We have a lab where we sometimes need to re-use the same tray for different resins. We usually scrape the tray and give it a quick IPA wipe to be sure, but we are wondering if too thorough cleaning to get the last drops out might actually do more harm than good, ie. is squegeeing most resin out enough, or should the tray be wiped clean?
It has been mentioned previously that having a “small” amount of previous resin remaining after scraping shouldn’t affect printing, but so that we can put a number on it and know that we are complying with official manufacturer instructions, could I get an estimate exactly how much is a “small amount”, in ml or percentage?
For example, when moving from gray -> clear resin and using the same tray, is having 5 % of gray resin remaining in the tray after scraping and having it mix with the clear resin ok, apart from any potential cosmetic issues?
I mix resins all the time. Generally, I pour any remaining resin out, letting it “dribble” for 5 minutes. What’s left in the resin tank can’t add up to more than a milliliter or so. Not an issue. It’s all soaked up by the Base part of the print, so by the time the actual model starts to print you’re in “pure” new resin…
I wouldn’t use IPA to wipe out the tank. IPA will attack the acrylic plastic and weaken it. The tank can crack and resin will leak out in to your printer.
What I do to remove resin from the tank, to not make a mess I tilt the tray a little and use a cheap plastic syringe to suck out the resin carefully from a corner. After a bit I use the scraper to squeegee the resin to a corner and make the bottom clean. After using the syringe and the scraper to get as much out as possible there’s very little left in the tray, I then just use a paper towel and wipe around the edges. What’s left even if you go from black to clear shouldn’t even be close to causing any problems.
I’ve actually mixed black and white. I poured black in to white in a swirly pattern, in the vain hope that the pattern would be preserved in some veiny/grainy way in the final print. But alas, all I got was slightly varying shades of grey. The compression of the first few layers effectively mixes the resin and ruins any possible swirly effect in the final print.
You should wait until after the part starts to print ( raft is fully formed and the supports have made it close to the 5 or 6mm height above base). Also, Do not fill the vat to the limit. The sooner the build platform is above the resin height the better for mixing resins to get the different colors to stay separated and not just mix. That’s how I got the patterns in my parts. I would have changed colors after a good blue layer but I was out of clear and didn’t want to turn the tips of the openers black. I didn’t think it would look right.
