PETG printing with CTC

Hello,

I have been printing PLA for years and am just starting to dabble with PETG. I had my bed heated to 75 deg C printing on Kapton with a brim, and the hot end was 230 deg C. (The printer still has the mk8 extruder hot end.) It worked! I printed a column with 10% fill and it came out very well. Print speed was around 35mm/s
 Then I tried a calibration block and everything went downhill. The infill stopped printing cleanly and the top surfaces could not be constructed. I tried changing extrusion temperatures, different fills and nothing worked for me. Here is an image of the fill:

After seeing this I cut the first print (see first picture) in half to see what the fill looked like there and it had came out good. Not sure what caused the change, I know this material is more abrasive and has is hard on the ptfe and nozzle in this hot end and am curious if this is the only reason for the trouble I am having. Thoughts?

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Here is a picture of the first print I had done with the PETG, I cut it in half to show the infill. This print came out good enough for what I would have needed. 

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PETG can be very tricky at times.

 

How much cooling did you use?

How much retraction?  

PETG is a VERY sticky material (one of the reasons it is not very good in bridging or supports). It can also clog your nozzle quite easily if you use a lot of retraction.

 

 

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I had a 120mm fan with a PWM slowing it to half speed. I had the retraction set at 1.5mm.

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I can't see how large your print is.

 

Personally, I print PETG on glass with 3DLac spray at a bed temp of 54 Centigrade and with 15-40% cooling depending on the model.

Using a bedtemp of 75 is a bit. 

If you try printing it again, when it start giving problems printing the layers, take a pin and try to get a feel on how solid and firm the underlying layers are. If they are still soft, You model is too hot.

 

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The cube was 20mm x 20mm and the column was around 25mm in diameter. I will try that though. Thanks for the advice! I could see that being the case. Also, I take it that printing with PETG requires greater amount of infill due to its tendancy to be soft and glob if given the chance?

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Hey Nate!

 

I print a lot with PETG and it just took some time to fine tune the settings, but more important was getting quality filament. I print with Matterhackers Pro PETG, Airwolf PETG and Makerbot PETG, and I cannot stress how important printing with quality material is. These PETG filaments are no more difficult to print than PLA is, whereas the cheaper stuff tended to be more of a struggle. 

 

You should be able to print PETG with normal settings (I typically use 3 shells, and 25-10% infill without an issue). I'm going to sway a bit from the norm here, and actually think you're printing too cool. I print with my PEI bed at 90degC, and with an extruder temperature of 247 (first layer is 250) and the fan at 65% (first layer of 0%). It looks like the printer is under-extruding, which would make sense if it's not hot enough. I'd also check for clogs in the nozzle, especially if you printed PLA before the PETG. The PLA will crystallize at the temps PETG prints at, and leave you with a clogged nozzle. Your calibration cube looks very similar to what happens with my Axiom if I don't fully clean the nozzle and hotend before switching to higher temp filaments. 

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Thanks for the advice!

 

Does PETG absorb water similar to PLA when storing? I am using the esun 1.75mm PETG and I have had it for a few months. I tried printing with it back when I got it but ran out of time while trying to get all the kinks figured out. I am wondering if this may have caused some issues too.

 

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Yup! PETG actually absorbs quite a bit more water than PLA does, I would definitely recommend keeping it in a dry box. 

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