1 layer hight with a .4 nozzle
-PLA at 220°c
-Heated bed at 60°c

Any help is much appreciated
-Cameron
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hoxsiew
Re: Weird Ripple
March 29, 2016 09:11AM
Seems like I got something similar once when my hotend bracket came loose from the x-axis slider (MK8-ish clone with aluminum bracket screwed to a printed X-slide). I just tightened up the mounting screws.
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the_digital_dentist
Re: Weird Ripple
March 29, 2016 04:04PM
The ripple looks periodic. Check for bent Z axis screws and for easy rotation of the filament spool.

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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Lzrstrm
Re: Weird Ripple
March 29, 2016 05:18PM
Quote
the_digital_dentist
The ripple looks periodic. Check for bent Z axis screws and for easy rotation of the filament spool.

If it was an Z axis issue wouldn't the ripple be throughout the whole object? My issue is only with the X axis
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the_digital_dentist
Re: Weird Ripple
March 29, 2016 07:38PM
Ah! In that case, check the x axis. Make sure there's no play in the extruder carriage, belt is tight, guide rails are tight in their mounts, and pulley is tight on motor shaft. It could still be related to bent Z screws if the bends happen to line up right.

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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Lzrstrm
Re: Weird Ripple
March 29, 2016 09:41PM
Quote
the_digital_dentist
Ah! In that case, check the x axis. Make sure there's no play in the extruder carriage, belt is tight, guide rails are tight in their mounts, and pulley is tight on motor shaft. It could still be related to bent Z screws if the bends happen to line up right.

I've heard elsewhere that it could be due to my Jerk? How would I go about calibrating that?
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the_digital_dentist
Re: Weird Ripple
March 29, 2016 09:52PM
It's unlikely to be jerk or acceleration settings because the y axis typically has much higher moving mass and such problems would usually show up there first. What are the acceleration and jerk settings? How fast are you printing?

Try wiggling the hot end, extruder, and extruder carriage. If they wiggle at all that's probably where the problem lies. Watch the machine closely as it is printing- does the x axis assembly shift as the Z axis moves up and down? Try jogging the Z axis and watch what the x axis does.

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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Lzrstrm
Re: Weird Ripple
March 29, 2016 10:52PM
Quote
the_digital_dentist
Try jogging the Z axis and watch what the x axis does.

As the Z axis moves up or down the print head wobbles slightly side to side. So does this mean that my rods are bent or is there another issue?
I've tightend all the belts and screws that I can see but no difference
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the_digital_dentist
Re: Weird Ripple
March 29, 2016 11:19PM
Do you see the ends of the Z axis screws wobbling as the Z axis jogs? If so, either the screws are bent or the coupling(s) to the motor(s) is off center, or both. I3 kits typically use threaded rods in lieu of lead screws because they are cheaper. Unfortunately, they are also usually bent and cause print quality problems such as the one you are experiencing.

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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Lzrstrm
Re: Weird Ripple
March 29, 2016 11:25PM
Quote
the_digital_dentist
Do you see the ends of the Z axis screws wobbling as the Z axis jogs? If so, either the screws are bent or the coupling(s) to the motor(s) is off center, or both. I3 kits typically use threaded rods in lieu of lead screws because they are cheaper. Unfortunately, they are also usually bent and cause print quality problems such as the one you are experiencing.

Ya the top of the rod rotates around the and doesn't stay in the center.
I've seen 3D printable couplers would something like that fix the issue? I'm not sure either about what screws you are talking about tongue sticking out smiley
Thanks for all your help smiling smiley
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chris33
Re: Weird Ripple
March 30, 2016 04:52AM
i seen a picture of one the problem is that having a bent threaded bar and being captive at the top makes the head move with the threaded rod not the guide rails

Check my rubbish blog for my prusa i3

up and running
[3dimetech.blogspot.co.uk]
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the_digital_dentist
Re: Weird Ripple
March 30, 2016 10:39AM
There are multiple design problems all working against a quality print result. Threaded rods are bent and pull the x axis as they wobble. The guide rails are flexible and allow the x axis to follow the bent Z axis screws even though they are supposed to prevent such motion. The frame flexes as the guide rails pull at it. Essentially, the design of the machine sucks.

If you replace the bent threaded rods with real lead screws most of the problem should go away.

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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Lzrstrm
Re: Weird Ripple
March 30, 2016 11:04AM
Quote
the_digital_dentist
If you replace the bent threaded rods with real lead screws most of the problem should go away.

I'm using lead screws now
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Lzrstrm
Re: Weird Ripple
March 30, 2016 11:11AM

This is a lead screw right?
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WalkerMaker
Re: Weird Ripple
March 30, 2016 12:39PM
Yep that's a lead screw. Basically the beefy older brother of threaded rods.

Edited 1 time(s). Last edit at 03/30/2016 12:40PM by WalkerMaker.
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Lzrstrm
Re: Weird Ripple
March 30, 2016 01:35PM
So essentially I need to replace my lead screws?
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hoxsiew
Re: Weird Ripple
March 30, 2016 01:36PM
Quote
WalkerMaker
Yep that's a lead screw. Basically the beefy older brother of threaded rods.

Not really. They serve two completely different roles. Threaded rods have 60° ISO threads which are designed for fastening things together (nuts and bolts) whereas lead screws (acme or trapezoidal) are designed for transmitting motion. Threaded rods will work, but they are far from ideal.
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Lzrstrm
Re: Weird Ripple
March 30, 2016 04:54PM
Would replacing the lead screw be a good idea?
The ones I'm using are 8mm.
I've printed Z axis stabilizers for each side but it's meant to have 8mm nuts in it but the nuts are made for threaded rods not lead screws. Is there anything like that I can print for lead screws to help stabilize them?
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chris33
Re: Weird Ripple
March 30, 2016 05:17PM
you z accelleration may be two fast

Check my rubbish blog for my prusa i3

up and running
[3dimetech.blogspot.co.uk]
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amigob
Re: Weird Ripple
March 30, 2016 05:20PM
I think you all are sending this guy on a goose chase,
He is saying he has the wobble on the X axe not on the Y or Z, if you look at the picture you see that it is a extrusion direction. Not in the Z. because then the layers would be perpendicular to the wobble.

So, if I where you i would check if you X-pulley matches you belt. So a mismatch of your belt and pulley
If your thumb is any thin like mine then you have a wobble period of 2.5mm so I think your pulley is 2.5mm teeth and your belt is 2mm or vice versa
Looking at the picture of the Y axes, I also think you have the same problem there.
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Lzrstrm
Re: Weird Ripple
March 30, 2016 05:39PM
Quote
amigob
I think you all are sending this guy on a goose chase,
He is saying he has the wobble on the X axe not on the Y or Z, if you look at the picture you see that it is a extrusion direction. Not in the Z. because then the layers would be perpendicular to the wobble.

So, if I where you i would check if you X-pulley matches you belt. So a mismatch of your belt and pulley
If your thumb is any thin like mine then you have a wobble period of 2.5mm so I think your pulley is 2.5mm teeth and your belt is 2mm or vice versa
Looking at the picture of the Y axes, I also think you have the same problem there.

Thank You! I will definitely check this once I'm home after work smileys with beer
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the_digital_dentist
Re: Weird Ripple
March 30, 2016 07:02PM
Check the centering of the lead screws in the shaft couplers on the motor. Do you see the screws wobbling as they rotate? They shouldn't- the lead screws should be an extension of the motor shaft.

Check everything for any sort of looseness or wobbliness. It takes longer to post here than it does to check every mechanical part of the machine.

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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JamesK
Re: Weird Ripple
March 30, 2016 08:23PM
I'm still not sure which sides I'm looking at in the photos. Is there any chance you could take a photo showing how it was sitting on the print bed, and add some arrows pointing out where the wobbles are?
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fredchan
Re: Weird Ripple
April 21, 2016 03:32AM
Ripple Eliminator for 3D Printer
[www.thingiverse.com]


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Lzrstrm
Re: Weird Ripple
April 23, 2016 03:01AM
Okay so I solved my Z wobble, the Z axis moves perfectly now but still hasn't solved my weird ripple in the Y axis sad smiley
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