Contactless Thread Measurement Using Intersection Points
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Solution Overview
Problem
Existing methods for measuring thread properties, such as those in ball screw drives, face challenges with contactless measurements due to inaccuracies in determining the base position and thread pitch, especially in multiple-thread scenarios, leading to significant inaccuracies and difficulties in precise positioning.
Innovation Solution
A contactless method using a distance sensor to detect intersection points with a reference value between maximum and minimum measurement signal values, calculating mean values from these points to determine thread pitch and lead, allowing for precise measurement of thread properties without physical contact, and enabling accurate determination of thread lead and angular displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a tactile probe is used to scan the spindle, then measurement contact is established, but measurement speed is reduced and the measurement process becomes more complex
Solution Approach 1:
The patent replaces the mechanical tactile probe system with a contactless measurement system using optical or electromagnetic fields. The distance sensor measures thread dimensions without physical contact, eliminating the mechanical interaction that limits measurement speed while maintaining precision through field-based detection methods.
2Measurement precision
If the base position of the thread is measured directly, then absolute thread values are obtained, but measurement accuracy deteriorates due to difficulty in detecting extreme values
Solution Approach 1:
Instead of directly measuring the difficult-to-detect base position (extreme value), the patent inverts the approach by measuring relative distances from easily detectable points on the thread flanks. The base position is then calculated indirectly through coordinate transformation, converting a difficult extreme value detection problem into a series of simpler relative measurements.
3Manufacturing precision
If the intermediate area between threads is measured, then complete thread geometry is captured, but measurement accuracy deteriorates due to plateau region poor resolution
Solution Approach 1:
The patent extracts and excludes the problematic intermediate area (plateau region) from direct measurement. By focusing measurements only on the thread flanks where clear geometric features exist, and calculating intermediate positions through mathematical interpolation rather than direct measurement, the system avoids the resolution limitations of the plateau region while still capturing complete thread geometry.
4Measurement precision
If multiple calculation steps are used to determine thread properties, then comprehensive thread analysis is achieved, but measurement time increases
Solution Approach 1:
The patent performs preliminary actions by pre-establishing reference systems and measurement coordinate transformations before actual thread measurement. By preparing the measurement framework in advance with predefined calculation relationships and reference geometries, the system reduces the computational steps required during actual measurement, thereby decreasing measurement time while maintaining comprehensive thread analysis capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables quick and precise measurement of thread properties, improving measurement accuracy and enabling high-precision thread production for ball screw drives, suitable for high-speed production and precise linear positioning.
Implementation Method 1
Since the measurement of the thread takes place in a contactless manner, for example with the aid of ultrasound
Data Source
AI summary
A method for measuring a thread includes moving a contactless distance sensor parallel to an axial direction of the thread, recording a measurement signal corresponding to a distance of the contactless distance sensor to a top of the thread, comparing the measurement signal with a reference value lying between a maximum value and a minimum value of the measurement signal, and determining intersection points of the measurement signal with the reference value. Further steps include combining pairs of intersection points, directly following one another, into measurement value tuples, calculating mean values of the measurement value tuples, and calculating a time-angle resolution from the mean values. In an example embodiment, the thread is for a spindle of a ball screw drive.