Equivalent Pulse Heat Transfer Model and Process Analysis for Laser Marking Based on Spot Overlapping
Currently,laser surface marking technology is extensively utilized.Establishing a heat transfer numerical model for line marking to predict material ablation depth holds significant importance for advancing laser marking technology.The energy coupling in the marking process is intricately complex,primarily due to the multitude of pulses needed for pattern marking and the variance in spatial positions and timing of each pulse's irradiation.This complexity makes direct calculation of the heat conduction process during marking challenging.This paper presents an analysis of the combined effects of spot overlap and energy accumulation.It identifies that during the laser lens's movement along the processing path,numerous instances of similar spot overlap patterns occur.From this observation,two distinct methods for calculating spot overlap are derived.In real-world applications,the influence of the first spot overlap calculation method on the entire line marking process is minimal and can be disregarded,allowing the second method to be utilized for further calculations.Given that the time interval between the actions of any two adjacent pulses in space remains constant,the material's energy absorption attenuation can be precisely determined through the cumulative effect of pulse energy.Consequently,by averaging the total energy,the equivalent single pulse energy and equivalent pulse heat transfer numerical model for each spot area are derived.Laser surface marking experiments were conducted on acrylonitrile/butadiene/styrene copolymer plates(ABS plates),followed by ultrasonic cleaning to prepare the material surface for analysis.The processed surfaces were then evaluated using a surface roughness measuring instrument and a three-dimensional ultra-depth-of-field microscope.The effectiveness of the proposed equivalent pulse heat transfer numerical model for line marking was assessed by comparing the measured depths to the predicted values,taking into account the behavior of the ABS plates at various temperatures.Surface roughness was utilized as a metric to evaluate the quality of the marking.An in-depth analysis was performed to understand the discrepancies between the experimental and theoretical results,bridging theory with practical outcomes.The findings are as follows:the material's ablation depth increases with the overlap rate,ranging from 91％to 99％,due to the effects of laser scanning velocity v or laser pulse frequencyf,with the highest material removal rate observed at a 99％overlap rate.Conversely,the ablation depth decreases as the overlap rate increases when considering the effect of spot diameter D,with the highest removal rate occurring at a 91％overlap rate.In scenarios influenced by three key parameters,an equivalent laser power density of I1=3.88W/μm2 generates significant recoil pressure,enhancing material removal and optimizing the energy efficiency of the laser marking process.In surface marking,the optimal coverage of the target area is crucial for achieving high-quality results.If the distance between lines exceeds the width of the line segment groove,then the overlapping of line segments fails to entirely cover the target area,leading to incomplete marking.Conversely,when the distance between lines is less than the width of the groove in the line segment,excessive material overlap can cause expansion and deformation,compromising the surface quality.However,setting the distance between lines to closely match the width of the groove ensures complete coverage of the target area without compromising surface quality,resulting in an effective marking outcome.This study further explores the dynamics of energy coupling in the spatial overlapping area of light spots and the accumulation of energy from adjacent pulses over time.By employing the concept of light spot diameter overlap,the overlap rate for each light spot area was estimated.Utilizing the principle of equivalent effect,an equivalent pulse heat transfer numerical model was developed,offering a more straightforward and efficient method for calculating the ablation depth of laser markings.
NETL
NSTL
万方数据
