Form Cure to hot? Or start with UV?

Hey there!

I recently had problems with big, planar parts in the Form Cure (Black resin, layer height 100 µm, printed w/o supports directly on build platform): As the Form Cure will heat up first and then hit the parts with UV, the semi-hardened resin would become hot and thus soft-ish and deform into any shape given by what is below that part. THEN the UV light would hit and harden the part into exactly that shape.

Is there any specific reason why the Form Cure would first heat up and then switch on UV? Why not vice-versa?

Did anybody try the other way round? I.e. first UV with low temp, then a second run at higher temp?

And why do we need elevated temperature? Does this accelerate the curing process? Or is there another reason?

TY!

I tend to let the Cure heat up and only put the parts in once the UV is already on.

As per Formlabs’ word the heat allows for a better curing inside the material, while UV at ambient temp only cures the surface and doesn’t get very deep.

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I let my parts dry from the wash tank for 20 min. lightly blow any extra resin off (rewash if needed) and then put in the cure oven I haven’t had any problems with sagging parts yet doing it this way I also leave the supports on until the next day in cases where the part doesn’t have any support designed in to it like a flat part.

Black is very susceptible to warping.
We print aircraft instrument panels and have to follow a specific process to avoid warping of large thin surfaces.
Letting the part dry in cold airflow for a couple of hour ( regular fan ) before putting in the post-curing chamber helps a lot. Our chamber has triple the UV density of Form Cure. and is temperature controlled. We start with UV at cold temperature, then ramp up.

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Yeah warping has been an issue for me too but I mostly use 3P resin so I don’t complain too much

Thanks Olivier, will try that (hanging in air)!

Just wanted to let you know that this indeed did help quite a lot. The Resin gets a little stiffer after a few hours (I assume due to loosing any soaked up IPA). After a few hours in air I put it into the UV chamber for 30 mins without and then 30 mins with heat. Right now works like a charm. TY!

Yes, indeed.
Great to see that we can help a bit!

Active drying with forced cold air is much, much better.
The quicker IPA evaporates, the better.
Note that the part will get a slightly more milky tint when it is well dry and ready for post curing.

Progressive heat ramping is also a factor to avoid warping. We ramp up to 50 degrees in 1 hour and leave for 20 minutes. We do not exceed 50 degrees with black ( only valid for black- other resin need more heat ). The high UV density helps deep curing while active cooling controls surface temperature. The slow temperature ramp up allows a more even molecular polymerization from skin to core.

This is especially true with very thick parts ( which could split in high heat/ fast ramp up condition ).

For very thin black parts, we keep the part on the build plate to cure in active cold air for 24 hours, then UV cure cold on the plate ( we have a chamber with a square window at the top) .

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