Drying filament - temperature precision  

RE: Drying filament - temperature precision

Posted by: laurel.w

I printed a very nice piece with Polysmooth. About a week later I printed the same piece, only to see a lot of stringing and much less evenness in translucency among layers. The instructions say, "If you notice that the surface quality of your prints are uneven and the color is not consistent it means the filament has absorbed too much moisture. You can dry PolySmooth at 60 degrees Celsius for 12 hours and start the print again." So probably this is more sensitive than your average PLA and I need to dry it out. (It's been 60-70% humidity here lately.)

I have a dehydrator for jerky, but it has no temperature control ( https://www.amazon.com/Presto-06300-Dehydro-Electric-Dehydrator/dp/B008H2OELY). After measuring for a while, its internal temperature fluctuates between 150-168 degrees F (65.5 - 75.5 C). Do you think this will be acceptable, maybe if I use it for more like 10 hours? Or do I have to buy a whole other dehydrator (ugh)?

 

( https://hackaday.com/2018/06/02/budget-dehydrator-gives-your-damp-filament-a-second-chance/

I have used my dehydrator for about a week now for much less time that 10 hours per batch of filament drying.  I wouldn't think you need that much time.  And some fluctuation SHOULD not be a problem.  PLA recommendations from Matter Hackers is 116 degrees/46 Celceus for 4+ hours.  I would think you can use the LOWER temperature with some fluctuation and stand a better experience than going over any recommended temperatures from the filament vendor.

My 2 cents.  Check with others that have more experience drying filament.  Also think about using your sensitive filaments from a dry box.  Something with dehydrator or desiccant in them.

Robin

My dehydrator is this one: https://www.amazon.com/gp/product/B07J5G6T6Q/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

RE: Drying filament - temperature precision

Here is a chart from Matter Hackers of filament drying times and temps.

NOTE: They show times for 500gm spools.  Add time for full or large spools.

RE: Drying filament - temperature precision

My dehydrator is higher than the Polysmooth recommended temp (also higher than the MatterHackers values) as I mentioned above. Since the filament specs recommended 60 degrees Celsius for 12 hours, I hoped that I could dry at a somewhat higher temp for less time.

I will try reaching out to Polymaker, but I suspect they will tell me something noncommittal like "you can try it but it might mess up your filament."

Yes, I am now considering a dry box. I didn't realize this filament was so sensitive until it was too late.

RE: Drying filament - temperature precision

I'd be careful exceeding 60c, you don't want filament strands deforming or fusing.  And the idea behind the length of time at bake is to ensure the entire filament - surface to core - is equalized moisture wise.  

If you are handy, and the circuitry in the unit is simple, you might be able to add a thermal switch in line with the heating element to lower the temps a bit.  These switches are pretty easy to use, just clip and insert in series with the heat element (if AC), and make sure the wires remain well insulated.  Heck, there may already be one in the unit, and you could just replace it with the temp you need.

https://www.amazon.com/uxcell-Normal-Thermostat-Temperature-Thermal/dp/B00EDMKK7O

And many dehydrators have this circuit:

RE: Drying filament - temperature precision

The glass transition temperature of PolySmooth per their website is 70 C so using a dehydrator that fluctuations between 65 - 75 C does not seem like it would be wise as you can get into melting the filament.  My suggestion is no.

RE: Drying filament - temperature precision

I would not be confident feeding my family jerky that was made in a dehydrator that is also used to dry filament. Off gassed organics from the filament are going to be in the dehydrator. Also oils from the food would ruin filament purity.

It may be a small amount, but cross contamination in either direction is not worth saving $110 or so for a dedicating one dehydrator for filament  https://www.amazon.com/gp/product/B01M6AZ863 The linked one has adjustable temperature and time and I've processed TPU, PLA, PETG, and Polycarbonate successfully in mine. 

RE: Drying filament - temperature precision

I have a vacuum chamber that I use for mold making/casting, and I also use it to boil the moisture out of liquid resins at room temperature.  Would this work for drying filament?  I don't see why not, but thought I'd see if anyone knows for sure that this would work or have tried it.

RE: Drying filament - temperature precision

vacuum drying works great

RE: Drying filament - temperature precision

what degree of vacuum?

how long?,
would a humidity sensor work in a vacuum?
regards Joan

RE: Drying filament - temperature precision

It's not a quick process

https://forum.raise3d.com/viewtopic.php?t=9757

RE: Drying filament - temperature precision

What people call a vacuum is relative.  For degassing resin, at least 29 in hg / .03 atmospheres / -98205.3 pascal is needed and the moisture usually boils off completely within 5-10 minutes.  Some people consider much less than that to be a vacuum, and that would take hours.

RE: Drying filament - temperature precision

Yeah - I was thinking the same, but a $200.00 2-stage pump mentioned somewhere actually says it will achieve 15 microns mercury, near 10 milli-Torr.  Not anywhere near space vacuum, but close enough without going to nitrogen cooled diffusion pumps.  In layman's terms, 15 microns means 99.995% of the air is gone.

https://www.engineeringtoolbox.com/vacuum-converter-d_460.html

RE: Drying filament - temperature precision

Sorry about disappearing halfway through this thread. We got into a very busy period preparing for, going on, and returning from vacation.

I hadn't thought about the dehydrator affecting food or vice versa. But since I am currently not handy with electronics (though I'd really like to get there), and since a second dehydrator is not a huge bank-breaker, I have to acknowledge that that's what I need to do. It's not even the cost as much as it is the storage space... but I don't think I have another path forward.

Time to research dry box approaches, as well ... those look pretty simple, at least.

RE: Drying filament - temperature precision

So I was about to purchase a Gourmia dehydrator, but my husband wants to know why I can't just buy a cheaper round one and modify it to act like a PrintDry, per this approach: https://www.reddit.com/r/3Dprinting/comments/89i3yh/has_anyone_bought_or_built_a_filament_dryer_did/dws1wn6/?utm_source=share&utm_medium=web2x   His argument is that it's a good deal cheaper and the Gourmia cannot be used as a while-printing dry box all in one. My thought is that the round type is probably less consistent in its temperature, and that it won't look nearly as nice in my office. I recognize the latter is not a great reason, and it would be nice to combine dry printing and dehydrator in one machine. But I'm a little skeptical. Any thoughts on this approach?

RE: Drying filament - temperature precision

I will comment as someone who purchased a PrintDry and later switched to a Gourmia 9 shelf dehydrator.

1. Yes, you can use the Gourmet as a "print from" dryer if you drill some holes, add fittings and PTFE tubing. Someone on this forum already did so and his thread is what starts me looking at switching. https://forum.prusa3d.com/forum/original-prusa-i3-mmu2s-mmu2-user-mods-octoprint-enclosures-nozzles-.../cheap-heated-5-x-spool-enclosure/#post-157326

2. The PrintDry is indeed quite a bit different in temp top vs bottom level. The top level is quite a bit cooler. It's been long enough ago that I don't have the temp figures any more. The Gourmia style is about 6C different back/front if you load it up with 10 spools and don't arrange them to avoid blocking airflow. With fewer spools or with them arranged to allow airflow, you are looking about 3C front/back difference.

3. Two spools at a time is quite limiting. I pre-process my spools before doubled bagged storage. It is practical to do that 8 at a time. At two spools capacity, the PrintDry just could not keep up with my needs. 

My PrintDry was gifted to a friend. I am very happy to have made the change and I now can keep a much larger percentage of my spool collection dry.

RE: Drying filament - temperature precision

@tim-m30

A couple of years ago I bought one of the $200 vacuum pumps off Ebay and it came with this vacuum pot. I didn't need it for the job so I put it up on the shelf and forgot about it until I read this thread. The pot is 9-1/2" dia x about 9-1/2" deep so it will hold 3 Prusa size spools. I used the pump for vacuum fixtures and it would bottom out the gauge in about 2 minutes. The box just says VACUUM PUMP. typical Chinese, no brand but it's going to be a whole lot faster than a dehydrator. Vacuum the  spools and then pop them into a zip lock bag. As far as letting in moist air when it's done, hydraulic system tanks, like on tractors sometimes have vents that have desiccant filters. More ideas......

RE: Drying filament - temperature precision

Posted by: @laurel-w

So I was about to purchase a Gourmia dehydrator, but my husband wants to know why I can't just buy a cheaper round one and modify it to act like a PrintDry

Technical considerations aside, has your husband ever purchased a car, truck, drill, chainsaw, riding mower or snow blower? For the same reason. Seriously, you only really need a Honda Fit.

RE: Drying filament - temperature precision

I invested in a 25 micron pump and chamber ... measurement accuracy is a needle gauge, meaning the system might achieve 200 um, or 10 um. I am presently trying to make "wet PLA" but having some trouble.  Seems PLA is a lot more resistant to absorbing water than this discussion suggests.  Nylon on the other hand ... not so much ... for nylon, think sponge. 

RE: Drying filament - temperature precision

Posted by: @tim-m30

I invested in a 25 micron pump and chamber ... measurement accuracy is a needle gauge, meaning the system might achieve 200 um, or 10 um. 

OK, I don't know who you are, but it's pretty clear you are not @tim-m30, the guy who was complaining that a $100 dehydrator cost as much as 20 spools of PLA filament. Just let him go unharmed and we won't get the authorities involved. This is obviously a ransom demand for the price of a vacuum pump. Just much much does this "vacuum pump" cost?