How to print hollow with Preform 2.20. and Form 1+


Can anybody please help me as I cannot print hollow models with Preform 2.20. and my Form 1+.

I have hollowed models in Chitubox and saved them as .STL. Preform will import the models and ask to repair them. Without repair I can auto-generate the necessary support (even inside the model) but the models will not print at all as the have integrity issues.

Is there a simple workflow to print hollow models? All cheap DLP resin printers seem to be able to handle this with ease only PreForm seems to be far behind on this topic.



It’s hard to tell given the information you’ve supplied. I don’t know the software.
By “hollow” do you mean that you’ve made s shell in Chitubos?

It’s possible that you need to flip the normals in the inner face.

Have you tried ignoring the repair requirement, ignoring the error message, and printing the resulting .form file? That might well work.

Good luck!


Thanks for your answer.

I have resisted printing the non-repaired models as these show small black triangle shaped holes in the shell where PreForm normally shows a light blue surface.

Do you have a workflow for printing hollow models? I am not bond to Chitubox…


If you’re seeing black triangles, you probably don’t have a water tight model, and therein lies your problem. They indicate a hole in your model. Might be flipped normals, might be a defect in the mesh or a problem with mesh vertices on the edges of those polys.

I use Zbrush, but it’s not inexpensive, and has a considerable learning curve. But it’s a wonderful tool. Beyond wonderful. Probably overkill for your needs.

Meshmixer, from Autodesk, is both free and useful. It has “analysis” features that can check the model for integrity, and repair it. It’ll also make a shell if that’s what’s needed. Figure on half a day to learn the basics. They have good tutorials and context sensitive help.

I’d work with it for a bit, and see if that solves your issue. I often use it in conjunction with Zbrush.

Good luck!


Thanks. Will give Meshmixer a try and see how it works!!


PS- do not forget to allow openings in your model for resin and for air- SLA machines can not print a hollow model unless both liquid resin can drain out… and air can get into the hollow to prevent suction.
In preform, areas that create suction will be colored yellow and called “cups”.


Good reminder. Will add venting holes and cross my fingers that PF 2.20. will work


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