How DRY is dry enough?

  • I have been printing for several years - usually with Nylons, TPU, filled materials. Most of my focus is on parts for actual use.

    I have tried drying filament in both a dehydrator (160 F) and in a vacuum (1x10 -4 Torr - sub 1 micron).

    In many cases, old filament will loose 2-6 grams of water weight from a partial spool - depending on the filament, time and conditions vary (a lot).

    I just finished printing a whole series of gears with a 0.8M pitch and using a 0.2mm nozzle to accurately generate the fine tooth pitch - These printed great - look great, measure great. solid and strong.

    SAME SPOOL 10 minutes later with a 0.8mm nozzle - the extruder sounds like a popcorn machine - lots of hissing, popping and steam at the nozzle.

    Has anyone else seen this nozzle dependent change in behavior?

    I have seen this with both plain nylon and Carbon Fiber Nylon - smaller nozzles are fine but I can only get large nozzles to work with "factory fresh" rolls of filament and some of those won't print with a 1.0mm

    I'm printing on a Raise 3D N2+ with bond tech feeders and an all metal hot end (capable of 300C).

    Any thoughts and input will be appreciated!

  • @mdvolle You not only got to dry it but you got to keep it dry. Especially Nylon. In a humid environment Nylon can hydrate to the point of "popping" within less than 20 minutes. So I not only dry it but I got a spool holder in the dehydrator and leave it in there when I am printing - do the Same with PETG even though you might get a couple hours out of PETG before its too wet to print nice. TPU is very similar to Nylon. You don't have to dry PLA, ABS and HIPS

    As for gears... .8 pitch is a bit pushing it - hope you dont have too much load on it . Even injection molded plastic gears even if its NYLON or POM should be 1mm or larger unless they are very light load. NYLON gives a bit and that is both good and bad. Now 1mm you can print with a .4 just have it dialed in right and you want plenty of perimeters. I often print them solid

  • I'm struggling with the keep it dry part - even though my indoor humidity has been running <30% and its significantly lower than that in the printer cabinet - I'll have to consider printing from a dry box.

    As for the gears - yes 0.8M is small but its also the standard for follow and remote focus systems on camera rigs - so its also very low load - The 0.2 nozzle actually renders a fairly good 0.8 profile but you can't run it too fast or the tooth form gets messy - 30mm/sec seems to be about the limit and 25 is better -

  • @mdvolle Agree Nylon and TPU like to print slow

  • Follow Up on my obstinate filament -

    Another trip back to the vacuum chamber and let sit at vacuum (starting at a 0.2 micron level) for 16 hours and my filament now behaves even with the 0.8mm nozzle - so there is apparently a point where melting smaller amounts at a slower rate "gets away with" wetter filament - but switching to the larger nozzles, bubbles form and its unusable -

    So far, for me, the vacuum approach has been superior to everything else I've tried BUT - I'm running at vacuum levels significantly lower than the inexpensive pumps and using the ballast valve to keep the oil in the pump hot enough to disperse the moisture as vapor - Happy to share what I've learned but it wasn't inexpensive -

  • @mdvolle Glad its working out for you I am printing from a converted food dehydrator with a lot of those little silica packs that have been dried in an oven - thanks for sharing

  • I read your discussion. Good information for creating a case. And I had a question: did you think to store the material in special thermal bags that maintain a constant temperature and humidity?

  • @isladuffy Little to pricey for me at this point. I just have it in a zip loc bag with some desiccant and before I print it put it in the dehydrator

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