Abstract: A coordinate measuring machine (CMM) is disclosed having improved manufacturability and low cost while maintaining high performance standards. The CMM includes a polymer composite gantry-style base incorporating a three-point support configuration in the X, Y, and Z axes. The X-beam is hollow, has a horizontal cross-sectional orientation, uses a passive ventilation technique, and is attached to the bearing at one end by a compliant mount. The Z-axis probe shaft incorporates a combined counterbalance/drive assembly and a compliant secondary rail guide mechanism. The X-axis and Y-axis drive screws have angular alignment capability using a spherical washer configuration. This combination of features serves to minimize non-repeatable errors and enhance the manufacturability of the CMM, providing substantial improvements in CMM design and construction.

Abstract: A coordinate measuring machine is described including a vertical probe shaft mounted on an X-axis carriage in turn mounted on a Y-axis carriage for movement along three orthogonal axes, in which the Y-axis carriage is guided and supported on a first guide beam fixed extending along one side of a machine base with air bearings mounted to the lower end of one upright engaging all four sides of the first guide beam. The Y-axis carriage is also supported on a second guide beam fixed extending along the other side of the base, with air bearings mounted to the lower end of the other upright engaging only the top and bottom surfaces. A lower crossmember beam connects the lower ends of the upright to increase stiffness of the Y-axis carriage. A cast aluminum table is supported on the base with three cast in support features projecting from the underside, configured to minimize thermal distortion, with a steel plate bonded into a recess in the upper surface.

Abstract: A coordinate measuring machine (10) having laser interferometers (80, 176, 196) arranged to measure "X" and "Y" carriage and probe motions, in which fiber optic cables (66,72) are used to deliver a laser beam from a laser beam generator (60) to at least some of the interferometers (2176, 196) in order to simplify the optical system and avoid the need for precision alignment of optical components in directing the beam from the laser generator (60) to the various interferometers (176, 196). The laser generator (60) is mounted either on or off the machine base (12). A special clamp (76) and adjustment flexure (74) is used to mount and align the fiber optic cable couplings (96) to beam splitters (64) dividing the laser beam from the laser generator (60) for use along each axis.

Abstract: A coordinate measuring machine (10) having a three point support for a work supporting table (24) mounted over a base (12) constructed of a thermally dissimilar material. A first fixed support, (26A) and a laterally compliant second support (26B) are located at the front of the machine. The second front support (26B) is comprised of a pair of webs (28) oriented to be compliant in the lateral direction to allow relative thermal growth between the table (24) and base (12) while being rigid in the longitudinal direction to prevent rotation of the table (24) about the fixed front support (26A). Stacked crossed roller bearings (38A, 38B) provide a frictionless third point of support at the rear of the table (24).

Abstract: A coordinate measuring machine (10) having laser interferometers (80, 176, 196) arranged to measure "X" and "Y" carriage (52, 16) and probe shaft (56) motions, in which fiber optic cables (66, 72) are used to deliver a laser beam from a laser beam generator (60) to at least some of the interferometers (17). A special clamp (76) and adjustment flexure (74) is used to mount and align the fiber optics (66, 72) to beam splitters (64) dividing the laser beam from the laser generator (60) for use along each axis. The adjusting flexure (74) comprises a series of plate sections (120, 122, 124) interconnected with a pair of webs (142, 164) allowing tilting about two orthogonal axes with a pair of adjusting screws (148). A pair of locking straps (154) secure the plates (120, 122, 124) in the adjusted position. A double clamp (76) having axially spaced clamping jaws (102, 104) is connected to the flexure (74) and provides a stable securement of the optical coupling (96) to the flexure (74).

Abstract: Axis correction or machine charateristic data is stored (108) in memory (110) within a control or measurement processor (36) of a CMM (10) (FIG. 8). The axis correction data includes error data representing 21 different geometry errors (FIG. 4A through 4C) of the CMM. As position information is required, the measurement processor captures the actual position signal from each machine axis sensor and uses this position signal to locate (112) a set of the axis correction data which describes the machine characteristics at that position. The measurement processor then mathematically combines (114) (FIG. 9) the position signal with the subset of axis correction data to obtain a corrected position signal having a corrected set of cooridinate values which describe the probe position in a true Cartesian coordinate system.

Abstract: Method (FIGS. 4A through 4C) and system (FIG. 3) are disclosed for automatically calibrating a coordinate measuring machine (CMM) (10). The system guides an operator through instrument set-up and data collection procedures. The system automatically converts the collected data into error compensation or axis correction data which represents 21 different geometry errors (i.e. pitch, yaw, roll etc.) of the CMM (10). The error compensation data is then transferred to a CMM measurement processor (36) for subsequent use by the CMM (10) during operation thereof to thereby compensate the CMM (10) for its entire measuring volume (102).

Abstract: 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.

Abstract: A coordinate measuring machine having an automatic failsafe protection system. The coordinate measuring machine (10) includes a vertically mounted probe shaft (42) which is preferably counterbalanced by an air counterbalance system (100). The automatic failsafe protection system (200) insures that, in response to a loss of air pressure (or in response to other possibly unsafe conditions), the vertically-mounted, air-counterbalanced probe shaft (42) will be prevented from falling down uncontrollably. The failsafe protection system (200) includes a pair of members (230, 240), with each member mounted adjacent to and on opposite sides of the probe shaft (42) and urged toward engagement with probe shaft by a spring (250). Air under pressure from an air cylinder (210) also acts upon the members (230, 240) to bias the members outwardly away from engagement with the shaft when normal (i.e. safe) operating conditions exist.

Abstract: A coordinate measuring machine (10) having a vertically mounted probe (32), the weight of which is offset by an air counterbalance system (100). The air counterbalance system is adapted to use a source of air under pressure acting upon a piston (127) coupled to the vertically mounted probe (42). A torque converter (130) is mounted between the probe (42) and the piston (127) allowing the piston (127) to have a shorter travel than the allowable vertical travel of the probe (42). The air counterbalance system (100) preferably has components selected and arranged to minimize friction and weight to avoid distorting the precision of measurements on the coordinate measurement machine.

Abstract: A probe for measuring coordinate positions on an object by sensing a displacement of the stylus which contacts the object. The probe is responsive to forces which result from the contact between the object and the stylus to indicate coordinate positions of the object. The probe includes a replaceable stylus having a shank portion defining an axis, with a transversely-extending portion extending from the shank portion for sensing forces exerted by objects in the axial direction away from the probe, while the stylus shank portion is responsive to forces in the radial and axial (toward the probe) directions. The probe is thus responsive to forces exerted on the stylus in any direction.