15. Molding and Casting

Weekly Assignment Requirement

Individual assignments

  • design a mold around the stock and tooling that you’ll be using, mill it (rough cut + (at least) three-axis finish cut), and use it to cast parts

Group assignment

  • review the safety data sheets for each of your molding and casting materials, then make and compare test casts with each of them

Description of Assignment Work

3D modeling

I saw some people who loved to create own custom keycap called “artisan keycaps” for the keyboard of computers before. I had thought that I wanted to try it by myself. I thought this week’s assignment was a good opportunity to do it so I tried to make the mold of it by understanding the process of the craftsmen.


Design 3D model

Using Fusion360, I designed a simple keycap with a embossed letter “O” on its surface. the reason I picked the shape of “O” was a easy to cut with the milling machine. and also I designed the connecting part to the keyboard on its backside. but actually I designed it as the mould directly because it was easier for me. the shape was confirming to the datasheet of button part of the keyboard.

Designed the embossed letter keycap

Design the mould

to create the mould, it needed to take complicated process. I had to make the mould for the mould by milling machine at first. then, I could create the mould for final object by moulding with first mould. using Carving & Milling Waxes for first mould and using silicone for the second mould. but when I tried to design on fusion360, I started from creating the mould for 3D model I had created already. then using it like negative for photograph, I convert it to a reverse shape (positive) as it could be the mould for the mould.

Put the 3d model simply to create the mould for the mould.
And also add the pillars for connecting the mould of the bottom side

Mould for the bottom side, this part would cover on the top side mould. It needed the wholes to release extra material

create rectangular solid overlapping with the model already designed and cutting off the doubled part.

Doing same thing to the bottom side. while I doing it, I found the pillar for connecting both moulds couldn’t be milled because of its square-cornered shape. So I changed their design to round shape before finishing the mould.

Order two moulds for milling. the outer shape should be within the size of Ferris File-A-Wax Blue(147mm x 88mm x 37mm).

Done! (But modified later…)

Miling the mold by SRM20

After finishing making 3D model of the mold, I cut it by SRM20.

Preparation for Milling from remote

We still have only partial access to the lab because of covid-19 so our instructors prepared the environment for milling from remote place. we could connect to the computer connecting to SRM20 and see its display via zoom.app and control it as well.

using SRM20 with the ⅛inch endmill. and controlling it from MODELA player 4.

for cutting, I would create two kinds of data. one was for rough cut and the other was for finishing.

this time, I only for making milling data. and I would actually mill them after releasing lab access completely

Before starting milling, my instructor gave an advise about length of the pillars. So I modified the model and then tried to create milling data(.mpj) from .stl data.

Set the model from the menu and proceed settings for rough cut.

Can view the estimated cutting time. My time for rough cut is 1h25m.

And for finishing was 1h13m.

Milling at the Fablab Kamakura

Finally, we got access to the lab though I prepared to cut remotely. I could use the data I had made remotely but I wanted change it slightly so I created cut data by MODELA Player4 again. after finishing it, I prepared modeling wax.

modeling wax

set the origin point at the center of the wax. it was nice to draw the point on its surface beforehand.

I used two type of drill bit. one was 1/8 inch for almost all part cut by this and the other was 1/32 inch for the fine part. latter one was not used normally but I wanted make the tiny structure partially so I used it.

the outcome was like this.

fail while cutting
when I cut the mold, the drill stopped suddenly and it happened three times. it caused by melting dust of wax. the edge of the drill coated by it then the blade didn’t work at all. that was why the machine stopped I guess.

the drill wearing wax like the image

I thought the reason it happened was the part I enclosed by pink line in the photo below. this ditch kept the dust and it had no space to escape from drill. so it was kept being drilled and it made heat then wax melted and sticked to the drill.

actually the ditch did not need to be cut. I just missed to set the cutting area. so it is really important to set the proper cutting area. and it also helpful to sweep dust sometimes while cutting.


finally I tried casting. I needed to do it twice at least. once for making the mold for the mold. and used the mold I made at the last.

preparing the material

I used two materials for casting. At first, I tried silicon to put into wax mold. and it would be the silicon mold for making the final outcome.

the material for the silicon mold.

If the two type of liquid mixed, the mixture would be harden and make the solid shape. the time to be fixed depended on the material so I had to check the instruction.

And mixing had to be done carefully because if used wrong amount of them might lead to incomplete curing. so the scale should be used. and mixing a lot was really important in this step.

Silicon casting to the mold for the mold

put the silicon material into the mold I cut.

I put it for about a day(actually it might be possible to make the time shorter) and it was successful in making mold by silicon.

unfortunately, I broke column in the mold when I remove the outcome from it. it had better make the bottom of columns bolder not to break them.

casting with the silicon mold

I used this material. this was gonna be hard and the color of it was white

I was surprised when I mixed the liquid of this. it got very hot. some of material get heat so I have to care to use it safely.

I put the material into the silicon mold. and then I put the lid part to the bottom part. the extra liquid leaked from the hole.

and after a day, I could get the outcome in good quality.

and I could attach it to the mechanical switch for the key board

Group Assignment

I review the wax for the mold named “Ferris File-A-Wax Blue” with its datasheet.
Please see the link below.

Kamakura Group assignment week15

Description of Important Weekly Learning Outcome

Before doing molding and casting, it seemed super difficult to do because it needed to make a mold and manage some kinds of chemical liquid. But I felt it was not so when I tried it in practice. 3D modeling and milling for the mold could be done as I made 3D stuff usually. and for casting, I mainly had care the amount of mixture of two type of liquid (and cleaning up after working also). The outcome was more beautiful than I expected. I thought I should try this kind of skill more.