US 4,365,301 AGranted

Positional reference system for ultraprecision machining

AssigneeThe United States of America as represented by the United States Department of Energy

InventorsJones B. Arnold, Robert R. Burleson, Robert M. Pardue

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Abstract

A stable positional reference system for use in improving the cutting tool-to-part contour position in numerical controlled-multiaxis metal turning machines is provided. The reference system employs a plurality of interferometers referenced to orthogonally disposed metering bars which are substantially isolated from machine strain induced position errors for monitoring the part and tool positions relative to the metering bars. A microprocessor-based control system is employed in conjunction with the plurality of position interferometers and part contour description data inputs to calculate error components for each axis of movement and output them to corresponding axis drives with appropriate scaling and error compensation. Real-time position control, operating in combination with the reference system, makes possible the positioning of the cutting points of a tool along a part locus with a substantially greater degree of accuracy than has been attained previously in the art by referencing and then monitoring only the tool motion relative to a reference position located on the machine base.

Claims7

Dependent claims

In an automatic controlled machining system including a spindle, means for rotating said spindle, a cutting tool holder for holding a cutting tool, a cross slide means for moving the cutting tool holder reversably along an x axis and an axial slide means for moving one of the spindle and the cross slide means reversably along a y axis, a positional reference system comprising:

a metering bar assembly including X and Y coordinate reflective reference surfaces disposed parallel to the X and Y axis slides of said machining system;
a mounting plate carried by said spindle for supporting a workpiece thereon to be rotated about an axis parallel to said Y axis;
a plurality of interferometers for monitoring the displacement of said tool holder and said mounting plate carried by said spindle at predetermined points thereon relative to the points of contact of said tool with said workpiece with reference to said X and Y coordinates of said metering bar assembly;
and
a control means responsive to the outputs of said plurality of interferometers and workpiece machining contour description data in the form of X and Y axis components of programmed displacement of the cutting tool relative to the centerline of rotation of said spindle for generating x and y axis error signals and applying said signals to the cross slide means and the axial slide means, respectively, so that the cutting tool is positioned relative to the workpiece according to the workpiece description data with positional reference of the tool holder and the workpiece to said metering bar assembly.

2 more elements

Dependencies are inferred from the claim text.