There is the option to build on the base, but what I dont understand is why it just basically adds a raft to the bottom of your model. Am I misunderstanding? It adds another layer of material that seemingly can’t be removed, so what would be the sense of adding this raft of extra material?
If you want to build to the platform as-is then don’t generate supports at all
There can be some cases where you want the raft if the model doesn’t have a lot of surface area or you’re concerned about how to get under the model, there’s ways to remove the raft after printing.
When you print directly on the build platform and generate supports, extra material is added at the bottom for compensation of the Z-axis compression at the first layers.
Depending on the resin and your needs for the final part, it can be a good option. The software does the best Formlabs knows to compensate for the compression of the first few layers and give you a part that is dimensionally accurate. I print on the build platform in Durable a lot, and for me, the result is usually a very small amount of cured resin around the edge of the base, that’s easy to trim off afterwards - typically an easier thing to clean up than support touch points themselves.
Of course I’m promoting Formlabs here, but in my opinion, Preform 3’s options to select a face to put on the build platfform, the ability to build on the build platform with additional supports, and the ability to use Mini-rafts instead of full rafts come together to get me better prints with nice smooth bases and significantly less support material.
My issue with building directly on the platform is scraping up the models lower edges with the metal tools. Because, the model is stuck SO good to the build platform using the tools provided, I always damage the model when I try to remove it if build on the platform direct.
See the creature with the big mouth? MURKMAW! I was afraid to print him directly on the build because normally I damage the edges a lot when I try to remove him.
I see. For model/miniature prints in the standard resins, here are some ideas that might help if you want to try MURKMAW! on the build platform again:
Bevel/chamfer the edges on your model/mesh before printing (if there’s room). Printing directly on the build platform will sometimes eat some of your bevel, but even then it can still help you get a scraper underneath with less damage to the edge.
Use a thinner/sharper scraping tool. The ones that ship with the printer aren’t bad for regular raft removal, but when you’re trying to get under a part on the build platform, a “flexible”-style putty knife can work even better.
Temperature change. Some people find that either putting their build platform in a freezer/cold place or heating it with a hair dryer will help the parts fall off, presumably due to differences in thermal expansion between the resin and the aluminum of the build platform.
If none of those are right for your parts, you may still be stuck with rafts or mini-rafts, but at least mini rafts use a bit less resin.
I’ve got to second the magic of a temperature change. I had a print I was certain I’d have to dissolve off of the platform in IPA - tried with all my strength and a lot of different implements of destruction to remove it. A half hour in the freezer and POP! Off it came.
Another forum participant has reported luck using canned air to freeze sections; I didn’t have any on-hand, but will be ordering some soon after seeing how much cold helped me out that last time.