Ripples in Print

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brad72
Posts: 19
Joined: Wed Jan 01, 2014 1:33 am

Ripples in Print

Post by brad72 » Mon Feb 24, 2014 7:33 am

I have noticed that I get ripples in my prints where the extruder as gone around a hole or a sharp edge. I am using a non genuine Premium ABS and I think I am extruding at around 235ºc (i have a 12 step, 5º temp mod). I calibrated the table and cleaned the nozzle so that is covered. I have checked the head to carriage magnets and they seem secure with little movement. The belts seem fine with a nice amount of tension on them.

To that end, can anyone shed some light on what could be happening. My first thought is belt stretch but short of replacing them I have no way to prove this. My other is the extruder is still a little too hot. Images below are fine speed with 0.2 resolution

Thanks

Image

Image

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DrewPetitclerc
Posts: 581
Joined: Sat Feb 12, 2011 7:39 am
Location: Silicon Valley California
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Re: Ripples in Print

Post by DrewPetitclerc » Mon Feb 24, 2014 5:24 pm

Rigidity of the mechanical system is at fault here. :geek:
The mechanical system from the nozzle tip all the way around to the build plate surface, through all mating surfaces and parts should be as rigidly held together as possible, the 2 most badly addressed points are
1. The nozzle assembly mount to the slide
2. The build plate mounting to the slide, any ability of the these to shift or vibrate during move direction change will induce the "wave" like patterns seen, any springs in these systems are going to allow for unwanted movement during operation.

To correct the extruder mount problem I use this solution:
http://pp3dp.com/forum/viewtopic.php?f= ... bb4c#p5476
This is a much more "rigid" mounting system.

To address the build plate problem I use this technique.
http://pp3dp.com/forum/viewtopic.php?f= ... bb4c#p5471
With this system you can still adjust pitch and yaw to tram the build plate to the nozzle but by increasing the compression forces through the 3 screws you can reduce the available vibration possibilities of the build plate.

I know the "Mini" has a different design of components but the same mechanical values need to be adhered too, so your material/part solution may need to be different. :ugeek:
Drew Petitclerc
Petitclerc Designs
Owner/Senior Principal Designer, prototype, tooling and test equipment design and 3D printing
http://flash-graphics.deviantart.com/
http://www.thingiverse.com/DrewPetitclerc

pleppik
Posts: 336
Joined: Sun Dec 11, 2011 2:14 pm

Re: Ripples in Print

Post by pleppik » Mon Feb 24, 2014 6:02 pm

Another thing you can try is printing in "fine" mode. This slows down the print speed, which decreases the amount of vibration when the head or platform changes direction suddenly.

brad72
Posts: 19
Joined: Wed Jan 01, 2014 1:33 am

Re: Ripples in Print

Post by brad72 » Mon Feb 24, 2014 9:40 pm

Thanks for the replies guys

Pleppik, my prints are being done in fine mode and unfortunately the ripples are still there.

Drew, checked over the mounts this morning and there certainly is play in the extruder but is seems to be more from bearing clearance in the lower right bearing causing the head to rotate in a slight arc and since the nozzle is 60mm from this bearing the error in multiplied. There is also a bit of resonance in the x-axis which seems like is coming from the stepper but only in a few spots of its travel

So plan of attack is to firstly replace the extruder linear bearings and maybe make up a new extruder mount that utilizes 4 linear bearing instead of the 3 the up currently has. then run some more tests on the x axis to trace down the resonance

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DrewPetitclerc
Posts: 581
Joined: Sat Feb 12, 2011 7:39 am
Location: Silicon Valley California
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Re: Ripples in Print

Post by DrewPetitclerc » Mon Feb 24, 2014 11:26 pm

Sounds like you understand the problem and have a good testing setup, hope you can correct the issues.
Hope it works out for you.
Drew Petitclerc
Petitclerc Designs
Owner/Senior Principal Designer, prototype, tooling and test equipment design and 3D printing
http://flash-graphics.deviantart.com/
http://www.thingiverse.com/DrewPetitclerc

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