Threaded Tube Shape Measurement Using Asymmetric Laser Projection
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Solution Overview
Problem
Current methods for measuring the shape of thread and seal parts on oil well pipes are inaccurate and time-consuming, particularly due to issues with shadowing in light projection methods and the limitations of contact probes in capturing curved and inclined features.
Innovation Solution
Employing a light-section method using slit-like laser light, where the optical axis of the light source passes through a point on the thread axis, allowing the laser light to extend within a plane including the thread axis, enabling precise measurement of thread and seal part shapes without shadowing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a light projection method is used to measure thread part shape, then measurement speed is improved, but measurement precision deteriorates due to shadowing of hook-like flank faces
Solution Approach 1:
The patent applies asymmetry by positioning the light source specifically on the thread axis rather than using symmetric or parallel projection. This asymmetric positioning ensures that the light ray passes through the thread ridge without being shadowed by the hook-like flank face, thereby maintaining measurement precision while achieving rapid measurement through optical projection
Solution Approach 2:
The patent replaces the mechanical contact probe method with an optical projection method. Instead of physically touching and scanning the thread surface with a probe, the system uses light projection and image capture to obtain the thread shape, significantly improving measurement speed while maintaining accuracy through proper light source positioning
2Measurement precision
If contact probes are used to measure thread and seal part shapes, then measurement precision is improved, but measurement time increases significantly
Solution Approach 1:
The patent replaces the mechanical contact probe system with an optical measurement system using light projection and image capture. This substitution eliminates the need for physical contact and sequential scanning, enabling simultaneous capture of the entire thread and seal part shapes, thereby maintaining precision while dramatically reducing measurement time
Solution Approach 2:
The patent transitions from one-dimensional sequential probe scanning to two-dimensional optical imaging. By projecting light and capturing the shadow image, the system obtains complete shape information in a single measurement, eliminating the time-consuming sequential scanning process of contact probes
3Loss of time
If sampling inspection is performed instead of total inspection, then inspection time is reduced, but quality assurance reliability deteriorates
Solution Approach 1:
The patent replaces mechanical contact inspection with rapid optical projection and image capture, enabling total inspection of all pipes in a production lot. The quick measurement capability allows every pipe to be inspected rather than relying on sampling, thereby maintaining high quality assurance reliability while keeping inspection time acceptable
Solution Approach 2:
The patent creates an optimal measurement environment by using optical projection that is not affected by mechanical contact issues. The light-based measurement system provides consistent, repeatable results for all pipes, enabling reliable total inspection rather than risky sampling inspection
4Productivity
If conventional light projection with parallel light is used, then measurement speed is improved, but measurement precision deteriorates for hook-like flank faces
Solution Approach 1:
The patent applies asymmetry by positioning the light source on the thread axis rather than using symmetric parallel projection. This specific positioning creates a measurement geometry where the light ray passes through the thread ridge without shadowing the hook-like flank face, maintaining both speed and precision
Solution Approach 2:
The patent changes the critical parameter of light source positioning from parallel projection to axis-aligned projection. By positioning the light source on the thread axis and directing light through the thread ridge, the system eliminates shadowing effects on hook-like flank faces while maintaining rapid optical measurement
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 approach allows for accurate and rapid measurement of thread and seal part shapes, including angles and curvatures, without the long measurement times associated with contact probes, and provides a quantitative evaluation of dimensional accuracy.
Implementation Method 1
applying laser light from the light source to the measurement target region and capturing an image of the applied laser light by the image capture device
Data Source
Figure 1A~1B
Figure 2A~2D
Figure 3A~3C
AI summary
The present invention provides a method for measuring an end portion shape of a threaded pipe or tube P, the method including: a thread axis detection step; a laser light positioning step; a laser light image capture step; and a shape calculation step. In the laser light positioning step, the light source 1 and the image capture device 2 are moved together so that: the optical axis LA of the light source is located so as to pass through a measurement point D (X1, Y1, Z1) on the thread axis A, the measurement point being located in the measurement target region within a plane NP including the thread axis; and the laser light L extends in a slit-like form within the plane.