Week13

Molding and Casting

Group assignment:

• Review the safety data sheets for each of your molding and casting materials
• Make and compare test casts with each of them
• Compare printing vs milling molds

Individual assignment:

• Design a mold around the process you’ll be using, produce it with a smooth surface finish that does not show the production process toolpath, and use it to cast parts.

Group things

This is where our group page is.
https://fabacademy.org/2026/labs/nagoya/assignments/week13/

A prequel story

I recently 3D printed “Rheostat Knobs - Cessna 172 Flight Simulator” and edited because original model was too loose for my potentiometer shaft.

Luckily, original designer shared FreeCAD file in distribution archive, I opened it with FreeCAD and exported to STEP file. And I opened it with Fusion and edited diameter of holes.

After a few times diameter change, I finally got 3D printed knob that fit to my potentiometer.

What to cast

For the theme for assignment this week, I initially thought about to cast a small airplane model. And for researching purpose, I tried to let Claude Code to draw a Cessna 172 model with Fusion. But I found it is too hard to make milling mold.

If you are interested in this, I played with OSCAR — Open Source CAD Automation Claude Code and Autodesk Fusion 360. There are FreeCAD MCP and BlenderMCP.

So, I changed plan to cast that knob.

Draw a mold

So I copied the inner knob data and draw a sketch on a bottom surface of the knob.

And then, extruded frames and Dowel holes and plugs.

CAM

The last issue was CAM software. I usually amn’t using CAM function of Fusion because it looks to complicated, but I decided to try Fusion CAM at this time.

To use CAM function on Fusion, change the workspace from DESIGN to MANUFACTURE. You can change it by big button let top of the window.

Then, goes to SETUP and choose a machine. At this time, I choose Autodesk Generic 3-axis the most similar machine we are going to use. For Post processing, I choose Grbl / grbl because this machine uses grbl for milling controller.

Next, we need to add tools (endmills). To add endmills, goes to UTILITIES tab - [MANAGE] - [Tool library].

Next is applying Stock. Since we are going to use 178 x 78 x 40 mm wax cube, I entered these numbers on Stock tab of Setup window. We can setup the position of work on material on this tab.

To generate a toolpath, MILLING tab - [3D] - [Adaptive Clearing]. This is for rough machining. For finish machining, MILLING tab - [3D] - [Parallel]. So that we have two g-code tiles, one is for rough, the other one is for finishing.

One tip, when you generate toolpathes, you’d better to set Selection on Machining Boundary at Geometry tab, and choose Machining Boundary Selection. Otherwise, generated tool path may mill outer side of the mold.

Milling

I used Candle to send g-code to machine again. I fixed wax cube with double sided tape and milled.

Printing

To complete a group assignment task Compare printing vs milling molds, I printed the mold. Because I’m going to use vacuum chamber to degassing, I thought I’d better to make it non-airtight. So I removed bottom shell layer and made it open-air.

Checklist

• Linked to the group assignment page and reflected on your individual page what you have learned
• Reviewed the safety data sheets for each of your molding and casting materials, then made and compared test casts with each of them
• Documented how you designed and created your 3D mold, including machine settings
• Ensured your mold has smooth surface finish, that does not show the production process (by postprocessing if necessary)
• Shown how you safely made your mold and cast the parts
• Described problems and how you fixed them
• Included your design files and ‘hero shot’ of the mold and the final object