Filament Dryer/Dispenser Revisited

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thingismith
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Filament Dryer/Dispenser Revisited

Postby thingismith » Tue Aug 01, 2017 2:37 pm

I made a filament storage/dispenser box using a storage box (with foam seal) and dessicants https://www.thingiverse.com/thing:2243469. The humidity would go down to 30% and stay. I thought this was sufficient, as my nylon (Taulman Bridge) prints would come out "good enough."

However, I've been having issues with warping and vertical expansion only on my overhangs (even with supports), and was told by a tech rep at Taulman that this was due to my nylon getting a little too moist (30% too high) and not printing hot enough (I was printing 230-240, he advised to print at 250-255). I tried printing in his range and heard the terrifying steam-pops, signifying that they were too wet.

He advised me to make Taulman's DIY filament dryer http://taulman3d.com/drying-materials.html using a 5 gallon bucket and a trouble-light. It claims it can lower the H% down to 0-10 with a 60W bulb. I tried throwing a trouble-light with a 75 W bulb in my box, it went up to 100 deg F, but only shaved off 5%- down to 25%.

Looking to experiment a little, I took out the light and put in a small dehydrator, Eva-Dry EDV-1100, and boy was that a step in the wrong direction! I think the water it collected in the tank immediately evaporated back into box.

I found on the web a unit called the printdry, which is basically a food-dehydrator with a plastic top.

Does anyone have any experience with Taulman's model, a modded food-dehydrator, or any other simple filament dryer? I saw some posts here from a couple of years ago about using a vacuum pump, but that seems a little too extreme for me, especially if these two models work. I'd like something I can keep in and dispense from, without having to run to the oven every time I want to print.

**Edit* I was also wondering whether anyone's attempted to dry a spool on the heat-bed. I heard 60 deg C for 6 hours works.

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thingismith
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Re: Filament Dryer/Dispenser Revisited

Postby thingismith » Thu Aug 03, 2017 3:08 pm

Just thought I'd post my findings of the Taulman dryer:

Built it to spec, with exception of a 75W bulb. I ran my 75W trouble-light for 10 hours, the temp got up to 110F, humidity only went down to 25%. I threw in some dessicant, bumped it down to 22% after 12 hours.

Wanted to see what would happen if I tried their 'on 2 hours, off 6 hours' method. Only after an hour of being off, the humidity jumped to 50%. I expect it would only be a matter of time for it match the outer humidity.

Conclusions: It's possible that my results were different from Taulman's because the ambient RH is at 70%, so maybe this would work in a dryer climate or warehouse. For me, I don't think it's worth the extra power it takes to power the bulb, the dessicant in an enclosed container has about the same effect, 5%, 8% max difference. I'm going to try adding more dessicant to my container, see if that makes any difference.

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Re: Filament Dryer/Dispenser Revisited

Postby TN Yankee » Fri Aug 04, 2017 11:18 am

I have used Taulman's bucket idea, and currently have one roll each of T-Lyne and PCTPE in it. OTOH, I haven't printed with either in several months, so I hope they're still good.

I used a few different bulbs I had on hand, installed in a small aluminum reflector clamp light from Home Depot. I also bought one of their ~ $2 snap on lids, and drilled several holes in it. I don't have it with me right now, but I think they may have been 1/4" diameter or a little less.

When I did these tests, the room was always 45-50%RH. I used two cheapo eBay humidity/temperature sensors in the bucket, one laying on the bottom as far from the bulb as I could get it, and the other about 6" down from the top of the bucket, roughly opposite the bulb. I had 4 identical sensors on hand, and all plus a consumer-grade temp & humidity monitor were within a 5% spread. The cheapo also can't display humidity values below 10%.

The 43W halogen in the bucket never dropped below about 25% RH, and a 75W halogen dropped to 10% at the top, 23% at the bottom within 90 minutes. Temperatures peaked at 49C (top) and 39C (bottom). When I turned the 75W bulb off externally (i.e. didn't open the lid), it went back to about room conditions in an hour. I then ran a 50W halogen bulb with the same bucket & sensor setup, and it went to 10% at the bottom (43C), 18% at the top (38C) in about 2 hours.

I stayed with the 50w bulb, and about a month later ran it overnight (getting same RH & temperature values as above), then quickly pulled off the lid with holes & installed the same type of lid, but with only 2 pneumatic fittings to pass the filament through. I also shut the lamp off and installed a 750g silica dryer canister in the bottom. The filament is fed out into PTFE tubing, which is capped off on the end. I left one sensor in the bucket, positioned at about the bottom of the spools, and it has stayed at 12-15% since last year.

Again, I haven't used the filament since then, so all this may have been a waste of time. Although I haven't used it with the nylons, I now have a large food dehydrator for drying filament, and am starting to learn what settings work with different filaments in it.

The big question for me has always been how dry is the filament on the inside of the spool, since any moisture it has absorbed or adsorbed has to travel past all the filament on top of it to get out. I know there are spool designs which have holes around the core, but I'm not about to unwind a new spool to manually wind it on a different spool.

Something to keep in mind as well, and that is the properties of silica gel. From what I've read, it's ability to absorb moisture below 40% RH is easily outpaced by molecular sieve https://www.sorbentsystems.com/desiccants_charts.html. I had to look into this at work, in an effort to keep our metal powders dry for our SLM metal additive system, and I can easily achieve single digit RH readings with a molecular sieve packet the same size as a silica gel packet, which at best will drop to about 14%RH. I actually use dew point measurements at work as they're more absolute, but RH is a little easier to compare to if someone isn't familiar with dew point. The molecular sieve packets I use at work have come from McMasterCarr.

I use silica packets at home as they're cheaper and I haven't needed to get filament down to 8%RH.

Hope this helps a little.

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Re: Filament Dryer/Dispenser Revisited

Postby Jimustanguitar » Fri Aug 04, 2017 12:19 pm

How are you measuring your humidity level? Are you measuring the air around the filament, or the filament itself?

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thingismith
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Re: Filament Dryer/Dispenser Revisited

Postby thingismith » Fri Aug 04, 2017 9:27 pm

@Jimustanguitar I'm measuring the air around, using a basic hygrometer/thermometer. I hear you'd need an expensive tool or go through some tests to find the amount of water absorbed by the filament. In the container it was near the bottom, up against the wall, and in the bucket it sat on top of the pole where the spools would be.

I should mention that my first container had both the Eva-dry dehumidifier, which is basically a container with silica gel crystals, and a Damp-Rid container with Calcium Chlorite. I didn't think the DampRid was working because water never fell to the bottom. After testing the trouble-light in the container the crystals got hard so I threw them out. Now my container won't go lower than 40%, and I even threw in a second Eva-Dry, no effect. I guess TN Yankee is right, the silica gels don't work so well.

@TN Yankee Thank you for sharing your experience! Did you drill holes in the bottom of the bucket? Maybe that makes a difference.

Next I'm going to try this food-dehydrator version I found on thingiverse https://www.thingiverse.com/thing:1618037. I'll post my results.

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Re: Filament Dryer/Dispenser Revisited

Postby TN Yankee » Sat Aug 05, 2017 12:20 am

No, I didn't drill holes in the bottom. During drying, the lid had several holes to allow moisture to escape. Maybe I'm not understanding your intention, but it seems to me by also drilling holes around the bottom would encourage air flow, in which case this system would never dry the filament out.

I bought this dehydrator last year during a Black Friday sale, plus a coupon, for about $30. While it pulls in fresh air, the combination of a big heater & fan effectively dries whatever is inside.

I've thought of weighing filament spools to track moisture, but from what I've read the differences are in the single digit gram range, and I'm not sure my little scale is reliable & repeatable enough for that. Plus, it would be a big pain. Given enough time (though how much time is unknown to me) the filament in a closed container will be at equilibrium with the air around it, so a humidity monitor works for me.

I've seen comments around the web about filament being too dry, but again the desired, specific moisture level for different materials is unknown to me. I shoot for below 25%RH and consider it good.

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thingismith
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Re: Filament Dryer/Dispenser Revisited

Postby thingismith » Sat Aug 05, 2017 1:34 pm

I only ask because Taulman instructs making the holes at the bottom and it seemed amazing to me that there'd be such low humidity over such a long time. I agree about the air flow, but it's not great at keeping moisture out when the light is off.

That's an amazing discount for a $200 dehydrator! What luck!

I haven't seen anything about too low humidity ... I can imagine there'd be problems if it's kept at too high a temp for too long.

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Re: Filament Dryer/Dispenser Revisited

Postby TN Yankee » Sat Aug 05, 2017 11:32 pm

You're right - I had forgotten about the bottom holes. I didn't put them in as I intended to be able to store the filament in the same bucket by switching lids, as I mentioned above. I, too, am surprised at the humidity levels they quote, considering they're cycling air through. Their shop must be at a fairly low level.

The "too dry filament" topic is something I've read anecdotally about, but this is the only one I can find at the moment: http://www.tridimake.com/2014/01/how-to-3d-print-nylon-and-trimmer-line.html.

Again, there are so many unknowns with "proper" moisture levels in different brands & colors of filament (due to additives), not to mention different thermoplastics altogether. Then, how many people track & post the humidity around their printers? I have to run a dehumidifier in my basement, printer or not, just to keep it around 43-44% during the summer. Someone in south Georgia or Utah will likely have very different ambient humidity levels, which affects how long their open filament stays at the "proper" moisture level. After I dry mine, I transfer it quickly to a kitchen/food storage container with advertised "air tight" lid (though it isn't), with some silica desiccant packs, an ebay humidity meter, and PTFE tubing running to the printer.

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Re: Filament Dryer/Dispenser Revisited

Postby thingismith » Sun Sep 10, 2017 1:31 pm

I read the article, it looks like the author reasons that a slight bubbling causes a roughness on the layer surface that's good for layer adhesion. I guess it makes sense, but I'm not entirely convinced. I think you can get just as good layer adhesion without bubbling.

Anyways, since my last post I've modified, built, and have been using that filament dehydrator I mentioned earlier, you can find the model here: https://www.thingiverse.com/thing:2520281. It's been great, I no longer get any steam whatsoever (unless I don't use it more than 24 hours and don't reel in the filament in my PTFE tube and heat it for a couple of hours). Before I would get moisture crackling above 140 deg, now I'm printing at 160 and there's no sign of moisture at all.

It beats having to take it back and forth to and monopolize the oven for 6 hours before wanting to print, and I don't have to wait as long to dehumidify the core because it heats the filament as it's being drawn out. Im sure it can be modified again too include a second spool in the dehydrator, but I don't need it (now), so maybe someone else will step up.

Only a couple of drawbacks: the fan in the dehydrator can be noisy at times, (usually just when it starts) and it can be a little difficult threading the filament back into the snoot and putting the cover back on while keeping the filament taut on the spool. If it falls off the spool on the last revolution, it can get caught on the base.


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