Minis in Alcohol and UV light

I work on a lot of minis and I had a few questions.

I normally work on ~30mm minis.

  1. I’ve been keeping them in the first vat of alcohol for about 6 min, then the second one for around the same time. Should I do longer or shorter?

  2. I normally keep them under the UV light for 20-40 min or so. Longer or shorter?

  3. During this whole process, whens the best time to snip off all the supports? I’ve been doing them after the bath and the uv steps

I noticed that when I dont keep them in the alcohol they tend to get the white spots or white flaking on them when I put them in the UV light from uncured resin on the surface?

I am hoping that the longer time in the alcohol vats at around 6min each are not making them weaker?

My kickstarter is also up with the prototypes I did on the Form2. The final minis will be mass produced in plastic. Thanks a lot if you can lend any support!

That’s a cool project you have going. Few of the users including my self don’t use IPA to clean the models but use a water based system instead.

IPA can distort thin and fragile models so if your using that then carefully snip the supports after post cure and use 2 baths as Formlabs suggests.

Water based system you can just take the supports off a fresh print when they are soft which reduces chipping. The parts don’t distort or become brittle if left in YM because it doesn’t soak into the model.

Post curing in either case is quicker when the part is submersed in clean water under a uv light. I use a reptile light and usually takes about 20 min or so, others use nail curing units. Without using water it will take longer.

There is a new formulation of YM coming out that is much more potent, you should be able to use a toothbrush or something similar to scrub up the models and not really need an ultrasonic bath. Heating is also not necessary as long as the YM is room temperature so a cheap ultrasonic machine would do the trick if you have one.

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The Support web page has details on post-print cleaning and curing.

I do some parts with very thin walls and have found that too long in the IPA will leave these areas of the print permanently “soft”, even with unlimited post-cure time. So I “agitate” my prints in the IPA, either by putting the lid on the IPA tank and shaking, or I put the parts on the basket and then just sort of pull/push it up and down in the tank (as fast as I can without sloshing IPA all over the place). Typically 4-6 minutes (depending on “shaken” or “stirred”) in each bath seems to work for me.

If you don’t want to just follow FL’s recommendation, determining the necessary rinse time has to be done empirically. It is a function of both the resin you’re using, how you rinse the parts, and also to some extent the shape/size of what you’re printing. When I print in Tough, I knew I didn’t wash long enough because I could see wet spots in areas like a tight corner or groove, after the part was completely dry (it’s tacky too, but until you do a post-cure the entire print is tacky).

As for when to remove the supports… For parts that have areas that are poorly supported by their own structure, I’ve found that leaving the print on the supports until the post-cure is completed reduces the chances that the print will bend/sag/deform during post-cure. Downside is that for delicate parts, you have to take much more care removing the cured supports. Your prints look pretty solid so this may not be a concern, and prying the supports off the print before post-cure, while the print is still “green”, reduces the severity of the pitting/blemishing that otherwise occurs when cured supports are removed.

For most of my prints, I also reduce the support point size to 0.40mm since these are easier to separate and leave smaller blemishes. If the print has very large printed areas this small a point size might not work. But your parts look small enough they ought to tolerate this small a point size just fine. For many of my prints, I can literally just “twist off” the base from the print. It’s really satisfying. Like popping a bunch of bubble wrap all at once.

You shouldn’t be getting white spots with the grey resin unless the parts are wet when you put them in the UV cure (IPA or tap water).

It might be better to explain what the IPA and post cures are used for rather than give another example of what may work for you.

The IPA bath is only there to get the excess resin off the part after printing. For the parts to remain strong you want the least amount of time in IPA that gets the excess resin off uncovering the fine details.

Post cure is the step that hardens the green part to a hard finish (or just not sticky for the flex material). The time for cure depends on each individual part and how thick/big it is. If the part isn’t sticky anymore it’s done.

For small intricate parts try a fine brush to clean the details. Dunk the part and brush in IPA and then use the brush to gently clean any intricate details. It may only take a couple of minutes to clean. A makeup brush works great.

I stopped dunking in a final bath of IPA. I just use a spray bottle with IPA to do a finish rinse. This eliminates the worry about the second bath getting full of resin. It’s clean every time with the spray bottle.

The recommendation from our support pages is to agitate the part for 30 seconds in the first bucket and then soak in the first bucket for 10 minutes. Do the same process in the second bucket for a total of 20 minutes of soaking (21 if you want to be technical).

I find that supports are easiest to remove shortly after the part comes out of IPA but prior to it being post-cured. The support points will have swelled and softened slightly in the IPA. So long as the part hasn’t been in IPA for too long (generally over an hour), the swelling and softening will reverse when the part is post-cured.

Post-curing recommendations vary by material. Here’s a link to our support page on post-cure time and temperatures for different materials.

If the part isn’t sticky anymore it’s done.

Not completely accurate, based on my understanding. Layers are not fully cured during the printing process, or they’d never peel. So the entire part is “green” when it comes off the printer. You wash excess resin off in IPA to just get rid of a coating that would otherwise obscure the surface of the print. You post-cure to cure the entire part both inside and out. So eliminating the surface tackiness does not mean the part is fully cured.

True, but for non-functional parts like the ones printed here it’s not necessary to get every little bit cured completely.