Mineral castings as material for chassis of precision machine tools

Chassis material overview

In precision engineering, the importance of the chassis to machine accuracy is often underestimated.The machine base defines the position between subsystems such as drive systems, measuring systems or machining equipment and is often the most expensive single component in a machine tool.The aim is to achieve a low-cost, highly integrated chassis.

In ultra-precision measurement and machining, the chassis must ensure the stable position of all subsystems and have high rigidity to cope with static and dynamically changing thermal loads as well as mechanical forces and torques.For high-speed machining, the machine base should provideHigh damping和stability.For precision applications, structuralThermal stability和long term stabilitybecome very important.

Commonly used materials for chassis are natural stone, cast iron, steel and ceramic.An alternative to these materials is mineral composites, and machine chassis made of mineral composites are called mineral castings.

The composition of mineral composites

Mineral composite material is a new type of composite material formed by using modified epoxy resin as adhesive, mineral particles as aggregate particles, and adding fillers.Mechanical properties resultsA high-density network from the mineral filler interface, sketched in Figure 1.

Figure 1. Sketch of infill network with different aggregate sizes

Properties of mineral composites

Mineral composite materials have good vibration damping performance, low thermal expansion rate and heat conduction speed. They can replace traditional cast iron, cast steel and other materials as precision machine tool components, which can greatly improve the processing accuracy of machine tools.However, mineral composite materials also have shortcomings such as insufficient mechanical properties, which restricts their wide application.

There are many difficulties in characterizing mineral castings: the selection of aggregates, the gradation of aggregate particles, the physical properties of the adhesive, etc. all affect the mechanical and thermal properties of mineral castings.

Shandong Nano mineral castings select the best physical propertiesnatural graniteIt is aggregate (Figure 2). After being crushed by a professional crusher, the contact angle between each other is less than 90 degrees, and the extension area is much larger than that of cobblestones with smooth surfaces. At the same time, the best mechanical properties are used.Epoxy resinAs an adhesive, it greatly improves the mechanical properties of mineral composite materials.

Figure 2: Single natural granite aggregate

The thermal properties of mineral castings also have a significant impact on the accuracy and performance of the machine, the most important being the values ​​of thermal conductivity, specific heat capacity and thermal expansion coefficient (Fig. 3).In addition, thermal properties also affect the mechanical properties of machine tools.

Figure 3: Thermal performance parameter table of German mineral casting materials provided by RWTH Aachen University

After comparing the test results at home and abroad (Figure 4, Figure 5), it was found that the mechanical properties of nano mineral casting materials are the highest, and the maximum volume density can reach 2.8g/cm3, which can better meet the needs of precision mechanical design.

Figure 4: Test results from the School of Mechanical Engineering, TU Ilmenau

Figure 5: Physical properties table of nano mineral castings (this data is provided by the test report of RWTH Aachen University)

Summary: Compared with the long development history of cast iron, the rise of mineral castings is still in its early stages of development. There is no unified standard and understanding around the world, resulting in many users being unable to judge the quality of mineral castings.The market demand for high-speed processing and precision applications is increasing day by day. How to occupy a place in the high-end market is a theme that drives many people with lofty ideals to have a deeper understanding of mineral castings.

Shandong Nano New Materials, as one of the first professional mineral casting manufacturers in China to independently research and put into production, has been mainly exporting to the European and American markets at first, and has accumulated rich experience in the industry, whether it is the selection of raw materials, formulas or process formation. and implementation have their own unique solutions.We hope to spread knowledge and help national enterprises improve themselves.