4.11 3D printing our gearwheel
I hardly need say that several AM processes are eminently capable of producing the overall shape of a gearwheel. There are, however, two issues to do with the performance of the product made this way that might affect whether we would choose to make a gearwheel by AM. The first has to do with the materials. However, with SLS now being used for a wide range of metal alloys, apart from many polymers, that, too, is hardly a limitation.
The second issue is about the surface texture of an AM-made part. Think back to the example of a Lego model of an aircraft engine in Figure 67. You can see that the surfaces have a texture on the scale of the building blocks. AM processes are similar, although on a different scale. The degree of approximation to the shape we actually want is determined by the thickness of each of the layers laid down during the process. And the layer thickness will be a classic compromise between the limit of capability of the process and the commercial viability based on production cycle time.
As regards the first of these, the best of current technologies (2013) allow layers down to around 50 µm thick. If surface features up to this size are tolerable in the finished gearwheel, it can be made this way. If not, it may be possible to add one further finishing process to add the final dimensions accurately, just as we saw with formed blanks although with far less material to remove in the final stage.