Bar Straightness Measurement via Static Equilibrium and Optical Detection
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Solution Overview
Problem
Current methods for measuring straightness errors in elongated metal elements, such as bars and pipes, are either too time-consuming for production line use or provide inaccurate, indirect measurements, especially when dealing with high-speed processing and variable bar lengths, and often fail to account for residual stress and deformation caused by cutting.
Innovation Solution
A measuring device that positions a bar on a surface plate to achieve static equilibrium, using optical sensors to detect the coordinates of multiple points along the bar's surface and a processing unit to calculate the longitudinal axis, allowing for precise determination of straightness errors through least-squares interpolation and comparison to a reference model, while minimizing static deformation and adapting to different bar sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional bearing and comparator method is used to measure straightness error, then measurement precision is improved, but measurement time increases making it unsuitable for production lines
Solution Approach 1:
The patent replaces the traditional mechanical bearing-comparator system with an optical measurement system using lasers and sensors. The mechanical rotation and manual comparison process is substituted by optical fields that automatically detect bar deflection, achieving high precision without the time-consuming mechanical operations.
Solution Approach 2:
The patent introduces optical fields (lasers) as intermediaries to measure bar straightness. Instead of direct mechanical contact and manual measurement, laser beams serve as mediators that interact with the bar surface and provide measurement data through optical sensors, enabling rapid non-contact measurement.
2Productivity
If laser sensors are used to measure material waviness before cutting, then in-line measurement is enabled, but measurement accuracy deteriorates due to material deformation and swinging at high speeds
Solution Approach 1:
The patent performs measurement after the bar has been cut and has reached a stable state, rather than measuring during high-speed transport. This preliminary stabilization action eliminates the deformation and swinging that occur at high speeds, ensuring accurate measurements while maintaining in-line measurement capability.
Solution Approach 2:
Instead of measuring the bar during high-speed transport (forward approach), the patent inverts the sequence by allowing the bar to slow down and stabilize first, then performing the measurement. This reverse approach eliminates the harmful effects of high-speed motion on measurement accuracy.
3Productivity
If multiple weight sensors with rolling plane are used to evaluate curvature, then in-line measurement is possible, but measurement reliability decreases due to frictions and unpredictable rollings
Solution Approach 1:
The patent replaces the mechanical weight sensor and rolling plane system with an optical measurement system. This substitution eliminates the frictions and unpredictable rollings inherent in mechanical contact, providing reliable measurements through non-contact optical detection while maintaining in-line measurement capability.
4Productivity
If optical sensors are used to measure bar straightness, then measurement speed is improved, but measurement precision deteriorates compared to traditional mechanical methods
Solution Approach 1:
The patent optimizes key parameters of the optical system including laser wavelength, beam diameter, sensor positioning, and sampling frequency. By carefully adjusting these parameters, the system achieves measurement precision comparable to traditional mechanical methods while maintaining the speed advantages of optical detection.
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 accurate, efficient in-line measurement of straightness errors in production lines, reducing measurement time and improving precision by accounting for residual stress and deformation, and providing direct, precise measurements of straightness errors across the entire length or specific portions of the bar.
Implementation Method 1
positions a bar on a surface plate so as to be arranged in a position of static equilibrium by virtue of its own straightness defect
Implementation Method 2
using optical sensors to detect the coordinates of multiple points along the bar's surface
Data Source
Figure 1~2a
Figure 2b~2e
Figure 3~4
AI summary
The present invention concerns a measuring device to measure straightness errors of elongated-shape elements, such as bars, pipes and the like, comprising a surface plate on which a bar is arranged in static equilibrium by virtue of its own straightness defect, detecting means to detect the development of the longitudinal axis of the bar, a controlling and processing unit to control and process data acquired by the detecting means. The detecting means acquire the coordinates of a plurality of points of the bar surface next to at least three cross sections and the controlling and processing unit is programmed to calculate the position of the longitudinal axis of the bar next to the three sections, starting from the coordinates of the above mentioned points. In one embodiment the device comprises movement means to move sensors which, in their turn, comprise: at least one track along which the movable sensors can be translated, and actuators driven by the controlling unit and intended for the movement of the movable sensors to known positions along the track in order to precisely control the position of the sensors along the track. In another embodiment the surface plate is defined by only one surface or else by a plurality of supports, and wherein the surface plate is combined with a rolling plane, where the bars roll, in its turn defined by only one surface or a plurality of supports, to force the bars to stop, after they initially rolled, in a position of stable equilibrium on the surface plate, the lying plane of the longitudinal axis of each bar being parallel to the surface plate itself in order to cause the straightness error of each bar to lie coplanar with the surface plate. In another embodiment the surface plate comprises at least one support, preferably at least two supports, each mounted on a respective fulcrum so as to tilt and having at least two bearing elements on opposite sides with respect to the respective fulcrum in order to minimize the static deformation of the bar caused by its own weight.