Castable resin Problem


I need to print on “casting resin” a sphere of 15 centimeters in diameter. The sphere will be used to make a rotomolding mold. Imagine the head of a baby doll.
I need to know if there is someone in this forum with experience in this resin to answer some questions:

1- I am having problems in getting smelters that work with the melting points of the molten resin of Formlabs

2-To reduce costs to the client, he thought to make the head of the baby hollow with a thickness of 1 cm. This would have some problem to melt or would it be better to make it solid?

3- Due to the high costs of the model, the client is afraid that a job with these characteristics will not work out well.


I’m not clear whether you need the final cast metal part to be a solid sphere or a hollow sphere, for the rotomolding mold that follows, but here are some thoughts

  1. The Form 2 build area is 14.5cm by 14.5cm (by 17.5cm) so you’ll have to print that sphere in multilple pieces.

  2. Formlabs Castable v2 and Castable Wax resins burn out, they don’t melt.

  3. You’ll save a lot of resin and your caster will have a much easier time burning out the resin if you print the pieces of your sphere as thin as possible. I think 2mm could work well, but thicker pieces might be easier to assemble and glue together before you hand it off to the caster for investment and casting.

  4. A solid 15cm sphere would take something like 1.7L of resin before adding supports, while a 2mm thick 15cm spherical shell would take about 140mL of resin before splitting it up and adding supports to the pieces. Even after splitting and supporting the pieces, printing a hollow sphere in parts should use much less than half the resin of trying to print the whole sphere solid.

3a. Even if it could fit, printing a solid 15cm sphere would be a challenge for the Form2 to peel the very large layers near the middle of the sphere. Printing a hollow sphere in pieces will mean parts with much smaller cross-sections, more like most Form 2 print jobs, increasing the chance of success. It also means that if one of the parts does fail, you can reprint that part instead of having to re-print the whole model again.

  1. I hesitate to say it, but if it’s just to get a solid metal sphere, I’m not sure if 3d printing is right for this job. You might be able to find someone who sells 15cm metal spheres already, or get a sphere turned on a lathe from round stock, or make a rubber mold from a 15cm sphere off some other material, and fill that with wax for investment casting. Of course, there could be lots of reasons why this project is more complicated than a simple metal sphere that I don’t understand, where it needs extra features that are much easier to print+cast than to machine.


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