3D printing moulds for silicone hands

This post details the construction of stop motion puppet hands which are cast in silicone from a 3d-printed mould. By 3d printing moulds, I hope to be able to re-print the same "base" hands at different sizes, for the different characters in the film. 3d printing also allows me a greater accuracy than using the traditional clay sculpt-mould-cast workflow. I can use the same 3d mesh and adjust accordingly (such as adding wrinkles for the older characters)

I took a photo of my own hand to use as reference and set it as the background image in blender, then roughed out the shape of the hand as 3d geometry:

Blocking out the hand mesh in Blender 3D

 

After some further refinements I was left with a low poly model that captured the amount of detail I was looking to achieve. (Using Blender's sculpt mode the details of the hand could be further refined at this point)

Completed hand mesh ready to turn into a 2 piece mould

 

Virtual 2 piece mould

Then I added two cube meshes to the scene and with heavy use of the Boolean modifier I created a two piece mould with keys for locking the mould halves when casting:

I also imprinted the back of each mould half with text for easy recognition:

The mould printed really well on my Zortrax 3d printer:

Final print of 2 piece mould

I cleaned up a few of the print lines by painting acetone directly onto the print in a series of "applications". This involved painting a layer over the print, covering it in a small enclosure until dried, and repeating 3-4 times.

Then I cast the pieces in silicone (Using the process I have described here)

Pigmented silicone and armature in mould

In the photo above you can see the wires are not sitting in the middle of each finger. In future casts I plan to put small hard "beads" made of sculpey oven-dry clay on the finger-tips to keep the wire in the middle of the fingers.

I pigmented the 20ml of silicone with 8 drops of Vallejo "earth" colour game air paint.

I plan to use this same paint to airbrush the 3d printed head of the character these hands belong to. Matching the colour of the face and hands will require some experimentation.

And below are the hands. The casting process leaves visible seam lines where the mould halves join. These can be carefully cleaned up with a Dremel rotary tool (using a "grinding stone" attachment). The hands come out of the mould looking very shiny, and a fine coating of baby powder (talcum powder / corn starch) helps reduce the glossiness.

Final silicone hands (palms)

Final silicone hands (dorsal)