# 3D Printing > General 3D Printing Discussion >  Problems with PetG

## Bastian

Hi all,

I have tried to print with PETG the other day and it was a complete fail. PLA works just fine but PETG has those spider webs and the quality of the print is poor, even tho' all settings are the same besides temp. I use 0.2mm layers, 240C and 60C for the bed. You guys have any idea why it makes those spider webs? I assume the PETG is too runny at 240C?

Thanks in advance for your help!

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## Bastian

Also do you see the difference in colour....it seems to change the shade of blue for some reason too?!

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## Geoff

Mayeb try slow down your printing, PETG on my printer needs to print rediculously slow, like 30ms feed rate :/ otherwise it gets lots of little air bubbles in it and goes stringy too.

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## Alibert

I think you should dry your PETG filament. It has a tendency to absorb a lot of water, which results in stream bubbles and also an increase in stringing.

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## NitroXpress

Hi,

230° is enough.
Print perimeters outside-in.
I have absolut no problems with stringing !

PETG is a much better material than PLA.
I only use PETG.
PETG does not absorb water !
I print PETG at 160mm/sec.
No need to slowdown the print.

High quality prints at 80mm/sec:

lizzard.jpg

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## beerdart

Try adding retraction.  PETG is stringy stuff.

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## Alibert

> PETG does not absorb water !


ALL filaments will absorb water to some level. Nylon is the most notorious one, but PETG also has its issues. As example, last Thursday I tried two PETG filament samples from Formfutura (received them in the post that same day). They came out totally messed up with steam bubbles when printed at 225 C. I have vacuum-dried them (70 C, 50-70 mbar for 8 hours) this weekend and will test them again coming Tuesday when I have time. I saved some of the extruded PETG with steam bubbles for taking pictures and comparison to give some feedback to Formfutura. I will post them here when I have them.

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## Geoff

> Hi,
> 
> 230° is enough.
> Print perimeters outside-in.
> I have absolut no problems with stringing !
> 
> PETG is a much better material than PLA.
> I only use PETG.
> PETG does not absorb water !
> ...


What printer? 

I don't know of any of mine that can go faster than 50mms with PETG and give a decent result - you also are using White, try a transparent PETG, extrudes completely differently.

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## Alibert

> PETG does not absorb water !


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.

PETG_Bronze_Formfutura1.jpg

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## dunginhawk

nitro.. would you post your retraction settings?
I use PETG almost exclusively, but i dont have it perfect yet. I have a blob once in a while, but im 95% of the way there.
thanks

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## 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?

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## 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.

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## 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 :-)

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## 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

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## 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.
> ...

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## 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  :Smile:

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## 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.

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## 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   :Smile: 

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!

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## 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  :Smile: . Again, big thank you!

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## 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. 
> ...


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?

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## Alibert

I don't know. I do know that a filament that prints well one day can print with a lot of steam bubbles a few days after, so less than 48 hours is my estimate. It will depend on the absolute humidity it is exposed to.

What most people do not realize is that relative humidity is a totally meaningless number unless it is given together with the temperature. The difference between absolute and relative humidity is explained here: http://info.zehnderamerica.com/blog/...the-difference

The equilibrium of water between air (gaseous state) and the polymer matrix (dissolved state) is governed by the concentration of water in the air (which is itself a function of temperature). Putting it simply, if the concentration is twice as high (expressed in g/m3, not %RH), then there are approximateley twice as many water molecules hitting the polymer surface per unit of time, and thus twice as many have a chance of entering the polymer matrix thus contributing to the water uptake.

So, given max abs. humidity at 15 C it might take a few days, given max abs. humidity at 35 C it might take mere hours.

If you live in a (sub-)tropical area, store your filament air-tight when not in use.

PS: In case you are wondering, I am a chemical engineer by profession   :Smile:

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## Bastian

Attachment 9210Attachment 9211Attachment 9212
here it is. You can see the huge difference. the dried filament is so much better it is unreal. Mate, big thank you for the tips!! Now we have proven the concept and are ready to establish production lines! People, dry your filament and you will have incredible better printing results!

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## Alibert

Glad to have been able to help. The attachement links are not working however, could you amend them? Youcan insert pictures in your posts.

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## Bastian

20160411_181825.jpg here 1

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## Bastian

20160411_180125.jpg new print

20160403_092905.jpg old print with strings

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## Alibert

Indeed the same kind of difference I found. And more proof that those who claim that PETG isn't susceptible to moisture are just parroting a misinformed sales pitch.....     :EEK!: 

Happy printing and you might contemplate your own vacuum drying oven....

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## NitroXpress

Hi all,

sorry for the late reply...

I don't know where you buy such low quality filament, that you have to dry it bevore printing...
My filament comes in a vacuum sealed package.
I use 8 different colors of PETG filament with my printer, unpacked since 1-8 months and there is no quality difference.

I use a retract of max. 0,25-0,5mm.printer.jpg

Also see my youtube video, printing at ~390mm/sec.
https://www.youtube.com/watch?v=j_ATq9Rnghs

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## curious aardvark

wow - that's one hell of  a printer !

So what brand pet do you use ?

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## NitroXpress

It is from https://reprapworld.com/?products/li...1590_1737_1682

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## NitroXpress

But the filament is only the "half rental"...
You need a perfect setup/calibration of your printer.

If you want to see "live printing" look here : http://itfs.dyndns.info:85
Sorry, but my internet upload speed is only 1 MBit

I tried different brands of PETG filament.
I think they provide the best quality/price ratio.
Be sure to select the filament with 0,05mm tolerance.

Also see my "boiled water test" https://www.youtube.com/watch?v=OxDOO06i5YU

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## Alibert

> I don't know where you buy such low quality filament, that you have to dry it bevore printing...


It is independent of the price/quality. I have had spools of cheap AND very expensive european made PETG have this problem straight out of the vaccuum packaging. This is most likely caused by the manufacturing process / feed stock itself. AND I have seen it develop over time when lying open too long in a humid ambient....

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## NitroXpress

You think it is most likely caused by the manufacturing process or feed stock...
Is this not a indicator for quality ?

I have printed a wind turbine with PETG.
And on the roof, is definitely a humid ambient.
If PETG absorbs so much water over the time, it have to crack in the winter when become frosted, or ?

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## Alibert

I think very few manufacturers extensively test the feed stock pellet when they come in, and maintain a rigid control over storage and handling. I have had a particular batch (color) from one supplier have this humidity problem right from the vacuum package, while six other colors (also batches I presume) were perfectly fine. I have also had very expensive high quality european made PETG filamant have this exact same problem.

The fact that you haven't tells that you either purchased from another source or just have had pot luck with your purchases. I go through a lot of ilament and have used up / am using about 20-30 kg of PETG alone in the past 6 months. So far one color from a chinese and all PETG from european source were problematic.

And again, when exposed to humid atmospheres, all polymers will take up water to some extent. How much depends on the type of polymer, the ambient temperature and the ambient absolute humidity expressed in grams of water per cubic meter of air. Forget relative humidity, it is meaningless (unless stated together with the temperature, so youcan calculte the absolute humidity from it) when it comes to gas-solid or gas-liquid equilibria.

I have had spools of PLA, ABS and nylon which were either too water-rich after manufacturing, or developed this issue after some time being exposed to the ambient. Regardless of source. It is just a physical characteristic of the polymer and can't be helped other than air-tight storage and drying when appropiate. If the manufacturer would thoroughly test each and every batch, and safeguard the handling an storage of the feedstock before it is being used that would solve the out-of-the-box problem (which, as a chemical engineer and knowledgeable of how batch manufacturing processes work, I do not think is done in practice). However, the ambient exposure problem remains. 

In central heated conditions (say 20C / 35% RH =  6 grams H2O/m3 absolute humidity) I can leave my spools of filament out open in my workshop for weeks. However with hot humid weather(say 35C / 95% RH = 38 grams H2O/m3)  the same spools absorb water in a matter of days to the point I have to vacuum dry them to be useful again.

Having said all the above, unless specifically quoted to be european or US made, most 'brand' filaments originate from the same manufacturing sites in China I suppose. If the box does not specifically say 'made in USA' or 'made in Europe' I would bet my money on chinese origins. No problem, the chinese make excellent stuff as my laptop, smartphone, smart TV's, (actually most electronics)  etc all can testify.

As to printed PETG being in the weather, frost will not harm it as the water molecules are so dispersed throughout the polymer and can not form ice crystals. When heating however, as in the nozzle, the water turns to steam which is a gas. This boils out of the polymer. Cold is not a problem, heat definitely is. Unless of course there are pockets of water in gaps in the printed object, which will form ice when freezing and thus expand and possibly crack the plastic. But that is a macroscopic issue, not one on a moleculer level.

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## Ama-fessional Molder

Correct me if I'm wrong, but are there not specification sheets available? 

It seems to me like the 3d printing industry is overly generic. The materials one particular manufacturer of filament might use could very well be entirely different grades compared to another.

Abs has hundreds, possibly over a thousand unique grades, and the same goes for every other polymer on the market. In my field we use material and grade specific spec sheets with exact Tg, melt points, processing temps, drying requirements, and a full list of mechanical properties.

I'd like to know if this data is available for filament, or if it's just "abs" or "nylon" that you buy and hope for the best.

Drying polymers is one of the things I am very well versed in also, and it looks like, again, this is something the 3d printing world has been left out on. "Humidity controls" are improper for drying and long term storage at elevated temperatures is one of the worst possible things you can do to a resin... yet I see a lot of people doing exactly that.

I want to start a thread on this stuff but there doesn't seem to be a lot of activity here.

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## Alibert

> or if it's just "abs" or "nylon" that you buy and hope for the best.


Yep, that pretty much sums it up. No real material spec sheets whatever, mostly boastful claims about how wonderful it is....




> "Humidity controls" are improper for drying and long term storage at elevated temperatures is one of the worst possible things you can do to a resin... yet I see a lot of people doing exactly that


I agree that raised temperature is not the best for the filament. It is also my opinion that drying gels are of little use too. I have a vaccuum oven for drying which goes down to 50-100 mbar. At 60-70C that is below boiling point of water.

Do you have experience with respect to vaccuum drying and how it may affect the filament?

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## Ama-fessional Molder

Vacuum drying is almost the ideal process in terms of manufacturing, because it is a rapid process with minimal exposure to heat. To my knowledge the only negative is cost of the units, but they are amazingly fast and often used on high precision processes.

Desiccant gels or beads are actually extremely effective, the problem is you need airflow _through_ the material for it to be effective in a reasonable amount of time. The way a proper polymer dryer works is that cool air is forced through a bed of desiccant, thus removing nearly all moisture from the air. Following this, the air is heated to a set process temperature and forced through the bottom of a hopper full of resin pellets.

The air is cooled off somewhat before returning to the desiccant bed because warm air wants to hold more moisture and transfer less to the desiccant. 

You are correct in that simply sticking desiccant gel or beads in the warm chamber is less than ideal. They certainly will absorb moisture, but you are limited by the fixed temperature point.

All that being said, the other primary issue is this:

Overdrying is impossible.*

You cannot dry a resin too much that it causes degradation. I see the word thrown around a lot in 3dprinting and even in my own industry. "Oh, it's just overdried." No, the proper term is oxidation. The material has been oxidized, and in most cases this destroys the properties of that material. This is what happens in the cases of people drying their spools for days or weeks at a time only to have them snap like dry twigs. _It is not an issue of being "overdried". 

_They leave their storage container at an elevated temperature for far too long and the materials actually begin to degrade from interaction with the oxygen in the environment. In theory, one could store them at any temperature below Tg in pure nitrogen and never have an issue, but that's pretty impractical, and not necessary.

The correct solution is limited drying time. For an example, on particular batch of ABS might call for a 170f drying temperature and dry time of 4 hours. After 4 hours at 170f, using a desiccant bed forced air drying system to maintain a very low dewpoint in the air (the "standard" is -40 degrees but some materials work fine with higher), the material should be down below the moisture content required for processing.

Of course in 3d printing, I don't know the exact requirements for drying, but the polymer processing requirements should be identical to injection molding. Thus far the closest thing to proper drying I have ever seen is the filadryer - but even that is ineffective for proper drying and does not get the moisture content low enough for reliable processing. 

Drying your material first, then mounting the spool and printing will no doubt give acceptable results, but the issue lies in the following hours during the print. Many materials can absorb moisture from the environment at a rate that would give you wet material within 30 minutes. A specific grade polycarbonate that I use only takes 15 minutes at 50% RH to exceed the minimum moisture content. That's a typical well controlled home environment.

I have some ideas in mind for a solution to the improper drying and storage I am seeing in this field, I just need some time and motivation to develop the drying unit. Once I do however, I will freely share it and my results with everyone. I just don't want to see some manufacturer steal what might turn out to be an effective design and start making money off of all of us. I guess I should look into open source copyrights? I digress.

And again, this is all coming from someone who doesn even own (yet, it's on the way) a 3D printer. I just know how polymers behave during processing conditions. The idea I have right now could very well turn out to be useless or totally impractical.

*_Some_ materials actually do require a specific moisture content during processing, however, you can always put moisture back into a material and run it through the drying process again. These are usually rare cases of highly engineered, custom resins that I believe would be extremely unlikely for you to use in 3d printing.

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## Ama-fessional Molder

TLDR version:


Even if a filament is stored "correctly" and comes from the factory "dry" in a vacuum sealed package, it will still potentially pick up enough moisture to give you inconsistent print quality. Especially if the seal has even a tiny puncture.

In regards to the comment on the other page about how you shouldn't have to dry it straight out of the package, I can tell you that we used to buy pre-dried nylon resin. It gave great results in the first half hour to hour of running, after that it would pick up too much moisture from the atmosphere and result in junk production. Even in a storage/feed unit kept at 10% RH (like so many I see on these forums) it will still pick up moisture beyond acceptable processing levels.

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## Alibert

Really nice to meet a knowledgeable person here!

I will do some calculations about the gel drier system you describe when I have some time. I have worked with saturated salt solution humidity standards in a past project and need to revive some of that knowledge.

As to the vaccum unit, I made a homebrew one using a thick-walled aluminium soup kettle and a 1" thick perspex lid with gasket and taps/guages. Basic, but it works like a charm using an external dual diaphramg pump and a silcone heater mat+control around the kettle. The pump was the most expensive part at about 140 euro's.

I would be very interested in learnign from your experience. Please keep up the dialogue!

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## Ama-fessional Molder

Well, I wouldn't use "gel" desiccant.

http://www.ppe.com/16pdf/0124.pdf

That's the stuff I use in my dryers, but the key is to circulate air* through* the bed of desiccant instead of just in it's general vicinity. A professional system will use 2 or 3 beds and cycle the air stream among them, regenerating the beds which are not actively drying and thus enabling endless drying capacity - at least until the desiccant breaks down over time. 

A dual bed system looks like this:
ZEKS Heatless Desiccant Flow Diagram Flat.jpg

The problem is that these systems are prohibitively expensive for the home user. You can spend several thousand dollars on a small drying unit. My suspicion is that even a high speed 3dprinter will never need more than about a kg/hr throughput, while the industrial ones are typically built for a minimum 4-5 kg/hr.

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## Barret

After view the photos attached,I think you could have a trial with below：
1.Turn the printer temperature to 250C.PETG is better material than PLA,the melt point is similar as abs.
2.set the printing speed slowly.

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