There’s been a lot of talk about post-cure methods. Everyone has their favorite, but it’s hard to be scientific about it. We now have the equipment to determine whether a part contains uncured resin, so we’re going to test the effectiveness of various methods.
Here’s the list of methods we’re already planning to test:
- Rinse in IPA, cure under UV lamp with in air
- Rinse in IPA, cure under UV in a nitrogen atmosphere
- Rinse in IPA, cure under UV while submerged in tap water
- Rinse in IPA, cure under UV while submerged in water with ammonium sulfite added (bonds with O2)
- Rinse in IPA, cure under UV while submerged in glycerin, then rinse with tap water
- Rinse in IPA, cure under UV, then submerge in water for 2 days
- Rinse in IPA, then alternate spraying with IPA and air (3x)
The resin is PR57K (Black Prototyping Resin).
The IPA rinse is a 5-minute soak in the first wash, then agitate for 30 seconds, then repeat for the second wash (10 minutes in IPA total).
UV post-curing time was 5 minutes for all samples. The UV curing box was an LC-3DPrint Box, which apparently is a NextDent product, although ours doesn’t have their logo on it. It outputs 300nm-550nm at 290W total. I don’t know how much 405nm is in there, so I emailed NextDent but haven’t heard back yet.
All the samples were cured in polypropylene cups that I was told would not block 405nm UV.
The idea behind #6 is that as the water is absorbed into the part, it frees trapped radicals, which continue the polymerization process.
#7 is technically not a post-cure method, but it serves as an additional control.
The model is a ASTM D638 Type V dog bone:
Update: Here are the results:
The results suggest that there’s not a huge difference in the effectiveness of any of the methods. Kind of a boring outcome, but it also frees you up from having to use overly complicated methods such as glycerin or nitrogen. Granted, these samples were dogbones, which don’t have any little crevices for resin to hide. If you’re regularly making prints that are difficult to clean, just stick with whatever method you’re using.