Bridge type coordinate measuring machine

摘要

A coordinate measuring machine (CMM) of the type including a bridge (26) supported for horizontal movement on a base (20) that has a table portion (18). The bridge includes cross members (28, 32) that extend above and below the table (18). The bridge (26) supports a probe (12) for vertical movement on a carriage (24) which, in turn, is supported for horizontal movement transversely to the horizontal motion of the bridge (26). The bridge (26) is guided laterally during its movement on the base by means of a rail guide (44) mounted centrally beneath the table (18), and air bearings (48) acting on the guide rail (44). This establishes accurate control over the movement of the bridge (26) on the base (20). Both the table (18) and guide rail (44) are constructed of granite, while the bridge (26) is of aluminum. This arrangement minimizes the effects of thermal expansion between on the components and increases the measuring accuracy of the CMM.