Force Model For Machining Research Articles

A MODEL-BASED ANALYSIS OF ORTHOGONAL CUTTING FOR SINGLE-CRYSTAL FCC METALS INCLUDING CRYSTALLOGRAPHIC ANISOTROPY

The anisotropy of workpiece crystals becomes prominent as the uncut chip thickness approaches to the grain size of the workpiece material. As such, in mechanical micromachining, precision machining, and diamond turning operations, the cutting forces exhibit significant variations with crystallographic orientations. In this work, a crystal-plasticity based model is used to analyze the effects of cutting geometry, friction and crystallographic anisotropy when machining face-centered cubic (fcc) single-crystals using ideally sharp cutting edges. The model adapts and combines Bishop and Hill's crystal plasticity theory with Merchant's machining force model. The total power, including the shearing and friction powers, is minimized over allowable shear angles to determine the shear angle solution and associated specific energies. The model is validated using data from the literature for both aluminum and copper single crystals; a good match is observed between the model predictions and experimental data, indicating the model's capability to capture crystallographic anisotropy and symmetry. The validated model is used to analyze the effects of rake angle, friction, and crystallographic orientation on specific energies and shear angles. Subsequently, a further simplification to the model is proposed through the use of Merchant's shear-angle formula.

Haptic modeling as an integrating tool for product development

This paper presents an integrated system structure for product development. Haptic modeling, due to its growing applications to different aspects of product development, is envisioned as the core technology for the proposed product development system structure. Because of the fact that haptic modeling is developed based on physical laws, it is anticipated as the natural link between the virtual world and practical applications. Since haptic shape modeling is based on material properties and related shaping methods that require high update frequency, this paper also proposes an effective spatial run-length encoding (S-RLE) algorithm for 3D representations of both object shapes and shaping tools. Force measurements from a robot machining system are used to determine the coefficients of a simple machining force model.

An Enhanced Force Model for Sculptured Surface Machining

The ball-end milling process is used extensively in machining of sculpture surfaces in automotive, die/mold, and aerospace industries. In planning machining operations, the process planner has to be conservative when selecting machining conditions with respect to metal removal rate in order to avoid cutter chipping and breakage, or over-cut due to excessive cutter deflection. These problems are particularly important for machining of sculptured surfaces where axial and radial depths of cut are abruptly changing. This article presents a mathematical model that is developed to predict the cutting forces during ball-end milling of sculpture surfaces. The model has the ability to calculate the workpiece/cutter intersection domain automatically for a given cutter path, cutter, and workpiece geometries. In addition to predicting the cutting forces, the model determines the surface topography that can be visualized in solid form. Extensive experiments are performed to validate the theoretical model with measured forces. For complex part geometries, the mathematical model predictions were compared with experimental measurements.

Cutting Force Model for Contour Surface Machining of Gear Indexing Cam with Flat End Milling

This paper presents a model to predict the cutting forces for flat end milling as machining gear indexing cam. Rotation feeding makes axial depth of cut and uncut chip thickness change during cutting process. The development of the model is based on the analysis of cutting edge expression. According to the existing the relationship of the local cutting force and chip load and assuming the cutter to be divided into a number of differential elements in the axial direction of the cutter, the model is derived by summarising the cutting forces produced by each differential cutter disc engaged in the cut. The equation for calculating uncut chip thickness of differential disc is educed. In order to avoid the complex computing for axial depth of cut of the entire edge, a unit square window function and its criterion are introduced to estimate whether a segment of edge is in engaging range.

An Enhanced Force Model for Sculptured Surface Machining

Abstract The ball-end milling process is used extensively in machining of sculpture surfaces in automotive, die/mold, and aerospace industries. In planning machining operations, the process planner has to be conservative when selecting machining conditions with respect to metal removal rate in order to avoid cutter chipping and breakage, or over-cut due to excessive cutter deflection. These problems are particularly important for machining of sculptured surfaces where axial and radial depths of cut are abruptly changing. This article presents a mathematical model that is developed to predict the cutting forces during ball-end milling of sculpture surfaces. The model has the ability to calculate the workpiece/cutter intersection domain automatically for a given cutter path, cutter, and workpiece geometries. In addition to predicting the cutting forces, the model determines the surface topography that can be visualized in solid form. Extensive experiments are performed to validate the theoretical model with measured forces. For complex part geometries, the mathematical model predictions were compared with experimental measurements.

Flute engagement in peripheral milling

Researchers have typically used a flexible model in an attempt to accurately simulate peripheral milling forces. The approach generally described in the literature divides the model into manageable pieces by modeling a cutter as several disk-like elements in its axial direction and by dividing the turning cutter into several angular increments. When the forces calculated at each differential element are integrated, it is important to consider the angle (δ λ) measured back as the flute engagement wraps up the helix. Therefore, flute engagement is very influential in determining the milling force profile and magnitude, and thus the effects of engaged flute length in the milling operation is of interest. In this paper, the concept of flute engagement is presented, and the equations calculating the engaged flute length (FL e) are derived. In addition, a method for determining the number of engaged flutes caused by the radial and axial depths of cut is presented. It is felt that the results of this research may provide the basis for a machining force model.

A New Model and Analysis of Orthogonal Machining With an Edge-Radiused Tool

A new machining process model that explicitly includes the effects of the edge hone is presented. A force balance is conducted on the lower boundary of the deformation zone leading to a machining force model. The machining force components are an explicit function of the edge radius and shear angle. An increase in edge radius leads to not only increased ploughing forces but also an increase in the chip formation forces due to an average rake angle effect. Previous attempts at assessing the ploughing components as the force intercept at zero uncut chip thickness, which attribute to the ploughing mechanism all the changes in forces that occur with changes in edge radius, are seen to be erroneous in view of this model. Calculation of shear stress on the lower boundary of the deformation zone using the new machining force model indicates that the apparent size effect when cutting with edge radiused tools is due to deformation below the tool (ploughing) and a larger chip formation component due to a lower shear angle. Increases in specific energy and shear stress are also due to shear strain and strain rate increases. A consistent material behavior model that does not vary with process input conditions like uncut chip thickness, rake angle and edge radius can be developed based on the new model. [S1087-1357(00)01302-2]

Modeling of Ball-End Milling Forces With Cutter Axis Inclination

In the machining of sculpture surfaces with ball-end mill, the cutter axis or workpiece is often inclined to generate an admissible orientation. This paper primarily presents an enhanced cutting force model for ball-end milling with cutter axis inclination. It involves the kinematic reasoning of cutting edge geometry, local helix angle and average chip thickness followed by the analysis of effects of axis inclination in the contact zone between cutter and workpiece. Thereupon, development of the analytical force model for inclined-axis machining is achieved using cutter angle domain convolution method. Experimental evaluation of the model is discussed, and experimental results and model predictions under various cutting conditions are compared in the frequency as well as in the angular domain. [S1087-1357(00)70601-0]

A Dual-Mechanism Approach to the Prediction of Machining Forces, Part 2: Calibration and Validation

The Dual-Mechanism Machining Force Model (DMMFM) developed in Part 1 of this paper is calibrated through a specially developed algorithm, then validated. The calibration results are used to study the total machining force predictive capabilities of both the traditional lumped shearing model and the DMMFM. It is shown that the Dual-Mechanism Approach contributes greatly to our ability to both physically explain the trends in the machining force data and to understand their implications. This is achieved through an interpretation of the individual rake face and clearance face forces that are predicted using the DMMFM. The interpretation is based on the relations of these rake face and clearance face forces to the process inputs resulting from their effects on the DMMFM coefficients through thermal energy generation and temperature, shear-strain level and shear-strain rate. Some implications of the knowledge of the individual rake face and clearance face forces, as predicted by the DMMFM, are also discussed.