Renishaw Plc

Renishaw Metrology Limited

David G Powley

David R McMurtry

Andrew Geoffrey Butter

Adrian C Welsford

Peter J Wells

Richard H Lewis

An analogue probe 100 includes a fixed structure 110 and a stylus supporting member 112 suspended relative to the fixed structure 110 by three serially connected pairs of leaf springs 114,116,118. Displacement of the supporting member 112 relative to the fixed structure 110 is transduced by three opto-electronic scale and readhead transducers 136,144;138,146;140,148. The distorting effect of bending moments applied to the tip 130 of the stylus 128 upon leaf springs 114,118 is counteracted by an increased spacing between upper ends of leaf springs of a given pair, relative to the spacing between leaf springs at their lower ends; the resulting arrangement forming a trapezium as opposed to a rectangle. This enables longer styli to be employed before distortion of the leaf springs causes failure of the opto-electronic transducers due to unwanted tilting of the supporting member 112.

Analogue probe

An analogue probe has a fixed structure and a stylus supporting member connected to the fixed structure by three serially mounted pairs of leaf springs interconnected by first and second intermediate members. The stylus supporting member supports an elongate stem upon which a cube, which supports three scales, is mounted. Readheads are mounted on the fixed structure, in register with the scales, to transduce movement of the stylus supporting member in three substantially orthogonal directions. The alignment of the scales about the yaw axis (extending in a direction perpendicular to the plane of the scale) determines the alignment of the measuring axes of the probe, while the straightness of the lines of the scales determines the straightness of the axes.

The disclosure pertains to a probe head (PH) for use in coordinate measuring machines and having a stylus (10) supported for axial displacement (D1) and angular displacements (D2,D3). A transducer (T1) senses axial forces (F1) on the sensing end (11) of the stylus due to engagement thereof with a workpiece 12. A strain gauge system (16) provided on the stylus senses transverse forces (F2) on the sensing end (11) of the stylus. The forces (F1,F2) are used to determine the orientation of the surface (12A) of the workpiece and a control system is described which responds to those forces to maintain the stylus normal to said surface (12A) during a scanning operation.

Surface-sensing device

Disclosed is a method of obtaining data to determine a rotation matrix R, for rotating the axes (x,y,z) of an analogue probe coordinate system (PCS) onto the axes (X,Y,Z) of a machine coordinate system (MCS). The head (14) of the machine is driven to bring a measuring tip (16) of a stylus (12) supported by the probe for movement relative to the head (14) into engagement with a kinematic location (20). With the tip (16) fixed in the location (20) the head is then moved to six different locations. The coordinate positions of the head (14) in the machine coordinate system (MCS), and the stylus (12) in the probe coordinate system are used to set up six simultaneous equations and thus determine the rotation matrix R.

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Alveston, United Kingdom

David G Powley