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therealnecroscope
(@therealnecroscope)
Active Member
Software layer shift?

Hearty grettings to all!

 

I recently got my very first 3D printer (Mk3s) and have been busy printing various simple objects from the included SD stls to a few things from the web. Just wanted to get a feel for the machine.

 

I have an extensive background in CAD and intend to use this machine for functional parts and prototypes.

Today I designed and printed a simple phone holder to mount it on a tripod and got some odd (to me) results...

The holder was printed in the orientation and location shown using supports. Stock machine, Prusament PLA, default .20 Quality settings, sliced model in P-Slicer 2.  The adjacent objects were also printed on this machine and don't show the same shifting, so I don't think it's a machanical issue.

 

Any thoughts on what could be causing this layer inconsistency?

 

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Posted : 25/05/2019 8:19 pm
therealnecroscope
(@therealnecroscope)
Active Member
Topic starter answered:
RE: Software layer shift?

Adding pics, hopefully...

Posted : 28/05/2019 9:30 pm
therealnecroscope
(@therealnecroscope)
Active Member
Topic starter answered:
RE: Software layer shift?

I intend to print large objects (80-90% of the available build volume) with lots of large planar faces so I need to get these artifacts figured out before I can continue scaling up.

Posted : 28/05/2019 9:48 pm
bobstro
(@bobstro)
Illustrious Member
RE: Software layer shift?

Is this a kit or pre-built? Those shifts usually correspond to some internal structural features. In most cases, those sorts of problems can be mitigated if not eliminated by (in recommended order):

  1. Calibrate extrusion (in case you have internal layers bulging).
  2. Calibrate Linear Advance (for even filament flow at different speeds).
  3. Adding a 3rd external perimeter (if only using 2).
  4. Slowing external perimeter speeds. I go with 25mm/s if finish matters.
  5. Experiment with different perimeter thicknesses.
My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 28/05/2019 10:16 pm
bobstro
(@bobstro)
Illustrious Member
RE: Software layer shift?

A lengthy discussion on this topic can be found here.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 28/05/2019 11:00 pm
therealnecroscope
(@therealnecroscope)
Active Member
Topic starter answered:
RE: Software layer shift?

Thanks for the reply!

 

This was a kit I assembled myself. No big deal. I have built cars, motorcycles, engines, etc. Also spent 20 years working on industrial CNC equipment. The mechanical stuff is not foreign to me but extrusion IS.

(I already have a full Bear kit and Misumi rods and bearings on the way.  Gonna build the Lack enclosure this weekend, then start printing both the Bear parts and Bunny extruder parts.  Working toward a setup to do quality higher temp filaments like 3DxTech CFPC.)

 

I printed many 40mm and 20mm cubes (one pictured on the right) in both vase mode and various other versions to tune the extrusion multiplier and attempt (fail) to get better seams.

 

Also printed the linear advance test tower a couple times and concluded that default "1" was fine, but (iirc) 1.05 was very slightly better.

 

Problem part is only .053" section thickness with 3 perimeters set in the slicer, solely for the threaded boss, so it's solid plastic in those thin areas. It looks fine at the layer level in the slicer.

It was printed at .45mm/s (default)

 

This post was modified 2 years ago by therealnecroscope
Posted : 29/05/2019 3:47 am
Sembazuru
(@sembazuru)
Prominent Member
RE: Software layer shift?

I might be grilling up a nice red herring here, but I wonder if the artifacts you are seeing on the phone holder is due to a combination of the print orientation and the movement of the bed in the Y axis. With the part in that orientation, a tall thin object wouldn't be well supported from wobbling as the bed moves forward and back. Two ideas I have to try for reprints:

  • Turn the object 90° on the z-axis and print so the long axis is parallel to the bed motion.
  • Turn the object 90° on the x-axis and print so the large, flat (is it? we can't see that side) surface is on the print bed.

Due to the mechanics of how the printer moves, simple orientation changes may affect print quality.

See my (limited) designs on:
PrusaPrinters - https://www.prusaprinters.org/social/1448-sembazuru/prints
Thingiverse - https://www.thingiverse.com/Sembazuru/designs...
Posted : 29/05/2019 7:09 pm
bobstro
(@bobstro)
Illustrious Member
RE: Software layer shift?
Posted by: therealnecroscope

[...] Problem part is only .053" section thickness with 3 perimeters set in the slicer, solely for the threaded boss, so it's solid plastic in those thin areas. It looks fine at the layer level in the slicer.

Any chance you could provide a link to the STL (good) or a 3MF project file with the settings and part you're using? It's hard to see exactly what's going on in those pictures.

I wound up creating small faster-to-print test parts to troubleshoot these sorts of problems

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 29/05/2019 7:33 pm
therealnecroscope
(@therealnecroscope)
Active Member
Topic starter answered:
RE: Software layer shift?

I truly appreciate the help!  I'm not afraid of digging deep to improve this machine (settings, hardware, myself, whatever) so any suggestion is more than welcome.

 

I am happy to upload the stl and/or 3mf.  I believe that can done right here...correct? Or do I need to host it elsewhere?

 

The idea of over-extrusion is interesting since the most affected sections are solid....but it seems like that should be consistent throughout the layer or even whole model.

 

I did actually consider changing the orientation but since some of my goal parts are too large to reorient it seemed like a band-aid.  Would rather identify and correct the root cause.

The part has only one flat face, which is placed on the bed in the pic.  The rest has radiused bits projecting beyond the "U". The tops of the "horns" are actually flared out a bit to help guide the phone into the channel.

Regardless, the part was printed with supports under the entire length and width so it was actually very stable.

Posted : 29/05/2019 9:44 pm
bobstro
(@bobstro)
Illustrious Member
RE: Software layer shift?
Posted by: therealnecroscope

I truly appreciate the help!  I'm not afraid of digging deep to improve this machine (settings, hardware, myself, whatever) so any suggestion is more than welcome.

You've come to the right place then! 😀 

I am happy to upload the stl and/or 3mf.  I believe that can done right here...correct? Or do I need to host it elsewhere?

I *think* you can zip any file and attach it to a message using the Choose file button at the bottom.

The idea of over-extrusion is interesting since the most affected sections are solid....but it seems like that should be consistent throughout the layer or even whole model.

After our communal investigation, my take-aways are that:

  • Thin outer perimeters can be affected by solid layers inside the part. An L-shaped shelf with a thick bottom can suffer from irregular patterns on the flat vertical surface (the left of our L shape) due to accumulation of over-extrusion on solid layers on the inside (the right bottom of our L shape). Fine-tuning extrusion multipliers and an extra perimeter can help with this. Tweaking extrusion width can help, but is a bit of a kludge.
  • Changes in extruder direction or flow can ripple through an entire layer. A flat vertical surface with a hole, for example, can suffer from ridges or gaps caused by speed changes associated with corners or holes. Speeds and fine-tuning Linear Advance can help with this.

I did actually consider changing the orientation but since some of my goal parts are too large to reorient it seemed like a band-aid.  Would rather identify and correct the root cause.

Agreed. Orientation can help but masks the true problem. The same with part cooling when you do extreme overhangs or bridging,

I've attached a zip file containing some smaller test pieces that I used for researching these issues. They're basically a thick base with a thin wall protruding from the top with each piece with a different wall thickness. You might try printing one (I'd go with 1.35mm) and see if you get the same distortions. If so, the test part can save you some time printing. If your part has some other odd features, perhaps we can slice up your STL into a manageable test print to save time.

Attachment removed
My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 29/05/2019 9:55 pm
therealnecroscope
(@therealnecroscope)
Active Member
Topic starter answered:
RE: Software layer shift?

I'm travelling right now but I'll look at those files this weekend. Thanks!

Hopefully the zipped 3mf will attach below...

 

Attachment removed
This post was modified 2 years ago by therealnecroscope
Posted : 29/05/2019 10:00 pm
therealnecroscope
(@therealnecroscope)
Active Member
Topic starter answered:
RE: Software layer shift?

I meed to find time to really search the forum and other published resources for Slicer to learn what all the parameters control amd how they interact with one another.

 

I also need to learn how to write custom g code so I can create tuning objects (tho, I bet they already exist somewhere)...say...a single perimeter tower that alters only the retraction length eveth 10 layers or so...

Posted : 29/05/2019 10:15 pm
--
 --
(@)
Illustrious Member
RE: Software layer shift?

People don't write custom gcode for anything serious. Just too much work.  Took me nearly three days to write enough gcode to print 12 adjacent one layer platforms for a silly extrusion test.

The photos look like you have belt tension issues, or even loose drive gears. 

There might also be some of the offset issue Bob is talking about, but you can test that by simply slowing down all perimeters to 15 mm/s and look for any improvements.  

Posted : 02/06/2019 8:16 am
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