Analytical and Thermal Modeling of High-Speed Machining With Chamfered Tools

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
Yiğit Karpat ◽  
Tuğrul Özel
Keyword(s):  
Heat Generation ◽  
High Speed ◽  
Thermal Modeling ◽  
Orthogonal Cutting ◽  
Cutting Conditions ◽  
Tool Geometry ◽  
High Speed Machining ◽  
Temperature Distributions ◽  
Dead Metal Zone ◽  
Chamfered Tools

High-speed machining offers several advantages such as increased flexibility and productivity for discrete-part manufacturing. However, excessive heat generation and resulting high temperatures on the tool and workpiece surfaces in high-speed machining leads to a shorter tool life and poor part quality, especially if the tool edge geometry and cutting conditions were not selected properly. In this study, analytical and thermal modeling of high-speed machining with chamfered tools in the presence of dead metal zone has been presented to investigate the effects of cutting conditions, heat generation, and resultant temperature distributions at the tool and in the workpiece. An analytical slip-line field model is utilized to investigate the process mechanics and friction at the tool-chip and tool-workpiece interfaces in the presence of the dead metal zone in machining with a negative rake chamfered polycrystalline cubic boron nitride tool. In order to identify friction conditions, a set of orthogonal cutting tests is performed on AISI 4340 steel and chip geometries and cutting forces are measured. Thermal modeling of machining with chamfered tools based on moving band heat source theory, which utilizes the identified friction conditions and stress distributions on the tool-chip and tool-workpiece interfaces, is also formulated and temperature distributions at the tool, cutting zone, and in the workpiece are obtained. These temperature distributions are compared with the results obtained from finite element simulations. The comparison of temperature fields indicates that the proposed model provides reasonable solutions to understand the mechanics of machining with chamfered tools. Models presented here can be further utilized to optimize the tool geometry and cutting conditions for increasing benefits that high-speed machining offers.

scholarly journals Mechanics of Machining With Chamfered Tools

1999 ◽  
Vol 122 (4) ◽  
pp. 650-659 ◽  
Author(s):  
H. Ren ◽  
Y. Altintas
Keyword(s):  
Strain Rate ◽  
Cutting Forces ◽  
High Speed ◽  
Orthogonal Cutting ◽  
Minimum Energy ◽  
Cutting Tools ◽  
Cutting Speed ◽  
Cutting Conditions ◽  
Tool Geometry ◽  
Analytic Model

Chamfered cutting tools are used in high speed machining of hardened steels due to their wedge strength. An analytic model is proposed to investigate the influence of chamfer angle and cutting conditions on the cutting forces and temperature. The model is based on the tool geometry, cutting conditions, steady state temperature in the shear and chip-rake face contact zones, strain, strain rate, and the corresponding flow stress of the work material. With the aid of a slip line field model, the cutting and friction energy in the primary, secondary and chamfer zones are evaluated. By applying the minimum energy principle to total energy, the shear angle in the primary deformation zone is estimated. The corresponding shear strain, strain rate and flow stresses are identified. The model leads to the prediction of cutting forces and temperature produced in three deformation zones. The model is experimentally verified by high-speed orthogonal cutting tests applied to P20 mold steel using ISO S10 carbide and CBN cutting tools. It is shown that the analytic model is quite useful in selecting optimal chamfer angle and cutting speed which gives the minimum tool wear and relatively lower cutting forces. [S1087-1357(00)00204-5]

Evaluation and Improvement of Productivity in High-Speed NC Machining

1999 ◽  
Vol 122 (3) ◽  
pp. 556-561 ◽  
Author(s):  
X. Yan ◽  
K. Shirase ◽  
M. Hirao ◽  
T. Yasui
Keyword(s):  
High Speed ◽  
Nc Machining ◽  
Cutting Conditions ◽  
High Speed Machining ◽  
Machining Time ◽  
Time Constants ◽  
Nc Program ◽  
Kinematic Factor ◽  
Two Factors

The productivity of machining centers is influenced inherently by the quality of NC programs. To evaluate productivity, first an effective feedrate factor and a productivity evaluation factor are proposed. It has been found that in high-speed machining, these two factors depend on a kinematic factor which is a function of (1) command feedrate, (2) average per-block travel of the tool, (3) moving vectorial variation of the tool, and (4) ac/deceleration or time constants. Then an NC program simulator has been developed to evaluate productivity. With the simulator, the machining time can be calculated accurately and the cutting conditions can be extracted. Finally, three NC programs were implemented on high-speed machining centers and analyzed by the simulator. It was found that in mold and die machining, the productivity can be improved by increasing the acceleration and average travel and reducing the vectorial variation of the tool rather than the command feedrate. [S1087-1357(00)01303-4]

A Fracture Mechanics Approach to the Prediction of Tool Wear in Dry High Speed Machining of Aluminum Cast Alloys: Part 2 — Model Calibration and Verification

Tribology ◽  
2005 ◽  
Author(s):  
Alexander Bardetsky ◽  
Helmi Attia ◽  
Mohamed Elbestawi
Keyword(s):  
Fracture Mechanics ◽  
Tool Wear ◽  
Model Calibration ◽  
High Speed ◽  
Cutting Conditions ◽  
Depth Of Cut ◽  
High Speed Machining ◽  
Wear Model ◽  
Wide Range ◽  
Cast Alloys

Experimental study has been carried out to establish the effect of cutting conditions (speed, feed, and depth of cut) on the cutting forces and time variation of carbide tool wear data in high-speed machining (face milling) of Al-Si cast alloys that are commonly used in the automotive industry. The experimental setup and force measurement system are described. The test results are used to calibrate and validate the fracture mechanics-based tool wear model developed in Part 1 of this work. The model calibration is conducted for two combinations of cutting speed and a feed rate, which represent a lower and upper limit of the range of cutting conditions. The calibrated model is then validated for a wide range of cutting conditions. This validation is performed by comparing the experimental tool wear data with the tool wear predicted by calibrated cutting tool wear model. The prediction errors were found to be less then 7%, demonstrating the accuracy of the object oriented finite element (OOFE) modeling of the crack propagation process in the cobalt binder. It also demonstrates its capability in capturing the physics of the wear process. This is attributed to the fact that the OOF model incorporates the real microstructure of the tool material.

FEM Simulation of the Residual Stress in the Machined Surface Layer for High-Speed Machining

2006 ◽  
Vol 315-316 ◽  
pp. 140-144 ◽  
Author(s):  
Su Yu Wang ◽  
Xing Ai ◽  
Jun Zhao ◽  
Z.J. Lv
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Surface Layer ◽  
Residual Stresses ◽  
High Speed ◽  
Metal Cutting ◽  
Orthogonal Cutting ◽  
High Speed Machining ◽  
Machined Surface ◽  
Cutting Model

An orthogonal cutting model was presented to simulate high-speed machining (HSM) process based on metal cutting theory and finite element method (FEM). The residual stresses in the machined surface layer were obtained with various cutting speeds using finite element simulation. The variations of residual stresses in the cutting direction and beneath the workpiece surface were studied. It is shown that the thermal load produced at higher cutting speed is the primary factor affecting the residual stress in the machined surface layer.

The Hammer QSD-Quick Stop Device for High Speed Machining and Rubbing

1981 ◽  
Vol 103 (1) ◽  
pp. 13-21 ◽  
Author(s):  
J. T. Black ◽  
C. R. James
Keyword(s):  
Plastic Deformation ◽  
High Speed ◽  
Cutting Conditions ◽  
High Speed Machining ◽  
Machined Surface ◽  
Orthogonal Machining

A quick stop device (QSD) was designed for use in orthogonal machining and rubbing experiments. QSD’s are used to obtain chip root samples that are representative of the deformation taking place during dynamic (actual) cutting conditions. These “frozen” specimens are helpful in examining the plastic deformation that occurs in the regions of compression and shear which form the chip; the secondary shear at the tool-chip interface; and the nose ploughing/flank rubbing action which operates on the newly machined surface. The Hammer QSD employs a shear pin mechanism, broken by a flying hammer, which is traveling at the same velocity as the workpiece. The device has been successfully tested up to 6000 sfpm (30.48 m/sec).

Surface Integrity of Die Material in High Speed Hard Machining, Part 1: Micrographical Analysis

1999 ◽  
Vol 122 (4) ◽  
pp. 620-631 ◽  
Author(s):  
T. I. El-Wardany ◽  
H. A. Kishawy ◽  
M. A. Elbestawi
Keyword(s):  
Tool Wear ◽  
Residual Stresses ◽  
Tool Steel ◽  
Surface Integrity ◽  
High Speed ◽  
Cutting Conditions ◽  
Metallographic Analysis ◽  
Tool Geometry ◽  
Machined Surface ◽  
Geometrical Defects

The effects of cutting conditions and tool wear on chip morphology and surface integrity during high speed machining of D2 tool steel (60–62 Hrc) are investigated experimentally and analytically in this paper. Polycrystalline Cubic Boron Nitride (PCBN) tools are used in this investigation. The chips and the subsurface of the workpiece are examined using optical and scanning electron microscopy. Microhardness measurements are performed on the surface and subsurface of the workpiece. The X-ray diffraction technique is used to measure the residual stresses induced in the machined surface. The paper is divided into two parts. Part 1 presents the results obtained from the micrographical analysis of the chips and the surfaces produced. Part 2 deals with microhardness and residual stresses of the machined surface. The micrographical analysis of the chips produced shows that different mechanisms of chip formation exist depending on the magnitude of the cutting pressure and tool wear. Saw toothed chips are produced during the machining of D2 tool steel if the cutting pressure exceeds approximately 4000 MPa. The metallographic analysis of the surface produced illustrates the damaged surface region that contains geometrical defects and changes in the subsurface metallurgical structure. The types of surface damage are dependent on the cutting conditions, tool geometry and the magnitude of the wear lands. [S1087-1357(00)00104-0]

Predictive Analytical and Thermal Modeling of Orthogonal Cutting Process—Part I: Predictions of Tool Forces, Stresses, and Temperature Distributions

2005 ◽  
Vol 128 (2) ◽  
pp. 435-444 ◽  
Author(s):  
Yiğit Karpat ◽  
Tuğrul Özel
Keyword(s):  
Shear Zone ◽  
Thermal Modeling ◽  
Orthogonal Cutting ◽  
Cutting Process ◽  
Field Analysis ◽  
Normal Stress Distribution ◽  
Modeling Approach ◽  
Temperature Distributions ◽  
Secondary Shear Zone ◽  
1045 Steel

In this paper, a predictive thermal and analytical modeling approach for orthogonal cutting process is introduced to conveniently calculate forces, stress, and temperature distributions. The modeling approach is based on the work material constitutive model, which depends on strain, strain rate, and temperature. In thermal modeling, oblique moving band heat source theory is utilized and analytically combined with modified Oxley’s parallel shear zone theory. Normal stress distribution on the tool rake face is modeled as nonuniform with a power-law relationship. Hence, nonuniform heat intensity at the tool-chip interface is obtained from the predicted stress distributions utilizing slip line field analysis of the modified secondary shear zone. Heat sources from shearing in the primary zone and friction at the tool-chip interface are combined, heat partition ratios are determined for temperature equilibrium to obtain temperature distributions depending on cutting conditions. Model validation is performed by comparing some experimental results with the predictions for machining of AISI 1045 steel, AL 6082-T6, and AL 6061-T6 aluminum. Close agreements with the experiments are observed. A set of detailed, analytically computed stress and temperature distributions is presented.

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