Form Measuring Instrument Centering Aspheric Workpieces
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Solution Overview
Problem
Conventional roundness measuring machines face challenges in accurately centering aspheric workpieces, leading to potential damage when the off-centering value is large, as the workpiece may exceed the measuring region or contain errors in detected values.
Innovation Solution
A form measuring instrument and method that involves rotating a workpiece about a first axis, using a contact piece to trace the surface in two perpendicular directions, calculating extremum positions, and adjusting the workpiece to align the maximum profile with the rotation axis, thereby ensuring accurate centering and preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional centering methods are used for aspheric workpieces, then the measuring process can be completed, but the workpiece may exceed the measuring region or contain errors when the off-centering value is large
Solution Approach 1:
The patent performs preliminary centering measurements by rotating the workpiece and detecting its profile before the main measurement. The extremum positions are calculated from these preliminary measurements, and the workpiece is pre-positioned based on these calculations. This preliminary action ensures that the workpiece is properly centered before the actual measurement, preventing it from exceeding the measuring region and avoiding measurement errors.
Solution Approach 2:
The patent replaces manual or mechanical centering adjustment with an automated computational system. The control unit calculates the extremum positions from measured data and automatically determines the required workpiece displacement. This substitution of mechanical adjustment with computational control improves both the precision and reliability of the centering process.
2Measurement precision
If multiple direct measurements are performed to ensure accurate centering, then centering precision improves, but the measurement time increases
Solution Approach 1:
The patent performs a single preliminary measurement to obtain the workpiece profile and calculate extremum positions. This preliminary action provides sufficient information for accurate centering without requiring multiple repeated measurements. The control unit processes this data to determine the exact displacement needed, achieving precise centering in one measurement cycle rather than through multiple trials.
Solution Approach 2:
The patent creates a computational model of the workpiece profile from the measured data. By fitting a curve to the measured points and calculating the extremum positions from this model, the system determines centering parameters without needing to physically reposition and remeasure the workpiece multiple times. This copying approach saves time while maintaining precision.
Data Source
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AI summary
Form measuring instrument includes: first measuring means which moves contact piece from first position in parallel with second axis to trace surface of workpiece, measure amount of displacement of contact piece, to obtain first profile; second placing means which rotates workpiece about first axis by 90 degrees to place workpiece at second position from first position; second measuring means which moves contact piece from second position in parallel with second axis to trace surface of workpiece, measure amount of displacement of contact piece, to obtain second profile; extremum position calculating means which fits circles to first and second profiles and calculate positions, in direction parallel with second axis, of first and second extremums indicating circles' extremums; and moving means which moves workpiece in direction parallel with second axis and direction parallel with third axis such that positions, in direction parallel with second axis, of first and second extremums become 0.