Waxing onto trees

The finished wax parts have to be assembled into so-called casting trees for the casting process. This is a prerequisite for batch-like processing in the casting process later on. As a result, not every part is cast individually but always a complete casting tree, which often holds over a hundred individual pieces. To be able to cast a batch, parts of the same alloy must therefore always be waxed onto this kind of casting tree, regardless of whether they belong to different orders or customers. The material thickness and the resulting allocation to a tree or the position on a tree is much more important.

One reason for dividing up and arranging the wax models is that, for example, solid parts have to be cast at a different temperature to thin parts. It is therefore not possible to just combine them randomly. Specific rules of thumb are in fact required and have to be observed. Just like the sprues that lead from the tree trunk to the waxes have to have a dimension appropriate to the part.

A wax tree usually consists of an approx. 20 cm long wax pin about as thick as a little finger. If you now heat the wax sprue where the wax parts are attached and a point on the tree trunk with a hot needle at the same time, the waxes can be attached. The two hot and therefore briefly liquid wax spots form a bond within seconds when cooling down. As the parts are placed around the trunk, a structure similar to a small fir tree is created from a variety of waxes. The wax parts must not be damaged by the hot needle, the bond on the tree must be strong enough to prevent any breakage and the parts must not be damaged with tiny drops of wax due to electrostatic charge.