Problems with PetG

[Bastian]

HI all, thank you very much for all the tips. I talked to the retailer and they said it does not absorb water, however looking at my prints I dont buy it. I tried to print two long thin prints next to each other and started to increase temperature from 225 to 245 every 15 min (about 1 cm in heights) to check if the stringing increases and the actual print quality. Basically finding the sweet spot. The result was that the temp between 235-240 looked the best with the naked eye. So I tried to reprint my big print ( I also changed the extruder as the other one seemed to leak) the result was a total fail. The print had big black blobs in them and broke apart during the print. feedrate was 40mms. The stringing however was less due to increased retraction and "combining" off.

Looking closely at the failed print, I can see inconsistent filament thickness and bubbles.
So my conclusion is that I should try the drying hypnosis. @Alibert how do you dry it in a vaccum? do you need a special machine?

[Alibert]

I have built my own homebrew version of this thingy: http://www.bestvaluevacs.com/5gvac.html

I bought a 25mm thick piece of perspex, drilled and tapped holes in it, milled a 3mm deep concentric depression and poured silicone rubber in it. Fitted the perspex with taps and gauge. That goes on top of a 30 liter aluminium soup kettle. A silicone heating ribbon with control unit, fibre-glass insulation and a deep-vacuum diaphragm pump completes it.
With this I can create an approx 50-70 mbar vaccuum and heat the whole thing to 70 C. That dries all filament extremely well in a matter of hours.

It will cost you money to get the whole thing together, though. But once you have one, it is a blessing. The vaccuum also does wonders for de-gassing epoxy resins and silicone rubbers before pouring.

Other people have reported success with drying in ovens (I tried that once and the reel melted, ruining three spools of filament) and on central heating radiators. I have tried both, but my experience is that nothing beats a vaccuum oven setup.

If you mail me a 20 cm or so of your filament, I can extrude it before and after vacuum drying and show you the pics. That will prove the water absorbtion issue one way or the other.

[curious aardvark]

I've only printed real small tings with pet. But yep I do remember it being a bit stringy.

The water thing is interesting - I'd say alibert proves the issue :-)

[Alibert]

Based on the PET polymer, I would expect PETG to also absorb water.

PETG despite what you might have been told before is crazy susceptible to moisture in it's raw resin form and above all the filaments we make both for ourselves and for contract jobs our PETG resin has to be dried in a resin drying silo able to reach negative 40f.I was surprised when one of the largest brands of USA made 3D printer filament approached us about taking over their PETG extrusion and the first thing they told me was that, "...PETG is great to run cause you don't need to dry it..." - boy were we surprised when we started running it only to find out we had to dry the PETG resin nearly double the time of an ABS or PLA.

found in this link: http://www.makergeeks.com/pefibymafi1c.html

[ServiceXp]

Great post, I would not have expected such a visible difference.

And here are the results of the PETG humidity test

I received a sample of the Formfutura Bronze PETG last Thursday and immediately tried it out the same day. When priming the extruder I noticed that the extruded filament (Flashforge Creator Dual, 225 C nozzle temperature, extruded using the display load filament feature) was very rough, indicating a LOT of absorbed water.

I vacuum dried the sample at 50 mbar / 70 Celsius for over 6 hours to get rid of the water. Today I repeated the extrusion, and made a comparison picture of the extruded filament of last Thursday (I save a bit) and today.

As can be seen, the sample as it arrived gave enormous amount of steam bubbles (bottom). After vacuum drying it is now extruded perfectly smooth (top).

Shame on Formfutura for sending out poor samples.

Attachment 9144

[Bastian]

Thanks for the offer mate. I will give it a go in the oven first as I sit in Brisbane Australia, by the time you get my sample I will have probably found a solution, but thanks again for all your help!!

I talked to my building manager (big on 3d printing), his father produces PET water bottles and he said, don't even bother with PET. The conditions of the filament has to be right and more so constant during the print. Any temp changes or exposure to humidity, which we have here equivalent to Florida, and your prints will never be good. Still will try but that chat wasnt of great motivational help

[Bastian]

Based on the PET polymer, I would expect PETG to also absorb water.


found in this link: http://www.makergeeks.com/pefibymafi1c.html

Exactly what my building manger said his father has to do before the plastic bottles are being produced. He was talking about seconds of contact with air-conditioned air before making it from one container to the actual extruding machine to achieve a repeatable result.

[Alibert]

Just make sure that you start your oven with low temperature and gradually increase it. Use the fan if your oven has one. I was too enthusiastic and the reels (the ABS filament itself only barely) melted and blobbed all over the filament. It was one gungked-together mess.

Also, PETG is a modified version of PET and has somewhat different characteristics. My expeirence so far is that some reels of PETG arrive perfect, others give steam bubbles and need serious drying before being useable. The post on Makergeeks indicates that even a number of filament manufacturers are unaware of the need to pre-dry the resin before extruding to filament.

Having said that, I have also had reels of ABS and PLA come in with the same problem. It seems to be more or less random and I think depends on the state the raw plastics were in before the manufacturer made filament out of them. As most of the filement is produced by a legion of relatively small companies in the USA, Europe, China and elsewhere, quality control on the resin/pellets going into the manufacturing process is difficult to say the least. Also, it is a smallish batch process due to the many colors etc. The final packaging (plastic wrap, bag of dessicant) tells you nothing about what state the raw pellets were in before the filament was made, so even a new perfectly packaged reel can still be moist and give poor prints right out of the packet.

Having means to dry filament is in my opinion a requirement in order to handle this, or you need to be sure of your supplier right down to the actual purchase, storage and handling of the batches of raw pellets,as well as postprocessing and storage of the reels. I do not expect to get that kind of assurance from any supplier.

A lot of people bash on so-called 'cheap' filament and claim you should buy only expensive quality. I have had mostly excellent experience with 'cheap' chinese filament and the same but also some very, very poor ones with USA/EU manufactured 'quality' filaments.

I found that the sizing accuracy of chinese producers (and all others) is excellent, only some batches are not dry enough and giving ghasly prints due to excessive steam bubbles. I have had ABS from one chinese supplier of mine being mostly perfect (5 colors), but the black one was too moist and needed vacuum drying before being as good as the others (near perfect).

So, investing in a vacuum oven does cost money, but with it you can make 'cheap' (chinese) filament near perfect (and a number of the expensive USA/EU ones too as my Formfutura trial demonstrated), so it will pay back for itself in the end. As someone who goes through several kilo's per week, that ROI is within a year just on basis of the price difference per reel, not counting throwing away whole reels which won't print

As Brisbane is very humid at times, you will have a permanent problem with all your filament (PETG, ABS and PLA alike) attracting moisture. So my advice is to get a good means of drying it, and pay good attention to air-tight storage.

Happy printing!

[Bastian]

Big thank you for all the help mate!! Will try the drying now and have a print tomorrow, (will post the two prints in comparison) will also set the air-con to dry hours before the print starts, just to get the (as perfect as possible) environment. I want to start producing a product once I have confirmed that I can print in PETG. I will take your advise and get a dryer as soon as we confirm that is possible. I might be in touch for some more help on that when we get there . Again, big thank you!

[Bastian]

Just make sure that you start your oven with low temperature and gradually increase it. Use the fan if your oven has one. I was too enthusiastic and the reels (the ABS filament itself only barely) melted and blobbed all over the filament. It was one gungked-together mess.

Also, PETG is a modified version of PET and has somewhat different characteristics. My expeirence so far is that some reels of PETG arrive perfect, others give steam bubbles and need serious drying before being useable. The post on Makergeeks indicates that even a number of filament manufacturers are unaware of the need to pre-dry the resin before extruding to filament.

Having said that, I have also had reels of ABS and PLA come in with the same problem. It seems to be more or less random and I think depends on the state the raw plastics were in before the manufacturer made filament out of them. As most of the filement is produced by a legion of relatively small companies in the USA, Europe, China and elsewhere, quality control on the resin/pellets going into the manufacturing process is difficult to say the least. Also, it is a smallish batch process due to the many colors etc. The final packaging (plastic wrap, bag of dessicant) tells you nothing about what state the raw pellets were in before the filament was made, so even a new perfectly packaged reel can still be moist and give poor prints right out of the packet.

Having means to dry filament is in my opinion a requirement in order to handle this, or you need to be sure of your supplier right down to the actual purchase, storage and handling of the batches of raw pellets,as well as postprocessing and storage of the reels. I do not expect to get that kind of assurance from any supplier.

A lot of people bash on so-called 'cheap' filament and claim you should buy only expensive quality. I have had mostly excellent experience with 'cheap' chinese filament and the same but also some very, very poor ones with USA/EU manufactured 'quality' filaments.

I found that the sizing accuracy of chinese producers (and all others) is excellent, only some batches are not dry enough and giving ghasly prints due to excessive steam bubbles. I have had ABS from one chinese supplier of mine being mostly perfect (5 colors), but the black one was too moist and needed vacuum drying before being as good as the others (near perfect).

So, investing in a vacuum oven does cost money, but with it you can make 'cheap' (chinese) filament near perfect (and a number of the expensive USA/EU ones too as my Formfutura trial demonstrated), so it will pay back for itself in the end. As someone who goes through several kilo's per week, that ROI is within a year just on basis of the price difference per reel, not counting throwing away whole reels which won't print

As Brisbane is very humid at times, you will have a permanent problem with all your filament (PETG, ABS and PLA alike) attracting moisture. So my advice is to get a good means of drying it, and pay good attention to air-tight storage.

Happy printing!

Mate, so I dried it and it is like a complete different filament so far, amazing! Now what I was wondering, do I have to dry it everytime I want to print? As we have a lot of humidity here, how long would it take to absorb the water again? Best guess woul dbe ok, just need an indication if we are talking hours or days/weeks?