jeffrey.b22
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What to try next to reduce stringing?

Thu Jun 14, 2018 10:07 pm

I built my MK3 a couple weeks ago, and have been quite pleased with the prints. However, I decided to print the sample frog from the SD card last night with my Hatchbox orange PLA, and it's showed me how bad my stringing problem is. So much to try to remove from between the webs and legs and body...

Anyway, I decided to try to start cataloging the stringing effect on my MK3. I found a small 4 post string test print, and started changing settings.Image

From top to bottom, I ran prints from my default 210C, to 205C, 200C, 195C. I ran a temperature tower and it petered out at 190C and wouldn't continue printing past that point.

Left to right, I was increasing the retraction length. The 2nd - 6th rows I eliminated attempting prints that previously showed no improvement, and then I tried comparing a couple prints with same settings on Stealth and Normal modes.

The best results so far seem to be around 200C and 7mm retraction. That seems like a lot of retraction for direct drive from what I've read, and I don't want to keep pushing it that far if it's not worth it.

Here's a close up of the results I'm seeing with default settings:
  • 215C first layer
  • 210C rest of the print
  • 0.8mm retract distance
  • 35mm/s retract speed
  • 170mm/s non-print move speed
  • Stealth mode
Image

Same settings, bumped to 5.0mm and 7.0mm retraction distance, looking better than defaults, but still fuzzier than I'd like:

Image

And same settings at 205C rest-of-print temp, 5.0mm and 7.0mm examples:

Image

And the end of my testing for today:

Right test is:
  • 215C first layer
  • 200C rest of the print
  • 7.0mm retract distance
  • 35mm/s retract speed
  • 200mm/s non-print move speed
  • Stealth mode
Left test is:
  • 215C first layer
  • 195C rest of the print
  • 7.0mm retract distance
  • 35mm/s retract speed
  • 200mm/s non-print move speed
  • Normal mode
Image


Very last one, increased the retract speed to 50mm/s, poor photo, but I would say it looks mostly like the last pair of tests above:

Image

curtis.c2
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Re: What to try next to reduce stringing?

Thu Jun 14, 2018 11:23 pm

try 45-55 retract speed, and get a better fan shroud. thats an awful lot of retraction for direct drive.

this should go without saying, but make sure your printer is actually printing *real* models well before going crazy over a beyond-worst-case stringing test.

jeffrey.b22
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Joined: Fri Mar 30, 2018 3:34 pm
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Re: What to try next to reduce stringing?

Fri Jun 15, 2018 12:09 am

Yes, I will give 45-55mm/s a try for the run of tests (210C/45-55mm, 0.8mm retract, and 195C/45-55, 5.0mm and 7.0mm retract) tomorrow.

I have printed many things on this printer so far, and have been quite happy with how things are coming out, up til the tree frog example. That one was just being so difficult to clean the stringing out of, it got me searching for improvements in that area.

Most of the other things I've been printing don't have lots of hops across empty spaces, so it hadn't been much of an issue before.

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devilhunter
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Re: What to try next to reduce stringing?

Fri Jun 15, 2018 1:38 am

Different filaments have different stringing properties, maybe try some different brand or filament color.
I have a few special PLAs (color changing, glow in the dark, particle infused) from aliexpress and amazon, and they are super stringy. Like double that of PETG.

Normal PLA from local retailer only strings a little bit.

eric.l25
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Joined: Thu Mar 08, 2018 7:02 am
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Re: What to try next to reduce stringing?

Sat Jun 16, 2018 12:34 am

I agree that you should try another brand of filament before going too much farther on this. That's a heck of a lot of stringing! I'm not sure I could force my MK3 to do that much stringing with PLA if I tried. I've never seen that result on my printer.

RetireeJay
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Joined: Tue Feb 13, 2018 10:47 pm
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Re: What to try next to reduce stringing?

Sat Jun 16, 2018 2:39 pm

I did some experiments a while back with the winged dragon print, and I found a couple of other adjustments (besides temperature and retract distance) that helped. By default, the "stock" Prusa settings include "wipe" and "raise the z before non-printing moves"; I eliminated both of those settings and the stringing problem got much better.

On the E3D extruder, it is strongly recommended to never retract more than 0.3mm or so, because you are pulling melted hot plastic into a cold zone where the plastic can solidify and create an extruder jam.

Right now, I'm printing a set of replacement plastic parts (before I need them!) for the MK3. For small parts, I'm printing 2 - 4 parts at a time, and I see no stringing at all between the parts. The filament I'm using is Max-G from 3DXTech. My extruder is at 240C, using no wipe, no Z raise, and 0.3mm retract.

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