Laser Engraving on Moving Paper Webs With Motion Compensation
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Solution Overview
Problem
Existing methods for engraving patterns on moving materials, such as paper or metal webs, face challenges in maintaining precision at high speeds, preventing damage to the material, and ensuring authenticity, particularly in reproducing sharp angles and controlling laser power during transient heating periods.
Innovation Solution
A method involving a laser engraving system that calculates and applies transformed patterns to account for web movement, adjusts laser power to compensate for transient heating, and uses precise control of galvanometers and focus to reproduce sharp angles and authenticity marks without slowing down the printing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser engraving is performed on a rapidly moving web, then productivity is improved, but manufacturing precision deteriorates due to web movement causing blurred or distorted engravings
Solution Approach 1:
The system dynamically adjusts the laser beam position and web conveying speed in real-time to maintain synchronization. The control unit continuously updates the relationship between laser beam position and web position based on detected web speed variations, allowing high-speed engraving while maintaining precision by adapting to changing conditions rather than relying on fixed parameters
Solution Approach 2:
A feedback mechanism detects the actual web conveying speed and uses this information to correct the laser beam positioning. The system measures web speed and feeds this data back to the control unit, which then adjusts the laser beam position to compensate for web movement, ensuring accurate engraving even at high speeds where web position varies dynamically
2Productivity
If galvanometer-operated mirrors are used for high-speed engraving, then productivity is improved, but manufacturing precision deteriorates at sharp angles due to mirror movement limitations
Solution Approach 1:
The patent replaces the mechanical galvanometer mirror system with a piezoelectrically controlled lens system. Instead of using moving mirrors that have inertia and cannot respond quickly to sharp angle changes, the invention uses piezoelectric elements to rapidly adjust lens focal length and beam direction, eliminating mechanical movement limitations and enabling precise reproduction of sharp angles at high engraving speeds
3Manufacturing precision
If laser power is increased to maintain engraving quality during transient heating, then manufacturing precision is improved, but object-affected harmful factors worsen due to risk of burning or perforating the support
Solution Approach 1:
The system uses periodic pulsed laser emission rather than continuous high power. By emitting laser energy in controlled pulses with appropriate duty cycles, the system delivers sufficient energy for quality engravings while allowing thermal diffusion between pulses, preventing cumulative heat buildup that would cause burning or perforation of the support material
Solution Approach 2:
The patent dynamically changes laser emission parameters including power level, pulse duration, and duty cycle based on real-time conditions. The control unit adjusts these parameters to optimize the balance between delivering enough energy for quality engravings and preventing excessive heat accumulation that would damage the support, adapting to transient heating effects without causing harm
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 high-speed, precise engraving of patterns on moving materials without damaging the substrate, ensuring accurate reproduction of sharp angles and preventing falsification, while maintaining document authenticity and printing speed.
Implementation Method 1
a laser beam that modifies or removes portions of material of the support
Implementation Method 2
a laser beam that modifies or removes portions of material of the support
Implementation Method 3
due to the speed at which the galvanometer-operated mirrors and lenses are moved
Implementation Method 4
the laser emitter is excited, the power has a transient behavior
Implementation Method 5
The lower the power used by a particular engraving process, the longer the influence that transient period will have. In particular, if pluralities of single holes or engravings have to be made in a quick succession
Data Source
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AI summary
A method for making laser engravings on a web (10) of paper, comprising the steps of prearranging a paper web (10) conveying means (86) configured for conveying said web in a predetermined direction; defining a working area (12) along a path of said web (10); prearranging an emitter (14) of laser pulses (15,15', 16) that have a power set to form engravings on said web (10); prearranging a movable pointing means, comprising a reflection means (22,23) and of focus means (33), arranged to send of said laser pulses (15,15', 16) to said working area (12); selecting an engraving pattern (20) to be engraved on said web (10) by said laser pulses (15,16) emitted as pulse packets in quick succession, said pattern associated with a first function (31) defined in said working area (12) with respect to a first reference (11) that is integral to said web (10); calculating an instruction file (24) containing pointing instructions for operating said pointing means (22,23,33) in such a way that a predetermined position of said movable pointing means (22,23,33) corresponds to each pulse packet, a predetermined position of said points on said working area (12) corresponding to said predetermined position of the movable pointing means; selecting an emission power (W) of said emitter of laser pulses (14); emitting laser pulses (14) through said emission power (W) by said emitter (14); operating said movable pointing means (22,23,33) according to said instruction file, so that said movable pointing means (22,23,33) sequentially reaches each predetermined position by continuously changing the direction of said laser pulses (15,16) in said working area (12) reproducing said pattern (20) on said web (10); wherein said step of computing an instruction file (24) provides a transform of said first function (31) from said reference system (11) that is integral to said web, (10) into a second reference system (13) that is integral to said emitter (14), wherein a second transformed function (32) is obtained, by said transform, which is defined in said working area (12), and said instructions of said instruction file (24) operate said pointing means (22,23,33) in such a way that said laser pulses (16) describe said transformed function (32) with respect to said second reference system (13), in said working area (12), such that said packets of laser pulses reach said web (10), and engrave said pattern on said web as if said web were motionless.