Optimal Process Planning for Laser Forming of Doubly Curved Shapes

2004 ◽  
Vol 126 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Chao Liu ◽  
Y. Lawrence Yao ◽  
Vijay Srinivasan
Keyword(s):  
Process Planning ◽  
Laser Scanning ◽  
Industrial Applications ◽  
Laser Forming ◽  
Field Calculation ◽  
Heating Condition ◽  
Scanning Velocity ◽  
Optimal Approach ◽  
Doubly Curved ◽  
Practical Constraints

There has been a considerable amount of work carried out on two-dimensional laser forming. In order to advance the process further for industrial applications, however, it is necessary to consider more general cases and especially their process planning aspect. This paper presents an optimal approach to laser scanning paths and heating condition determination for laser forming of doubly curved shapes. Important features of the approach include the strain field calculation based on principal curvature formulation and minimal strain optimization, and scanning paths and heating condition (laser power and scanning velocity) determination by combining analytical and practical constraints. The overall methodology is presented first, followed by more detailed descriptions of each step of the approach. Two distinctive types of doubly curved shape, pillow and saddle shapes are focused on and the effectiveness of the proposed approach is validated by forming experiments.

Experimental and 3D Finite Element Studies of CW Laser Forming of Thin Stainless Steel Sheets

2000 ◽  
Vol 123 (1) ◽  
pp. 66-73 ◽  
Author(s):  
Guofei Chen ◽  
Xianfan Xu
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Laser Scanning ◽  
Continuous Wave ◽  
Laser Forming ◽  
Beam Diameter ◽  
Element Analysis ◽  
Scanning Velocity ◽  
3D Finite Element ◽  
Steel Sheets

Laser forming as a springback-free and noncontact forming technique has been under active investigation over the last decade. Previous investigations are mainly focused on forming of large and thick workpieces using high power lasers, with less work on precision, micro-scale bending of small and thin sheets. In this work, a 4 W continuous wave argon ion laser is used as the energy source, and the laser beam is focused to a beam diameter of tens of micrometers to induce bending of thin stainless steel sheets. When the laser scanning velocity is above 8 mm/s, bending can be explained by the temperature gradient mechanism, while decreasing the scanning velocity leads to the buckling mechanism of bending. The bending angle is measured at various processing conditions. A fully 3D finite element analysis is performed to simulate the thermo-elasto-plastic deformation process during laser forming. Experimental measurements and computational results agree in trend, and reasons for the deviation are discussed.

Process Design of Laser Forming for Three-Dimensional Thin Plates

2004 ◽  
Vol 126 (2) ◽  
pp. 217-225 ◽  
Author(s):  
Jin Cheng ◽  
Y. Lawrence Yao
Keyword(s):  
Process Design ◽  
Laser Scanning ◽  
Three Dimensional ◽  
Thin Plates ◽  
Laser Forming ◽  
Heat Condition ◽  
Bending Strain ◽  
Doubly Curved ◽  
Made In

Extensive efforts have been made in analyzing and predicting laser forming processes of sheet metal. Process design, on the other hand, is concerned with determination of laser scanning paths and laser heat condition given a desired shape. This paper presents an approach for process design of laser forming of thin plates with doubly curved shapes. The important feature of this method is that it first calculates the strain field required to form the shape. Scanning paths are decided based on the concept of in-plane strain, bending strain, principal minimal strain and temperature gradient mechanism of laser forming. Heating condition is determined by a lumped method. Effectiveness of the approach is numerically and experimentally validated through two different doubly curved shapes.

The Effect of Nonconventional Laser Beam Geometries on Stress Distribution and Distortions in Laser Bending of Tubes

2006 ◽  
Vol 129 (3) ◽  
pp. 592-600 ◽  
Author(s):  
Shakeel Safdar ◽  
Lin Li ◽  
M. A. Sheikh ◽  
Zhu Liu
Keyword(s):  
Laser Beam ◽  
Laser Scanning ◽  
Thermal Stresses ◽  
Laser Forming ◽  
Beam Diameter ◽  
Hydraulic Systems ◽  
Tube Bending ◽  
Laser Bending ◽  
Scanning Velocity ◽  
Laser Tube

Laser forming is a spring-back-free noncontact forming method that has received considerable attention in recent years. Compared to mechanical bending, no hard tooling, dies, or external force is used. Within laser forming, tube bending is an important industrial activity with applications in critical engineering systems such as heat exchangers, hydraulic systems, boilers, etc. Laser tube bending utilizes the thermal stresses generated during laser scanning to achieve the desired bends. The parameters varied to control the process are usually laser power, beam diameter, scanning velocity, and the number of scans. The thermal stresses generated during laser scanning are strongly dependent upon laser beam geometry. The existing laser bending methods use either circular or rectangular beams. These beam geometries sometimes lead to undesirable effects such as buckling and distortion in tube bending. This paper investigates the effects for various laser beam geometries on laser tube bending. Finite element modeling has been used for the study of the process with some results also validated by experiments.

Experimental Investigation on 3D Laser Forming of Metal Sheet

2004 ◽  
Vol 471-472 ◽  
pp. 568-572 ◽  
Author(s):  
Li Jun Yang ◽  
Yang Wang ◽  
M. Djendel ◽  
L.T. Qi
Keyword(s):  
Laser Scanning ◽  
Laser Energy ◽  
Processing Parameters ◽  
Experimental Results ◽  
Laser Source ◽  
Laser Forming ◽  
Scanning Strategy ◽  
Temporal And Spatial Distribution ◽  
Scanning Velocity ◽  
Scanning Strategies

In this article, the relations between the formed shapes and process parameters had been studied for 3D laser forming of sheet metals. The investigation was performed on Stainless 1Cr18Ni9Ti sheet using a Nd:YAG laser source. The scanning strategies were being investigated to potentially achieve a more uniform temporal and spatial distribution of the laser energy, possibly leading to reduced part distortion, by scanning the beam across the sheet surface with both continuous and segmented irradiation geometries. The experimental results revealed that the cross spider scanning strategy could form square and circle sheets into spherical domes. And the radial lines scanning strategy could form rectangle sheets into saddle shapes. It was also apparent from the experimental results that the height of the center of the formed sheet increased with the increasing of the laser power and scanning numbers. The height of the formed square sheet firstly decreased with the laser scanning velocity increasing and began to decrease at a certain processing parameters by cross spider strategy, in which the circle sheet was opposite with the square sheet, and in which the rectangle sheet decreased with speed increasing.

Near Optimal Approach to General Manufacturing Feature Extraction

1995 ◽  
Author(s):  
Jian (John) Dong ◽  
Sreedharan Vijayan
Keyword(s):  
Feature Extraction ◽  
Process Planning ◽  
Planning System ◽  
Manufacturing Cost ◽  
Design Data ◽  
Feature Extraction Method ◽  
Automatic Feature Extraction ◽  
Starting Point ◽  
Planning Function ◽  
Optimal Approach

Abstract Computers are being used increasingly in the process planning function. The starting point of this function involves interpreting design data from a CAD model of the designed component Feature-based technology is becoming an important tool for this. Automatic recognition of features and extraction of feature information from CAD data can be used to drive a process planning system. In this paper a new approach to automatic feature extraction called the Blank-Surface Concave-edge (BS-CE) approach is illustrated. This approach attempts to remove as much of the blank material with a given machine setup as possible. Hence intuitively one can say that the manufacturing cost of material removal may be minimized if this technique is employed. This feature extraction method is explained along with examples of its implementation. An analysis of alternate feature extraction results is performed and the cost of manufacture is compared to demonstrate the near optimal performance of this technique.

Towards Combining Digitization Techniques in the Generation of Reverse Engineering Data Sets

1999 ◽  
Author(s):  
C. J. Rolls ◽  
W. ElMaraghy ◽  
H. ElMaraghy
Keyword(s):  
Reverse Engineering ◽  
Computer Aided Design ◽  
Laser Scanning ◽  
Single Point ◽  
Laser Scanner ◽  
Coordinate Measuring Machine ◽  
Industrial Applications ◽  
Data Sets ◽  
Error Characterization ◽  
Measuring Machine

Abstract Reverse engineering (RE), may be defined as the process of generating computer aided design models (CAD) from existing or prototype parts. The process has been used for many years in industry. It has markedly increased in implementation in the past few years, primarily due to the introduction of rapid part digitization technologies. Current industrial applications include CAD model construction from artisan geometry, such as in automotive body styling, the generation of custom fits to human surfaces, and quality control. This paper summarizes the principles of operation behind many commercially available part digitization technologies, and discusses techniques involved in part digitization using a coordinate measuring machine (CMM) and laser scanner. An overall error characterization of the laser scanning digitization process is presented for a particular scanner. This is followed by a discussion of the merits and considerations involved in generating combined data sets with characteristics indicative of the design intent of specific part features. Issues in facilitating the assembly, or registration, of the different types of data into a single point set are discussed.

Mechanical and Electrical Properties of Micro-Lines Fabricated by Laser-Assisted Maskless Microdeposition

2008 ◽  
Author(s):  
Hamidreza Alemohammad ◽  
Ehsan Toyserkani
Keyword(s):  
Mechanical Properties ◽  
Laser Radiation ◽  
Laser Scanning ◽  
Processing Parameters ◽  
Electrical Performance ◽  
Nanoindentation Test ◽  
Layer By Layer ◽  
Direct Write ◽  
Effective Energy ◽  
Scanning Velocity

The present paper is concerned with the analysis of the microstructural properties of silver micro-lines produced by Laser-Assisted Maskless Microdeposition (LAMM). LAMM is a laser based direct write method used in microscale layered manufacturing. In LAMM, liquid-suspended nanoparticles of a variety of materials are deposited in a layer-by-layer fashion and cured by a laser radiation. In this work, conductive micro-lines of silver with widths of 20 μm are fabricated, and their microstructures as well as electrical and mechanical properties are studied. Investigations show that the microstructures are affected by the laser power and the laser scanning velocity. To find the effect of laser processing parameters on the electrical performance of the samples, the conductivity of the samples are expressed in terms of the effective energy absorbed during laser radiation. It is shown that the conductivity of the sintered samples is increased up to 2 × 105 S.m−1 by raising the effective energy density. In addition, mechanical properties, i.e. modulus of elasticity of one of the fabricated samples are obtained using the nanoindentation test.

Analysis and Prediction of Edge Effects in Laser Bending

2000 ◽  
Vol 123 (1) ◽  
pp. 53-61 ◽  
Author(s):  
Jiangcheng Bao ◽  
Y. Lawrence Yao
Keyword(s):  
Residual Stress ◽  
Edge Effects ◽  
Laser Scanning ◽  
Laser Forming ◽  
Stress Distributions ◽  
Rate Dependency ◽  
Laser Bending ◽  
Numerical Investigations ◽  
Wide Range ◽  
Scanning Path

Laser forming of sheet metal offers the advantages of requiring no hard tooling and thus reduced cost and increased flexibility. It also enables forming of some materials and shapes that are not possible now. In single-axis laser bending of plates, the bending edge is found to be somewhat curved and the bending angle varies along the laser-scanning path. These phenomena are termed edge effects, which adversely affect the accuracy of the bending and result in undue residual stress. Numerical investigations are carried out to study the process transiency and the mechanism of the edge effects. Temperature dependency of material properties and strain-rate dependency of flow stress are considered in the numerical simulation to improve prediction accuracy. Numerical results are validated in experiments. Patterns of edge effects and resultant residual stress distributions are examined under a wide range of conditions. A more complete explanation for the mechanism of the edge effects is given.

Numerical Simulation of Direct Metal Laser Sintering of Single-Component Powder on Top of Sintered Layers

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Bin Xiao ◽  
Yuwen Zhang
Keyword(s):  
Laser Scanning ◽  
Three Dimensional ◽  
Processing Parameters ◽  
Laser Sintering ◽  
Liquid Pool ◽  
Sintering Process ◽  
Direct Metal Laser Sintering ◽  
Three Dimensional Model ◽  
Gaussian Laser Beam ◽  
Scanning Velocity

A three-dimensional model describing melting and resolidification of direct metal laser sintering of loose powders on top of sintered layers with a moving Gaussian laser beam is developed. Natural convection in the liquid pool driven by buoyancy and Marangoni effects is taken into account. A temperature transforming model is employed to model melting and resolidification in the laser sintering process. The continuity, momentum, and energy equations are solved using a finite volume method. The effects of dominant processing parameters including number of the existing sintered layers underneath, laser scanning velocity, and initial porosity on the sintering process are investigated.

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