Dino injection mold manufacturing

I designed a two-piece velociraptor toy in CAD, routed the CNC in CAM and injection molded it - all with inspiration from a local elementary kid's drawing.

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Mastering "thinking like an injection-molder"

There are many manufacturing constraints with designing a mold and its negative part, of which mastering was incredibly fun.

Skills

Timeline

Location

Tolerancing

Design for Manufacturing

CAD & CAM

Injection Molding

3 months

Teammates

Evanston, IL

Kaitlyn Ko

Peter Hartman

Claudia Gabison

Highly repeatable process

Minimal part defects

Well-toleranced fit of a two piece part using only plastic

4x4" aluminum molds

Project requirements

First,

We brainstormed machinable and injectable geometries and decided on a pin-fit between the two part halves

I drew out pin locations that allowed for uniform part thickness within the minimum tooling diameter.

We also 3D printed a mock-up to verify that the part balanced well

I then modelled and shelled the part in SolidWorks, pin-pointing acute angles that would need to be filleted for CNC routing

To maximize this velociraptor's size, it was positioned across the diagonal of the mold.

Next, the CAM

We used NX CAM to create core and cavity molds.

*Notice that we machined holes to press-fit dowel pins to create holes in the part instead of machining protrusions

*A sprue was added to the cavity, and we filed small runners into the molds as a last step

*Note that sharp angles are acceptable on the core

*The pin height is customized to the part width at its cross-section using a fixed dowel height, which led to many mold re-models

Sprue with width based on flow rate

Two-injection points

Cross-hatching for venting

Surface finish is more rough on core (interior)

Zeroing the z-axis of each tool on the CNC became evidently crucial to this (as well as the number of finishing passes)

Holes for part alignment

viola! (many machining

hours

later)

finally, the injection molding

We fine-tuned mold temperature, clamping force, and injection time to perfect a dino without flash, sink or air pockets.

One of the cavities was also manually aligned with its core so that the dinosaur could stand on a perfectly-flat seam.