PETG not so wonderful?

Seems all over I was reading how wonderful PETG was. So I bought 1kg from Hatchbox. I have only ever printed in PLA, for about 3 years now. But I decided to try PETG. I decided to swap out my PLA hot end and put another hot end in so I did not contaminate or mix materials, as I had read some people had trouble with that. So brand new hot end, machine tuned perfectly using PLA.

Things people said about PETG were that it needed to be a bit farther from the bed, so I did this. That it was very stringy, yes I can confirm stringy, like cotton candy. This is where the troubles began for me. I printed at 240 and 250, it did seem there was a bit less stringing at 250. The bed temp was 75 and it it glass. The problem was all the strings lay all over, then they collect on the nozzle tip, form a ball which is later then dragged around and eventually deposited somewhere on the print, causing a big bump that the nozzle must pass over again, which then collect more stringy crap. I tried Cura, as I use it exclusively for all my PLA, and never a problem. Then I tried Slic3r, as it has more control over when to do infill, types, perimeters, and retraction. I was able to get some improvement, but never enough that I could print a handsize part without ending up with multiple areas of trouble. I had serious lifting/warping issues with PETG, so I turned all fans off, that cured the warping, and people said it made layer adhesion stronger.

Bottom line I used .1kg and have decided to call it quits, too much trouble, back to printing my parts with PLA. I swapped the hotends, I did get good and doing this anyway, and am now happily printing in PLA with no issues.

Are there others that had similar experiences as well? From the reviews of PETG all you see is how wonderful it is.

I've had some good results in my limited experience, mostly with transparent. It does string, but everything was a lot better when I reduced the speed a LOT, down to 30mm/s. On my CoreXY I generally print PLA and ABS at 100mm/s!

My final opinion was that it was less trouble than ABS because it doesn't warp, more durable in the long term than PLA because it doesn't degrade over time (much), but the slow printing was just too annoying.

Mine was purple, I was trying to print on an I3 at about 30mm/s Just too much trouble for me I guess LOL, I hear my PLA running now doing just fine

It did take a bit of tuning for me, but the toughness of the final parts was worth it. Stringing is an issue, but when you get it dialled in (fast travel moves mostly), the results are worth it.

I prefer ABS for parts that have fine detail, but for larger functional parts like brackets, I find PETG to be a good fit.

Edit: Are you using coasting? This can help to reduce the stringing as well.

Edited 1 time(s). Last edit at 02/22/2017 03:20AM by nebbian.

For what it's worth I'm printing exclusively PETG now. Switched from ABS and not looking back much... Except where print speed is an issue, PETG does print nicer at 30mm/s which is slower than I'd like. No strings though (I print eSun PETG at 250 C, 75 bed adhesion), a little bit of warping happens on larger parts but fixed by large enough brim. All in all, a very good material, I'm building a hexapod robot out of it.

It's different, and has its pros and cons. You need to print slower, especially infill, you sometimes get blobs on the nozzle, I get much less blobs with 3dprima petg than with generic petg I've tried. I also wonder if a Teflon coated nozzle might work (like frying pan style coating on the outside of the nozzle).

But the final parts are very strong. My micro delta design uses large petg triangular frame parts and is built by hammering mgn12h rails into the petg frame. Try this with pla or abs and you'll end up with a pile of shards.

Try a different brand in case it was the material that wasn't good enough, try the settings suggested by others. But if you don't need tough, slightly flexible, functional parts then its not really doing what it does best.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

I've not tried printing petg, but I do print in colorfabb nGen and carbonfill quite alot. I believe I've seen stated elsewhere that ngen is a type of PET, and Carbonfill is PETG although don't take my word for that!

With nGen I get no gunk on the nozzle but it is seriously liquid stuff and it just flows out the nozzle. This is great but it strings a lot and if you havn't tightened down the nozzle it leaks too, leading to some underextrusion. It is very specific about temperature. Colorfabb states 220-240c. 230c for me leads to little stringing but awful layer adhesion. Large parts nearly always crack, it is very important to let the piece cool down completely so that any expansion from the heated bed and cooling can settle in slowly. 235c seems a nice spot so far but creates a lot more stringing. It requires almost zero cooling. I have printed 70degree overhangs on small parts with no problems and it bridges fantastically, despite what some guides say. I get no blobs forming on the nozzle (unless it leaks).

Carbonfill blobs alot. Its quite annoying and describes the issue you are having. Temperature is important for carbonfill as otherwise layer adhesion is shit, but it makes fantastic looking prints with a great matte finish. Upping the temperature makes more blobs, its important to hit the sweet compromise between the two. Blobbing is helped by using an E3D sock, but this just means that blobs fall off before they become a wrecking ball. It can be handy to have more infill, just so the nozzle passes it more often and scraps the nozzle clean inside the print where you don't care. A cleaning brush could be very handy here, with the slicer told to move to the brush between every few layers.

Perhaps some Teflon spray?

Edited 1 time(s). Last edit at 02/22/2017 06:54AM by Origamib.

Or coat the outside of the nozzle in tungsten disulphide if you can get it to stick.

I'm expecting a ddmaterial tungsten nozzle maybe that will help, I'm not sure of the coefficient of friction for elemental tungsten.

I forgot to mention that I print petg at 210 and even if the perimeters are not perfectly laid down the parts are still incredibly strong. I use fan at full speed.

Edited 1 time(s). Last edit at 02/22/2017 08:17AM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

One thing to note, the Hatchbox PETG temps that are printed on the side are only guidelines. I've had better luck controlling strings if I print at 230 or 235 which was lower than what is printed on the side of Hatchbox PETG spools, but the biggest thing is printing below 30mm/s. Anything faster and it doesn't seem to like it very much. I had some nice looking parts that were very brittle because the infill was printed at 60mm/s. Reprinting it at 30mm/s and it was solid and not brittle.

Im trying to dial in petg too.

So far. 35mm/s. 235c bed 90c. Had warping problems earlier. But not sure if it was bed temp. Or fan lowered to 40%. That did the trick.

Still stringing alot. blobs on the nozzle.

Retract is 45mm at 60 mms.

Any ideas?

Stringing is inevitable, there might be a sweet spot on extruder temp where the stringing is minimal but the filament is still melted enough to adhere well but I never found it I just blast the part with a flame afterwards.

Blobs on the nozzle are also inevitable but some brands do this more than others.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Some PETG settings I use for my prints:

)print slow and steady: no speed changes (except for travel moves) and a low speed in general will minimize stringing
)slow retraction with a high retraction distance to reduce stringing even more
)a few degrees hotend-temp more than recommended and your prints will break across the layers instead along the layers. Layer adhesion is incredible with PETG printed hot. Turn off your fan to increase layer adhesion even more.
)don't expose to humidity - there are many different flavours of PETG; many are hygroscopic and therefore you'll want it to be stored dry
)source your PETG... the printability of PETG varies massively from manufacturer to manufacturer. For example I have had very bad experience with Formfutura's HDglass and the PETG from Filoalfa but the PETG from Extrudr or DasFilament prints perfectly fine.

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unwohlpol

)a few degrees hotend-temp more than recommended and your prints will break across the layers instead along the layers.

I had this happen to me recently when I was trying to separate a joint that had too small a clearance. It's quite impressive looking at a solid cross section of plastic I'm printing my petg at 250C.

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)source your PETG... the printability of PETG varies massively from manufacturer to manufacturer.

Agreed, I didn't particularly enjoy working with my first roll of PETG, but since switching to MG chemicals I'm using it more and more. I made some carabiners for my dog's harness and the combination of high strength and moderate flex is perfect.

I am quite concerned that I manage to print it really well but at much lower temperatures than you guys use (I use 3Dprima at 220 deg C layer 1 and 210 after that). I almost treat it like PLA but maybe 10 degrees hotter all around. But if it works it works.

Whilst its a very different material to PLA and ABS both in the way you print it and in the objects you make from it, it is for functional parts unbeatable unless you need them to be very stiff, and even then it can do this if thicker, or reinforced in the right way.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Unbeatable? I must admit I like it a lot, that bit of flex is often really useful. But sometimes the extra stiffness and lightness of ABS is useful, and sometimes the higher print speeds of PLA is great. Nylon is even harder wearing than PETG for parts that get harsh treatment (but I hate the slow print speeds and the smell). I really must get around to trying PC at some point. I wish there was one plastic that was best for all purposes, as it would be easier to remember how to print it well, but I haven't found it yet.

I haven't printed nylon, I have a few samples but never got around the playing with them. So that's a fair point. Perhaps I'd be better saying out of PLA, ABS and PETG I'd rate PETG the best for functional parts. I can never get great surface quality, but this doesn't matter for bits of printer. I mainly use ABS and actively dislike PLA, using it only occasionally. Polycarbonate sounds interesting. So many materials and so little time. My micro delta design uses one piece petg top and bottom frame horizontals, with linear rails hammered into them, I couldn't even imagine the carnage trying that with PLA.

Edited 2 time(s). Last edit at 02/28/2017 05:45PM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

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DjDemonD
My micro delta design uses one piece petg top and bottom frame horizontals, with linear rails hammered into them, I couldn't even imagine the carnage trying that with PLA.

That sounds like a neat design. I like the idea of a small delta - sounds like a really fun project and if some plans work out I may end up with some spare nema14 motors. I could watch delta kinematics for hours

You're right, pla is very unforgiving if you need a tight fit on something. I've broken a few parts that way. With abs I like the ability to file and drill it, and to bond or seal parts with acetone. There are a lot of options for working with it. There's almost none of that available with nylon. You can't even really file it, it's so tough it just laughs at the file.

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So many materials and so little time

So very true!

Does PETG have a solvent that's not on a watch list or which is not highly toxic?

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Not sure. I found one reference to mixtures of MEK and methylene chloride. It might be worth experimenting with an aggressive paint stripper.

I use methylene chloride. It's pretty much the least toxic of the chlorocarbons and was once used to make decaf coffee.

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JamesK
Not sure. I found one reference to mixtures of MEK and methylene chloride. It might be worth experimenting with an aggressive paint stripper.

Some time ago I was given a small pot of MEK to thin some special paint - the caution my friend gave me was "Inflammable is not the word for MEK... explosive is a better word!".

Many of the organic solvents can be problematical if the fumes are allowed to build up. I wonder why MEK is more of a problem than, say, acetone which has a lower boiling point and higher vapour pressure. But yes, agreed, take care with any of these chemicals. They are flammable and potentially bad for your health if you breath too much of it.