I’m reading an interesting post about washing resin prints.
The post was from Formlabs’ CRO Nick Graham, who discussed how many washes might be required for resin 3D printing.
“Washing” in resin 3D printing is the process of removing stray liquid resin left on print surfaces. Resin 3D printing is a wet affair, and it is critical to remove that toxic resin before curing.
That’s not only because of the toxicity, but also because if you cure a wet print, that liquid resin will solidify and be added to your print. This would definitely mess up any fine details and dimensionality.
Normally this is done by washing the prints in a bath of IPA after printing. The resin dissolves into the IPA, and is whisked away from the print. After washing, the print must be dried and then be cured in a UV chamber.
Graham’s question is this: how many wash stages do you use? He recommends two.
By far the majority of resin 3D printer operators tend to use a single wash stage.
The problem is that the IPA gradually accumulates dissolved resin. Sometimes you can see this as the IPA gets increasingly cloudy. As that increases, the IPA is less effective in washing the print because the liquid is saturated with resin. It’s at that point you would replace it with fresh IPA and start over.
Graham recommends a two-stage wash, as that is the standard within Formlabs. The idea is pretty simple: the first stage eliminates most of the resin from a print, while the second cleans off the final small amounts. The first stage absorbs the bulk of the liquid resin, and therefore requires swapping with fresh IPA more frequently.
I’ve used this approach myself often, because I found a single wash stage usually left the print a bit sticky. Really, it should be squeaky clean if all the resin is truly washed away.
I’ve also seen single-stage IPA baths so dirty that they cannot possibly wash away all the resin: if you put a clean part in that dirty IPA, it would come out with some resin on it.
Graham reports that he’s seen operations that perform up to five washes in a row, which seems overkill, but would certainly work.
Two-stage washes are especially important for production operations, where parts are repeatedly washed. This takes a toll on the IPA, which becomes saturated quite rapidly. If only a single stage were used, the parts would simply not be clean enough for curing.
My advice is to follow Graham’s suggestion. If you are doing any kind of resin 3D printing, set up a separate second wash station and use it. They are not expensive, nor is IPA. But the increase in part quality would be worth it.
Via LinkedIn
