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I was wondering if, in your experience, it's practical/cost-effective for heads?
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Is it practical? - Yes. Once you learned what a 3d-printer can do (how to make models, what materials and settings work best, how to cut a 3d-object for 3d-printing,...) it's pretty reliable.
Cost-effective? - That depends how much you value your own time. I can build a puppet without a 3d-printer. But if I do that I have to do the work. With the 3d-printer I only have to provide the model and I can do something else while the 3d-printer does the work.
It took some time to find the right settings for the 3d-printer and to learn constructing the heads. I've made 3d-models for 3d-animations in the past, so I already knew how to make a 3d-model for rendering - I just had to find a way to make my models watertight and with the correct thickness.
Making a new head is very easy now - I have made a basic-head model that I can change in minutes. Being able to make several copies of one head that match perfectly is also really cool.
This year I made 14 basic puppet and 3 costume heads - if I had made them by hand I would not have had the time to make more when three puppet-heads.