Week no.12

  • Molding and Casting

Assignments :
  • Design a 3D mold
  • Fabricate by Machinning it
  • Cast parts from it

CAD Design

For this week assignment I planned to make a mold for a bottle opener I once saw, which is actually a skull form (cool!). Since I was making it from zero, I looked the internet and found a reference image of the model:

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And so I began to draw the 3D model in CREO Parametrics "sculpting it" in flexible modeling (FreeStyle) until I was satisfied with the part design:

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The resulting 3D model :

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Mold Design

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Before creating the Mold I ran a draft analysis looking for "Negative angles" that could potentially stuck parts inside the mold.

After a few surface adjustments I manage to get a clean mold part.

The next steps for creating the mold cavities were:

  • Create the "Blank" to be machined
  • Create the mold "split-line" based on the draft analysis
  • Create the split surface
  • Split the mold in two cavities
  • Define and create the cast openings and guide pins.

The splitted mold cavities are now ready for CAM.

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Machining the Mold Cavities

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So the CAD model is assembled in manufacturing workspace and all the parameters like physical parts, cut strategies, speeds and feeds needs to be filled in CAM simulation. The output is a G-code file with the CNC machine instructions. More detailed steps are:

  • Define the CAD part to be machined (reference Model)
  • Define and assembly the "Blank" - Aluminum (100x100x50mm)
  • Define Fixtures
  • Create Work Center - FANUC 3 axis CNC
  • Create Cutting Tools - Plunge, End Mill, BallNose
  • Create operations - Facing, roughting, finishing x3
  • Define cutting parameters
  • Create tool path - machining time
  • Simulate surface finishing
  • Export machine G-Code
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FAIL : Choose carefully your strategy and cut parameters! It was a difficult part to make in Aluminum, since it demanded a tiny mill tool (2mm diameter) for finishing and cut the detail of the small choosed part. As the 2mm end mill broke, the strategy shifted to make a mold from a softer and milling safe material like Polyacetal to preserve my last 2mm tool !

Mold Machining - second attempt !

Ok, it is not a injection mold and I´m not looking for durability. So I cutted 2 blocks of Polyacetal and ran the manufacturing again !

Finnaly I got the jobb done and could cast some polyurethane resin parts from my mold. I also 3D printed the design CAD for comparsion.

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And here is a video of the milling process: