Introduction
Slide 29
We have just seen how to make the crown adaptor by machining in the block. The other method, in a context of mass production, is to machine with preformed parts or blanks. We start with a rough part with a form similar to that of the finished part. Thus we economize material and the machining time, as only the surfaces with very tight tolerances will be machined.
On this rough part, we machine the notches, then we drill the holes and do the countersinking, and finally make the central bore.
Slide 30
We are going to look at three methods to obtain preformed blanks, or performs, though others exist and could be used.
In this case, a mould of the part is made using sand, based on a model. This process cannot be automated because the feeder heads[2] and flow pipes[3], necessary in casting, must be made by hand.
Casting with a pattern plate: [4]
This process is similar to the previous one but this time it can be automated because all the elements necessary for casting are integrated in the two half boxes.
In this case the mould is made of steel and can therefore be reused.
