Dynamic Chip Formation and its Significance to Machining Stability

1973 ◽  
Vol 187 (1) ◽  
pp. 273-283 ◽  
Author(s):  
D. F. Pearce ◽  
B. R. MacManus
Keyword(s):  
Cutting Force ◽  
Chip Formation ◽  
Chip Thickness ◽  
High Amplitude ◽  
Contact Length ◽  
Tangential Component ◽  
Shear Angle ◽  
Uncut Chip Thickness ◽  
Phase Measurements ◽  
Specific Contact

The physical processes of dynamic chip formation were examined experimentally using direct photographic techniques; motion in the cutting zone was frozen by synchronizing an intense stroboscopic flash to particular positions in the waveform of the cutting force. Measurements obtained under conditions of controlled vibratory machining gave instantaneous values of the uncut chip thickness, tool-chip contact length, effective shear angle and cutting force. At a given amplitude of uncut chip thickness the peak-to-peak variation of contact length was seen to attenuate with increasing frequency, an effect which was shown to be significant in causing relatively high amplitude shear angle oscillations. Amplitude and phase measurements of the tangential component of the cutting force on wave removal were directly related to the deduced waveform of specific contact length, a process yielding considerable predictability. Measurements were made of the damping inherent in the cutting process; results obtained by applying the techniques of impulse response testing showed the sensitivity of this damping to both the amplitude and the frequency of the variation of the uncut chip thickness. Internal damping resulting from the process of chip formation is not uniquely positive or negative but may vary, depending upon the combination of these parameters.

Dynamic Chip Formation and its Significance to Machining Stability

1973 ◽  
Vol 187 (1) ◽  
pp. 273-283 ◽  
Author(s):  
D. F. Pearce ◽  
B. R. MacManus
Keyword(s):  
Cutting Force ◽  
Chip Formation ◽  
Chip Thickness ◽  
High Amplitude ◽  
Contact Length ◽  
Tangential Component ◽  
Shear Angle ◽  
Uncut Chip Thickness ◽  
Phase Measurements ◽  
Specific Contact

The physical processes of dynamic chip formation were examined experimentally using direct photographic techniques; motion in the cutting zone was frozen by synchronizing an intense stroboscopic flash to particular positions in the waveform of the cutting force. Measurements obtained under conditions of controlled vibratory machining gave instantaneous values of the uncut chip thickness, tool-chip contact length, effective shear angle and cutting force. At a given amplitude of uncut chip thickness the peak-to-peak variation of contact length was seen to attenuate with increasing frequency, an effect which was shown to be significant in causing relatively high amplitude shear angle oscillations. Amplitude and phase measurements of the tangential component of the cutting force on wave removal were directly related to the deduced waveform of specific contact length, a process yielding considerable predictability. Measurements were made of the damping inherent in the cutting process; results obtained by applying the techniques of impulse response testing showed the sensitivity of this damping to both the amplitude and the frequency of the variation of the uncut chip thickness. Internal damping resulting from the process of chip formation is not uniquely positive or negative but may vary, depending upon the combination of these parameters.

scholarly journals Prediction of Nonlinear Micro-Milling Force with a Novel Minimum Uncut Chip Thickness Model

Micromachines ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1495
Author(s):  
Tongshun Liu ◽  
Kedong Zhang ◽  
Gang Wang ◽  
Chengdong Wang
Keyword(s):  
Cutting Force ◽  
Chip Thickness ◽  
Micro Milling ◽  
Force Model ◽  
Force Coefficient ◽  
Uncut Chip Thickness ◽  
Milling Force ◽  
Minimum Uncut Chip Thickness ◽  
Cutting Force Coefficient ◽  
Milling Force Model

The minimum uncut chip thickness (MUCT), dividing the cutting zone into the shear region and the ploughing region, has a strong nonlinear effect on the cutting force of micro-milling. Determining the MUCT value is fundamental in order to predict the micro-milling force. In this study, based on the assumption that the normal shear force and the normal ploughing force are equivalent at the MUCT point, a novel analytical MUCT model considering the comprehensive effect of shear stress, friction angle, ploughing coefficient and cutting-edge radius is constructed to determine the MUCT. Nonlinear piecewise cutting force coefficient functions with the novel MUCT as the break point are constructed to represent the distribution of the shear/ploughing force under the effect of the minimum uncut chip thickness. By integrating the cutting force coefficient function, the nonlinear micro-milling force is predicted. Theoretical analysis shows that the nonlinear cutting force coefficient function embedded with the novel MUCT is absolutely integrable, making the micro-milling force model more stable and accurate than the conventional models. Moreover, by considering different factors in the MUCT model, the proposed micro-milling force model is more flexible than the traditional models. Micro-milling experiments under different cutting conditions have verified the efficiency and improvement of the proposed micro-milling force model.

Voxel Based Cutting Force Simulation of Ball End Milling Considering Cutting Edge Around Center Web

2018 ◽  
Author(s):  
Isamu Nishida ◽  
Takaya Nakamura ◽  
Ryuta Sato ◽  
Keiichi Shirase
Keyword(s):  
Cutting Force ◽  
End Milling ◽  
Chip Thickness ◽  
Previous Method ◽  
Cutting Edge ◽  
Force Model ◽  
End Mill ◽  
Uncut Chip Thickness ◽  
Ball End Mill ◽  
Tool Rotation

A new method, which accurately predicts cutting force in ball end milling considering cutting edge around center web, has been proposed. The new method accurately calculates the uncut chip thickness, which is required to estimate the cutting force by the instantaneous rigid force model. In the instantaneous rigid force model, the uncut chip thickness is generally calculated on the cutting edge in each minute disk element piled up along the tool axis. However, the orientation of tool cutting edge of ball end mill is different from that of square end mill. Therefore, for the ball end mill, the uncut chip thickness cannot be calculated accurately in the minute disk element, especially around the center web. Then, this study proposes a method to calculate the uncut chip thickness along the vector connecting the center of the ball and the cutting edge. The proposed method can reduce the estimation error of the uncut chip thickness especially around the center web compared with the previous method. Our study also realizes to calculate the uncut chip thickness discretely by using voxel model and detecting the removal voxels in each minute tool rotation angle, in which the relative relationship between a cutting edge and a workpiece, which changes dynamically during tool rotation. A cutting experiment with the ball end mill was conducted in order to validate the proposed method. The results showed that the error between the measured and predicted cutting forces can be reduced by the proposed method compared with the previous method.

Investigation of the Dynamics of Microend Milling—Part I: Model Development

2006 ◽  
Vol 128 (4) ◽  
pp. 893-900 ◽  
Author(s):  
Martin B. G. Jun ◽  
Xinyu Liu ◽  
Richard E. DeVor ◽  
Shiv G. Kapoor
Keyword(s):  
Cutting Force ◽  
Chip Formation ◽  
Model Development ◽  
Chip Thickness ◽  
Fault System ◽  
Formation Mechanisms ◽  
Force Model ◽  
Line Field ◽  
Fault Parameters ◽  
Microend Milling

In microend milling, due to the comparable size of the edge radius to chip thickness, chip formation mechanisms are different. Also, the design of microend mills with features of a large shank, taper, and reduced diameter at the cutting edges introduces additional dynamics and faults or errors at the cutting edges. A dynamic microend milling cutting force and vibration model has been developed to investigate the microend milling dynamics caused by the unique mechanisms of chip formation as well as the unique microend mill design and its associated fault system. The chip thickness model has been developed considering the elastic-plastic nature in the ploughing process. A slip-line field modeling approach is taken for a cutting force model development that accounts for variations in the effective rake angle and dead metal cap. The process fault parameters associated with microend mills have been defined and their effects on chip load have been derived. Finally, a dynamic model has been developed considering the effects of both the unique microend mill design and fault system and factors that become significant at high spindle speeds including rotary inertia and gyroscopic moments.

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

1999 ◽  
Vol 122 (3) ◽  
pp. 384-390 ◽  
Author(s):  
Jairam Manjunathaiah ◽  
William J. Endres
Keyword(s):  
Shear Stress ◽  
Deformation Zone ◽  
Lower Boundary ◽  
Chip Thickness ◽  
Rake Angle ◽  
Shear Angle ◽  
Force Model ◽  
Uncut Chip Thickness ◽  
Edge Radius ◽  
Machining Force

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]

The Constant Force Component due to Material Separation and Its Contribution to the Size Effect in Specific Cutting Energy

2005 ◽  
Vol 128 (3) ◽  
pp. 811-815 ◽  
Author(s):  
Sathyan Subbiah ◽  
Shreyes N. Melkote
Keyword(s):  
Size Effect ◽  
Cutting Force ◽  
Orthogonal Cutting ◽  
Chip Thickness ◽  
Constant Force ◽  
Specific Cutting Energy ◽  
Force Component ◽  
Uncut Chip Thickness ◽  
Cutting Energy ◽  
Material Separation

The contribution of material separation in cutting ductile metals to the constant force component, and, hence, to the size effect in specific cutting energy is explored in this paper. A force-decomposition-based framework is proposed to reconcile the varied reasons given in literature for the size effect. In this framework, the cutting force is broken down into three components: one that is decreasing, another that is increasing, and the third that remains constant, with decreasing uncut chip thickness. The last component is investigated by performing orthogonal cutting experiments on OFHC copper at high rake angles of up to 70deg in an attempt to isolate it. As the rake angle is increased, the resulting experimental data show a trend toward a constant cutting-force component independent of the uncut chip thickness. Visual evidence of ductile tearing ahead of the tool associated with material separation leading to chip formation is shown. The measured constant force and the force needed for ductile crack extension are then compared.

Machinability Study Using Chip Thickness Ratio on Difficult to Cut Metals by CBN Cutting Tool

2012 ◽  
Vol 504-506 ◽  
pp. 1317-1322 ◽  
Author(s):  
Sivaprakasam Thamizhmanii ◽  
Hasan Sulaiman
Keyword(s):  
Stainless Steel ◽  
Cutting Force ◽  
High Speed ◽  
Cutting Tool ◽  
Cubic Boron Nitride ◽  
Chip Thickness ◽  
Shear Angle ◽  
Thickness Ratio ◽  
Depth Of Cut ◽  
Alloy Steels

Machinability is the one of the criteria in determining the life of the cutting tool. In this experiment, hard and difficult to cut materials like hard AISI 440 C stainless steel and hard SCM 440 alloy steels were discussed. However, machinability of the material is considered to be poor due to its inherent characteristics. The machinability studies on AISI 440 C stainless steel and SCM 440 alloy steels had not been carried out by researchers. Machinability indices used in such cases have the characteristics such as cutting force, surface roughness, tool wear etc. In the case of high-speed machining of said materials machinability indices such as chip thickness (RC), shear angle (Ф), surface integrity, and chip analysis are of prime importance. Most of the researchers have not given due consideration to these vital machinability indices necessary for understanding of high-speed cutting of said materials. In this work, an experimental investigation was carried out to understand the behavior of difficult to cut materials, when machined with Cubic Boron Nitride (CBN) insert tool. The results and analysis of this work indicated that the above-mentioned machinability indices are important and necessary to assess the machinability of said materials effectively. The operating parameters used were cutting velocity 100, 125, 150, 175 and 200 m/min with feed rate of 0.10, 0.20 and 0.30 mm rev-1 with constant depth of cut of 1.0 mm. The length of turning was 150 mm and 300 mm. Machinability of both materials and tool was evaluated in terms of roughness, flank wear, cutting force, chip thickness ratio and shear angle.

On Tool Instability During Machining

1991 ◽  
Author(s):  
C. Sahay ◽  
R. N. Dubey
Keyword(s):  
Cutting Force ◽  
Shear Deformation ◽  
Static Analysis ◽  
Cutting Forces ◽  
Chip Thickness ◽  
Uncut Chip Thickness ◽  
Frictional Interaction ◽  
Machining System ◽  
The Relationship

Abstract The present paper describes the role of the tool in vibrations of a machining system. The cutting force has been assumed to be constant. The shear deformation of the tool is considered. The quasi-static analysis of the situation yields a maximum allowable uncut chip thickness, which shows how the frictional interaction at the tool face and the ratio of the components of cutting forces alter this value. The relationship also expresses the effect of tool dimensions and work material on the vibration of the tool.

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