Rotary Table Calibration for Load-Induced CNC Position Errors
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Solution Overview
Problem
CNC machining systems face accuracy issues due to the mass and shape of workpieces, particularly in machining components like turbine disks, which affect the positioning and orientation of workpieces during machining processes.
Innovation Solution
A method and system that utilize a cantilevered arm and rotary table within a machining tank, with a measurement artifact to determine positional deviations under loaded and unloaded conditions, allowing for compensation and precise positioning and orientation adjustments using a CNC controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a workpiece with substantial mass is positioned on the rotary table, then the workpiece can be machined, but the positioning accuracy of the CNC system deteriorates due to gravitational effects on the cantilevered arm
Solution Approach 1:
The system performs preliminary calibration measurements in an unloaded condition to establish reference positions and orientations of the first axis. These reference values are stored and used to compensate for gravitational effects during subsequent loaded machining operations, allowing the system to predict and correct positioning errors before they occur
Solution Approach 2:
The system measures the actual position and orientation of the first axis under loaded conditions, compares these measurements with the reference unloaded values, and determines positional deviations. These deviation values are fed back to the CNC controller to adjust and correct the positioning accuracy during machining operations
2Manufacturing precision
If the rotary table rotates the workpiece about the first axis, then the workpiece can be positioned for machining, but the orientation accuracy deteriorates due to gravitational sag of the cantilevered arm
Solution Approach 1:
The system performs preliminary calibration to establish reference orientation values of the first axis in the unloaded condition. These reference orientation values are stored and used to compensate for gravitational effects on the cantilevered arm during subsequent loaded machining operations
Solution Approach 2:
The system measures the actual orientation of the first axis under loaded conditions, compares these measurements with the reference unloaded orientation values, and determines orientation deviations. These deviation values are fed back to the CNC controller to adjust and correct the orientation accuracy during machining operations
Data Source
AI summary
A method for calibrating a machining system includes providing the machining system which includes a base, a cantilevered arm, and a rotary table positioned at the second arm end of the cantilevered arm. The rotary table is rotatable relative to the cantilevered arm about a first axis. The first axis has a first unloaded position and a first unloaded orientation with the machining system in an unloaded condition. The method further includes installing a measurement artifact on the rotary table, measuring a first position of the measurement artifact, and installing a load on the rotary table. The first axis has a first loaded position and a first loaded orientation with the machining system in a loaded condition. The method further includes measuring a second position of the measurement artifact and determining a positional deviation of the second position from the first position.