1,720,989 research outputs found
Automated characterization of the material removal rate in laser manufacturing of TiAI6V4 and inconel 718
No full textIn this paper a system for the automatic determination of the material removal rate during laser milling process is presented. ”Laser milling” can be defined as an engraving process with a strictly controlled penetration depth. In industrial applications, when a new material have to be machined or a change in the system set-up occur the user has to perform a time-consuming experimental campaign in order to determine the correlation between the material removal rate and the process parameters. In these cases the numerical models present some limits due to the elevated calculation time requested to simulate the laser milling of industrial features. In the proposed system, based on a regression model approach, the empirical coefficients, that provide the material removal rate, are automatically generated by a specific software according to the different materials that have to be processed. A description of the automated method and the results obtained in engraving TiAl6V4 and Inconel 718 superalloy with a fiber laser are presented. The system can be adapted to every combination of material/laser source
Laser Hardening Modelling: Comparison between Induction and Laser Hardening on a Mechanical Part
No full textIn this paper a numerical model for simulation of hypo eutectoid steel laser hardening process is presented. The Finite Difference Method (FDM) was used to solve the heat transfer and the carbon diffusion equations for defined workpiece geometry. The model is able to predict the thermal cycle into the target material, the phase transformations and the resulting microstructures according to the laser process parameters, the workpiece dimensions and the physical properties of the workpiece. The effects of the overlapping laser beam tracks on the resulting microstructures can be also considered. Besides the original material microstructure is taken into account in the simulation process by means of a digitized photomicrograph in which the initial ferrite-pearlite distribution is acquired. Several experimental tests were then carried out on a torque limiter hub made of C43 UNI 7847 and laser hardened by means of CO2 laser or induction source. The comparisons were made between the geometry of the two different surface hardenings and the hardness profiles
Laser Ablation Modeling for CNC Machine Tool Application in Mould Manufacturing
No full textIn this paper an original mathematical model of laser ablation is presented. Laser ablation optimisation is quite a complex activity due to the high number of parameters involved and nowadays the most common way to optimise the process, in industrial environments, is based on a “trial and error” activity.In order to reduce the set-up time, which can be very long when different materials and shapes have to be processed, a mathematical model is presented where the process parameters are related to the most important machining results such as ablated volume, temperature in work piece, resulting surface conditions, etc... The plasma plume effects on the machining operations are also considered. Comparisons between the theoretical and experimental results are also presented
A numerical model for laser Ablation with Plasma
No full textIn this paper a 3-D transient model for laser ablation modeling with plasma plume characterization is presented. The plasma plume was considered in local thermodynamical equilibrium (LTE) and the energy balance permits to evaluate the plume temperature, ion distribution and pressure under the assumption that the gas expansion, from the surface target, produces a sonic front. The plume energy balance is influenced by the energy lost for irradiation from the plume and by the quantity of laser beam energy reflected from the target surface. Then, the physical state of the plasma plume was evaluated by means of the energy balance into the plume which makes it possible to determine the plasma temperature, the plasma ionization and, subsequently, the optical thickness of the plasma. This model predicts the time dependent laser energy delivered to work-piece according to the process parameters and it represents a part of a laser milling simulator previously developed by the authors. A simplified model of the plume geometry is also performed.Numerical simulations have been conducted to quantify this influence on the plasma plume physical state. Several simulation runs are presented in order to show the LAS accuracy and facilities
3D Transient Simulation Model for Laser Micromilling Processes
No full textIn this paper a laser milling simulator package is shown and discussed. The software system has been developed to simulate the micromanufacturing process using solid state lasers with pulse width in the range of 10–100 ns, but it can simulate every spatial and temporal distribution of the laser beam, so it is well suited to simulate both continuous and pulsed emission and every kind of laser spot distribution and trajectory. The system can simulate the effect of the laser beam on the workpiece, keeping into account the surface conditions, the evolution of the work-piece temperature field, the phase changes in the material and, at the end, the ablation rate. Particular attention has been focused in considering the influence of the plasma plume. Modeling and simulating the plasma plume creation and expansion is a very hard task, in the proposed package a simplified model is developed avoiding the fluid dynamic effects. In this work two empirical tuning parameters are considered: the first one is a global dispersion factor that keep in account the fraction of energy lost in the environment by the plume; the second one is a spreading factor that permits to model the irradiated energy of the laser beam hitting the workpiece and due to the plasma plume. The direct and coupled effects of these two parameters are evaluated and discussed
An Efficient Model for Laser Surface Hardening of Hypo-Eutectoid Steels
No full textThis paper presents a model able to predict the austenization of hypo-eutectoid steels during very fast heat cycle such as laser hardening. Laser surface hardening is a process highly suitable for hypo-eutectoid carbon steels with carbon content below 0.6% or for low alloy steels where the critical cooling rate is reached by means of the thermal inertia of the bulk. As proposed by many authors, the severe heat cycle occurring in laser hardening leads to the pearlite to austenite microstructures transformation happening to a temperature much higher than the eutectoid temperature Ac1 and, afterwards, all the austenite predicted during the heating phase become martensite during quenching. Anyway, all these models usually generate a predicted hardness profile into the material depth with an on–off behavior or very complicated and time consumed software simulators. In this paper, a new austenization model for fast heating processes based on the austenite transformation time parameter Ip→a is proposed. By means of the Ip→a parameter it is possible to predict the typical hardness transition from the treated surface to the base material. At the same time, this new austenization model also reduces the calculation time. Ip→a was determined by experimental tests and it was postulated to be constant for low-medium carbon steels. Several experimental examples are proposed to validate the assumptions and to show the accuracy of the model
Laser Ablation of Metals: A 3D Process Simulation for Industrial Applications
No full textA model for laser milling simulation is presented in this paper. A numerical model able to predict the physical phenomena involved in laser ablation of metals was developed where the heat distribution in the work piece, the prediction of the velocity of the vapor/liquid front, and the physical state of the plasma plume were taken into account. The model is fully 3D and the simulations makes it possible to predict the ablated workpiece volume and the shape of the resulting craters for a single laser pulse or multiple pulses, or for any path of the laser spot. The numerical model was implemented in C++ and an overview of the code capacities is presented
An automated procedure for laser milling of textures for mould manufacturing
No full textIn this paper an algorithm for texture generation by means of laser milling process is presented. The aim of this work is to develop an original software that automatically generates texture on general surfaces (cylinder, sphere, plane, cone) particular useful in mould manufacturing (automotive, leather, plastic molding, automotive and packaging).The geometries representative of the textures were obtained from bitmap images on two levels (white and black) or with a continuously variable density. The algorithm digitalizes the bitmap of the base texture and project it on the acquired surface realizing many replicas of it in order to cover all the working area. The system subdivides the single features of the texture and makes a triangulation of it (each pixel two triangles). The depth inside the material depends on the color gradient of the bitmap. The algorithm subdivide the texture in singles optical working areas and inside these areas the scanning heads deflect the laser beam and remove the material layer by layer as in milling
The influence of plasma plume in laser milling for mold manufacturing
Full text linkThe paper refers to the modeling of the plasma plume influence on the shape of the crater obtained by means of nanosecond pulsed laser milling. A transient model of the physical state of the plasma plume is developed according to the laser parameters. Two empirical coefficients are proposed in the model in order to evaluate the plasma plume self-emission energy lost towards the environment and the energy spread from the plasma towards the target surface. These two coefficients, directly correlated to the depth and to the width of the crater, can be experimentally determined, due to the difficulty of their analytical quantification, and they can be used for tuning a complete plasma plume software package for laser milling simulation named LAS (Laser Ablation Simulator) already developed by the authors. In this paper their influence on the crater shape will be proved by means of several simulation runs
Process Planning in Laser Milling
No full textThe present work defines a strategy to perform an automatic setup procedure for a laser milling manufacturing process. The manufacturing system is constituted by a milling CNC machine structure coupled with a DPSS Nd:YAG Laser source. This work shows the criteria developed to evaluate the influence of process parameters on material removal rate when processing mild steels and aluminium alloys. The method, based on a statistical approach, was performed by experiments executed using DOE techniques and developing a regression model validated by a ANOVA Analysis. It can be easily applied to other materials and it represents an useful tool to asses the right process parameters in roughing and in finishing operations. A basic manual approach is presented and the automatic procedure developed is in detail explained. The implemented Software System automatically generates a part program to laser milling a set of pockets, using different laser parameters, then permit to scan them by an optical sensor and to calculate the empirical coefficients to use in the regression model that provide the material removal rate
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