joaojoao
Posts: 43
Joined: Sat Sep 02, 2017 11:02 am

PLA vs PETG

Hi,
Can anyone try to explain to me why my printer keeps clogging (and skipping) with PLA (specially white and black PLA) and works fine with PETG? I think it problably has anything to do with the diferent transitional temperatures of both PLA and PETG. Because PLA have lower transitional temperature maybe the cooling fan at the cold end can´t cold enought the PLA filament and it works with a temperature above the 40ºC I think it shouldn´t run. PETG have a much higher transional temperature, so it work on a "harder" or more solid state in the cold end..
What do you think?
arhi
Posts: 483
Joined: Thu Oct 06, 2016 5:13 pm

Re: PLA vs PETG

the "cold end" of your "hot end" is too hot.
with higher printing temp petg can withstand higher temp of the cold side of a hot end due to higher Tg and also your cold side of hotend is releasing more heat to the ambient due to higher temperature (higher the temp difference between your cold end and ambient more watt/mm2 you will dissipate)

all in all, in order to not have issues with PLA, make sure your cold side of hotend is properly cooled

additionally, reduce max retraction length, on most hotends 1mm is safe for PLA, PETG can survive 1.5-2mm on most hotends... (some will allow much higher values but you really need a very bad hotend not to be able to work with 1mm retraction with PLA )
gcodestat integrates with Simplify3D and allow you to
Calculate print time accurately (acceleration, max speed, junction deviation all taken into consideration)
Embed M117 codes into G-Code
Upload your G-Code directly to Octoprint
open source and unlicence
joaojoao
Posts: 43
Joined: Sat Sep 02, 2017 11:02 am

Re: PLA vs PETG

thanks for your reply!
Indeed I´m working with 2mm of retraction, and recently turn on my fireplace wich increases the room temperature where the printer is.
The winter is comming.. ;)
arhi
Posts: 483
Joined: Thu Oct 06, 2016 5:13 pm

Re: PLA vs PETG

joaojoao wrote: The winter is comming.. ;)
winter brings one huge advantage to us 3d print users... the air in our houses is lot dryer then normal so the filament get very dry and print quality increases :D especially when using hygroscopic filaments :D

not all is dandy 'cause dry air also increases buildup of static electricity so poorly designed printers with poorly designed electronics tend to "auto reboot" and even "self erase eeprom/flash" or "kill the electronics" due to high voltages creeping over the printer... (I measured 15kV building up on rapman's extruder that was mostly acrylic body, and 15cm sparks were not that rare during long winter prints, and restarting electronic ruined many prints... original solution was to add wet towel over the body of the printer :D later we added some protection circuitry and properly grounded the whole thing)
gcodestat integrates with Simplify3D and allow you to
Calculate print time accurately (acceleration, max speed, junction deviation all taken into consideration)
Embed M117 codes into G-Code
Upload your G-Code directly to Octoprint
open source and unlicence
wirlybird
Posts: 1374
Joined: Sun Jul 17, 2016 1:32 pm

Re: PLA vs PETG

You really need to post some details of the setup so we don't just guess at things.

What printer, slicer, temps for PLA and for PETG, what speeds?
joaojoao
Posts: 43
Joined: Sat Sep 02, 2017 11:02 am

Re: PLA vs PETG

printer: hellobeeprusa from portuguese hellobeecreative
PLA: 215ºC , 2mm retraction @25mm/s , 45mm/s speed
PETG: 240ºC , 1mm retraction @25mm/s , 40mm/s speed

slicer: Simplify3D
wirlybird
Posts: 1374
Joined: Sun Jul 17, 2016 1:32 pm

Re: PLA vs PETG

joaojoao wrote:printer: hellobeeprusa from portuguese hellobeecreative
PLA: 215ºC , 2mm retraction @25mm/s , 45mm/s speed
PETG: 240ºC , 1mm retraction @25mm/s , 40mm/s speed

slicer: Simplify3D

One thing I can see is your PLA retraction is a bit high. For a direct drive you really want to stay under 2mm. On my Prusa MK2 I generally run at .8mm and 35mm/s.
Also your PLA temp might be a bit high also. Try running at 200-205 and see. 40mm/s print speed is pretty good to start out with. Also go with a .2 layer to get things dialed in.
joaojoao
Posts: 43
Joined: Sat Sep 02, 2017 11:02 am

Re: PLA vs PETG

ok, I already decrease my retraction and speed and temp, and it seems to be working fine..thanks!
wirlybird
Posts: 1374
Joined: Sun Jul 17, 2016 1:32 pm

Re: PLA vs PETG

Great news!!!

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