Old-Fashioned Key
16 May
Week11 Moulding and Casting; Wax;
---3D Design---
I designed a 3D model of an old-fashioned key in Fusion 360. To make a negative mould, I split the model into half and added four fixtures around the corner, one air tube, one inflow tube, a base and a wall to it.
---Generate RML File---
To mill the shape, I used fabmodules.org to generate two RML files - one for rough cut and another for finish cut. I uploaded the STL file to the site and chose the export file as RML format. I got the correct size in mm by typing in 25.4 in the 'units/in' to change the units designed in mm to be compatible with the inches, the one used in fabmodule. After I pressed 'calculate height map' a colored map should be generated.
Then I moved on to choose the process as rough cut and finish cut respectively. I selected SRM-20 as the machine. The tool I used was 1/8 inches' flat endmill. When I was done with the settings, I clicked on 'calculate' and I saved the file after the below picture was generated.
---Moulding---
Blend Oomoo 30 A and B with 1:1 ratio in volumn and stir thoroughly for at least 3 minutes to get a fine purple color of it. Pout it evenly to the milled wax. Either tie it somewhere to flatten it or use a vacuum bag to get rid of extra air.
The passive mould should be ready in 6 hours. And then blend the casting powder with water and use an injection tool to inject the liquid through the inflow hole carefully. Then fix the two-part moulds tightly and leave it for 3 hours.
☞ Problems
In my first attempt, the design was too tiny and delicate therefore the cast turned out to be extremely fragile. Therefore in my second attempt I adjusted the diameter of the key rod and it turned out to be fine.
☞ Tips
Always take down the details of the origin position during the rough cut as you're very likely to use it again in the finish cut. (I've encountered twice the milling machine was powered off and didn't remember anything during the last job.)
The design file can be downloaded here:keychain-thickness-adjusted.f3d