Designing the Mold

For Week 14, the assignment was molding and casting. I wanted to create a reusable mold that could be machined on the Makera Carvera CNC machine. My final idea was to make a cross-shaped ice cube mold using a block of Delrin.

The Delrin block I used was approximately 20 mm thick and measured about 150 mm by 100 mm.

At first, I wanted to make a much more detailed mold design. I tried several ideas including a rocket, skull, axe, and other complicated shapes. I started some of these designs in Tinkercad, but I kept running into problems when moving the files into the CAM software.

The models would either fail to import correctly or turn into strange triangle shapes that did not machine properly.

Fixing the Design

After fighting with the more detailed designs, I decided to simplify the project and create a cleaner shape that would be easier to design and machine. I switched to a simple cross shape and rebuilt the design in FreeCAD instead of Tinkercad.

This fixed many of the problems because the file worked much better with the CAM software and the toolpaths became easier to control.

The biggest issue with the earlier designs was that they were too complicated for the workflow I was using. Once the imported model turned into a collection of triangles, it became difficult to tell what the CNC machine was actually going to cut.

To fix this, I simplified the mold design, rebuilt it in FreeCAD, and focused on creating one clean pocket for the cross shape.

Machining on the Makera Carvera

Once the new design was ready, I used the Makera Carvera CNC machine to mill the mold out of the Delrin block. For the cutting tool, I used a long flat end mill because I needed the bottom of the mold pocket to remain smooth and flat.

I chose the flat end mill because this was not a detailed 3D sculpture anymore. I needed a clean pocket with a flat bottom, and the simple cross shape worked better with that toolpath strategy.

Final Mold Result

After the machining was complete, the cross mold came out successfully in one piece. This was a huge improvement compared to the earlier failed designs.

The final cross shape was much cleaner, and the Delrin worked well as a mold material because it machined smoothly and released the casting easily.

This project was frustrating at first because the rocket, skull, and axe designs kept failing. Simplifying the design into a cross shape made the entire process work much better.

The cross ice cube finally came out successfully with help from my daughter because dad was getting frustrated during the process. This reminded me that fabrication takes patience, testing, and sometimes a second set of hands.

What Went Wrong

• The original rocket, skull, and axe designs were too complex.
• Some files did not transfer correctly from Tinkercad to CAM.
• The CAM software created strange triangle geometry.
• The early designs were difficult to toolpath and machine.
• The project had to be simplified for the CNC process to work.

What Fixed the Problem

• I simplified the design into a cross shape.
• I rebuilt the model in FreeCAD.
• I used a 20 mm thick Delrin block.
• I used the Makera Carvera CNC machine.
• I selected a long flat end mill.
• I simplified the toolpath strategy.

What I Learned

This week taught me a lot about molding, casting, CNC machining, and file preparation. I learned that the design process matters just as much as the machining process itself.

I also learned that Delrin is a good material for reusable molds because it cuts cleanly and produces a smooth finish.

The biggest lesson from this assignment was to start simple, prove that the process works, and then make designs more advanced later once the workflow is reliable.