Coordinate measuring machine simplified as CMM, refers to the measurable in 3D space range, it can calculate all kinds of geometry shape according to the points data collected through measuring probe and calculated through software system. Coordinate measuring machine is a new type of high efficient 3D dimension precision measuring instruments developed in the 1960s, with its high precision flexible and excellent digital capability, become an important means of modern design, development, manufacturing, processing and manufacturing, and quality assurance. According to the structure classification, it can be divided into movable bridge structure, fixed bridge structure, gantry structure, cantilever structure, transverse arm column structure and so on.
Movable bridge structure: one of the most widely used forms of structure, its structure is simple and compact, rigid, and has more open space. The work-piece is mounted on the fixed worktable, so the weight of the work-piece has not much influence on the overall dynamic performance of the measuring machine, and the relative bearing capacity is stronger. But X axis of this kind of structure located on the bridge side, the deflection causes larger abbe error, so compared to fixed bridge , the accuracy will be slightly lower.
Fixed bridge structure: the most important difference between fixed bridge CMM and the movable CMM is that of the fixed bridge, directly connected with the bottom of the base, X axis scale and central drive mechanism installed in the table below, the workbench be moved along the base of the guide rail. Its main components have good motion stability and small motion error, which is suitable for high precision measurement, but the table load capacity is small and the structure is not open well, mainly used in the high precision medium and small models.
Gantry structure: moving parts just beam, the whole structure rigidity, CMM measuring range is larger also can guarantee the accuracy of measurement, suitable for large models, the disadvantage is that pillar limits the work-piece loading and unloading, one driver will bring bigger abbe error, and bilateral drive mode is relatively complex.
Cantilever structure: simple structure, has the very good open structure, but when the carriage on the cantilever Y to exercise, will make the change of cantilever deformation, so the measurement accuracy is not high, generally used for measuring accuracy is not too high, small three coordinate measuring machine.
Transverse arm column structure: also known as horizontal arm type CMM, which is widely used in automobile industry. Its structure is simple, the dimension also can be bigger, but because the transverse arm is outstretched out will produce bigger deformation, the measurement accuracy is not high, use in medium, big model.
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