How is such a kit created?
PB600-Kit: Making of ...
CAD-Model
For vacuum formed parts an exact mold is necessary. For this model the body mold was created as a 3-dimensional model in a CAD-system. To do this scale drawings on paper are needed of the different views, to get the correct dimensions for the CAD-model. Modern bodies consist of so-called free form surfaces, which are not easy to handle, even with powerful CAD software.
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| Views of the CAD-model |
Milling
| Based on the CAD-model the tool paths for a
numerical controlled 3-axis milling machine are calculated.
First the model needs to be divided into machineable sub
parts. For the calculation of the tool paths the dimensions
of the milling tools and the machine parameters are needed.
The picture to the right shows the simulation of the tool path for the right air intake. You can already see the final shape. The pictures below show the milling machine and how an air intake is machined. |
 Simulation of milling process |
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| 3-axis milling machine, numerically controled | Machining of an air intake |
| A picture of the
different parts for the driver cabin mold is shown to the right.
The cabin mold itself is made out of 5 parts (front, 2 sides,
back and roof).
The machined parts have scallops due to the tool paths, which need to be carefully sanded by hand. The used material is Sika-block, which is a kind of plastic especially suited for milling of forms. The pictures below (vacuum forming) show the final form of the driver cabin. The gray window areas were painted with primer and sanded with fine grain paper, because the porous surface of the material would show through and make the windows milky. |
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Vacuum Forming
For vacuum forming the material must be heated and then very quickly be drawn over the mold.
The vacuum forming box is shown below, the necessary low pressure (vacuum) is created by up to 3 vacuum cleaners. The PVC-sheets are fixed with screws to a frame and heated up in the kitchen range at 230 degrees C for about 2-3 minutes. Then everything has to happen quickly: take the frame out of the oven and draw it over the mold. After a few seconds the PVC cools down and gets solid, and the task is finished.
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| Vacuum forming box with mold | Vacuum forming | Finished driver cabin |
Glossar:
CAD: Computer Aided Design
PVC: Polyvinylchlorid = as hard PVC it's perfectly suited for vacuum
forming
