The low coefficient of linear expansion of granite is generally regarded as a particularly advantageous thermal property. In fact, compared to steel and grey cast iron, the rock expands only about half as much with an increase in temperature.
However, the thermal conductivity of granite, which is only about 1/10 of the value of the above mentioned metallic design materials, is at least as beneficial for the building of precise grinding machines. This makes granite-based machines extremely stable against short-term external temperature changes and thus directly leads to more accurate grinding results over a longer period of time.
Just like the thermal characteristics, the special damping properties of granite are advantageous in the design of high-precision manufacturing machines. The material damping of this rock is approx. 10 times higher than that of the steel and cast iron materials usually used. In the operation of a grinding machine, this damping of vibrations manifests itself above all in higher achievable surface quality and lower tool wear.
Even though the damping of the overall system depends not only on the materials used but also, among other things, on the design of the joints, we literally lay the foundation for our high-quality precision machines by using granite as the basic material.
One property of granite that has less to do with physical constants and more to do with creativity and manual work is the free formability of the raw material. When designing our machines, we are not bound to existing casting models, but can, if necessary, adapt each machine individually to its intended use. In this way, even one-off pieces and special machines can be produced economically.
Granite also shows its advantages over most design metals when it comes to manual processing: By manually lapping guide and fitting surfaces, flatness and straightness can be produced with micrometre precision, which in turn form the perfect precondition for our precision machines.
Ideally, a grinding machine should maintain its accuracy for many years. What could be a better basis for this than a machine bed that has almost no internal stress. In contrast to the casting or welding of classic machine beds, the production of a granite bed does not create any stresses in the material that first have to degrade over years. The rock has already aged in the earth's crust over millions of years, during which time the material stresses have been relieved. Therefore, our granite-based machines are not anchored in the ground, but are allowed to stand freely on adjustable machine feet. As a side effect, the granite bed often shows unique patterns that only a natural product can produce.
Let's be clear about this: The granite blocks for our machines are also taken from nature - like almost every raw material - and have to be transported and processed. However, the amounts of energy required to manufacture such products are many times lower compared to common design materials. In the case of cast iron and steel materials, a huge volume has to be extracted in mines and then processed into the final product in several temperature-intensive processes.
These steps are not necessary when using natural stone. Here, a block is quarried from a quarry and then processed by machine and hand. The finished machine bed is also highly resistant to corrosion, which makes our granite machines with standard stainless steel guards very durable machines that maintain their precision even after years of use. Finally, the duration of use of a product also makes a decisive contribution to its eco-balance.