Foam

Soft foams are highly susceptible to tear out and melting.  Some foams can be machined effectively with spiral cutters, whilst others require oscillating or drag knives for effective cutting. Router bits used on foam are designed to shear the material very delicately and have polished flutes to allow the chips to glide over the tool with minimal friction.

Some softer materials such as foams or carboard are not able to be routed effectively. The rotational cutting motion of a router bit is too aggressive and tears out the fibres of the material. Instead, these materials may be cut using a drag knife, oscillating knife or some other knife system. Some knife systems can effectively cut through foams over 100mm thick. Oscillating knife aggregates can be supplied for an existing machine if the machine is compatible.