Renishaw Plc

Leo Christopher Somerville

Kevyn Barry Jonas

David R McMurtry

Geoffrey McFarland

Nicholas John Weston

Martin Simon Rees

Ian William McLean

Ian William Mclean

A series of nominally identical production workpieces are measured on a workshop coordinate measuring apparatus. They are corrected using correction values generated by comparing coordinate values of a reference workpiece measured on the workshop apparatus with corresponding values derived from external measurements. To reduce the care and skill required, the external measurements are used to determine reference values of a geometric property of a feature of the reference workpiece, rather than coordinate values corresponding directly to those made on the workshop apparatus. Corresponding coordinate values are then generated from knowledge of the perfect form of the feature of the reference workpiece.

Method and apparatus for inspecting workpieces

This invention concerns a gauge artifact including a base for mounting on a table of a coordinate positioning machine and a platform including at least two portions having a nominally identical geometric property. The platform is locatable relative to the base in at least two positions such that each of the at least two portions having the nominally identical geometric property can be presented at a common location relative to the base. The platform may be arranged such that the positions of the portions having a nominally identical geometric property can be interchanged by movement of the platform between at least two distinct positions. The positions may be interchanged through rotation of the platform. The invention also concerns a method of checking a coordinate measuring machine.

Gauge artefact and method for checking a coordinate positioning machine

A series of nominally identical production workpieces is measured on a measuring apparatus. To correct for temperature variations, one of the workpieces forms a master artifact, the dimensions of which are known. The artifact is measured on the measuring apparatus at two or more temperatures, producing two or more corresponding sets of measured dimensional values of the master artifact at the respective temperatures. One or more error maps, look-up tables, or functions are generated which relate the measured dimensional values of the artifact to the known dimensions of the artifact. The error map(s), look-up table(s) or function(s) are dependent on the respective temperatures at which the artifact was measured. Correction values derived from the error map(s), look-up table(s) or function(s) are used to correct the measurements of production workpieces in the series. These correction values are determined in dependence upon the temperature at which the workpiece measurements were obtained.

A method and corresponding apparatus are described for recalibrating coordinate positioning apparatus after a disturbance, such as a stylus replacement. The coordinate positioning apparatus includes a platform, a measurement probe and a probe head for reorienting the measurement probe relative to the platform. A calibration data set is taken for the coordinate positioning apparatus that includes datum data for a plurality of orientations of the measurement probe. The datum data includes at least first datum data for a first nominal orientation of the measurement probe. After a disturbance to the coordinate positioning apparatus, the calibration data set is updated by acquiring one or more position measurements and calculating a first correction from the one or more position measurements. The first correction describes any change in the first datum data following the disturbance and is used to update the datum data for plurality of different orientations of the measurement probe. Corresponding apparatus is also described.

Method for recalibrating coordinate positioning apparatus

A method for measuring a surface profile using a surface sensing device mounted on an articulating probe head in which the probe head is moved along a nominal path relative to the surface profile, an at least approximation of the surface normal of the surface profile, the surface profile is sensed with the surface sensing device and the distance or force of the surface sensing device relative to the surface profile substantially in the direction of the surface normal. The surface normal may be determined by approximating at least one section to a curved profile which can be mathematically parameterised.

Method for scanning the surface of a workpiece

A method of measuring an object using a surface sensing device mounted on a coordinate positioning apparatus. The method has the steps of measuring a single surface point of a feature of the object with the surface sensing device, moving the surface sensing device along a path around the feature at a fast speed, thereby taking measurements along the path, including at the surface point, determining the difference between the measurements of the surface point and using the difference determined to apply a correction to the object or subsequent objects having the same feature.

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St. Charles, IL, United States of America

Leo Christopher Somerville