Coordinate measuring machines (CMMs) are some of the most widely used machines in different manufacturing industries due to their accuracy and precision in measuring geometries of objects. One of the important components of CMMs is the base on which objects are placed for measurement. One of the common types of materials used to make CMM bases is granite. In this article, we are going to look at different types of granite bases used in CMMs.
Granite is a popular material for CMM bases because it is stable, hard, and has a very low coefficient of thermal expansion, which means its dimensions are not easily affected by temperature changes. The design of granite bases varies depending on the type of CMM and the manufacturer. However, here are some of the different types of granite bases used in CMMs.
1. Solid Granite Base: This is the most common type of granite base used in CMMs. Solid granite is machined to the required specifications and gives good stiffness and stability to the overall machine. The thickness of the granite base varies depending on the size of the CMM. The larger the machine, the thicker the base.
2. Pre-Stressed Granite Base: Some manufacturers add prestressing to the granite slab to enhance its dimensional stability. By applying a load to the granite and then heating it, the slab is pulled apart and then let to cool to its original dimensions. This process induces compressive stresses in the granite, which helps improve its stiffness, stability, and longevity.
3. Air Bearing Granite Base: Air bearings are used in some CMMs to support the granite base. By pumping air through the bearing, the granite floats above it, making it frictionless and hence reducing the wear and tear on the machine. Air bearings are especially useful in large CMMs that are moved frequently.
4. Honeycomb Granite Base: A honeycomb granite base is used in some CMMs to reduce the weight of the base without compromising on its stiffness and stability. The honeycomb structure is made from aluminum, and the granite is glued on top. This type of base provides good vibration damping and reduces the warm-up time of the machine.
5. Granite Composite Base: Some CMM manufacturers use granite composite materials to make the base. Granite composite is made by mixing granite dust and resin to create a composite material that is lighter and more durable than solid granite. This type of base is corrosion-resistant and has better thermal stability than solid granite.
In conclusion, the design of granite bases in CMMs varies depending on the type of machine and the manufacturer. Different designs have different advantages and disadvantages, which make them suitable for different applications. However, granite remains one of the best materials for making CMM bases due to its high stiffness, stability, and low thermal expansion coefficient.
Post time: Apr-01-2024