I tried to make "HANIWA". This is a doll of soil made in the Japanese ancient times. I like this character and wanted to some goods.Reference: Tokyo National Museum
I decided to make arm parts separately because the famaous posture of it, especially arms, is difficult to cast. In that case, it is necessary to make holes from three directions. So I made three kinds of molds as follows.
I modeled mold data with Fusion 360. At first, I made HANIWA data, and the molds were made by subtracting from it.This is a part for arm hole. The left side is the real shape. But, in order to save time, after milling roughly(the right side), I shaped the parts manually.
The material for molding that I used was hard wax. I cut a block of it with band saw.
I used a hot glue to fix the material on the platform, because hard wax cannot be bonded with double-sided tape.
After shaping the surface, I milled a set of mold with SRM-20.
The arm hole parts was milled in the same way. And then I shaped them by a saw and metal file.At last, I drilled two holes on the back side as a gate and air path.
The material for casting is ulethan resin. While weighing, the urethane and curing agent were mixed so as to have the same weight.
After stirring, I immediately poured urethane from the gate. After a few minutes, chemical reaction proceeded and it turned white.It was left for 2 hours until curing was over.
The following movie is shows how it was taken out.
Arm parts were made with 3D printers. Using 3D printer, I can easily test with many patterns.
Two air pocket genarated on the top of the object. I think it was wrong to have the wide side as the top. I should set a gate and air path on the head or bottom of model.
There was a gap between the front and the back molds.
The deep area of model was not cut. I think the size of endmills that I used were wrong. I think the mill used for rough cutting was too thick and the mill used for finishing was too short.(But I only had them.)
The flule length was too short, so the neck part hit the mold. But I didn't have longer ball endmill. So I excluded this area from the processing range when I mill the other mold.
I created a positive model with Fusion 360.
I milled the model with SRM-20. So I set a milling conditions using SRP-Player first.
I used modeling wax for positive mold. At first, I shpaed a surface of a material.
Rough cutting was done with φ5mm square endmill.
Finishing was done with φ3mm ball endmill.
I used the following material to make a mold. This is a silicone that can also be used for making food.
I mixed A and B in a weight ratio of 1: 1.
I poured it to the wax model.
After 8 hous, I removed the silicon mold from the wax model.
A negative mold of silicon was completed.
I casted final object using silicon mold. The material of final object was the same urethan resin as above. At first, I painted silicon to the silicon mold as a release agent.
I mixed the main agent and the curing agent at the same weight ratio and then poured into the mold.
After 1 hour, I removed the object from the mold. The final object was completed.
I didn't make exactly the same objects, but I tried the two processes. So I describe the differences between them.