Epoxy granite machine tool beds – why are they used ?
CNC machine tool beds are increasingly being made of Epoxy granite, a composite of granite aggregate and epoxy resin.
Granite aggregate is what is used in concrete in buildings. The epoxy resin is something like good old Araldite or Feviquick (can fix everything except broken hearts, according to its ad campaign), or epoxy flooring that you see on shop floors. Epoxy granite is also called epoxy concrete, for the obvious reason that it is a close cousin of the concrete that we use in building. Same granite aggregate, but epoxy instead of cement. The link above shows you how easy it is to make an epoxy granite casting.
Compared to Cast Iron, epoxy granite’s vibration damping is about 10 times more, density is about 1/3, and it has higher corrosion resistance (which means it does not have to be painted). Quite a few high accuracy and high speed CNC machine tool bds are today made of epoxy granite. Making the castings too is an easier process. Since the raw materials are at room temperature, you can have accurate moulds made of other materials instead of sand moulds. The resultant casting is almost close to the final shape, requiring very little machining. The only problem is that (unlike cast iron), you cannot machine the casting. All holes and other features must be included in the casting itself. Confusingly, this stuff is known by a huge variety of names – mineral casting, polymer concrete, resin concrete, epoxy concrete, artificial granite, epoxy granite, or artificial stone.
