Im using more or less the full range of resins.
My Question can you leave then curing for too long, or is more better
Thanks
My understanding is that by having suggested times, it is possible to over-cure. To add to that, Untreated UV resins will degrade over time when exposed to constant light.
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You can definitely over-cure parts. You can end up with a brittle part. Formlabs provides recommended curing times and temps for their resins - I try to stick pretty close to that. The standard resins don’t need a post cure.
That said I have started to use a water bath for curing and have gotten much better results, so it is a little more complicated than just giving a time.
Formlabs has a cure station which looks to be really nice and I use a Curebox from Wicked Engineering. Both of those will do a great job curing your parts correctly.
I am not sure what you mean by the standard resins don’t need a post cure. They 100% need a post cure, as recommended by Formlabs unless you want squishy parts. It shouldn’t even be called a post-cure. It is THE cure. Parts are not finished in the Form 2, they are not finished after wash, they are only finished after curing them in UV light, preferably at the temperatures and times recommended by FL.
In terms of over cure, sure technically you can. It is just a matter of how long it takes, and which resin you are using. Something like Flexible, durable, and tough are going to be more susceptible to over cure whereas the standard resin will change color but the properties won’t change significantly until you leave it in for hours extra. There is no official study for over cure so just stick to FL’s recommendations. Use a timed and heated cure box (Wicked or FL or custom DIY) and you will be good to go!
Over curing can also cause prints to warp, I get very good results with the timings consistent.
UV light will accelerate the degradation of many organic and inorganic compounds so it can be important to avoid over-curing parts. After printing, parts are in a green state where only a portion of the photopolymerization reactions are completed. UV curing ensures that all of the photopolymerization reactions have occurred and enables the final part properties. The UV curing guidelines are designed to ensure that most all of the photopolymeriztaion reactions have completed without exposing parts to excessive UV.
I typically leave our Form 1+ parts in the bay window in our kitchen until they’re no longer ‘tacky’…maybe 10 - 15 minutes if the sun shining there. The few times I accidentally left parts in the window (or out in the backyard even,) all day long, the parts became discolored and very easy to break (i.e., brittle as described by other posters.)
Properly cured parts are strong in comparison. They can still shatter if you drop them though. If it’s a little under cured, the part can retain a little flexibility, which could be an advantage I guess. (BTW, I typically used Clear or Gray resin. I’ve never used the tough or flexible stuff.)
If the parts are not going to be painted, I’ll at least give them a coat of clear UV protection to prevent them from over-curing. I think this helps but I’ve never really tested to see how much. (Hmm…okay, I’ll test that after the holidays.) 