Abstract: A calibration system for measuring position errors in a coordinate measuring machine having a fixed table and a movable element is provided. The system includes a straightedge assembly attachable to the table and a sensing fixture attachable to the movable element. The straightedge assembly includes a straightedge having a first reference surface that is parallel to a predetermined direction and a second reference surface perpendicular to the first reference and parallel to the predetermined direction. The sensing fixture includes a fixture housing and sensors on the housing for sensing the position of the movable element relative to the straightedge and generating position error signals representative of position errors of the movable element as the sensing fixture is moved in the predetermined direction along the straightedge. The sensors provide position error signals representative of displacement, straightness, pitch, yaw and roll errors of the movable element.

Abstract: A transmission for reducing the pulley ratio between a drive shaft and a transmission shaft. The transmission is adapted to convert a higher speed rotary motion to a lower speed linear motion. The transmission has two pulleys rigidly mounted together on a shaft and the pulleys have a different number of teeth. A pair of belts are mounted on the drive shaft and a follower shaft, each one of the belts engages one of the transmission pulleys. One belt on the transmission shaft engages a pulley on the top of a first transmission pulley and another on the bottom of a second transmission pulley. When the drive shaft imparts motion to the belts, the belts move the transmission between the drive shaft and the follower shaft. By arresting the movement of one of the belts by a clutch/brake, the transmission can be converted into a two speed transmission. If the belts are independently driven, one each by two motors, the transmission becomes operable in an infinite number of pulley ratios.

Abstract: A multi-probe system for dimensional metrology. This system utilizes a probe base that is attachable to a coordinate measuring machine and that includes a plurality of probes mounted at spaced-apart locations on the base. The probes are interconnected with the coordinate measuring machine and generate measurement signals based upon interaction with a workpiece. By providing a plurality of probes on a single assembly, multiple measurements can be made on a workpiece in a single measurement cycle.

Abstract: A transmission for reducing the pulley ratio between a drive shaft and a transmission shaft. The transmission is adapted to convert a higher speed rotary motion to a lower speed linear motion. The transmission has two pulleys rigidly mounted together on a shaft and the pulleys have a different number of teeth. A pair of belts are mounted on the drive shaft and a follower shaft, each one of the belts engages one of the transmission pulleys. One belt on the transmission shaft engages a pulley on the top of a first transmission pulley and another on the bottom of a second transmission pulley. When the drive shaft imparts motion to the belts, the belts move the transmission between the drive shaft and the follower shaft. By arresting the movement of one of the belts by a clutch/brake, the transmission can be converted into a two speed transmission. If the belts are independently driven, one each by two motors, the transmission becomes operable in an infinite number of pulley ratios.

Abstract: Devices for verifying the dimensional accuracy of a measuring instrument are provided. In one embodiment, a verification block has a substantially planar surface and a known nonplanar surface adjacent thereto. During verification, a probe attached to the CMM moves along the nonplanar surface while simultaneously contacting the planar surface and measures the features of the nonplanar surface. Any difference between the measured features and the known features of the nonplanar surface is an indication of inaccuracies in the CMM. Other embodiments of the invention include structures which compare CMM measured readings with known readings by an encoder as it moves along a linear scale. In another embodiment, the measured readings are compared to readings provided by opto-electric switches. In still another embodiment, a cam is rotatably mounted to the end of the probe of the CMM and moves the probe along the z axis as the cam moves along a surface.

Abstract: A coordinate measuring machine includes a support structure, an articulated arm having a first end pivotally connected to the support structure and a second end that is movable in a horizontal plane. A Z-ram assembly is mounted to the second end of the articulated arm. The Z-ram assembly includes a Z-ram housing and a probe that is vertically movable with respect to the Z-ram housing. The probe is movable within a measurement volume defined by the articulated arm and the Z-ram assembly. The coordinate measuring machine further includes a measuring assembly for determining coordinates of the probe in the measurement volume. The articulated arm preferably includes first and second arm assemblies that have a parallelogram configuration to prevent substantial rotation of the Z-ram assembly as the articulated arm is moved in the horizontal plane. The angles of the articulated arm are preferably measured using a sensor which includes a pattern of parallel, straight grating lines.

Abstract: A device for measuring an angle between pivotally connected, intersecting sides of a parallelogram includes a grating having a pattern of parallel, straight grating lines formed on a substrate, and a read head. The grating is mounted in a fixed position with respect to a first side of the parallelogram. The read head includes a sensor positioned for sensing displacement of the grating lines in response to an angular change between the intersecting sides of the parallelogram and generating a scale reading. The read head is mounted in a fixed position with respect to a second side of the parallelogram that is parallel to the first side. In one embodiment, the grating includes a single pattern of grating lines and is used to measure an angular change relative to a reference angle. In a second embodiment, the grating includes first and second grating patterns and is used to measure an absolute value of the angle between the intersecting sides of the parallelogram.

Abstract: A coordinate measuring machine has a single vertical column mounted to a horizontal table for moving in the x-direction, and a carriage mounted on the column for vertical movement in the z-direction. The column is moved with a motor that drives a rack and pinion. The carriage supports a y-rail that moves in the y-direction. A first damper is positioned over the z-rail in the -y direction so that the column is intermediate the damper and the probe. A second damper is positioned at an end of the y-rail near the probe. The dampers reduce both large amplitude transients, as well as steady-state vibrations that are caused by the motor cogging and gearing between the motor and the rack and pinion.

Abstract: A vibration dampening system particularly for use in a gantry-type coordinate measuring machine. The vibration dampening system includes a vibration damper in the gantry structure, a vibration damper in the Z-rail, and means in the supports for the base for dampening vibrations, all of which work together cooperatively to damp vibrations in the coordinate measuring machine. The vibration damper in the gantry structure and in the Z-rail each comprises a substantial mass suspended by pads of material having high energy absorbence and a low rebound resilience. The vibration dampening means in the table means includes a layer of material which is highly energy absorbent and has a low rebound resiliency, and which is disposed between two rigid plates positioned between each supporting leg of the table and an underlying floor. The vibration dampening system is tuned to provide maximum energy absorbency at major modes of vibrations in the machine during acceleration and deceleration.

Abstract: A vibration damper disposed in a gantry-type coordinate measuring machine. The vibration damper includes a block having a substantial mass suspended from the moving gantry-type structure by highly energy absorbent pads having a low rebound resilience. The vibration damper is preferably spaced from the point at which the gantry-type structure is coupled to the drive therefor.

Abstract: Apparatus for counterbalancing a vertically movable element of a machine includes an air cylinder attached to the movable element on the axis of movement and having a small axial opening at its upper end. A piston located in the air cylinder is attached to a fixed machine element by a nonelastic, flexible member such as a thin, nylon-jacketed wire passing through the axial opening in the cylinder. Air under pressure sufficient to counterbalance the weight of the movable element is supplied to the space between the piston and the axial opening in the cylinder. The flexible member makes the counterbalancing assembly relatively insensitive to misalignment and vibration. Air is permitted to leak around the piston to reduce friction and to relieve pressure buildup during downward movement. In another embodiment, the air cylinder is attached to the fixed machine element.

Abstract: A gas bearing system for maintaining high static stiffness while damping high and low frequency vibrations. The system includes a bearing shoe having a primary reservoir which is supplied with gas through a primary restrictor, and an auxiliary reservoir. A secondary restrictor couples the primary reservoir to the auxiliary reservoir. Gas passes through ports from the primary reservoir into the gap between the bearing surface of the bearing shoe and a bearing surface of a rail. The secondary restrictor has a resistance to flow of gas therethrough greater than the resistance to flow of gas through the ports but less than the resistance to flow of gas through the primary restrictor. This arrangement provides damping over a larger frequency range than is known in the prior art. Such a system is particularly suitable for use in a gantry-type coordinate measuring machine.

Abstract: Methods for determining nonrigid error parameters that result from deflection or deformation of machine elements and correcting scale readings in a coordinate measuring machine. The nonrigid error parameters are a function of probe position along two directions. In a bridge type coordinate measuring machine, the y-direction error parameters are a function of probe position in both x and y directions and thus exhibit nonrigid behavior. Nonrigid error parameters are measured by making error measurements at a plurality of corresponding points along two parallel, spaced-apart measurement lines. The error measurements are substituted into simultaneous equations for the error parameters, and the equations are solved for the coefficients. The coefficients are used to determine the axial errors at any point in the measuring volume. The axial errors are subtracted from the scale readings.

Abstract: A calibration system for measuring the parametric errors in a coordinate measuring machine having a first element and a table which are movable in three dimensions relative to each other. The apparatus comprises a reflector assembly attachable to the first element, a laser measuring assembly attachable to the table for directing a plurality of laser beams at the reflector assembly and for sensing laser beams reflected from the reflector assembly and generating displacement, straightness, pitch, yaw and roll error signals, and means for mounting the laser measuring assembly to the table in three different orientations and for mounting the reflector assembly to the first element in three different orientations. In each of the orientations, the reflector assembly and the laser measuring assembly are aligned for measurement of parametric errors at a plurality of selected positions along the direction of the laser beam. The parametric errors along each direction of movement are stored in a computer.

Abstract: A method for automatic probe offset compensation in a machine for measuring coordinates of a workpiece surface by contacting points on the surface with a probe having a prescribed diameter and sensing and recording the coordinates of the probe. The method can be applied to planar surfaces and circularly curved surfaces. The method includes determining a direction point in space just prior to contact with the workpiece surface, determining a directional vector between the direction point and the first contact point, and determining the angle of the directional vector relative to a normal to the surface. When the angle is within a predetermined range of acceptance, the direction point is considered valid. In the case of a planar surface, the measured surface is shifted by the probe offset in a direction opposite the normal vector so that the measured surface and the workpiece surface coincide.

Abstract: A base assembly for a machine tool includes a support arrangement between a metal base and a granite worktable which eliminates distortion caused by differential thermal expansion and contraction and which isolates the base from deformation due to the weight of a workpiece. The support arrangement preferably includes three spaced-apart blocks, each with a V-groove track, attached to the bottom of the granite worktable. The axes of the V-groove tracks intersect at a common point. The metal base includes three spherical projections located for engagement in each of the V-groove tracks. The support arrangement permits the granite worktable and the base to expand, contract and distort separately, while providing vertical support and lateral and rotational restraint. Several configurations of tracks and projections are disclosed.

Abstract: A surface grinding machine capable of being computer operated and having a multi-function capability for performing conventional slot and surface, plunge, side wheel, creep feed and short stroke grinding in any desired combination or sequence. A table containing a workpiece is driven by a highly tensioned, circulating primary belt drive system capable of providing a desired grind with a desired length and speed upon command. The base is formed as a unitary body, and the table travels on ways which are formed integrally with the base. The column containing the grinding wheel assembly moves with respect to the workpiece along cross ways transverse to the table ways which are supported along their length by the base. The column drive is coupled to the column by a mechanically and thermally isolated ball screw nut mount which eliminates screw nut shoulder weave and reduces thermal conduction into the column.

Abstract: A linear actuator for converting rotary motion to linear motion including an elongated rotary threadless shaft and a rider assembly mounted for movement axially of the shaft and carrying rollers mounted for rotation about their respective axes with their surface in frictional contact with the shaft. The roller's axes are disposed at an acute angle with respect to the shaft so that as the shaft is rotated the rider assembly will move along the shaft and carry with it such parts to which it may be attached.