Cantilevered Rotary Table Calibration for Load-Induced Axis Deviation

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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 with a rotary table and a measurement artifact to calibrate the machining system by measuring positional deviations under loaded and unloaded conditions, allowing for determination of corrected positions and orientations to improve accuracy, especially in systems using WEDM processes within a dielectric fluid environment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a cantilevered arm structure is used to support the rotary table, then the system can achieve compact design and ease of operation, but the mass of workpieces causes gravitational deformation that deteriorates positioning accuracy

Engineering Contradiction:

Improveease of operationVSAvoidpositioning accuracy

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The system performs preliminary calibration by measuring the positions of measurement artifacts with the rotary table in the unloaded condition to establish a baseline coordinate system. This preliminary action allows the system to later compensate for gravitational deformation caused by workpiece mass during machining operations.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses measurement artifacts and sensors to continuously monitor the actual positions of the rotary table and cantilevered arm. This feedback is used to determine deviations from the baseline coordinate system and apply real-time compensation to maintain positioning accuracy despite gravitational effects.

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If the rotary table rotates about multiple axes to position workpieces, then the system achieves versatility in machining orientations, but the mass and shape of workpieces cause varying gravitational effects that worsen positioning accuracy

Engineering Contradiction:

ImproveversatilityVSAvoidpositioning accuracy

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system determines the mass and center of gravity of each workpiece and uses these parameters to calculate compensation values. By changing the operational parameters based on workpiece-specific characteristics, the system maintains positioning accuracy across different workpiece masses and orientations.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If measurement artifacts are used to calibrate the system, then positioning accuracy can be improved through compensation, but the complexity of the calibration process increases

Engineering Contradiction:

Improvepositioning accuracyVSAvoidcalibration complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Measurement artifacts serve as intermediaries between the rotary table and the coordinate measuring machine. These artifacts provide known reference positions that facilitate the calibration process, allowing the system to establish accurate baseline coordinates without requiring direct measurement of the rotary table itself.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system creates a virtual copy of the physical coordinate system through digital modeling of the measurement artifact positions. This digital baseline coordinate system can be stored and reused, simplifying subsequent calibration operations and reducing the complexity of repeated calibration processes.

Inventive Principle:

Principle #26Copying

Data Source

PatentEP4227747A1System and method for correcting machine load effect on kinematic accuracy

Publication Date: 2023.08.16 PRATT & WHITNEY CANADA CORP

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AI summary

A method for calibrating a machining system (32) includes providing the machining system (32) which includes a base (40), a cantilevered arm (42), and a rotary table (34) positioned at the second arm end (48) of the cantilevered arm (42). The rotary table (34) is rotatable relative to the cantilevered arm (42) about a first axis (54). The first axis (54) has a first unloaded position and a first unloaded orientation with the machining system (32) in an unloaded condition. The method further includes installing a measurement artifact (64) on the rotary table (34), measuring a first position of the measurement artifact (64), and installing a load (62) on the rotary table (34). The first axis (54) has a first loaded position and a first loaded orientation with the machining system (32) in a loaded condition. The method further includes measuring a second position of the measurement artifact (64) and determining a positional deviation of the second position from the first position.