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Should PETG prints look the same as PLA prints?  

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Mel
 Mel
(@mel)
Active Member
Should PETG prints look the same as PLA prints?

I still struggle with my PETG prints. Obviously, I started my printing journey with PLA and my MINI+ gave always great results out-of-the-box without any tweaking. Now I bought the 2kg rPETG spool to try something new and I wonder if it is normal they aren't as perfect as I was used to from the PLA experience.

Of course there is way more stringing with PETG and that was to be expected. But apart from that I feel PETG does also print way less delicately than PLA. I need to consider higher tolerances for mechanics to work (at least .25mm where I was able to work with .1mm using PLA) and fine details disappear in PETG (e.g. small holes <= 1mm in filament swatches get closed) which were clearly working in PLA.

On that I did not read anything in the usual filament comparison texts on the web so now I wonder: Is that totally normal and I have to live with these differences - or do I need to tweak printer settings and can get to the same print quality I experienced with PLA?

 

Posted : 13/04/2022 2:57 pm
mark
 mark
(@mark-3)
Reputable Member
RE: Should PETG prints look the same as PLA prints?

PETG does indeed string more than PLA and has issues like elephants foot (spreading at the bottom), corners that are not as sharp and worse tolerances. It also should be dried for best results. It makes a big difference in print quality. It is more robust than PLA for structural items. In general it won't be as pretty as PLA even if you do everything right, but you can improve things.

Regards,

Mark

Posted : 14/04/2022 5:57 am
BogdanH
(@bogdanh)
Honorable Member
RE: Should PETG prints look the same as PLA prints?

From my experience, PETG prints look almost the same as PLA prints on my Mini (Prusament filament at default settings used). To avoid elephant foot, I decrease bed temperature by 10°C -it still stick very good on textured sheet and result is good. As for stringing and print accuracy: always properly dry PETG before use!
If small details (i.e. holes for bolts & nuts) are needed with high precision, then that needs to be taken into account when designing the part. For example, if hole of 3mm diameter is needed, then it should have diameter of about 3,2mm in design -depends on filament and print settings.

[Mini+] [MK3S+BEAR]

Posted : 14/04/2022 10:29 am
jsw
 jsw
(@jsw)
Famed Member
RE: Should PETG prints look the same as PLA prints?

A few differences I've noticed between PLA and PETg.

In general, both of these are good for general-purpose noncritical printing, but both have their strengths and weaknesses.

The surfaces of PETg prints usually have more of a shine or luster than do PLA prints.

PLA prints appear to be a bit harder and stronger than PETg prints, but I have no actual data, other than naive observation, to back this up.  Some claim that PETg produces stronger prints than PLA. (flip-slap!)

I've found that PLA is significantly better than PETg for prints that require small precise detail work.  Specifically, small gears print better and more easily with PLA than with PETg.  Small detailed pieces, such as the fire escape handrails for model railroad buildings (see photo below) print MUCH better with ABS or PLA than with PETg.

PETg will have a greater ambient temperature tolerance than PLA.  I've heard folks complain of PLA prints deforming in hot cars, but not for PETg prints.  Some say that PETg has greater sunlight tolerance than does PLA.

Parts with taller unsupported cylinders (such as an AAA battery 'contact slug') print better and more consistently with PLA.  I recently tried one of these with PETg because that's what I had loaded in the printer.  A print with PLA was more cosmetically appealing.

Posted : 15/04/2022 9:18 pm
rinkel
(@rinkel)
Estimable Member
RE:

I usually print PETG for functional parts, where the cosmetics are not really important. I usually do get good tolerances though, but i had one spool of PETG filament where my circled holes in Z direction were oval, not a true circle. This did not happen on my other PETG brands.

Yes, PLA looks much better cosmatically. But PETG should be perfect for functional parts.
I however started to take a look at PLA+ for functional parts. It is much more like PETG when it comes to strength, but has a matte look and feel, a bit like ABS. I really like the look and feel. As a bonus: it prints like normal PLA.
It's a bit more expensive though.

Maybe the TS can post some pictures to explain.

As an example: I also reprinted all of the MINI's orange parts, in PETG with all the screwholes and other delicate cuttings. This worked out just fine. However, i did not print anything with small holes like 1mm.

 

Posted : 16/04/2022 8:29 pm
Mel
 Mel
(@mel)
Active Member
Topic starter answered:
RE: Should PETG prints look the same as PLA prints?

Thanks for all your input! I will take my filament roll to the oven and I have bought a lot of silica gel already. Also there is a new roll of PETG incoming, maybe the recycled version I tried first has less quality overall. So I am trying Signal White next and see where this is going.

Posted : 26/04/2022 7:21 pm
rinkel
(@rinkel)
Estimable Member
RE: Should PETG prints look the same as PLA prints?

In my experience: Not all PETG are equal.
Same goes for color: White is more difficult to print.
I have had good experience with Polymaker PETG but less with Fiberlogy, eventhough there are good reviews on youtube.
I have not tried prusament PETG though, but my guts says it will be good.

 

Posted : 26/04/2022 10:13 pm
Crab
 Crab
(@crab)
Estimable Member
RE:

I don’t have enough experience, but I feel that there is a wide range of differences between PLAs. I’ve tried PolyTerra, which I found had a nice matte finish, but was fairly prone to breaking along seams. PolyTerra PLA+ Is a bit better for strength and had a silky finish. While I found PolyLite PLA was shiny and more like PETG. I think manufacturers put so many different things in their PLAs they are hard to compare. (I did use the Silver Prusa PLA that came with my kit and it was quite a bit better than the PolyTerra PLAs)I have used Prusa and PolyLite PETG. I had all kinds of issues, originally, with bed adherence, bridging, using supports, and stringing. The bed adherence was fixed by tuning the Z and buying a rough PEI and dialing that in. Now my rough PEI bed is much more consistent with PETG than my smooth with PLA. All the other issues were temperature related (for me). When I turned down the temp about 20F and turned the fan on 80% (constant), my bridging was much better. I pretty well used the stock profiles of PrusaSlicer. The Prusa PETG (Galaxy Black) is really nice but the Poly also works well now. In fact, PETG is my favorite filament in printing some RJ45 holders, spool rollers, and a ton of cube-style puzzles. It has a nice gloss, the parts slide easily over each other and it is much more flexible than the PolyTerra PLAs. I have found that depending on the model, I often have to tweak slicer settings, but I not experienced enough to know exactly the effect they all have. So getting back to the original question.. I think one should be able to make PETG and PLA very similar dimensionally, but flexibility, gloss and strength are different. I did like the PolyLite PLA better for texture, but it was also a bit finicky for temperature. I’ve ordered some Eryone PLA to compare.  Right now, I prefer PETG over PLA and have had amazing performance with the rough PEI plate. Love that.

Posted : 26/04/2022 10:40 pm
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