What are the Common Structural Materials of CMM

With the development of coordinate measuring machine (CMM) technology, CMM has been used more and more widely. Because the structure and material of CMM have great influence on the measurement accuracy, the precision of CMM is more and more demanding. Here are some common structural materials.

1. Cast Iron

Cast iron is a commonly used material, mainly used for bases, sliding guides, columns, supports, etc. It has the advantages of small deformation, good wear resistance, easy processing, low cost, and the coefficient of linear expansion closest to the parts (steel), and is the earliest used material for CMM. Cast iron is still the main material used in some measuring machines. But it also has disadvantages: cast iron is susceptible to corrosion, wear resistance is lower than granite, and its strength is not high.

2. Steel

Steel is mainly used for cover and support structure, and some measuring machine bases are also made of steel. Low carbon steel is generally used and must be heat treated. The advantages of steel are good rigidity and high strength. Its defect is easy to deform, which is because after the steel is processed, the internal residual stress is released to cause deformation.

3. Granite

Lighter than steel and heavier than aluminum, granite is a commonly used material. The main advantages of granite are small deformation, good stability, no rust, easy to do graphic processing, high flatness, easy to reach a higher platform than cast iron, suitable for the production of high-precision guide rail. Now many coordinate measuring machines are using this material, workbench, bridge, axis guide, Z axis, all made of granite. Granite can be used to make tables, boxes, columns, beams, guides, supports and so on. Due to the small thermal expansion coefficient of granite, it is very suitable for use with air bearing guide. All series of DIPSEC CMM uses granite as guide rail and workbench material.

Granite also has some disadvantages: although it can be made of hollow structures by pasting, it is more complex; Solid construction quality is large, not easy to process, especially the screw hole is difficult to process, the cost is much higher than cast iron; Granite material is brittle, easy to collapse during rough processing.

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