Galvanizing Nozzle Control via Laser Distance Measurement
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Solution Overview
Problem
Existing methods for controlling coating thickness uniformity in hot dip galvanizing processes face challenges due to non-constant nozzle-to-strip distance, strip shape complexity, and limited actuator availability, leading to difficulties in achieving uniform coating across the strip width.
Innovation Solution
A method involving the measurement of actual nozzle-to-strip distance profiles, followed by calculations using linear and quadratic regression to correct for skewness and crossbow, with physical adjustments to nozzle positions and strip shape using contactless actuators to optimize coating uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional air-knife blowing method is used to control coating thickness, then coating deposition is achieved, but coating weight uniformity deteriorates due to non-constant nozzle-to-strip distance and strip shape variations
Solution Approach 1:
The system performs preliminary measurement of the actual nozzle-to-strip distance profile using laser triangulation before coating deposition, and pre-calculates the required corrections using linear and quadratic regression. This allows the correction parameters to be determined in advance, enabling precise control of coating uniformity during the actual galvanizing process.
Solution Approach 2:
The patent replaces complex mechanical measurement systems with optical measurement (laser triangulation method). Instead of using mechanical probes or contact-based measurement devices, the system uses laser beams and optical sensors to non-contactively measure the nozzle-to-strip distance profile, simplifying the measurement mechanism while improving precision.
2Shape
If multiple deflector rolls are used to correct strip crossbow, then strip flatness improves, but device complexity and adjustment difficulty increase
Solution Approach 1:
The system uses laser measurement to continuously monitor the actual nozzle-to-strip distance profile and provides feedback on strip shape deviations. This feedback information is processed through regression analysis to determine the optimal adjustment parameters for deflector rolls, enabling precise and automated adjustment rather than manual trial-and-error positioning.
Solution Approach 2:
The patent transforms the physical adjustment of multiple deflector rolls into parameter optimization problems. By using linear and quadratic regression analysis on the measured distance profile, the system calculates optimal adjustment parameters (positions and angles of deflector rolls) that will achieve the desired strip flatness, converting a complex mechanical adjustment task into a mathematical optimization task.
3Measurement precision
If polynomial regression of high order is used to fit nozzle-to-strip distance profile, then measurement precision improves, but calculation complexity and time increase
Solution Approach 1:
The patent segments the distance profile correction into two distinct components: linear regression for skewness correction and quadratic regression for crossbow correction. This segmentation allows each type of distortion to be addressed separately with the appropriate mathematical model, reducing overall calculation complexity compared to using a single high-order polynomial for the entire profile.
Solution Approach 2:
The system extracts and separates the dominant distortion patterns from the measured distance profile. By identifying and removing the linear component (skewness) first, then the quadratic component (crossbow), the method isolates the most significant sources of non-uniformity and corrects them separately, avoiding the need for complex high-order polynomial fitting while achieving sufficient precision.
4Manufacturing precision
If manual adjustment of deflector rolls is performed, then operational simplicity is maintained, but manufacturing precision of coating uniformity deteriorates
Solution Approach 1:
The system implements an automated feedback control loop where laser measurement continuously monitors the nozzle-to-strip distance profile, regression analysis automatically calculates the optimal correction parameters, and the system automatically adjusts the deflector roll positions and nozzle alignments. This closed-loop feedback system eliminates manual adjustment while achieving high coating uniformity precision.
Solution Approach 2:
The system performs self-correction by automatically measuring its own geometry (nozzle-to-strip distance profile), analyzing the measured data through regression, and adjusting its components (deflector rolls and nozzles) based on the analysis results. This self-service capability allows the system to maintain optimal performance without continuous manual intervention.
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 effectively reduces nozzle-to-strip distance variations and improves coating weight uniformity by compensating for strip shape imperfections and vibrations, resulting in a more uniform and flat coating across the metal strip.
Implementation Method 1
measuring an actual distance profile between the nozzles and the strip along a direction transverse with respect to a running strip direction, and in a vicinity of the nozzles
Implementation Method 2
wiping excess coating thickness carried away by the strip on one or both sides of the strip by wiping nozzles blowing a gas on the strip
Data Source
AI summary
A method for controlling and optimizing a transverse uniformity of a coating thickness on at least one side of a running metal strip in an industrial galvanization installation, the coating being deposited by hot dip coating in a pot containing a liquid metal bath, includes at least the steps of: heating the strip substrate to a temperature higher than a pot temperature; passing the strip through the bath by wrapping the strip around at least a first deflector roll or sink roll followed by at least one second deflector roll, the second deflector roll improving a flatness of the strip; wiping excess coating thickness carried away by the strip on one or both sides of the strip by wiping nozzles blowing a gas on the strip at an exit of the liquid metal bath; and measuring an actual distance profile between the nozzles and the strip.