Curing the resin after print

My prints come out from Form 2 not completely cured, no matter how well I wash it in IPA.
I have read about people making their own post-print curing machines. I have purchased a 7watt UV bulb with the wavelength 405nm, installed it in a box with aluminum foil glued to the walls inside, and tried curing parts with it. However after a few hours I didn’t see any difference between the parts that were left outside or inside the box.
Could anyone please tell me how much wattage do I need to be able to cure the resin and how long does it normally take for the resin to completely cure? Is it safe to look at the light?
Thank you very much in advance,
Gus

There’s a bit of variance in requirements for different resins. You’ll definitely want to check out some of our newest research on post-curing settings, including temperature, wavelength and wattage. 405 nm is great. Temperature and time matter quite a bit - usually 45 or 60 °C, and you’ll want at least 1.25 mW/cm2. The best wattage depends how big your box is.

Here’s an overview: http://formlabs.com/support/finishing/post-curing-prints/
And more details on the research: http://formlabs.com/media/upload/How-Mechanical-Properties-of-SLA-3D-Prints-Are-Affected-by-UV-Curing.pdf

Also, it helps if you place the object in a container with water. Oxygen prevents curing and the outside won’t cure as well just by being exposed to air so putting it in water will make the whole thing cure well. I used the curing method here: https://www.youtube.com/watch?v=mahcMOpeZkM
I do something like 30 minutes in a water container and 30 minutes out of the water and it works fine.

We quit soaking them in alcohol for the “prescribed” ten minutes. Now we only do a minute or so to rinse the liquid resin off, then soak them in water. Seems to work much better.

Those are for different purposes, the alcohol cleans off the liquid resin so that you get sharp details, the water helps the print to cure fully. You want to try and get as much of the liquid resin off the print before curing so that it gets the best result.

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