Drying Times and Temps in Dehydrator  

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guy.k2
(@guy-k2)
Noble Member

For those who lack a filament drying system, get one. Even spools from unopened, factory sealed bags can be moist enough to spoil print results. I use a low cost dehydrator and can process up to TEN 2Kg spools at a time. Typically I dry four to five spools at once.

I use a Gourmia GFD1950 Premium Countertop Food Dehydrator   https://www.amazon.com/gp/product/B01M6AZ863

There are many similar models, but this has been running well for me.

The dehydator replaced my former PrintDry system. I switched to the food dehydrator so I could  process more than two spools at a time. 

The dehydrator's thermostat reading (once it reaches steady state) matches my thermistor probes within a couple degrees F. I load the spools with the dehydrator cold without ill effects. No apparent need to pre-heat the dehydrator.

My temperatures and processing times

Mine differ a bit from recommendations on the PrintDry website, but have never ruined any spools with overcooking. My experience is with 2 Kg spools. Smaller or partial spools are dryable with shorter times. Keys are to stay below filament glass transition temperature and also allow enough hours at temperature to outgas and diffuse water vapor from deep inside the spools. You cannot achieve drying with just putting a spool into a box with desiccant.

Post drying, most filaments yield less stringing at higher print temperature. Also, those nasty extrusion gaps from water vapor expanding in the hot end are gone. For Priline polycarbonate (with/without carbon fiber) drying allows another 15 to 20C hotter nozzle during printing without stringing.

Temps listed here are in F because the Gourmia dehydrator only has F degrees readout and changes temp in 7F increments.

PETG 158F (70C) x 4 to 8 hours -- This is a bit hotter than PrintDry recommends. Initially, I dried PETG at 149F (65C), but after some 24 hour long tests showed my PETG is fine at 158F, I just dry PETG at 158F. Comes out fine and lets me process PETG at same time as polycarbonate

Polycarbonate 158F (70C) x 10 to 20 hours -- Makes a huge difference in stringing especially if you plan to print at high end of temperature range for better fusion. Drying a fresh factory sealed spool just 5 hours helps, but is not really long enough.

Silica Gel Sachets 158F (70C) x 10 to 20 hours -- These regenerate in same run as PETG and PC. They simply go in bottom of dryer.

PLA 149F (65C) x 4 to 8 hours -- Mid temp and relative slow water absorption allows shorter drying time.

TPU 129F (54C) x 10 to 24 hours -- low temperature means extended drying time. Still stringy even when dry.

Ninja Flex 122F (50C) x 24 hours -- comes from factory without any real humidity protection. Really low temperature requires a long time to dry. Large difference in overhang performance wet vs dry.

 

Posted : 08/09/2019 9:01 am
niko.x, jbacci, bobstro and 1 people liked
guy.k2
(@guy-k2)
Noble Member

Err. I mean 9F adjustment increments. Can't edit original post.

Posted : 08/09/2019 9:07 am
guy.k2
(@guy-k2)
Noble Member

Good grief! 1 KG spools, not 2.

Posted : 08/09/2019 9:23 am
guy.k2
(@guy-k2)
Noble Member

Like usual, the product goes out of stock after I mention it. Fortunately, there are near identical alternatives.

https://www.amazon.com/dp/B072JZLPBC

 

 

Posted : 13/09/2019 11:07 am
guy.k2
(@guy-k2)
Noble Member

Here are 9 spools loaded into dehydrator. A piece of cardboard keeps top four from crushing lower spools. As front cover is lowered, I pull some of the top spools forward for better air flow. It actually works even without pulling any top spools forward. I measure a 2C difference between front and back of dehydrator as it is heating up.

These PETG spools will be processed for 15 hours at 158F. Silica packs are regenerated at same time. DOUBLE bagged in zip locks they remain ready for use for weeks. Single bagged, expect only 1-2 weeks of dryness in a 30% RH room.

For critical, PETG prints at 260C (E3D + brass nozzle) for maximum layer fusion, a spool gets 4-5 hours touch up just before printing. When freshly dried, my PETG prints cleanly with minimal stringing even at 260C. When wet -- you get a LOT more stringing.

Polycarbonate gets 8 hours of touch up drying just before use - even if stored double bagged and indicator says it is still OK. It's worth drying PC fully to get best results.

Once you are accustomed to the print quality of truly dry spools, you won't be satisfied even with a fresh out of factory bag spool.

Why pre-dry and double bag spools even knowing they gradually absorb moisture? They are dryer than if I didn't pre-dry. Often, I can just grab and go. Critical prints need less touchup drying time if I start with a dryer spool.

Posted : 20/09/2019 12:24 pm
bobstro
(@bobstro)
Famed Member
Posted by: @guy-k2

Here are 9 spools loaded into dehydrator.

Do you more-or-less store your current "ready rack" of filament in the dehydrator, then double-bag & desiccant for long term storage when not using a spool? If the dryer were somewhat sealed, I could see running it for a few hours daily at a safely low temp to keep the air dry, even if not actually drying saturated filament. Something like a heated drybox.

[...] These PETG spools will be processed for 15 hours at 158F. Silica packs are regenerated at same time. DOUBLE bagged in zip locks they remain ready for use for weeks. Single bagged, expect only 1-2 weeks of dryness in a 30% RH room.

I've noticed the desiccant saturates even in single bags. I'll have to give the double-bag approach (I'm using 2 gallon ziploc bags) a try.

[...] Once you are accustomed to the print quality of truly dry spools, you won't be satisfied even with a fresh out of factory bag spool.

I've been tossing spools into my PrintDry on an ad-hoc basis. One concern I have is whether repeated drying can be too much of a good thing. I'm hesitant to throw a $50 spool in repeatedly if it'll become brittle or otherwise damaged. Do you see any issues drying a spool of PETG for a few hours literally before each print?

Why pre-dry and double bag spools even knowing they gradually absorb moisture? They are dryer than if I didn't pre-dry. Often, I can just grab and go. Critical prints need less touchup drying time if I start with a dryer spool.

My hope would be that bagging would reduce the touch-up drying time required, but that's hard to measure in reality. What are your current thoughts on the "dry box" storage approach? Is it worth even doing much more than bagging if a regular "dry before each print" regimen works?

Thanks for sharing all the deep dives you do into these topics. A lot of it is way beyond what I'm likely to do, but there are amazingly helpful bits of information in every post.

 

This post was modified 9 months ago by bobstro
My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 20/09/2019 3:59 pm
david.a66
(@david-a66)
Honorable Member

unless you are using "freezer" baggies, a regular baggie is NOT vapor tight

Posted : 20/09/2019 4:53 pm
bobstro
(@bobstro)
Famed Member
Posted by: @david-a66

unless you are using "freezer" baggies, a regular baggie is NOT vapor tight

I've been using the Ziploc 2 gallon freezer bags. Even with these, the desiccant packets change over a week or two, so I'm going to give double-bagging a try. Mind you, I haven't had any particular issues and filament is printing well, so the bags are far from useless, but storage for longer periods is an issue. @guy-k2's "toast before printing" approach is probably the best, but I'm not that good at planning my prints ahead of time.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 20/09/2019 5:01 pm
bobstro
(@bobstro)
Famed Member
Posted by: @guy-k2

[...] Once you are accustomed to the print quality of truly dry spools, you won't be satisfied even with a fresh out of factory bag spool.

When looking through the comments on the Maker's Muse video on filament longevity, I noticed this comment:

I headed up a NASA study regarding using 3D printing in space. One of our findings was that ABS and Nylon filaments did not create a measurable amount of particulates when extruded if they were desiccated to 25% RH prior to using them. They put off large amounts of particulates when stored at 50% RH then extruded. That's a great reason by itself to dry your filaments.

So not only does "pre-toasting" yield better results, but it might well go a long way towards addressing concerns about UFPs.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 20/09/2019 5:22 pm
guy.k2
(@guy-k2)
Noble Member

Nice find regarding the particulates.

Sometimes, I'm just dense. I just realized the dehydrator has slots for it shelves. I am now suspending my 2nd layer of spools on a dowel between the existing supports. No more cardboard protector.

+1 on freezer bags here. A single bag just isn't enough. The mylarized bags are better, but you can't see your filament.

I don't print from the dehydrator as a continual dryer, but the original poster of  using this style dehydrator does so. https://forum.prusaprinters.org/forum/original-prusa-i3-mmu2s-mmu2-user-mods-octoprint-enclosures-nozzles-.../cheap-heated-5-x-spool-enclosure/#post-155370

My typical process is to place active spool in a plastic container with silica packs. That gives me about 36 hours with PETG. Polycarbonate can go about 18 hours before it gets too wet. I probably should redo my container with better seals.

This post was modified 9 months ago by guy.k2
Posted : 21/09/2019 9:40 am
guy.k2
(@guy-k2)
Noble Member

These parts were printed with Stronghero PETG translucent red, an economy PETG that would typically string badly out of factory sealed bag. Printed at 260C nozzle temp with BNBSX extruder, E3DV6, brass nozzle, and 0.9 degree XY motors. To illustrate how little stringing happens despite the high print temperature, I have NOT post processed these pieces at all. They are straight off the print bed. You can see a few, thin wisps, but the overall results are clean and with very good layer fusion. You simply cannot get this filament to behave this well at 260C without drying.

I encourage you to click and look at the full resolution images. Remember this is one of the cheapest PETG's you can buy on Amazon. With proper drying, it yields gorgeous red, well formed, clean strong prints. Skip drying and try printing at 260C. You'll be in cobweb city.

 

 

This post was modified 9 months ago by guy.k2
Posted : 21/09/2019 9:32 pm
david.a66 liked
guy.k2
(@guy-k2)
Noble Member

Bunnies Scienced...

Two, fresh out of factory sealed bag PETG spools were weighed, dried 12 hours at 158F, and re-weighed to measure how much water was removed.

Overture PETG (comes in metallized, resealable, vacuum bag, with one packet of silica)

1258 gm --> 1258 gm

 

Stronghero PETG (comes in plain plastic vacuum bag, non-resealable, with one packet of silica)

1135 gm --> 1131 gm (4 gm of water was removed via heated drying)

 

Overture was already dry when it arrived. That means it was dried at the factory and its metallized bag did a great job keeping moisture out.

Stronghero was wet on arrival. 4 ml of water was in the spool despite it being in a factory sealed bag. That's a significant amount in what most people would treat as a "fresh dry" spool.

A spool may arrive dry, but you can't actually know. Dry the fresh filament before use can you know? 

Experiment continues with spool left out of their bags. We will measure how their masses changel

Posted : 24/09/2019 2:18 am
bobstro
(@bobstro)
Famed Member
Posted by: @guy-k2

[...] A spool may arrive dry, but you can't actually know. Dry the fresh filament before use can you know? 

Experiment continues with spool left out of their bags. We will measure how their masses changel

Would be interested in seeing how a fully-dried spool fares after various time intervals in a ziploc bag with a packet of desiccant!

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 24/09/2019 3:19 am
chocki
(@chocki)
Prominent Member

Nasa has the best dryer in space going - a total vacuum !, as long as the temperature does not drop immediately below 210 Kelvin, the filament should dry out nicely 😀 

Normal people believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet....
Posted : 24/09/2019 6:01 pm
bobstro
(@bobstro)
Famed Member
Posted by: @chocki

Nasa has the best dryer in space going - a total vacuum !, as long as the temperature does not drop immediately below 210 Kelvin, the filament should dry out nicely 😀 

I'll keep that in mind next trip up. 🙂

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 24/09/2019 7:34 pm
CybrSage liked
chocki
(@chocki)
Prominent Member

Houston - We have a problem...

 

I have been looking at PETG shelf life and the effects of temperature and would like to point this article out.

Physical Aging. The process of physical aging, or free-volume relaxation, is a slow but perceptible densification of amorphous polymers toward the thermodynamic equilibrium state. The rate of aging is greatly accelerated at temperatures close to the glass-transition temperature, Tg. For example, significant aging can take place for PETG (T* 80°C) at preconditioning or drying temperatures of 50°­60°C. This physical aging process is frequently accompanied by dramatic changes in the polymer's physical properties.

https://www.mddionline.com/shelf-life-prediction-methods-and-applications-0

Normal people believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet....
Posted : 24/09/2019 8:10 pm
burtronix liked
chocki
(@chocki)
Prominent Member

That cold vacuum of space is looking good. What I did also find is that PETG is very transparent to microwaves, so I wonder if zappin a reel in a microwave would excite the water molecules enough to aid their release from the PETG without raising the temperature enough to hit Tg.

Normal people believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet....
Posted : 24/09/2019 8:13 pm
guy.k2
(@guy-k2)
Noble Member

The article was primarily aimed at validation of simulated aging using heat exposure to simulate aging . I don't think it is particularly useful in deciding whether or not to dry filament prior to use. We completely rearrange the molecular structure during printing anyways.

Having filament drying seem hazardous or mysterious is a disservice to our printing community. It's particularly easy to dismiss the benefits when one lacks a drying system and has not been drying ones filaments. Those of us who have experienced the benefits of being able to dry our filaments just would like others to have better prints. Being able to dry a 1/3 used spool also means your spools never have to be spoiled. It is incredibly freeing. When I finish a print job, the spool goes back into the dryer so it is in prime condition for the next job.

Many of my spools undergo multiple drying cycles and have not deteriorated in any vital manner. There may be a slight amount more brittleness  precluding 180 filament folding, but nothing that affects the ability to print the filament. What IS noticeable is that prints are cleaner when the spools have been dried. Less stringing, better layer fusion, and smoother surface finish are big plusses in my book.

Posted : 24/09/2019 9:36 pm
chocki
(@chocki)
Prominent Member

Sorry I wasn't trying to put people off drying their filament, but just pointing out that it can and does affect the filament but hoping that we could discuss the article to see how much or little impact it may have in the 3d printing world, I'm sure in medical circles or even carbonated drinks production, this aging could and does have a pronounced affect.

Sorry if my posting came over negative, I'm trying to work and participate on a forum at the same time and agree that maybe I didn't stop to think before posting long enough.

And I do and will continue to dry my filaments because I too agree the benefits far outway any small insignificant affect that drying might have on 3d Printing.

Normal people believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet....
Posted : 24/09/2019 9:49 pm
burtronix liked
guy.k2
(@guy-k2)
Noble Member

Uh.... definitely didn't mean to pull such an apology out of you.

Please don't over stress and I apologize if I came over so overbearing .

I just wanted to avoid dissuading the less experienced from drying their filaments.

 

Posted : 24/09/2019 10:22 pm
CybrSage liked
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