Comment on TPU wall thickness for shoes
HumanPenguin@feddit.uk 1 month agoJust to confirm. Hygroscopic does not mean the material is unsuitable for wet conditions as a finished product.
Your comment suggested that was your assumption.
The issue is that FDM (and all plastic 3d printing) depends on the molecular bods reforming as plastic is melted and reshaped. Almost all physical materials absorb moisture from the air. But some more than others. Highly hygroscopic materials when melted below glass transition temps. The moisture within the molecular bonds dramatically affects the materials’ ability to rejoin and reform those strong bonds. This results in some very odd effects on the final product, making effective production impossible.
The general rule is heat (30 to 90c depending on material) and time is needed to remove the absorbed water before printing.
I am currently struggling with this myself with ASA. As its my first time trying it. (im new to all this).
ExtremeDullard@lemmy.sdf.org 1 month ago
<quote>for every 5c below the perfect temp for your material, the time doubles.</quote>
Great info, that!
We always keep the dryer at 45C (not sure why, we just do…) I just looked it up and it looks like 65C for 8 hours is a minimum for TPU. So unless my colleague left the spool of TPU in it over the weekend - which I doubt - it would not have been enough. Unless he took the spool right out of the vacuum-sealed bag with the silicagel packet in it. I don’t know. I’ll ask him.
HumanPenguin@feddit.uk 1 month ago
I am rapidly discovering. That spools do not seem to arrive dry.
Also, desiccant will not dry a spool. It keeps the air dry and will prevent a dry spool becoming wet. With ASA, I am learning you always need to dehydrate before first use. But am hoping using desiccant and vacuum bags will limit the time needed when reusing an open spool.
PlasticExistence@lemmy.world 1 month ago
They will limit, but not by as much as you’d want. Plastic bags still allow moisture to pass through even when they’re airtight. I live in a swamp, so drying is a necessity before every print.
riodoro1@lemmy.world 1 month ago
Yeah. Those bags hardly do anything when the spool sits for months on a shelf.