Milling Force Coefficients Research Articles

ANALYTICAL MODELING OF MICRO END-MILLING FORCES WITH EDGE RADIUS AND MATERIAL STRENGTHENING EFFECTS

The study aims at developing a predictive analytical force model for the micro end-milling operation taking into account the material strengthening as well as the edge radius effects that come into play at the micro level. The mechanistic models for macro end-milling process have been extensively reported in literature and such models predominantly use milling force coefficients which are empirically determined from end-milling experiments. The proposed model for micro end-milling is based on determination of milling force coefficients from fundamental oblique cutting approach. The edge radius effect has been accounted by analyzing the rubbing action similar to the rolling of a cylinder over work surface. Johnson-Cook material model has been modified based on the strain gradient plasticity theory incorporating the increase in material strength with decreasing uncut chip thickness. From the micro orthogonal cutting experiments, a good agreement between the experimental and predicted shear strength values is observed. The force model is validated against measured forces in end-milling experiments carried out on the KERN Evo 5 axis micro machining center. The feed and lateral forces are predicted within 10% deviation on an average.

Research on Feedrate Optimization Based on Cutting Force Model with Double Effect for the Ball-End Milling

A new cutting force model of ball-end mill with double effect is developed through analysing the machining process by using differential geometry. The cutting force model is needed to be revised for the component force in Z direction because of the offset to the actual results. The cutting force and the ball-end milling force coefficients can be given with numerical method. A feedrate optimization strategy is also proposed based on the developed cutting force model and tested effectively.

The Identifications of Milling Force Coefficients and Eccentricity Based on Multi-objective Optimization in Frequency-domain

Based on the assumption of orthogonal cutting,cutter geometry,and the strict model of the cutting load,a model of milling force is developed with the effects of eccentricity of cutter.Through a Fourier transform,the expression of milling force in frequency domain is obtained.By comparing the harmonic component of simulation results with the harmonic component of measurement results,the multi-function of residual harmonics are obtained by using matrix calculation in frequency domain.Then,a method based on multi-objective optimization in frequency domain is improved for the cutting force coefficients and eccentricity of tool identification.Experimental studies are also carried out to verify the accuracy of the cutting force coefficients and eccentricity of tool obtained by the proposed method.Results indicate the error of predicted results obtained by the proposed method is in the range of 2% to 6%.The efficiency and accuracy of the proposed method are also verified by comparing with the results presented in reference,especially for the milling processes with large cutter eccentricity ratio.

Analytical prediction of chatter stability in ball end milling with tool inclination

The paper presents an analytical method to predict chatter stability in ball end milling with tool inclination. The chatter stability limits in ball end milling without the tool inclination have been predicted in the previous study by deriving directional milling force coefficients and then solving a simple quadratic equation. However, the tool is generally inclined and not perpendicular to the cut surface in practice. Therefore, a new method is developed to compute the directional milling force coefficients considering the tool inclination. It is confirmed that the chatter stability predicted by the proposed method agrees well with the experiments.

3D Ball-End Milling Force Model Using Instantaneous Cutting Force Coefficients

Application of a ball-end milling process model to a CAD/CAM or CAPP system requires a generalized methodology to determine the cutting force coefficients for different cutting conditions. In this paper, we propose a mechanistic cutting force model for 3D ball-end milling using instantaneous cutting force coefficients that are independent of the cutting conditions. The uncut chip thickness model for three-dimensional machining considers cutter deflection and runout. An in-depth analysis of the characteristics of these cutting force coefficients, which can be determined from only a few test cuts, is provided. For more accurate cutting force predictions, the size effect is also modeled using the cutter edge length of the ball-end mill and is incorporated into the cutting force model. This method of estimating the 3D ball-end milling force coefficients has been tested experimentally for various cutting conditions.

Determination of Cutting-Condition-Independent Coefficients and Runout Parameters in Ball-End Milling

This paper presents a systematic and practical method for determining cutting-condition-independent coefficients in ball-end milling. An approach for estimating the runout offset and its location angle is also described based on a single cutting force measurement. An in-depth analysis of the characteristics of these cutting coefficients, which can be determined from only a few test cuts, is provided. The size effect is also modelled, including the characteristics of the ball-end mill geometry, and incorporated into the cutting force model. This method of estimating the 3D ball-end milling force coefficients was tested experimentally for various cutting conditions and gave excellent cutting force predictions. Also, the estimated values of the runout offset agreed well with the measurements.

Nonlinear dynamics of milling processes

In this article, dynamics and stability of milling operations with cylindrical end mills are investigated. A unified–mechanics–based model, which allows for both regenerative effects and loss–of–contact effects, is presented for study of partial–immersion, high–immersion and slotting operations. Reduced–order models that can be used for certain milling operations such as full–immersion operations and finishing cuts are also presented. On the basis of these models, the loss of stability of periodic motions of the workpiece–tool system is assessed by using Poincare sections and the numerical predictions of stable and unstable motions are found to correlate well with the corresponding experimental observations. Bifurcations experienced by periodic motions of the workpiece–tool system with respect to quasi–static variation of parameters such as axial depth of cut are examined and discussed. For partial–immersion operations, consideration of both time–delay effects and loss–of–contact effects is shown to have a significant influence on the structure of the stability boundaries in the space of spindle speed and axial depth of cut. The sensitivity of system dynamics to multiple–regenerative effects, mode–coupling effects and feed rate is also discussed.

An Improved Method for the Determination of 3D Cutting Force Coefficients and Runout Parameters in End Milling

This method of estimating 3D end milling force coefficients was experimentally verified for a wide range of cutting conditions, and gave significantly better predictions of cutting forces than any other methods. The estimated value of the runout offset also agreed well with the measured value.

A study on instantaneous cutting force coefficients in face milling

In this paper, the characteristics of instantaneous cutting force coefficients in face milling are studied. In order to estimate instantaneous cutting force coefficients in face milling, the relationships between instantaneous cutting force coefficients and measured cutting force signals are derived. A series of experiments are then conducted to study the natures of instantaneous cutting force coefficients. The relationships between instantaneous cutting force coefficients and other cutting parameters are also established. It is found that the normal force coefficient is mainly affected by chip thickness and cutting speed; the vertical force coefficient is mainly affected by chip thickness, cutting edge length and cutting speed; and that the horizontal force coefficient is not only affected by chip thickness, cutting speed and length of cut, but also the variation rate of chip thickness.

Prediction of Milling Force Coefficients From Orthogonal Cutting Data

The mechanistic and unified mechanics of cutting approaches to the prediction of forces in milling operations are briefly described and compared. The mechanistic approach is shown to depend on milling force coefficients determined from milling tests for each cutter geometry. By contrast the unified mechanics of cutting approach relies on an experimentally determined orthogonal cutting data base (i.e., shear angle, friction coefficient and shear stress), incorporating the tool geometrical variables, and milling models based on a generic oblique cutting analysis. It is shown that the milling force coefficients for all force components and cutter geometrical designs can be predicted from an orthogonal cutting data base and the generic oblique cutting analysis for use in the predictive mechanistic milling models. This method eliminates the need for the experimental calibration of each milling cutter geometry for the mechanistic approach to force prediction and can be applied to more complex cutter designs. This method of milling force coefficient prediction has been experimentally verified when milling Ti6Al4V titanium alloy for a range of chatter, eccentricity and run-out free cutting conditions and cutter geometrical specifications.

Improved modelling of cutting force coefficients in peripheral milling

Titanium is one of the most widely used metals in the aircraft and turbine manufacturing industries. Accurate prediction of cutting forces is important in controlling the dimensional accuracy of thin walled aerospace components. In this paper, a general three-dimensional mechanistic model for peripheral milling processes is presented. The effects of chip thickness, rake angle and cutting geometry on chip flow, rake face friction and pressure, and cutting forces are analyzed. A set of closed form expressions with experimentally estimated cutting force factors are presented for the prediction of cutting forces. The model is verified experimentally in the peripheral milling of a titanium alloy. For a given set of cutting conditions and tool geometry, the model predicts the cutting forces accurately for the chip thickness and rake angle ranges tested.