Tips/Tricks for printing with PVA?

Hi All,
My son put his graduation money toward a 3D printer this summer, but he suffers from some learning disabilities so Dad (me) has the fun of building/maintaining/figuring out what can and can't be done so he can print the items he finds on thingiverse/wherever. I'm not complaining-- I find it far more enjoyable than I thought I would going in (and I knew I would enjoy it-- just not this much).

So we've built a Tricolor Mendel-3 and have jumped right into printing a lot-- the machine is only about a month old so we are really newbies still. So far, we have only done a couple 2-color prints (some dice and calibration and some keychains with raised monograms in a different color). I know we have some calibration issues, but they seem minor and in general we're pleased with many of the prints we have made. We purchased some PVA and I tried using it yesterday for the first time and it was really not at all successful. In some quick research, I think we made a mistake by opening the spool a month ago due to its hydrophillic nature. The filament is quite pliable and with a bowden tube style extruder, I suspect we're suffering from a lot of compression issues within the tube. I read one post (on another forum I think) how someone keeps their PVA in low humidity and only removes the number of meters required for any job, but then can use generally stock settings.

When our machine printed PVA, it seemed to ooze a lot and come out when it should have completed printing. I took a wild guess in slic3r and doubled the retraction and added an extra 2mm on resumption (it always seemed to ooze after it was supposed to be done and it seemed to be slow starting) and while I was able to compete a print where I used the PVA as a support material (not so much for support, but in hopes of creating a nice clean underside to a 45 degree slanted piece that, while it printed without support was quite unpolished on the bottom). I thought if I could support it with a solid layer of PVA the PLA above would come out much more refined and nice. The PVA seemed to take forever to dissolve and once removed, it was really no better than without support and in fact in some ways was worse as the PVA extrusion problems led to new PLA problems due to the unevenness of the PVA extrusion.

So I'm interested in any tips/tricks anyone knows when printing with PVA. Also, specifically, I'd like to know if we can do anything to 'repair' our spool of PVA if it is at all possible. I had a couple desiccant packets from other spools and one of these vacuum sealing ziplock bags, so at the moment I have the spool vacuum sealed with 2 packets, but I really don't know if this will have any positive effect on the PVA, though, I can't imagine it would hurt. I think this is likely a far more ideal way to store a spool after it is opened, and will likely do this with any new spools we may buy. I thought of filling the bag with rice first too, but thought I would ask here for any tried/true advice, or if it is a hopeless cause once the damage is done.

Then, in general-- if anyone has any tips/tricks for PVA (especially PVA that has been exposed to standard humidity for considerable time) I'd love to read about it. I searched the entire reprap forum for PVA and couldn't believe I found no posts, so either I did something horribly wrong on my search, or there has not been a lot of chatter about it.

Thanks in advance!

... an airtight box with desiccant for storing filament is sure a good idea ... regardless of the material

For drying old filament you can temper it at a safe temperature (maybe 60degC for PVA?) for some hours ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

I have seen a fruit dessicator recommended for drying filament, but I don't have one.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
VDX
... an airtight box with desiccant for storing filament is sure a good idea ... regardless of the material

For drying old filament you can temper it at a safe temperature (maybe 60degC for PVA?) for some hours ...

Sounds like a plan. I had bought a bunch of these ziplock vacuum seal bags to help put some of my mother's belongings into storage when she downsized and have a few left over. Now I have a good use for them!

So far we've not yet learned the pain of abused PLA/ABS. All our spools print at expectation. However, perhaps we need to raise our expectations.

Quote
dc42
I have seen a fruit dessicator recommended for drying filament, but I don't have one.

I may cut off a few meters and give this a try. We just happen to own a fruit dehydrator. Thanks for the suggestion.