Printed on Form 4b. The cure settings are listed as only 20minutes and 60*C; however, my parts were soft and flexible after 20 minutes. Any other recs for post cure? I’m using a form cure; however, the setting for biomed durable is not listed on the device.
Hey @GuidanceAirway !
Thanks for taking the time to post your question! I reached out to some members of our team who are familiar with the softer Biomed materials and they had a few quick clarifying questions!
Are these parts you’re printing particularly thin? Thinner walls can definitely make that material a little softer than you might like post-cure.
Another thing they mentioned is to ask whether the parts have stiffened up at all after more time outside of the cure when they’ve cooled off? It sounds like this is pretty common with those materials as well where it can feel pretty soft right after the heat of the cure, but it stiffens as it cools.
Are your parts staying as flexible as they were right out of the Cure? Or have they gotten a little better since then?
The primary part is a syringe. The wall thickness is 1.25mm.
There is a snap fit feature with a wall thickness of 2mm.
It did stiffen somewhat after it cooled off, however it’s still too flexible for the snap fit to function. I did add another 10 min of curing at 60C which didn’t change the properties much.
I used Form Wash solution instead of IPA, I’m aware that impacts biological validation. I’ll attach some pics.
You probably need something stiffer for snap fit. Durable and biomed durable is softer than very ductile thermoplastics such as polypropylene.
If you need the 100% biocompatability I would try to make this in like biomed clear or amber. Otherwise tough 1500 is a reasonable bet.
Are you all having reasonably reliable success printing biomed durable?
Yes. I didn’t have any issues. Supports were 0.55mm and 0.8 for my support concentration which were about double the amount of supports that would have been if I printed in clear.
At the bottom is the snap fit feature. The arms avg. ~2mm thick in the smallest dimension. I get almost a rubbery response from them. I worry Biomed clear will be too brittle similar to clear v5. The overall feel for the entire structure is somewhat soft, not as soft as a TPU but not rigid enough for mechanical work. For instance on that print is also a lever which bends too easily.
Biomed clear is stiff and like clear v5, but it is a bit less brittle and pliable in my experience, but this may not be as good as you need. Only way to find out is print and try unfortunately…
If you are just prototyping this (based on the fact you are washing with non-biomed workflow) Tough 1500 is probably what you are looking for here. A bit stiffer than durable, but still pliable and quick to spring back, I would wager that a Tough 1500 snap bracket here would work. It is certified for skin contact, but not mucosal membrane contact long term, etc.
Unfortunately however in terms of a true biocompatible ABS or polypropylene like plastic that is ductile/ impact resistant while having enough stiffness for a snap hinge in Formlabs’ library you may be out of luck. Durable is pretty impact resistant but it is soft by nature as you have found.
Edit: one option may be for you to invest in an open material license and print Loctite MED series material such as Loctite MED 412/413. Loctite MED413 < Loctite Additive Manufacturing
The datasheet for these indicate them to be an ABS/ Tough 1500/2000 like biocompatible material if you truly need complete biocompatiblility long term wise for testing.
OK, as follow up most likely I had some uncured resin thru-out the feature. I did a repeat wash (I’m using formlabs wash solution) and it did start to stiffen up. The snap feature is slightly more flexible than desired but may be feasible with thickening of the wall.