Peripheral Milling Of Thin-walled Workpiece Research Articles

Chatter prediction for the peripheral milling of thin-walled workpieces with curved surfaces

Workpiece dynamics is the dominant factor which should be taken into consideration in chatter prediction of peripheral milling of thin-walled workpieces. Usually, material removal, tool position and varying dynamic displacements of the workpiece along the tool axis influence the workpiece dynamics. However, these three aspects were not considered simultaneously in the existing researches.This paper comprehensively investigates the effect of varying workpiece dynamics on the stability in peripheral milling of thin-walled workpieces with curved surfaces. A new dynamic model of tool and workpiece system is proposed to consider the dynamic behavior of tool and workpiece as well as the influences of engagement and tool feed direction. Interaction between tool and thin-walled workpiece is modeled at discrete nodes along the axial depth of cut. An efficient method based on structural dynamic modification scheme is developed to characterize the effect of material removal upon the in-process workpiece dynamics. This is done by only performing modal analysis on the FEM model of initial workpiece, while mode shapes and natural frequencies of the in-process workpiece can be calculated without re-building and re-meshing the instant FEM model at each tool position.The proposed model and method are verified by the milling process of two thin-walled workpieces concerning a plate and a workpiece with curved surface. Comparisons of numerical and experimental results show that chatter can be accurately predicted for the peripheral milling of thin-walled workpieces.

Study on Virtual Machining Process of Peripheral Milling of Thin-Walled Workpiece

Thin-walled workpiece is easy to deform in machining. In order to predict the dimensional error of machined surface of thin-walled workpiece, computer simulation technology is studied, which is called virtual machining process. For the simulation of workpiece deformation, much numerical analysis should be done. Research indicates using FEA (Finite Element Analysis) in each step of simulation process needs too much time to meet the requirements of industrial application. Therefore it is important to decrease the simulation time. In this paper, a new method is proposed to realize rapid analysis of workpiece deflection in virtual machining process, which combines rapid analytical solution method with a few times of accurate FEA, thus greatly decreases the time required for whole simulation. For the simulation, several peripheral milling process models are presented with increasing order of sophistication and accuracy, which can be applied to simulate cutting process with the effect of workpiece deformation caused by cutting force. In the final section, the comparison between simulation results and experiments shows the proposed methods and models can closely predict dimensional error and texture of machined surface of flexible workpiece.

Systematic Simulation Method for the Calculation of Maximum Deflections in Peripheral Milling of Thin-Walled Workpieces with Flexible Iterative Algorithms

Due to the deflection of tool and workpiece induced by cutting force, there is a high complexity associated with the prediction of surface form errors in the peripheral milling process of thin-walled workpieces. And the prediction of surface form errors induced by cutting deflection is the precondition for process optimization and error compensation. This paper proposes a systematic simulation procedure suitable for surface form errors prediction in peripheral milling of low rigid thin-walled workpiece. Some key algorithms with the judgment of contacts between the cutter and the workpiece, the flexible iterative algorithm as well as the tool/workpieces deflection prediction using FE model are developed and presented in detail. Comparisons of the form errors and cutting forces obtained numerically and experimentally confirm the validity of the proposed algorithms and simulation procedure.

Two efficient iterative algorithms for error prediction in peripheral milling of thin-walled workpieces considering the in-cutting chip

Due to the deflection of tool and workpiece induced by cutting force, there is a high complexity associated with the prediction of surface form errors in peripheral milling of thin-walled workpieces. Based on the systematic study of in-cutting chip, this paper proposes a new efficient iterative algorithm named flexible iterative algorithm (FIAL)， which is suitable for surface form errors prediction in peripheral milling of low rigid thin-walled workpiece. In FIAL, an iterative scheme for calculations of tool/workpiece (TW) deflections are developed by considering the former convergence cutting position, and in the scheme a new important variable Δ is proposed for the calculation of radial cutting depth which never been considered before. Based on FIAL and the analytical study of in-cutting chip, a double iterative algorithm (DIAL) is brought forwarded to calculate the positions and magnitude of the maximum surface form errors, which always take the peak point include in each iterative step. Comparisons of the form errors and cutting forces obtained numerically and experimentally confirm the validity of the proposed algorithms and simulation procedure. The experimental and analytical results have shown that FIAL is faster in the iteration convergent speed and more accurate than the rigid iterative algorithm in surface form errors prediction, and DIAL is proved to be valid in the maximum errors prediction.

The Flexible Iterative Algorithm for Calculations of Static Form Errors in Peripheral Milling Thin-Walled Components

This paper proposes a new efficient iterative algorithm which named flexible iterative algorithm (FIAL) with a general approach suitable for surface form errors prediction in peripheral milling of thin-walled workpiece. First, a FEA-Based model is presented to analyze the surface dimensional errors in peripheral milling of thin-walled workpieces. Then the FIAL is discussed in detail for the procedure of deformation prediction. From FIAL, an iterative scheme for the calculations of tool/workpiece deflections considering the former convergence cutting position are developed，in the scheme a small variable must be included in the calculation of radial cutting depth which never been considered in the literatures before.The proposed approach is validated and proved to be efficient through comparing the obtained numerical results with the test results.

Strategies for error prediction and error control in peripheral milling of thin-walled workpiece

This paper aims at developing efficient strategies for controlling the force-induced surface dimensional errors in peripheral milling of thin-walled structures. Emphasis is put on how to select the feed per tooth and depth of cut simultaneously for tolerance specification and maximization of the feed per tooth simultaneously. Three methods are presented. The first one proceeds by optimally selecting the maximum feed per tooth without tolerance violation. The second one is to find the appropriate cutting parameters by solving a linear programming problem. To show the efficiency of the first two methods, the third one, i.e. the so-called mirror error compensation method taken from references, is also addressed for comparison. Mechanistic model for cutting force estimation, cantilever beam model for cutter deflection estimation and finite element method for workpiece deflection estimation are used in all three methods. Besides, improvements on the calculation scheme of the surface dimensional error have been made and both numerical and experimental results are adopted for verification.

Efficient Algorithms for Calculations of the Maximum Surface Form Errors in Peripheral Milling

An efficient flexible iterative algorithm with a general approach is presented for calculations of surface form errors in peripheral milling of thin-walled workpiece. An efficient finite-element model for tool/workpiece is presented to analyze the surface dimensional errors in peripheral milling of aerospace thin-walled workpieces. The efficient flexible iterative algorithm is proposed to calculate the deflections and the maximum surface form errors as contrasted with the rigid iterative algorithm used in the literatures. Meanwhile, some key techniques such as the finite-element modeling of the tool-workpiece system; the determinant algorithm to judge instantaneous immersion boundaries between a cutter element and the workpiece; iterative scheme for the calculations of tool-workpiece deflections considering the former convergence cutting position are developed and the method for calculating the position and magnitude of the maximum surface form errors are developed and presented in detail. The proposed approach is validated and proved to be efficient through comparing the obtained numerical results with the test results.

Efficient algorithms for calculations of static form errors in peripheral milling

This paper aims at developing numerical algorithms to predict the form errors in peripheral milling of thin-walled workpieces using finite element method. Some crucial algorithms associated with the judgment of contacts between the cutter and the workpiece, iterative corrections of radial and axial cutting depths as well as the workpiece's rigidity without remeshing are developed and presented in detail. By means of numerical tests, it is shown that the proposed approach is efficient and flexible. 3D irregular volume elements such as tetrahedral elements, prismatic elements, hexahedral elements or a combination of them can be freely used to predict form errors of machining workpieces.

Optimal fixture design in peripheral milling of thin-walled workpiece

In order to optimize the positions of the locators in peripheral milling of a thin-walled workpiece, a finite element model along with an accurate cutting forces model is proposed in this paper. The finite element model takes into account the thickness variations of the workpiece in peripheral milling. The locators on the secondary locating surface directly influence the surface errors in peripheral milling of thin-walled workpiece, so this paper deals with the optimization of the positions of the locators on the secondary locating surface. A method including two steps is presented. In the first step, the initial positions of the locators are determined by adding the locators at the position with the maximum deformation. In the second step, a heuristic algorithm is proposed to optimize the positions of the locators. Finally, a simulation example is used to illustrate the method.

Numerical Prediction of Static Form Errors in Peripheral Milling of Thin-Walled Workpieces With Irregular Meshes

The finite element formulation is studied in this paper to predict static form errors in the peripheral milling of complex thin-walled workpieces. Key issues such as cutter modeling, finite element discretization of cutting forces, tool–workpiece coupling and variation of the workpiece’s rigidity in milling are investigated. To be able to predict static form errors on the machined surface of complex form, considerable improvements are made on the proper modeling of the material removal in milling and the iterative calculations of tool-workpiece deflections. A general simulation approach is developed based on 3D irregular finite element meshes. By using illustrative examples, rigid and flexible models are compared with existing ones to show the validity of the approach.

Finite-element modeling of static surface errors in the peripheral milling of thin-walled workpieces

The present study develops a finite-element model along with an adequate end milling cutting-force model to analyze the surface dimensional errors in the peripheral milling of thin-walled workpieces. The helical fluted end mill is modeled with the pre-twisted Timoshenko beam element that can more accurately simulate the specific geometry and structural behavior of the cutter. The workpiece is modeled with a 3D isoparametric 12-node element that can take into account the geometry and thickness variations of the workpiece during peripheral milling. This study neglects the dynamic effect during milling and assumes that the tool and the workpiece deform to their static equilibrium positions at any milling instant. For a flexible cutting system, the effect of cutting system deflections on the cutting force distribution must be included. Hence the cutting force distribution and the cutting system deflections are solved iteratively by the modified Newton–Raphson method in this study. After the converged cutting system deflections are obtained at each cutting step, the surface dimensional error of the workpiece at the corresponding grid point can be computed easily. From the present study it is found that there will exist serious surface dimensional errors in the peripheral milling of very flexible components even the metal removal rate is very small. The present simulation model is verified experimentally and is helpful in determining the cutting parameters without performing real cutting experiments.