Best moisture-free filament strategy?

[jeffhuber]

Cope413 - just wanted to say thank you. You are seriously a wealth of clear, well-backed information, and a really friendly to boot! thank you!

[Dreyfusduke]

Yes, I misspoke. I was at one point storing it in a pressurized container (4-5psi), because compressed air is very dry.

.

This is an incorrect idea. Compressed air is just simply more air with a higher boiling point. More air at 50% humidity is just simply more humid air. Most compressed air that comes from professional compressors at factories is followed immediately by a dryer unit. THIS dries the compressed air to keep iron or steel airlines from rusting or lots of moister getting to machinery. Simply running compressed air through your home compressor does nothing more than to actually increase the amount of moisture in the container.

That being said, if someone can make a cheap alternative to a vacuum oven ( most are a few thousand dollars and pretty small) you could lower the pressure to about 29HG or so, then that is the same effect on moister (water) as 212 degrees F at room temperature. These vacuum pumps are rather expensive, but some AC vacuum tester pumps are pretty cheap. Even if the pressure was only reduced to about 27HG, then a person would only have to heat the chamber to a little less than 100F to boil the water. This would not heat warp the material in any way.

[Mac The Knife]

I wonder how well a pressure cooker would handle the vacuum. throw your spool in the pressure cooker, put a vacuum on it, and throw it in the oven.

[dtgriscom]

I wonder how well a pressure cooker would handle the vacuum. throw your spool in the pressure cooker, put a vacuum on it, and throw it in the oven.

I bet the gasket is designed to handle force headed outwards, not force headed inwards. It might even be designed to leak under any sort of vacuum in order to make it easier to take off the top.

Interesting idea, though.

[Dreyfusduke]

Unfortunately, a vacuum oven isn't cheap. The container and heating element (pretty weak and straightforward) is the easy part. The pumps are really expensive. The cheaper AC checker pumps just don't pull enough vacuum to get the job done and they fail often.

[teoman]

An old fridge can be cannibalized for it compressor pump. It does pull a pretty good vaccum.

[cope413]

Yes, I misspoke. I was at one point storing it in a pressurized container (4-5psi), because compressed air is very dry.

.

This is an incorrect idea. Compressed air is just simply more air with a higher boiling point. More air at 50% humidity is just simply more humid air. Most compressed air that comes from professional compressors at factories is followed immediately by a dryer unit. THIS dries the compressed air to keep iron or steel airlines from rusting or lots of moister getting to machinery. Simply running compressed air through your home compressor does nothing more than to actually increase the amount of moisture in the container.

That being said, if someone can make a cheap alternative to a vacuum oven ( most are a few thousand dollars and pretty small) you could lower the pressure to about 29HG or so, then that is the same effect on moister (water) as 212 degrees F at room temperature. These vacuum pumps are rather expensive, but some AC vacuum tester pumps are pretty cheap. Even if the pressure was only reduced to about 27HG, then a person would only have to heat the chamber to a little less than 100F to boil the water. This would not heat warp the material in any way.

Well running my compressor with an air-water separator got my container to 4% rh. I was only able to get to 12% with desiccant at 1atm.

[Dreyfusduke]

Yes. An air separator will help with some moisture, but the act of compressing the air itself does nothing. If you have a larger compressor, sometimes you can get the water to condense on the sides and flow to the bottom. Releasing the air from the tank usually stirs this back up and you can watch water blow out the nozzle. This is why most machinery has a water separator as well as a dryer unit after the compressor. Also, a refrigerator does pull a pretty good vacuum, but not enough needed and the seals will blow. You would still have to heat the chamber to about 150 or so for boiling point. You need to get down to about -26HG or so do really do some good. To get down to -29HG ( boil water at room temperature) requires very very expensive pumps.

[bdjohns1]

You would still have to heat the chamber to about 150 or so for boiling point. You need to get down to about -26HG or so do really do some good. To get down to -29HG ( boil water at room temperature) requires very very expensive pumps.

For certain values of expensive:

http://www.harborfreight.com/25-cfm-vac ... 98076.html

[Dreyfusduke]

draws down to 75 microns. Most pumps say they draw down to 50 microns. In a 2ft cubic chamber, the most you will get from this pump is about -23hg at best. It will probably only last a month or so if you do this daily as well. Owned many. LOL The only way you can do it often and down to -29HG is to get a better made pump. These cheap pumps just simply don't work well.

[Dreyfusduke]

For example, we used a Pro-Set 10 micron pump (12cfm double stage) in order to get a chamber down to -29hg. The pump was about $1k. For a professional vacuum oven, the replacement pumps are about $5k.

[Dreyfusduke]

I am working with a local company here that makes a very nice vacuum pump and heated chamber. The chamber heating pad just sticks to the bottom and is on a timer. It can pull down to -28HG or so at my current elevation (Chicago) and with the added heating pad on bottom, could remove all moister from material in a very short amount of time with very little heat stress to the filament. Probably only 90 degrees or so. Like a hot summer day, but the water would boil at this temp. I suspect the cost would be less than $500. Not bad if you print lots and lots of nylon.

[geneb]

Is it small enough to fit on the heated bed of the v2? That could save you the cost of the heater pad if it did.

g.

[dtgriscom]

You don't need to lower the pressure/raise the temperature all the way to water's boiling point to dry out nylon; witness that the "put it in an oven and heat to 170-200F" protocol works.

[cope413]

I'm pretty sure I print more nylon that almost anyone (60+ lbs of the trimmer line to date), and I would love a vacuum dryer, but $300 is likely too steep for 99% of users.

It would be interesting to see if there is any difference between vacuum dried and standard oven dried filament. I doubt 1 drying cycle has much effect on the nylon, but 2-3 definitely could, and I would guess that 4+ would be significantly negative.

Vacuum drying eliminates that issue.

[Dreyfusduke]

Yeah, $300 plus dollars is still kinda expensive, but it can dry out the nylon in about an hour instead of up to 12 hours in a regular oven and take a chance on warping your roll. Not sure how the heat stresses the filament or multiply uses for that matter.

[jckrieger]

I wonder how well a pressure cooker would handle the vacuum. throw your spool in the pressure cooker, put a vacuum on it, and throw it in the oven.

I bought a 42 quart pressure cooker from Amazon.com. I installed an NPT to R-12 style refrigerant fitting in the top and can pull a full vacuum on the cooker and hold it there overnight with no leaks. The Harbor Freight A/C gage manifold reads 30" Hg. I was also curious if the pressure cooker could hold the vacuum without collapsing... 14psi on that large lid and bottom surface generates a lot of force! If anyone is interested I can post pictures.

[Mac The Knife]

Nice. The one I found on Amaon is $400 bucks? I didn't think they'd be that high.

[jckrieger]

Nice. The one I found on Amaon is $400 bucks? I didn't think they'd be that high.

The pressure cooker was $45 and the adapter fitting was about $2.50.

[jckrieger]

First print and a picture of what the vacuum chamber looks like. There is absolutely no visible steam while printing after having the trimmer line in the vacuum chamber for about 3 hours.

[img]http://i202.photobucket.com/albums/aa44/jckrieger/first_nylon_print_zps28d3d17e.jpg[/img]
[img]http://i202.photobucket.com/albums/aa44/jckrieger/vacuum_chamber_zpsac51bba7.jpg[/img]

[Cedric_K]

Hi everybody

Before all, please excuse my unperfect english, it's not a mother tongue for me

I introduce myself as an absolute begginner with 3D print (never done, but soon...)

I work in plastics for 8 years, especially injection molding, and we have exactly the same issue, but worse, we can't make conform parts with a moistured material..

There are differents materials, some are not sensitive to moisture, other who are real "sponges" to a molecular level.

2 devices are used for that : the hopper dryer, which is no more than an oven... It had a resistance downside, a big fan, a grid basket, containing the pellets, and it is closed while working. Resistance heats (depends to the material : 70°c for PLA, 90°C pour PA66 (nylon) and ABS, 120°C for lexan (pc) and up to 160°C for PEI and PEEK). Some materials like PP, LD/HDPE, HIPS, don't need that). The time to keep into this "oven" is between 2h and 4h... (4h for abs). The fan enable hot air circulation into the pellets. After that, the moisture rate is near to 1%.

For some high performance material likes PEI, PC, PEEK, it's not enough, we use dessicant dryer, , this is not only heated air, but, dried air in closed loop, in an absolutely closed box, which is used, because these materials, are too hygrometric, and need a 0,1% rate of max moisture to be transformed.

Issue with these materials taking back moisture, is that when melted into an extruder, are heated more than 100°C, and the moisture becomes steam, makes the material more fluid, and make like 'foaming' into the material, its very bad for esthetic and mecanic of the part, and make the transformation harder. It always plays on shrinkage of the material (so much warping issues with abs in 3D print...) and dimentionnal.

UNDERSTAND that the moisture is not around the material, but INSIDE the material, that's why your trials with vaccum system are perfectly useless. Trying to keep filaments away for moisture is also a useless idea.. The material will take bake moisture a bit longer, but after a few hours, they have recovered the maximal water they could... The only way is to oven your filaments, and to vaccum under plastic bag immediately after drying. Plastic bag must be perfectly 'waterproof'. So you can keep a good filament for days, or weeks... depending how 'waterproof' your vaccum packaging has been...

Don't hesitate if need further info...

[artexmg]

Quick question, how could you measure the moisture *inside* the filament? is it an easy way? (not the environment surrounding it, but the filament itself?)

Thanks!

[nitewatchman]

This is a test we have to perform on Nylon Injected Parts in my day job. Here we are intentionally adding water after molding to "temper" or increase the impact strength of the nylon for railroad tie pads for concrete ties.

To measure the sample is accurate weighted in it's wet condition then placed into an oven at 250F - 300F for three hours. After removal it is immediately weighted again and the moisture loss calculated.

Warning, part will usually not survive due to distortion.

[artexmg]

This is a test we have to perform on Nylon Injected Parts in my day job. Here we are intentionally adding water after molding to "temper" or increase the impact strength of the nylon for railroad tie pads for concrete ties.

To measure the sample is accurate weighted in it's wet condition then placed into an oven at 250F - 300F for three hours. After removal it is immediately weighted again and the moisture loss calculated.

Warning, part will usually not survive due to distortion.

Great! thanks. Point taken that it is a potentially destructive method

[artexmg]

Hi everybody

Before all, please excuse my unperfect english, it's not a mother tongue for me

I introduce myself as an absolute begginner with 3D print (never done, but soon...)

I work in plastics for 8 years, especially injection molding, and we have exactly the same issue, but worse, we can't make conform parts with a moistured material..

There are differents materials, some are not sensitive to moisture, other who are real "sponges" to a molecular level.

2 devices are used for that : the hopper dryer, which is no more than an oven... It had a resistance downside, a big fan, a grid basket, containing the pellets, and it is closed while working. Resistance heats (depends to the material : 70°c for PLA, 90°C pour PA66 (nylon) and ABS, 120°C for lexan (pc) and up to 160°C for PEI and PEEK). Some materials like PP, LD/HDPE, HIPS, don't need that). The time to keep into this "oven" is between 2h and 4h... (4h for abs). The fan enable hot air circulation into the pellets. After that, the moisture rate is near to 1%.

For some high performance material likes PEI, PC, PEEK, it's not enough, we use dessicant dryer, , this is not only heated air, but, dried air in closed loop, in an absolutely closed box, which is used, because these materials, are too hygrometric, and need a 0,1% rate of max moisture to be transformed.

Issue with these materials taking back moisture, is that when melted into an extruder, are heated more than 100°C, and the moisture becomes steam, makes the material more fluid, and make like 'foaming' into the material, its very bad for esthetic and mecanic of the part, and make the transformation harder. It always plays on shrinkage of the material (so much warping issues with abs in 3D print...) and dimentionnal.

UNDERSTAND that the moisture is not around the material, but INSIDE the material, that's why your trials with vaccum system are perfectly useless. Trying to keep filaments away for moisture is also a useless idea.. The material will take bake moisture a bit longer, but after a few hours, they have recovered the maximal water they could... The only way is to oven your filaments, and to vaccum under plastic bag immediately after drying. Plastic bag must be perfectly 'waterproof'. So you can keep a good filament for days, or weeks... depending how 'waterproof' your vaccum packaging has been...

Don't hesitate if need further info...

Hi Cedric, this is interesting information.

As I understand, the idea of lowering pressure in a vacuum chamber, is to get the water boiling point down to around 40 C /100 F (at ~1 PSI), which, besides of being more convenient, will reduce the possible damage (by heat) to the filament, and, I guess, would also increase the amount of potential drying cycles. Does it make sense?