Optical Thread Profile Measurement for Pipe Ends
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Solution Overview
Problem
Current methods for quality control of external threads on pressurized pipes, such as those used in oil and gas pipelines, are inefficient and costly due to the need for manual spot checks, which can lead to delayed detection of thread quality issues and increased rejects and complaints.
Innovation Solution
A method and device for optical measurement of external threads using tangential illumination and high-resolution CCD cameras with telecentric lenses, allowing for continuous, 100% inspection during production without interrupting the process, with the ability to evaluate thread profiles in real-time and correct for pipe positioning errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual spot checks are used for quality control, then the measurement process is simple, but the inspection coverage is insufficient and quality issues are detected late
Solution Approach 1:
The patent replaces manual mechanical measurement with an optical measurement system that uses light sources, cameras, and image processing to automatically capture and evaluate thread profiles. This substitution enables 100% inspection coverage while maintaining measurement accuracy, resolving the contradiction between reliable quality control and inspection productivity.
Solution Approach 2:
The patent changes the measurement parameters by using optical properties (light reflection, image capture) instead of mechanical contact measurement. This allows for non-contact, high-speed capture of thread geometry parameters, enabling comprehensive inspection without slowing down production.
2Reliability
If 100% inspection is implemented, then quality control coverage is complete, but the measurement time exceeds the production cycle time
Solution Approach 1:
The patent implements continuous optical measurement during the thread cutting process itself, rather than requiring separate measurement steps. The optical system continuously captures thread profiles as they are being formed, enabling 100% inspection without adding time to the production cycle, thus resolving the contradiction between complete quality coverage and measurement time loss.
Solution Approach 2:
The measurement is performed during the thread cutting process itself, capturing data as the thread is being formed rather than after completion. This preliminary measurement approach allows for real-time quality control without extending the overall production time.
3Measurement precision
If conventional optical methods are used, then the setup is simple, but the thread profile cannot be accurately recorded
Solution Approach 1:
The optical measurement system is divided into distinct functional modules: light sources positioned at specific angles, cameras for image capture, and separate image processing algorithms. This segmentation allows each component to be optimized for its specific function while maintaining overall system manageability, resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The patent uses optical intermediaries (light sources, lenses, cameras) to indirectly measure the thread profile without direct mechanical contact. This intermediary optical path enables accurate capture of thread geometry while keeping the physical measurement system relatively simple and non-invasive.
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
Enables complete and accurate quality control of external threads during production, minimizing rework and complaints by providing immediate feedback on thread quality, allowing for timely adjustments to the thread cutting process.
Implementation Method 1
the lighting device being aligned with the screw in such a way that the light beams are emitted essentially perpendicular to a flank of the thread
Implementation Method 2
a correspondingly designed camera with a telecentric lens. The use of telecentric components has the advantage that the measuring system remains unaffected by extraneous light from sunlight and hall light
Data Source
Figure 1~2
AI summary
The invention relates to a method and device for optically measuring external thread profiles, particularly at the ends of pipes, wherein the thread is previously synchronously produced in a production line and is continuously measured in line from start to finish of the thread prior to further processing. The aim of the invention is to allow cost-effective inspection of the thread during synchronous production of the thread. For this purpose, the profile of the previously produced thread is illuminated and/or scanned tangentially to the pipe cross section by means of a relative movement including rotation and translation, and by an optical measuring unit comprising a camera, and the scanning speed is adjusted such that the time for scanning the thread profile, considering the required local resolution of the camera, is within the cycle time for the production of the next thread, wherein the image of the thread contour is captured by the camera and the optical signals are then evaluated and compared to target specifications.