Cutting Mechanisms and Their Influence on Dynamic Forces, Vibrations and Stability in Micro-Endmilling

2004 ◽  
Author(s):  
Xinyu Liu ◽  
Martin B. G. Jun ◽  
Richard E. DeVor ◽  
Shiv G. Kapoor
Keyword(s):  
Cutting Force ◽  
Cutting Forces ◽  
Elastic Recovery ◽  
Chip Thickness ◽  
Process Stability ◽  
Minimum Chip Thickness ◽  
Vibration Model ◽  
Dynamic Cutting Force ◽  
Dynamic Forces ◽  
Cutting Mechanisms

A dynamic cutting force and vibration model of the micro-endmilling process that accounts for the dynamics of the micro-endmill, influences of the stable built-up-edge, and the effects of minimum chip thickness, elastic recovery, and the elastic-plastic nature in ploughing/rubbing has been developed. Experimental validation has been performed, and the model is shown to predict the cutting force and tool vibration within an average of 12%. Using the model developed, effects of the minimum chip thickness and elastic recovery on the cutting forces and vibrations as well as process stability of the micro-endmilling process have been examined. The results indicate that the large edge radius relative to the feedrate causes the process stability to be sensitive to feedrate, resulting in the low feedrate instability phenomenon. The elastic recovery significantly increases the peak-to-valley cutting forces and enlarges the unstable feedrate range.

Dynamic cutting force prediction for micro end milling considering tool vibrations and run-out

2018 ◽  
Vol 233 (7) ◽  
pp. 2248-2261 ◽  
Author(s):  
Xuewei Zhang ◽  
Tianbiao Yu ◽  
Wanshan Wang
Keyword(s):  
Cutting Force ◽  
Cutting Forces ◽  
End Milling ◽  
Chip Thickness ◽  
Milling Process ◽  
Force Model ◽  
Dynamic Cutting Force ◽  
Micro End Milling ◽  
Tool Vibrations ◽  
End Milling Process

An accurate prediction of cutting forces in the micro end milling, which is affected by many factors, is the basis for increasing the machining productivity and selecting optimal cutting parameters. This paper develops a dynamic cutting force model in the micro end milling taking into account tool vibrations and run-out. The influence of tool run-out is integrated with the trochoidal trajectory of tooth and the size effect of cutting edge radius into the static undeformed chip thickness. Meanwhile, the real-time tool vibrations are obtained from differential motion equations with the measured modal parameters, in which the process damping effect is superposed as feedback on the undeformed chip thickness. The proposed dynamic cutting force model has been experimentally validated in the micro end milling process of the Al6061 workpiece. The tool run-out parameters and cutting forces coefficients can be identified on the basis of the measured cutting forces. Compared with the traditional model without tool vibrations and run-out, the predicted and measured cutting forces in the micro end milling process show closer agreement when considering tool vibrations and run-out.

Investigation of the Dynamics of Microend Milling—Part II: Model Validation and Interpretation

2006 ◽  
Vol 128 (4) ◽  
pp. 901-912 ◽  
Author(s):  
Martin B. G. Jun ◽  
Richard E. DeVor ◽  
Shiv G. Kapoor
Keyword(s):  
Dynamic Model ◽  
End Milling ◽  
Elastic Recovery ◽  
Chip Thickness ◽  
Thickness Effect ◽  
Depth Of Cut ◽  
Minimum Chip Thickness ◽  
Microend Milling ◽  
The Stability ◽  
Cutting Mechanisms

In Part II of this paper, experimental and analytical methods have been developed to estimate the values of the process faults defined in Part I of this paper. The additional faults introduced by the microend mill design are shown to have a significant influence on the total net runout of the microend mill. The dynamic model has been validated through microend milling experiments. Using the dynamic model, the effects of minimum chip thickness and elastic recovery on microend milling stability have been studied over a range of feed rates for which the cutting mechanisms vary from ploughing-dominated to shearing-dominated. The minimum chip thickness effect is found to cause feed rate dependent instability at low feed rates, and the range of unstable feed rates depends on the axial depth of cut. The effects of process faults on microend mill vibrations have also been studied and the influence of the unbalance from the faults is found to be significant as spindle speed is increased. The stability characteristics due to the regenerative effect have been studied. The results show that the stability lobes from the second mode of the microend mill, which are generally neglected in macroscale end milling, affect the microend mill stability significantly.

Analysis of the effect of tool posture on stability considering the nonlinear dynamic cutting force coefficient

2021 ◽  
pp. 1-19
Author(s):  
Zepeng Li ◽  
Rong Yan ◽  
Xiaowei Tang ◽  
Fang Yu Peng ◽  
Shihao Xin ◽  
...  
Keyword(s):  
Cutting Force ◽  
Nonlinear Dynamic ◽  
Chip Thickness ◽  
Cutting Depth ◽  
Force Coefficient ◽  
Critical Cutting Depth ◽  
Dynamic Cutting Force ◽  
Cutting Force Coefficient ◽  
Tool Posture ◽  
Instantaneous Uncut Chip Thickness

Abstract In aviation and navigation, complicated parts are milled with high-speed low-feed-per-tooth milling to decrease tool vibration for high quality. Because the nonlinearity of the cutting force coefficient (CFC) is more evident with the relatively smaller instantaneous uncut chip thickness, the stable critical cutting depth and its distribution against different tool postures are affected. Considering the nonlinearity, a nonlinear dynamic CFC model that reveals the effect of the dynamic instantaneous uncut chip thickness on the dynamic cutting force is derived based on the Taylor expansion. A five-axis bull-nose end milling dynamics model is established with the nonlinear dynamic CFC model. The stable critical cutting depth distribution with respect to tool posture is analyzed. The stability results predicted with the dynamic CFC model are compared with those from the static CFC model and the constant CFC model. The effects of tool posture and feed per tooth on stable critical cutting depth were also analyzed, and the proposed model was validated by cutting experiments. The maximal stable critical cutting depths that can be achieved under different tool postures by feed per tooth adjustment were calculated, and corresponding distribution diagrams are proposed for milling parameter optimization.

Improved dynamic cutting force modelling in micro milling of metal matrix composites part II: Experimental validation and prediction

2019 ◽  
Vol 234 (8) ◽  
pp. 1500-1515
Author(s):  
Zhichao Niu ◽  
Kai Cheng
Keyword(s):  
Cutting Force ◽  
Metal Matrix Composites ◽  
Cutting Forces ◽  
Metal Matrix ◽  
Micro Milling ◽  
Force Model ◽  
Matrix Composites ◽  
Cutting Force Model ◽  
Side Milling ◽  
Dynamic Cutting Force

The effects of cutting dynamics and the particles' size and density cannot be ignored in micro milling of metal matrix composites. This article presents the improved dynamic cutting force modelling for micro milling of metal matrix composites based on the previous analytical model. This comprehensive improved cutting force model, taking the influence of the tool run-out, actual chip thickness and resultant tool tip trajectory into account, is evaluated and validated through well-designed machining trials. A series of side milling experiments using straight flutes polycrystalline diamond end mills are carried out on the metal matrix composite workpiece under various cutting conditions. Subsequently, the measured cutting forces are compensated by a Kalman filter to achieve the accurate cutting forces. These are further compared with the predicted cutting forces to validate the proposed dynamic cutting force model. The experimental results indicate that the predicted and measured cutting forces in micro milling of metal matrix composites are in good agreement.

A Mechanistic Model of Cutting Forces in Micro-End-Milling With Cutting-Condition-Independent Cutting Force Coefficients

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Han Ul Lee ◽  
Dong-Woo Cho ◽  
Kornel F. Ehmann
Keyword(s):  
Cutting Force ◽  
Cutting Forces ◽  
End Milling ◽  
Cutting Conditions ◽  
Thickness Effect ◽  
Force Model ◽  
Cutting Force Coefficients ◽  
Force Coefficients ◽  
Micro End Milling ◽  
Cutting Mechanisms

Complex three-dimensional miniature components are needed in a wide range of industrial applications from aerospace to biomedicine. Such products can be effectively produced by micro-end-milling processes that are capable of accurately producing high aspect ratio features and parts. This paper presents a mechanistic cutting force model for the precise prediction of the cutting forces in micro-end-milling under various cutting conditions. In order to account for the actual physical phenomena at the edge of the tool, the components of the cutting force vector are determined based on the newly introduced concept of the partial effective rake angle. The proposed model also uses instantaneous cutting force coefficients that are independent of the end-milling cutting conditions. These cutting force coefficients, determined from measured cutting forces, reflect the influence of the majority of cutting mechanisms involved in micro-end-milling including the minimum chip-thickness effect. The comparison of the predicted and measured cutting forces has shown that the proposed method provides very accurate results.

Virtual Five-Axis Flank Milling of Jet Engine Impellers: Part 1 — Mechanics of Five-Axis Flank Milling

2007 ◽  
Author(s):  
W. Ferry ◽  
Y. Altintas
Keyword(s):  
Cutting Force ◽  
Cutting Forces ◽  
Orthogonal Cutting ◽  
Chip Thickness ◽  
Friction Angle ◽  
Flank Milling ◽  
Cutting Force Prediction ◽  
Jet Engine ◽  
End Mills ◽  
Five Axis

Jet engine impeller blades are flank-milled with tapered, helical, ball-end mills on five-axis machining centers. The impellers are made from difficult-to-cut titanium or nickel alloys, and the blades must be machined within tight tolerances. As a consequence, deflections of the tool and flexible workpiece can jeopardize the precision of the impellers during milling. This work is the first of a two part paper on cutting force prediction and feed optimization for the five-axis flank milling of an impeller. In Part I, a mathematical model for predicting cutting forces is presented for five-axis machining with tapered, helical, ball-end mills with variable pitch and serrated flutes. The cutter is divided axially into a number of differential elements, each with its own feed coordinate system due to five-axis motion. At each element, the total velocity due to translation and rotation is split into horizontal and vertical feed components, which are used to calculate total chip thickness along the cutting edge. The cutting forces for each element are calculated by transforming friction angle, shear stress and shear angle from an orthogonal cutting database to the oblique cutting plane. The distributed cutting load is digitally summed to obtain the total forces acting on the cutter and blade. The model can be used for general five-axis flank milling processes, and supports a variety of cutting tools. Predicted cutting force measurements are shown to be in reasonable agreement with those collected during a roughing operation on a prototype integrally bladed rotor (IBR).

A Micromilling Experimental Study on AISI 4340 Steel

2009 ◽  
Vol 407-408 ◽  
pp. 335-338 ◽  
Author(s):  
Jin Sheng Wang ◽  
Da Jian Zhao ◽  
Ya Dong Gong
Keyword(s):  
Experimental Study ◽  
Surface Roughness ◽  
Cutting Force ◽  
Spectrum Analysis ◽  
Chip Thickness ◽  
Experimental Results ◽  
Minimum Chip Thickness ◽  
Aisi 4340 Steel ◽  
4340 Steel ◽  
Aisi 4340

A micromilling experimental study on AISI 4340 steel is conducted to understand the micromilling principle deeply. The experimental results, especially on the surface roughness and cutting force, are discussed in detail. It has been found the minimum chip thickness influences the surface roughness and cutting force greatly. Meanwhile, the material elastic recover induces the increase of the axial micromilling force. The average cutting force and its spectrum analysis validate the minimum chip thickness approximation of AISI 4340 is about 0.35μm.

Dynamic Simulation of the Micro-Milling Process Including Minimum Chip Thickness and Size Effect

2012 ◽  
Vol 504-506 ◽  
pp. 1269-1274 ◽  
Author(s):  
François Ducobu ◽  
Edouard Rivière-Lorphèvre ◽  
Enrico Filippi
Keyword(s):  
Size Effect ◽  
Cutting Forces ◽  
Mechanistic Model ◽  
Orthogonal Cutting ◽  
Chip Thickness ◽  
Milling Process ◽  
Cutting Conditions ◽  
Micro Milling ◽  
Minimum Chip Thickness ◽  
Physical Phenomena

Micro-milling with a cutting tool is a manufacturing technique that allows production of parts ranging from several millimeters to several micrometers. The technique is based on a downscaling of macroscopic milling process. Micro-milling is one of the most effective process to produce complex three-dimensional micro-parts, including sharp edges and with a good surface quality. Reducing the dimensions of the cutter and the cutting conditions requires taking into account physical phenomena that can be neglected in macro-milling. These phenomena include a size effect (nonlinear rising of specific cutting force when chip thickness decreases), the minimum chip thickness (under a given dimension, no chip can be machined) and the heterogeneity of the material (the size of the grains composing the material is significant as compared to the dimension of the chip). The aim of this paper is to introduce some phenomena, appearing in micromilling, in the mechanistic dynamic simulation software ‘dystamill’ developed for macro-milling. The software is able to simulate the cutting forces, the dynamic behavior of the tool and the workpiece and the kinematic surface finish in 2D1/2 milling operation (slotting, face milling, shoulder milling,…). It can be used to predict chatter-free cutting condition for example. The mechanistic model of the cutting forces is deduced from the local FEM simulation of orthogonal cutting. This FEM model uses the commercial software ABAQUS and is able to simulate chip formation and cutting forces in an orthogonal cutting test. This model is able to reproduce physical phenomena in macro cutting conditions (including segmented chip) as well as specific phenomena in micro cutting conditions (minimum chip thickness and size effect). The minimum chip thickness is also taken into account by the global model. The results of simulation for the machining of titanium alloy Ti6Al4V under macro and micro milling condition with the mechanistic model are presented discussed. This approach connects together local machining simulation and global models.

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