WhiteHare
Posts: 22
Joined: Sat Jun 02, 2018 6:41 pm

How to keep corners good when printing fast?

Sat Jun 16, 2018 9:45 am

Here's a test object that I'm printing at 3000mm/min using a 0.8mm volcano nozzle and PETG filament and linear advance K=20. Layer height is 0.4mm and extrusion width is 0.96mm. The corners look acceptable to me:
3000mm.jpg
However, if I increase the speed to 4000mm/min, the rest of the model stays fine, but the corners look terrible:
4000mm.jpg
What can I do to keep decent corners a higher speeds?

MasterFX
Posts: 206
Joined: Tue May 20, 2014 10:23 am

Re: How to keep corners good when printing fast?

Sat Jun 16, 2018 12:03 pm

This looks for me more like a cooling problem. Did you turn your fan on? I mean 66mm/s isn't that fast, but since you are printing only perimeters (or Vase Mode) each layer takes not that long, and therefor the filament from the layer below isn't cooled down enough.

zemlin
Posts: 256
Joined: Mon Feb 01, 2016 11:36 am

Re: How to keep corners good when printing fast?

Thu Jun 21, 2018 4:19 pm

I'd call that going too fast.

You might improve the results by increasing the nozzle temperature which will reduce the viscosity, elasticity, and tensile strength of the extruded bead and might improve the layer bonding.

wirlybird
Posts: 1035
Joined: Sun Jul 17, 2016 12:32 pm

Re: How to keep corners good when printing fast?

Fri Jun 22, 2018 6:05 am

It doesn't seem to be exceptional fast but one thing is that PETG doesn't like to be printed fast. I am guessing you are on a MK2 or MK3?

I normally print PETG at a max of 40mm/s on my MK2.

TheBum
Posts: 55
Joined: Fri May 18, 2018 10:13 pm

Re: How to keep corners good when printing fast?

Fri Jun 22, 2018 11:11 am

wirlybird wrote:
Fri Jun 22, 2018 6:05 am
I normally print PETG at a max of 40mm/s on my MK2.
Same on my Snapmaker. and even then the corners are a little rough.

User avatar
dkightley
Posts: 1892
Joined: Tue Mar 10, 2015 3:09 pm

Re: How to keep corners good when printing fast?

Fri Jun 22, 2018 12:59 pm

It doesn't seem to be exceptional fast...….
I'd agree there......but having looked at the nozzle size I begin to wonder if the hot end is not coping properly with the amount of plastic it is being asked to heat and extrude. I think its a flow rate issue as opposed to a speed issue!
Doug Kightley
Volunteer at the National Tramway Museum http://www.tramway.co.uk
Railway modeller and webmaster at http://www.talkingtgauge.net

jgwinner
Posts: 8
Joined: Sat Mar 09, 2019 4:09 pm

Re: How to keep corners good when printing fast?

Sat Mar 09, 2019 9:44 pm

Did you figure out what it was?

== John ==

zemlin
Posts: 256
Joined: Mon Feb 01, 2016 11:36 am

Re: How to keep corners good when printing fast?

Tue Mar 12, 2019 10:04 am

Coming back to this topic with some additional experience, I'd also suggest running an extrusion width about 1.2 x of the nozzle diameter. The plastic expands naturally when it exits the nozzle. Trying to maintain an extrusion width equal to the nozzle diameter requires the stream to be stretched a bit and can pull in on the corners.

jgwinner
Posts: 8
Joined: Sat Mar 09, 2019 4:09 pm

Re: How to keep corners good when printing fast?

Thu Mar 14, 2019 8:26 pm

Thanks. I just checked, and for some reason my profile was at 100% of the width. I changed to "auto" and it set it at .48mm (vice .4mm, same size nozzle)

== John ==

zemlin
Posts: 256
Joined: Mon Feb 01, 2016 11:36 am

Re: How to keep corners good when printing fast?

Fri Mar 15, 2019 7:52 am

jgwinner wrote:
Thu Mar 14, 2019 8:26 pm
Thanks. I just checked, and for some reason my profile was at 100% of the width. I changed to "auto" and it set it at .48mm (vice .4mm, same size nozzle)

== John ==
Let me know if that helps. My reply was somewhat speculative. Confirmation would be good.

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