Experimental Study on the Minimum Undeformed Chip Thickness Based on Effective Rake Angle in Micro Milling

Micro milling is widely used to manufacture micro parts due to its obvious advantages. The minimum undeformed chip thickness, the effective rake angle, and size effect are the typical characteristics and closely related to each other in micro milling. In this paper, the averaging method is proposed to quantitatively estimate the effective rake angle in the cutting process. The minimum undeformed chip thickness is explained based on the effective rake angle and determined to be 0.17 rn (tool cutting edge radius). Then, micro milling experiment was conducted to study the effect of the minimum undeformed chip thickness. It is found that the minimum undeformed chip thickness results in the unstable cutting process, the uneven peaks on cutting force signal, and the dense characteristic frequency distribution on frequency domain signal. The dominant ploughing effect induces the great specific cutting energy and the deteriorated surface roughness due to the minimum undeformed chip thickness.

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Topography and Surface Roughness of Floor in Groove Micro Milling

Journal of Mechanics ◽

10.1017/jmech.2014.68 ◽

2014 ◽

Vol 30 (6) ◽

pp. 667-678 ◽

Cited By ~ 2

Author(s):

S. Kouravand ◽

B. M. Imani ◽

J. Ni

Keyword(s):

Surface Roughness ◽

Elastic Recovery ◽

Chip Thickness ◽

Cutting Process ◽

Micro Milling ◽

Tool Geometry ◽

Proposed Model ◽

Milling Operation ◽

Micro Parts ◽

Finishing Processes

AbstractMicro milling operation is a fabrication process to create 3D parts from tens of micrometers to a few millimeters in size using a tool with diameter less than 1mm. Micro groove is one of the common features observed in the micro parts. The surface roughness of micro grooves plays an important role in their performance. Since most of the finishing processes could not be easily performed on the micro grooves, it is of extreme importance to find a relationship between micro milling parameters and the surface roughness profile. In this paper, in order to anticipate the profile and surface roughness of the groove floor a model is proposed based on the kinematic of cutting process and tool geometry. The effects of minimum chip thickness, elastic recovery, size effect and tool deflection are included in the model. Relationship between position of points on the floor surface of groove and kinematics of cutting process are derived. In next step, simulations of proposed model are performed in the ACIS environment. Finally, using the DOE method surface roughness is investigated stochastically. The simulated and measured surface roughnesses are compared together that confirm the validity of proposed model.

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Impact of Spindle Speed on Micro-Milling Stability

Volume 4: Dynamics, Control and Uncertainty, Parts A and B ◽

10.1115/imece2012-88071 ◽

2012 ◽

Author(s):

Eric B. Halfmann ◽

C. Steve Suh

Keyword(s):

Slip Line ◽

Chip Thickness ◽

Rake Angle ◽

Micro Milling ◽

Work Piece ◽

Formation Mechanisms ◽

Lumped Mass ◽

Effective Rake Angle ◽

Helical Angle ◽

Force Mechanism

Milling efficiency is hampered by excessive tool vibrations that negatively impact the work-piece quality. This is more of a concern in micro-milling where sudden tool breakage occurs before the operator can adjust cutting parameters. Due to different chip formation mechanisms in micro-milling, an increased tool-radius to feed-rate ratio, and higher spindle speeds, micro-milling is a highly non-linear process which can produce multiple and broadband frequencies which increase the probability of tool failure. Micro-milling is studied through the development and analysis of a 3-D nonlinear micro-milling dynamic model. A lumped mass, spring, damper system is assumed for modeling the dynamic properties of the tool. The force mechanism utilized is a slip-line field model that provides the advantages of being highly dynamic by accounting for the constantly changing effective rake angle and slip-line variables. Accurate prediction of the chip thickness is important in correctly predicting the dynamics of the system since the force mechanism and its variables are a function of the chip thickness. A novel approach for calculating the instantaneous chip thickness which accounts for the tool jumping out of the cut and elastic recovery of the work-piece is presented. The effective rake angle and helical angle is accounted for resulting in a 3-D micro-milling model. The model is shown to resolve the high frequency force components that are seen in experimental data available in literature. Also, exciting the system at various spindle speeds results in dynamic states of motion that negatively impact the process through increased vibration amplitude and a broad frequency bandwidth.

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High Speed Non-Linear Micro-Milling Dynamics

ASME 2012 International Manufacturing Science and Engineering Conference ◽

10.1115/msec2012-7287 ◽

2012 ◽

Cited By ~ 1

Author(s):

Eric B. Halfmann ◽

C. Steve Suh

Keyword(s):

Slip Line ◽

Chip Thickness ◽

Rake Angle ◽

Micro Milling ◽

Work Piece ◽

Formation Mechanisms ◽

Effective Rake Angle ◽

Non Linear ◽

Force Mechanism ◽

Milling Dynamics

The efficiency of the milling process is limited due to excessive vibrations that negatively impact the tool and work-piece quality. This becomes even more of a concern in micro-milling where sudden tool breakage occurs before the operator can adjust cutting parameters. Due to different chip formation mechanisms in micro-milling, an increased tool-radius to feed-rate ratio, and higher spindle speeds, micro-milling is a highly non-linear process which can produce multiple and broadband frequencies which increase the probability of tool failure. This paper investigates micro-milling through the development and analysis of a 3-D nonlinear micro-milling dynamic model. A lumped mass, spring, damper system is assumed for modeling the dynamic properties of the tool. The force mechanism utilized is a slip-line field model that provides the advantages of being highly dynamic by accounting for the constantly changing effective rake angle and slip-line variables. Accurate prediction of the chip thickness is important in correctly predicting the dynamics of the system since the force mechanism and its variables are a function of the chip thickness. A novel approach for calculating the instantaneous chip thickness which accounts for the tool jumping out of the cut and elastic recovery of the work-piece is presented. The derivation for the effective rake angle is given and the helical angle is accounted for resulting in a 3-D micro-milling model. The results of simulating the model demonstrate its capability of producing the high frequency force components that are seen in experimental data available in literature. The advantages of using this approach over the constant empirical force coefficient approach when studying micro-milling dynamics is discussed and the instability of the system is investigated utilizing instantaneous frequency.

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Microstructure-Based 3D FE Modeling for Micro Cutting Ferritic-Pearlitic Carbon Steels

Volume 1: Materials; Micro and Nano Technologies; Properties, Applications and Systems; Sustainable Manufacturing ◽

10.1115/msec2014-4011 ◽

2014 ◽

Cited By ~ 2

Author(s):

M. Abouridouane ◽

F. Klocke ◽

D. Lung

Keyword(s):

Size Effects ◽

Chip Thickness ◽

Rake Angle ◽

Carbon Steels ◽

Micro Milling ◽

Fe Model ◽

Two Phase ◽

Workpiece Material ◽

Micro Cutting ◽

Feed Force

The mechanics of the cutting process on the microscopic level differ fundamentally from the conventional macro cutting. For example, the tool edge radius influences the cutting mechanism in micro machining significantly with regard to the effective rake angle, the minimum chip thickness, the dominance of ploughing, and the related elasto-plastic deformation of the workpiece material. These phenomena, known as size effects, have a profound impact on the cutting force, process stability, and resulting surface finish in micro cutting. Therefore, microstructural effects in microscale cutting require quite different assumptions to be made concerning underlying material behaviour during micro cutting and have led to the need for new modeling approaches to account for such effects. This paper presents a three-dimensional finite element approach to incorporate microstructure into micro cutting simulation based on the concept of a representative volume element (RVE) and constitutive material modeling as well as using the Lagrangian formulation proposed in the implicit FE code Deform 3D™. Micro drilling and micro milling tests using solid carbide tools with different diameters (d = 50 μm − 1 mm) were performed on ferrite-pearlite two-phase steel AISI 1045 for the verification of the developed 3D multiphase FE computation model regarding chip formation, feed force, and torque. The developed 3D multiphase FE model was successfully used to predict size effects in micro cutting.

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Finite Element Modeling of Chip Formation in the Domain of Negative Rake Angle Cutting

Journal of Engineering Materials and Technology ◽

10.1115/1.1590999 ◽

2003 ◽

Vol 125 (3) ◽

pp. 324-332 ◽

Cited By ~ 53

Author(s):

Y. Ohbuchi ◽

T. Obikawa

Keyword(s):

Finite Element ◽

Finite Element Modeling ◽

Orthogonal Cutting ◽

Cutting Speed ◽

Chip Thickness ◽

Rake Angle ◽

Undeformed Chip Thickness ◽

Element Modeling ◽

Single Grain ◽

Serrated Chips

A thermo-elastic-plastic finite element modeling of orthogonal cutting with a large negative rake angle has been developed to understand the mechanism and thermal aspects of grinding. A stagnant chip material ahead of the tool tip, which is always observed with large negative rake angles, is assumed to act like a stable built-up edge. Serrated chips, one of typical shapes of chips observed in single grain grinding experiment, form when analyzing the machining of 0.93%C carbon steel SK-5 with a rake angle of minus forty five or minus sixty degrees. There appear high and low temperature zones alternately according to severe and mild shear in the primary shear zone respectively. The shapes of chips depend strongly on the cutting speed and undeformed chip thickness; as the cutting speed or the undeformed chip thickness decreases, chip shape changes from a serrated type to a bulging one to a wavy or flow type. Therefore, there exists the critical cutting speed over which a chip can form and flow along a rake face for a given large negative rake angle and undeformed chip thickness.

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Experimental Study on the Chip Geometry and Shear Angle in Micro-Cutting Aluminum 7050-T7451

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.443.657 ◽

2010 ◽

Vol 443 ◽

pp. 657-662

Author(s):

Jun Zhou ◽

Jian Feng Li ◽

Jie Sun

Keyword(s):

Cutting Speed ◽

Chip Thickness ◽

Rake Angle ◽

Shear Angle ◽

Micro Scale ◽

Effective Rake Angle ◽

Al 7075 ◽

Chip Geometry ◽

Cutting Experiments ◽

Machining Characteristics

In this paper, the micro-scale machining characteristics of a non-ferrous structural alloy, aluminum 7050-T7451 is investigated through a series of cutting experiments. The effects of cutting speed and undeformed chip thickness on the chip geometry, cutting ratio, effective rake angle and shear angle in orthogonal micro-scale cutting of Al 7075-T7451 are presented. Explanations for the observed trends are also given.

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Finite Element Analysis of Cutting Forces in High Speed Machining

Materials Science Forum ◽

10.4028/www.scientific.net/msf.532-533.753 ◽

2006 ◽

Vol 532-533 ◽

pp. 753-756 ◽

Cited By ~ 3

Author(s):

Jun Zhao ◽

Xing Ai ◽

Zuo Li Li

Keyword(s):

Finite Element ◽

Cutting Force ◽

Cutting Forces ◽

High Speed ◽

Fem Simulation ◽

Chip Thickness ◽

Cutting Conditions ◽

Cutting Process ◽

Undeformed Chip Thickness ◽

High Speed Cutting

The Finite Element Method (FEM) has proven to be an effective technique to investigate cutting process so as to improve cutting tool design and select optimum cutting conditions. The present work focuses on the FEM simulation of cutting forces in high speed cutting by using an orthogonal cutting model with variant undeformed chip thickness under plane-strain condition to mimic intermittent cutting process such as milling. High speed cutting of 45%C steel using uncoated carbide tools are simulated as the application of the proposed model. The updated Lagrangian formulation is adopted in the dynamic FEM simulation in which the normalized Cockroft and Latham damage criterion is used as the ductile fracture criterion. The simulation results of cutting force components under different cutting conditions show that both the thrust cutting force and the tangential cutting force increase with the increase in undeformed chip thickness or feed rate, whereas decrease with the increase in cutting speed. Some important aspects of modeling the high speed cutting are discussed as well to expect the future work in FEM simulation.

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ON MECHANICS OF UNSTEADY CUTTING PROCESS WITH VARYING UNDEFORMED CHIP THICKNESS : 3RD REPORT : INFLUENCES OF STRAIN HARDENING OF WORK MATERIALS

Bulletin of JSME ◽

10.1299/jsme1958.17.1356 ◽

1974 ◽

Vol 17 (112) ◽

pp. 1356-1364

Author(s):

Mikio OGURI ◽

Hiroshi FUJII ◽

Hiromichi MORI ◽

Tadao OTA

Keyword(s):

Strain Hardening ◽

Chip Thickness ◽

Cutting Process ◽

Undeformed Chip Thickness

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A Study on Cutting Force in Micro End Milling with Ultrasonic Vibration

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.97-101.1910 ◽

2010 ◽

Vol 97-101 ◽

pp. 1910-1914 ◽

Cited By ~ 5

Author(s):

Xue Hui Shen ◽

Jian Hua Zhang ◽

Tian Jin Yin ◽

Chun Jie Dong

Keyword(s):

Cutting Force ◽

Ultrasonic Vibration ◽

End Milling ◽

Chip Thickness ◽

Normal Direction ◽

Micro Milling ◽

Short Service Life ◽

Micro Parts ◽

Micro End Milling ◽

Cutting Effect

The applications of micro end milling have been gradually broadened to meet the ever-increasing demands for micro parts. In micro milling, premature tool failure and short service life are major problems. In this study, micro end milling with ultrasonic vibration in normal direction is investigated. Kinematical analysis is done to describe the exact trajectory of the tool tip when vibration is applied. Based on which, an analytical model of chip formation is proposed. By accurate calculation of instantaneous chip thickness, the cutting forces in micro end milling with and without ultrasonic vibration are predicted and verified by a slot-milling experiment. As a result, it is found that ultrasonic vibration in normal direction is helpful when reducing the cutting force owing to intermittent cutting effect.

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