Thread Profile Measurement Using Dual-Axis Scanning and Self-Alignment
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Solution Overview
Problem
Existing thread profile measurement methods, such as the three-wire method and uniaxially movable profile measuring instruments, require complex processes and devices to accurately measure thread profiles, especially for pitch diameter and orientation, due to alignment and vertex detection challenges, particularly when measuring female threads without a cylindrical portion.
Innovation Solution
A method using a uniaxially movable profile measuring instrument to perform scanning measurements along two axes opposed across the center axis, detecting displacements between thread crests and roots to calculate inclination and axis deviation, allowing for precise alignment and adjustment to obtain accurate contour data and characteristic values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the three-wire method is used to measure thread profile, then measurement accuracy can be achieved, but the process becomes complicated requiring preparation of measurement needles, positioning, and calculation
Solution Approach 1:
The patent extracts and eliminates the complex intermediate steps of the three-wire method (measurement needle preparation, positioning, and calculation) by directly using a stylus to trace the thread profile and automatically generating measurement results, thereby maintaining accuracy while simplifying the process
Solution Approach 2:
The patent replaces the manual mechanical three-wire method with an automated stylus-based tracing system that uses a profile measuring instrument to directly capture thread profile data, eliminating the need for physical measurement needles and manual calculations
2Measurement precision
If scanning measurement is performed at multiple points using a coordinate measuring machine to obtain three-dimensional profile information, then comprehensive thread profile data can be obtained, but the device and process become complicated
Solution Approach 1:
The patent extracts only the essential measurement function needed for thread profile characterization, eliminating the need for a full coordinate measuring machine system by using a simple uniaxially movable profile measuring instrument that captures sufficient data along the thread axis
Solution Approach 2:
Instead of using a complex multi-axial coordinate measuring machine to scan at multiple points, the patent inverts the approach by using a simple uniaxial instrument that moves along the thread axis, allowing the thread profile to be measured through single-pass tracing
3Device complexity
If uniaxially movable profile measuring instrument is used to simplify the measurement device, then device complexity is reduced, but measurement capability is limited to only thread contour and pitch along the center axis
Solution Approach 1:
The patent adds a second measurement dimension by performing scanning measurements at two opposite positions (first and second axes) across the thread center axis, enabling extraction of pitch diameter information in addition to contour and pitch data from the uniaxial movement
4Adaptability or versatility
If scanning measurement is performed at opposite positions to obtain pitch diameter, then measurement versatility is improved, but alignment and vertex detection adjustments become necessary
Solution Approach 1:
The patent implements self-alignment by utilizing the thread's own geometric features (opposite crests and roots) as reference points, allowing the measurement system to automatically establish proper alignment without requiring manual vertex detection or alignment adjustments
Data Source
AI summary
A method includes: performing a scanning measurement of a female thread along first and second axes extending along a center axis of the thread and opposed to each other across the center axis; determining characteristic values of the thread from contour data of the thread obtained through the measurement; obtaining the contour data including first contour data associated with the first axis and second contour data associated with the second axis by performing the measurement; detecting a thread displacement along the center axis between a crest associated with the first axis and a crest associated with the second axis at each of first position and second position on the center axis; calculating inclination and deviation of the first and second axes from the thread displacements detected at the first and second positions; and adjusting an attitude of the thread for the measurement to eliminate the inclination and deviation.