Corner bulging on 90 degree features in 2019

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Mount PrintMore
Posts: 34
Joined: Mon Apr 14, 2014 4:09 am

Corner bulging on 90 degree features in 2019

Post by Mount PrintMore » Wed Nov 06, 2019 3:24 am

What is the latest and greatest thinking on corner bulging on sharp features?
I've been trying to dial the last bit of performance out of my machine, and this corner bulging is about the final thing I'd like to improve.

I tried a bunch of different acceleration and jerk settings, as well as fiddled a bit with the ooze control settings, but nothing seemed to actually change the resulting part.

The only thing I have found that "fixes" the issue is to turn the outline underspeed way down (like down to 20% or so). Obviously, this slows the print down substantially.

I'm using Simplify3D for slicing.

There was extensive discussion a while back about perhaps extruder acceleration contributing to the issue.
viewtopic.php?t=4844

I tried turning up and down the extruder acceleration as well as the extruder jerk. None of it seemed to matter.

Here's things I tried:
Default is M201 X900 Y1000 Z30 E2000
M205 S0.00 T0.00 B20000 X4.00 Z0.40 E1.00

The forum thread above suggested turning down the extruder accel
M201 X1000 Y1000 Z30 E100

I tried even lower:
M201 X900 Y1000 Z30 E20

I tried cranking up the extruder jerk
M201 X900 Y1000 Z30 E2000
M205 S0.00 T0.00 B20000 X4.00 Z0.40 E20.00

----------------------------------------------------------
If anyone is interested, I've attached the test files I've been running. I've been putting all 3 on the build plate at once and running them all with the same settings.
Attachments
Thru.stl
(293.58 KiB) Downloaded 45 times
Solid.stl
(111.7 KiB) Downloaded 10 times
Cup.stl
(178.33 KiB) Downloaded 10 times

airscapes
Posts: 365
Joined: Wed Jan 31, 2018 11:36 pm

Re: Corner bulging on 90 degree features in 2019

Post by airscapes » Wed Nov 06, 2019 4:57 am

Got a picture of what you are are talking about.. you talking about the Z change bulge? I typically put fillets on all my edges when I design an part even if it is .06 just to eliminate sharp corners as I don't like them.. the Z lumps are a pain and I have found that it is more pronounced when extruded properly and is worse with certain filament types, PLA being the worst.. I think due the the fact that it does not flow as nicely as ABS.. So lets see what you are talking about.. I have more or less accepted that 3Dprinting is not the end all be all and is just a means to prototype quickly.. not going to look like an injection molded part nor be able to skip the post process sanding filling painting an whatever if you want a "finished" surface texture... but that is just me.

Mount PrintMore
Posts: 34
Joined: Mon Apr 14, 2014 4:09 am

Re: Corner bulging on 90 degree features in 2019

Post by Mount PrintMore » Wed Nov 06, 2019 1:12 pm

I have a hard time taking pictures, as there is no natural light in my workshop (all LED shop lights) and this time of year the days are quite short.
I took this this am in my kitchen with my camera set to "night mode"...

I don't believe the corner bulge I'm talking about here is related to the zaxis motion.

It is more to do with the relation of the extrusion flow and the X/Y motion.

I'm running an M2, 24 Volts, V4 hotend. I just run the standard 0.35mm nozzle, and am currently running Hatchbox PLA.

My default printspeed is 4800 mm/min. I normally do a 60% underspeed for the outlines.

The thin wall cube was small enough it triggered the separate de-rate for too short of a layer time, which put the printspeed down to 20% of normal.

The parts with a '2" on them are the typical results I get.
The parts with an "8" on them were run with the print speed slowed down to 20%.
Attachments
003_Num2_RE.jpg
004_Num8_RE.jpg
002_Cube_RE.jpg
001_Overview_RE.jpg

airscapes
Posts: 365
Joined: Wed Jan 31, 2018 11:36 pm

Re: Corner bulging on 90 degree features in 2019

Post by airscapes » Wed Nov 06, 2019 3:58 pm

Well, if I did the math correct you are trying to print these tiny model as 80mmS .. You are getting the correct results.. Dragging a round squished molten plastic thread around a 90 degree turn at light speed.. They made a move about this.. Tokyo Drift.. :D

I will attempt to attach 3 sets of photos, each set of models was printed at progressively slower speed.
First was 50mms Second was 30mms and the Third is 20mms which is the speed I would have started with if I was printing something this small and I wanted it accurate.
thru 50mms.jpg
solid 50mms.jpg
cup 500s.jpg
Last edited by airscapes on Wed Nov 06, 2019 4:01 pm, edited 1 time in total.

airscapes
Posts: 365
Joined: Wed Jan 31, 2018 11:36 pm

Re: Corner bulging on 90 degree features in 2019

Post by airscapes » Wed Nov 06, 2019 3:59 pm

30mms
thru 30mms.jpg
solid 30mms.jpg
cup 30mms.jpg

airscapes
Posts: 365
Joined: Wed Jan 31, 2018 11:36 pm

Re: Corner bulging on 90 degree features in 2019

Post by airscapes » Wed Nov 06, 2019 4:00 pm

20mmS
thru 20mms.jpg
Solid 20mmS.jpg
cup 20mms.jpg

airscapes
Posts: 365
Joined: Wed Jan 31, 2018 11:36 pm

Re: Corner bulging on 90 degree features in 2019

Post by airscapes » Wed Nov 06, 2019 4:02 pm

Two words will fix this, SLOW DOWN! :-)

BTW the photos were take with this cheapo USB microscope on the low magnification setting
https://www.amazon.com/dp/B00XNYXQHE?aa ... B00XNYXQHE

Mount PrintMore
Posts: 34
Joined: Mon Apr 14, 2014 4:09 am

Re: Corner bulging on 90 degree features in 2019

Post by Mount PrintMore » Wed Nov 06, 2019 6:11 pm

The overall size of the part doesn't really impact the bulging corners directly. You get the same amount of bulge whether the part is the size of a quarter or the size of a dollar bill. The only caveat to this is depending on your acceleration settings, a large part allows the machine to get to higher speeds, and perhaps exaggerates the problem.

The impact on print time of slowing down is much more severe on a larger part.

These small test parts are just the smallest/fastest examples I could come up with that highlight the problem.

Let's say for example, I was printing a gear with a pitch diameter of 6 inches. I wouldn't want these blobs in two places on each tooth. Slowing down the perimeter print speed to 20 mm/sec will easily double the print time.

The car analogy is a good one. A race car doesnt drive the entire track at the speed it can take the slowest turn. Instead it accelerates and brakes to maximize velocity/minimize time.

It's been a while since I really looked around to see what other people were doing, so I thought I'd ask. If the answer is still "go slow", I guess it is what it is.

While researching this the other day, I stumbled across a note in the Marlin documentation that caught my eye. There is a feature called S_CURVE_ACCELERATION .

It's not in the config.h from MakerGear, as it appears to be a newer feature. Anyone fiddled with this?

Thanks for the lead on the microscope. That would really be handy. Every year it seems like all the stuff I'm working on shrinks....

airscapes
Posts: 365
Joined: Wed Jan 31, 2018 11:36 pm

Re: Corner bulging on 90 degree features in 2019

Post by airscapes » Wed Nov 06, 2019 7:22 pm

I would guess that there are improvements to this with some of the newer controller boards and firmware. Unfortunately the is another can of worms to replace the board and firmware.. I am just a hobbies so this is not something that bother me, I guess I have accepted the fact that FFF is not injection molding or machining, post production work is a requirement. Wish that was not true, but for now I am still thrilled to be able to model something from nothing and fabricate a functional part that works most times. It does work for everything, but really helps with things that can't be fabricated at home by any other means.
Good luck on your quest!
Doug

Gwhite
Posts: 237
Joined: Tue Jul 11, 2017 3:38 pm

Re: Corner bulging on 90 degree features in 2019

Post by Gwhite » Fri Nov 08, 2019 9:41 pm

From what I've read, "Linear Advance" might help, but it appears to require installing new firmware in the controller board. I looked into this, and decided it was going to be too complicated for me to bother with at the moment.

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