1 Topic by adamjohnson.it4 (edited by adamjohnson.it4 2017-03-01 03:52:22)

  • adamjohnson.it4
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Topic: Burnt Spots in PETG Prints

Hello everyone, we've recently been trying to print this model for a customer which is a large flat box top with hinges that require supports, and they need it to be at least partially translucent so we've been using clear PETG. However, we keep getting these burnt spots in the print. We're printing on an Airwolf3D Axiom with eSun Natural (clear) PETG filament.

The settings we're using work great with other models using green PETG from the same manufacturer, but twice we've printed this model and both times we ended up with a burnt spot in the print, although it was in different spots on each. Any suggestions to get rid of this issue? Think we should try reducing the extrusion multiplier? Are we printing at too high a temperature? Usually this issue with PETG is from needing more Z offset, but I'm not sure how to adjust Z offset in Cura or Apex (Airwolf's version of Cura) and it seems strange that other large PETG prints in a different color have come out perfectly using the same settings.

Any suggestions would be a great help, we really need this order and this just isn't consistent with our usual quality.

Thanks,
Joe, Access 3D Services

Edit: After hearing back from our Engineer/Designer he suggested that due to the different color we should try reducing the hotend temperature, so I've lowered it from 250 to 240 since we've been successful with other PETG prints at that lower temperature. I've also read suggestions elsewhere that the printing should be at a consistent speed so I've set all of the outlines, infill, etc. to print at the same speed, as well as reducing the extrusion multiplier to 96% for PETG to reduce stringing. Hopefully all these things combined yield a better result, but I'd still be interested to read anyone else's suggestions. Thanks,

https://www.3dprintingforum.org/filedata/fetch?photoid=104525

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2 Reply by jagowilson

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Re: Burnt Spots in PETG Prints

What nozzle size and layer height? PETG likes at least a 0.6mm nozzle and 0.3mm layer height.

3 Reply by carl_m1968

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Re: Burnt Spots in PETG Prints

I use a .3 nozzle with PETG and PETG+ all the time with no issues.  Different colors will require different temps as the pigments absorb more heat. Natural will require the lowest heat.I print black at 255. You also need to go slow with PETG. I would never try to print PETG at more than 30mm/s. I usually use 25mm/s with good results. The first layer for PETG is very important. It needs to be about half of your desired layer. You don't want it picking up fragments or strings as those stick to the head, then burn, and then get dropped in your print.

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4 Reply by heartless

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Re: Burnt Spots in PETG Prints

i have run PETG through a 0.4 nozzle with no problem.

but yeah, heat is probably your biggest factor.

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