Measurement Cycle Generation with Variable Stand-off Distances
Solution Overview
Problem
Existing methods for generating measurement cycles using touch trigger measurements on machine tools often result in measurement errors due to a single, pre-set stand-off distance and probing feed-rate, which can lead to inaccurate measurements and increased cycle times, especially when dealing with complex objects like small bores or pockets.
Innovation Solution
A method that defines different stand-off distances and calculates corresponding probing feed-rates for each touch trigger measurement point based on its specific requirements, ensuring accurate measurements without globally reducing the feed-rate, thus optimizing cycle time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single pre-set stand-off distance is used for all measurement points, then the measurement cycle is simple to program and execute, but measurement errors occur when the stand-off distance is too short and cycle times increase when the stand-off distance is too long
Solution Approach 1:
The patent applies local quality by assigning different stand-off distances to different measurement points based on their specific geometric characteristics and accessibility. Instead of using a uniform stand-off distance for all points, the system calculates and applies optimized stand-off distances locally at each measurement point, thereby improving measurement accuracy without unnecessarily increasing cycle time across the entire measurement cycle.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the stand-off distance parameter for each measurement point rather than maintaining a fixed value. The system calculates optimal stand-off distances based on the specific requirements of each measurement point (such as feature size, location, and accessibility) and modifies the measurement cycle to use these varied parameters, resolving the contradiction between accuracy and productivity.
2Productivity
If the stand-off distance is reduced to decrease cycle time, then productivity improves, but measurement errors increase due to acceleration effects
Solution Approach 1:
The patent applies local quality by determining appropriate stand-off distances for different measurement points based on their specific characteristics. For measurement points where high speed is critical and acceleration effects can be managed, shorter stand-off distances are used to improve productivity. For points where measurement accuracy is paramount, longer stand-off distances are maintained to eliminate acceleration errors, thus locally optimizing the trade-off between speed and accuracy.
Solution Approach 2:
The patent implements parameter changes by calculating and applying different stand-off distance values for different measurement points rather than using a single reduced value for all points. This allows the system to minimize cycle time overall while maintaining measurement accuracy at critical points where reduced stand-off distance would cause unacceptable errors.
3Productivity
If a high probing feed-rate is used for all measurement points, then cycle time is reduced and productivity increases, but measurement errors occur due to acceleration at the instant of measurement
Solution Approach 1:
The patent applies local quality by assigning different feed-rates to different measurement points based on their specific requirements. For measurement points that are easily accessible and tolerate higher speeds, higher feed-rates are used to improve productivity. For points where measurement accuracy is critical or geometric constraints exist, lower feed-rates are applied to eliminate acceleration effects, thus locally optimizing the balance between speed and accuracy.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the probing feed-rate parameter for each measurement point rather than maintaining a uniform high feed-rate throughout the cycle. The system calculates optimal feed-rates based on stand-off distances, feature geometry, and measurement requirements, modifying the measurement cycle to use these varied parameters to achieve both high productivity and high accuracy where needed.
4Measurement precision
If the probing feed-rate is globally reduced to ensure accurate measurements, then measurement precision improves, but cycle time increases and productivity decreases
Solution Approach 1:
The patent applies local quality by applying lower feed-rates only at specific measurement points where measurement accuracy is critical or where geometric constraints (such as small bores or pockets) prevent the use of larger stand-off distances. For other measurement points where high speed can be maintained without compromising accuracy, higher feed-rates are used, thus locally optimizing the trade-off and avoiding a global reduction in productivity.
Solution Approach 2:
The patent implements parameter changes by calculating and applying varied feed-rate values for different measurement points rather than using a single reduced feed-rate for the entire cycle. This allows the system to maintain high measurement accuracy at critical points while preserving high productivity at non-critical points, thereby improving overall measurement precision without unnecessarily extending the total cycle time.
Data Source
AI summary
A method for generating a measurement cycle for inspecting an object using a measurement probe carried by a coordinate positioning apparatus, computer program and apparatus, wherein the measurement cycle includes a measurement path where the measurement probe moves relative to the object enabling inspection of the object using a series of touch trigger measurements. The method includes defining multiple touch trigger measurement points on the surface of the object. Each of the touch trigger measurement points has an associated stand-off position from which the measurement probe accelerates towards the touch trigger measurement point wherein the touch trigger measurement points separate from the associated stand-off position by a stand-off distance The method further includes defining different stand-off distances for at least some of the touch trigger measurement points and calculating a probing feed-rate for use when acquiring each touch trigger measurement point based on the stand-off distance associated therewith.