Cases

A Magics user was asked to make this engine block using investment casting. To guarantee that the part would have the right measurements afterwards, it was necessary to add material to the insides of the holes. This was done by offsetting these surfaces. When offsetting, each triangle is moved perpendicular to its normal and so the hole will become smaller. To perform only an offset of the marked surfaces in figure 1 a local offset is needed. Afterwards, when the shrinkage had already taken place, the excess material was milled away until the part had the required measurements.

The concerned company however didn't only order a sintered prototype, but also wanted to make a very small series of the engine block using investment casting. Since the chosen technique to make the metal part (the engine) was investment casting, the master part had to be made in wax. This wax part then was covered with ceramic material to create a shell. After melting down the wax, the shell was used for casting aluminum.

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This method created the following problem: the ceramic not only had to cover the outside of the part, but also had to fill precisely the cavities of the part, so that the final aluminum parts would have the exact same shape as the original master. As you can see on the section on figure 2, the cooling channels of this engine were very small, especially between the holes and the outside of the engine (see arrows). To make the pouring of the ceramic into the small cooling channels possible, the people of the foundry asked to create little doors on the sides of the engine to enable an easy reach of the cooling channels. These doors then should be removed to pour the ceramic into the cooling channels. The doors themselves also needed to be produced using investment casting. Afterwards, when the aluminum parts – made by casting into the ceramic moulds – were finished, the separately made aluminum doors were welded on the engines. With Magics, such little doors are easy to create, while drawing them with a traditional CAD-program would take a lot more time. So Magics is both time-saving and cost-reducing.

The creation of the little doors started by cutting two squares into the part: a larger square around a smaller one (figure 2). With 'Shift + indicate' the Magics user cut along a straight line. Next, everything but the cut parts was unloaded. Since only the outside is needed to create the doors, there was still too much selected. So, using 'separate marked' only the front shells (figure 3) were selected. The rest was thrown away.

After that, the outside square was selected (figure 4) and turned so that its side was visible.

Then the Magics user cut the square in half (figure 5).

The inside half of this square was unloaded because it wasn't needed anymore. Then the smaller square was made visible again (figure 6).

With 'merge parts', the smaller square and the outside half were joined. To connect those parts to each other, first the inner edge of the larger part and the outer edge of the smaller part had to be deleted. The remaining hole was filled by creating triangles at each corner and by using the 'fill hole' function onto the remaining holes (figure 7). This is only one strategy to make this door, of course there are many other possibilities.

The finished door was saved and could now be used to make a prototype of the door.
Next the original STL file of the engine block was loaded. Via the 'boolean' function then the door was subtracted from the part. This way an opening to cast the ceramic in was obtained (figure 8). The Magics user created other doors wherever they were needed using the same method. The doors and the part with the openings were made separately and welded together in the final stage.

figure 9