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jtghoops13

PET-G Problems

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I purchased an Ultimaker 2 extended+ about 2 months ago. I printed with PLA during this time. Recently have decided to start printing with PET-G. Does anyone have any recommendations with this filament. I have flirted with different temperatures ranging from 245-260C at the nozzle with the build plate between 60-100. Each print seems to be warping. I'm not sure what I need to do with the fans and retraction settings. I am using CURA Does anyone have any recommendations?

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picture please. your "warping" might not mean what my "warping" means. I assume you mean: "it's absolutely perfect except some or all corners are lifting and absolutely no other problems!". If that's what you mean than that is very common with higher glass temp materials (basically anything besides PLA).

There are many solutions - the best involve getting it to STICK LIKE HELL although PET has a reputation for sticking so well that pieces of glass bed come off into the print. Some solutions:

1) Corners MUST be rounded. Having a sharp corner concentrates the pulling force on it. If your corner must be sharp then add brim. Adding brim also helps big time for other reasons - spreading the lifting force out over larger area and not letting air get inder (vacuum held down part, lol).

2) cover the front of the machine. This is probably mandatory with PET and ABS as if you don't you probably get bad layer adhesion also anyway. So just do this.

3) Cover the top - not well - just put a stupid box on it. Tape it on. Don't try to get fancy with scissors or anything. This should bring air temp during printing up to 40C to 50C. Don't go over 50C as steppers will not be happy.

4) squish the bottom layer well into the glass - just turn your 3 screws CCW (raise glass towards nozzle) by a half turn. Turn them equal amount. Don't worry about leveling procedure - ignore that.

5) Clean glass. Consider adding very very thin layer of PVA but this can again cause your part to remove some glass chunks! So this is last resort (second to last - last resort is to use raft - but don't do that! Not necessary!)

6) Hot build plate. Keep it above glass temp of material. Look it up. I'm guessing around 100C is best. Not certain. This also helps heat the air in your box. In fact let it stay hot for a good 15 minutes before starting the print.

7) Less fan - this won't help warping so much as help your layer adhesion issues which you haven't noticed yet :)

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Thank you for your detailed answer. I am gonna do some further testing using your advice. Have you experienced a certain fan level that seems to be ideal? I have played around with no fan and a small percentage of fan normally less than 25%. It appeared to me that some levels were not cooling enough and the next level was interfering with it. Any recommendations are greatly appreciated.

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For PETG you need to dial in your nozzle temp to a small window of about +- 5c. I use eSun brand mostly and it seems to like 238 - 243 best. The temp can stray up and down outside of that range, but you can see differences in the print as a result. Example: temp way too low = very slow extrusion. temp a little low: lines printed next to each other stay separate instead of merging into 1. temp a little too high = lots of stringing. Temp way too high = inconsistent extrusion diameter of lines being printed.

I like to make the temp such that minor occasional stringing occurs across open spaces. It seems like then I get very strong parts with good layer bonding.

Ideal bed temp for my projects have been 75C. I use a coat of hair spray (applied when bed is cold), and it keeps the print fixed in place until the bed cools down. I haven't experienced warping unless there's a large flat bottom layer. But I do have the machine's front and top covered.

Good luck!

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kapton? That's old technology. Now we use glass with glue. I did many prints on kapton on aluminum bed but I love glass - so much easier to get it to stick.

Remove kapton, clean the hell off the glass - get it perfectly clean. Try soapy water in the sink, maybe use alcohol or acetone to get all the glue residue off - then you need a thin layer of pva (found in glue stick, hairspray, wood glue). I prefer wood glue - I mix it in a jar 90% water, 10% wood glue). Paint it on the glass while in the machine, heat it up and it dries to invisible. hairspray is best for a noob but you have to remove the glass every time or you get glue all over your machine's working parts.

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@jtghoops13 - in addition to the capton comment above...

For ABS at least (never printed PET) which is also a high glass temp material, you don't need any fan at all for the part you showed (vertical walls - not the slightest overhang) but it will look better and come out more accurate with a tiny amount of fan. And if you print much smaller parts you need fan also or they won't cool down before the next layer is applied.

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Usually the issue is not so much the glue but that you aren't squishing your filament enough into the glass. You want it squished nicely like the blue filament below:

skirt.thumb.png.6b55ac68e85d4be60c98ec88f89bf5ca.png

skirt.thumb.png.6b55ac68e85d4be60c98ec88f89bf5ca.png

Edited by Guest

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 hairspray is best for a noob but you have to remove the glass every time or you get glue all over your machine's working parts.

 

Yes definitely remove the glass to apply the spray. I only need to reapply the spray once every 25 prints or so, though. You can see marks where previous prints have been, but there's still a layer of spray on the glass and it keeps on working

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Thank you for your response.  In objects printed with flat bottom what did you find useful and securing it down?  I currently use kapton tape.

 

I'd slow the print speed. If you notice with PETG , it likes to go up toward the hot nozzle and stick to the nozzle whenever possible. It'll defy gravity to move toward that heat. In this way PETG's warping differs from ABS I think. ABS is shrinking as it cools. I'm sure PETG does this slightly as well, but more of the peeling up is caused by that soft plastic wanting to follow the hot nozzle IMO. Even on medium-sized prints when using this material, the plastic will be soft a few layers deep because it maintains heat for a long time after extrusion. I think slowing the print helps the plastic stay stuck to the glass.

Like @gr5 , I don't use Kapton. I use a heated glass bed with hair spray for PETG. For PLA I use glue stick, but for PET the extreme-hold spray works better for me, with less cleanup required

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Would you recommend pausing after first layer is laid and physically squashing that layer into the plate?

No. By then it's too late. You need to do it while the plastic is above 200C which only lasts maybe 10ms (one hundredth of one second). You simply turn the leveling screws (turn all 3 equal amounts) a small amount to get the plastic to squish better. If you use the leveling procedure then after turn all 3 screws about half turn CCW. Or just use my visual guide above and level it "live" when bottom layer is printing.

You should be doing the "live" leveling anyway on every print until you can do it without thinking.

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Hi,

We are using the Ultimaker 2 extended with 3DX tech PETG 3mm Black filament and nozzle of size 0.4mm, the first layer of the print is good, but once it starts printing the second and the third layer, the print layers gets completely ruined with the black PETG filament forming strings and material start to accumulate around the nozzle which keeps on dragging as the print continues. We would like to know how can we tackle the situation of material accumulation and stringing? Your expertise is highly appreciated.

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I have used PET (or is that PETG?) from the brand ICE. This has an indicated temp range of: 215°C...250°C. I found that it prints well at 220 to 225°C. Lower temp causes underextrusion, higher causes too much stringing and hairs. Layer bonding is quite good when printing slow: 25...30mm/s, if using no fans. I use no brims, no raft. Heated bed: ca. 80...90°C. At 70...80°C it comes off and warps, so 10°C more made a huge difference in sticking.

 

To prevent warping, I print with fans off, on bare glass. No treatment of the glass, except from cleaning well (no soap, no detergents, only pure water). But printing without fans causes poor overhangs, and it has difficulty closing gaps on top of models, like a roof.

 

When I need to print good overhangs, I need fans for cooling. Then I need glue on the glass bed (gr5's method: 10% white wood glue in water). But this chipped the glass once: while cooling, I heard weird cracking sounds, and when pulling off the model, part of the glass bed came with it. I think it already chipped the glass during cooling, at least partially, not as a result of moderate pulling.

 

So, as long as I don't need much overhangs, I prefer to print on bare glass, no bonding, bed=90°c, nozzle=220...225°C, speed=25...30mm/S, no fans.

 

Try a small test model first, a solid bar (e.g. 10mm wide x 10mm high x 50mm long) with some overhangs and sharp corners, for example, because these cause high warping forces. If that works well, other models should work well too.

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Hi,

I tried printing with the model as mentioned, but no luck yet with the PETG. Stringing and material accumulation at the nozzle still persists. We have tried a variety of combination with respect to hothead temperature, fan speed, retraction distance, retraction speed, bed temp, printing speed etc. Is there another way/settings I could use this PETG for better output results? Thank you.

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