Clear PETG blemishes  

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fabnavigator
(@fabnavigator)
Eminent Member

@swiss_cheese

I'm glad you clarified that about spiral vase mode.

I'm using Prusament clear PETG and the default temperature is 250C, so I won't change that for now.

The default filament override retraction settings are length = 1.4 and lift z = 0.2. Are you suggesting I change the length to 0.2?

The default external perimeter width is 0.45mm. I'll try 0.65mm, but I expect that the walls will touch.

Posted : 24/01/2021 6:36 pm
Swiss_Cheese
(@swiss_cheese)
Reputable Member

At 0.65 the walls will touch,I didn't think you were going to try and fit anything in between them, and that gives the clearest result. the retractions set to 0.2 in filament override will push the retractions to the far right on the model and all the retraction and detraction will occur at the right end giving a clear wall. now as for the Prusa PETG, I print with it and my experience is that it prints best in its upper range Prusa has it marked as printable from 240-260C I find that some of their PETG filaments print better at 265C, I wouldn't be afraid to try printing it hotter If you find that 250C isn't giving the result you want. I mentioned that I was using Overture PETG and it's top end temperature according to the manufacture it 250C, however their clear/transparent prints best for me at 252C, there white prints best for me at 232C, the take away here is to play around with your temps and see what temperature that specific filament prints best at. If your not failure with them Temp towers are a good method for checking these.

Let us know how things turn out,

Good Luck

Posted : 24/01/2021 8:04 pm
fabnavigator
(@fabnavigator)
Eminent Member

@swiss_cheese

I did one test at 260C, 0.65mm outside perimeter, and 0.2 retraction length. It looked very good. Almost as good as in spiral vase mode. I will try some other combinations when I get some time. I also eventually need to print my final design, which isn't as simple as this test box.

Thanks for your help. I'll post more results as I get them.

Posted : 25/01/2021 4:54 pm
g monkey
(@g-monkey)
Eminent Member

I have been printing some model windows with Prusament PETG and found that if I turned retraction off completely then the bubbles disappeared (0.6mm nozzle with one perimeter set, but on a window pane this becomes two perimeters).  I recently used some transparent PC and they came back - until I dried the filament in a dehydrator for several hours.

Posted : 25/01/2021 5:12 pm
fabnavigator
(@fabnavigator)
Eminent Member

@g-monkey

There is definitely some consensus that retraction is the cause of the bubbles. I wonder if anyone has a theory about why retraction causes the bubbles, considering they don't line up with the retraction location.

Posted : 25/01/2021 5:41 pm
Swiss_Cheese
(@swiss_cheese)
Reputable Member

@fabnavigator

Each and every model requires different tuning, sometimes you have to make adjustments to your g-code to print one kind of model feature different from another in the same model, and sometimes we have to make compromises and allow for an unwanted blemish here, to avoid it there, (if you catch my drift). In this case you are doing experiments to lean how your material and printer are responding to a given situation, and this information will help you to gain the control you need to tune features in future models. as for the bubbles, they can caused by moisture in the material, nozzle temps to high (boiling the filament) or irregular shaped nozzle (worn out nozzle) those are the ones I'm aware of.

This post was modified 1 month ago by Swiss_Cheese
Posted : 25/01/2021 6:05 pm
fabnavigator
(@fabnavigator)
Eminent Member

@swiss_cheese

I would expect that if I had any of those possible causes of  bubbles that I would see it in spiral vase mode. Retractions are pretty much the only difference between spiral vase mode and printing this model layer by layer.

Posted : 25/01/2021 8:53 pm
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