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Peace Lutheran College

Very young students use CAD and CNC to produce 3D models

Over the past years Dennis Bliesner has been employed in various roles at Peace Lutheran College, Kamerunga, Cairns, Queensland, Australia. For the latest several years he has been the sole Technical Studies Teacher. Peace Lutheran College has been established twelve years and has a small Secondary department and Middle School.

The founding Principal had the foresight to generously equip the workshop with a good variety of technology education equipment including an Adept CIM Centre (CNC Lathe and Mill). Dennis felt challenged to put this (at the time mostly unused) CNC equipment to use in a learning environment. He has experimented with high temperature silicon rubber to form molds for white metal casting. This allows students to design and produce artifacts with minimal manual skills, once a computer model has been generated.

Kangaroo in Cosmic Blobs
Kangaroo in DeskProto
Kangaroo from the Cosmic Blobs library, in Blobs and in DeskProto.

Dennis takes classes from grade six through to grade twelve. He tells that he has had the best response from the younger students who are not aware of the old traditional Manual Arts metal and woodworking curriculum and are very adept at working in computers.

The youngest students are 11 - 12 year old (Middle School youngest group). They use a CAD program called Cosmic Blobs (unfortunately no longer available), which has been especially made to be used by creative kids. The illustration above shows that the user interface of this program (made by SolidWorks) is completely different from any other 3D CAD program. Based game experiences the kids easily get acquainted with the program.

The kangaroo is an example geometry from Cosmic Blobs Library (please find student work pictures below). It has been exported as STL file and next imported into the DeskProto Entry edition. Toolpaths have been calculated using the DeskProto Wizard, and have been saved for machining on the CIM Centre mill.

Machined kangaroo
Silicon rubber kangaroo mold
The machined model and the silicon rubber mold.

A positive model of the kangaroo has been machined in tooling board. Note that in order to keep things easy half a kangaroo has been machined, the result being the relief of a kangaroo. All DeskProto editions allow scaling per axis in order to create a convenient relief depth.

This machined model (left picture) next is used to make a mold (negative model of the kangaroo) by casting silicon rubber over the tooling board. This silicon model (right picture) next has been used as a mold to cast white metal (an alloy, mostly tin-lead, that melts at low temperature).

Unfinished model in white metal
Finished model: kangaroo ornament
The resulting casting, before and after finishing.

The resulting metal casting has been finished by making it round, drilling the hole, polishing the kangaroo shape and coloring the background. The result is a pendant ornament for a chain.

Small products like this pendant are designed both in both 2D and 3D. DeskProto Lite was used (now called the Entry edition) for toolpath generation to allow both 2D and 3D designs to be machined.

Key Tag design in Pro/Desktop
The model being machined
CAD design for a Key tag in Pro/Desktop, and machining it on the CIM Centre.

The secondary students design in PTC Pro/Desktop, both in 2D and in 3D. The key tag shown above has been modelled in 3D, by simply extruding a 2D contour. Not that simply though: note the draft angle the pin that is meant to create a hole in the tag. Draft: the top of the pin is thinner than its base, which makes it much easier to remove the casting from the mold.
The mold has been machined in tooling board, using parallel toolpaths - as can be seen in the illustration.

Casting in white metal
The resulting metal key tag
Casting the molten metal into the mold, and the resulting tag.

White metal can be melted using a standard domestic cooker: an easy process. It will require some experience though to achieve the correct temperature: too cold will result in the mold not being completely filled, and too hot will damage the mold.
The metal key tag as shown is directly after cooling down, it has not yet been finished.

Cosmic Blobs model of a fish
The same fish in DeskProto
This fish was made by Kate (11 year old), following the tutorial on the blobs web site.

It is rather exceptional (unfortunately) to see such young students apply 3D CAD and 3D CAM, so one might be curious about what they can achieve. Hence a few samples of their results is show. All five models have been modelled by 11 to 13 year old students using Cosmic Blobs.

Two fish halves being machined
A machined fish model
The fish being machined, and the resulting fish model.

The fish project is shown in four illustrations: 1 the model in Cosmic Blobs, that was exported as STL file. 2 the STL file in DeskProto with the calculated toolpaths. 3 these toolpaths being executed on the CNC milling machine and 4 the resulting model. The fish model was machined in two separate halves, to be connected later to form a complete fish.

Banner advertisement for DP Lite
Banner advertisement for DP Lite (Now DeskProto Entry Edition) featuring this fish model.

We used this project for a nice banner advertisement on

Cosmic Blobs model of a police officer
Cosmic Blobs model of a pig
A police officer by Josh and a cute pig by Maddi.

Note that all these pictures show 3D models, that the kids can rotate on screen to view from all sides, and that can be used to create physical models by means of DeskProto and a CNC milling machine.

Cosmic Blobs model of a caterpillar
Cosmic Blobs model of an alien
A caterpillar by Stella and an alien: unlimited imagination.