Chatter Stability in Micro Milling Processes Considering Ploughing and Process Damping Effects

2009 ◽  
Author(s):  
Ramin Rahnama ◽  
Mozhdeh Sajjadi ◽  
Simon S. Park
Keyword(s):  
Time Domain ◽  
Chip Thickness ◽  
Experimental Tests ◽  
Micro Milling ◽  
Chatter Stability ◽  
Workpiece Material ◽  
Process Damping ◽  
Milling Operations ◽  
Milling Operation ◽  
Cutting Mechanisms

Micro milling operations utilize miniature tools to remove workpiece material, in order to create the desired 3D miniature components. One of the challenges in a micro milling operation is the unstable phenomenon called regenerative chatter. The occurrence of chatter in the micro domain, as in macro machining, is detrimental to part finishes and significantly reduces the longevity of tools. There are two different cutting mechanisms in micro milling operations, which are determined by the critical chip thickness. When the chip thickness is less than the critical chip thickness, no chip forms and ploughing occurs; whereas, when the chip thickness is greater than the critical chip thickness, a chip forms and shearing cutting happens. During each rotation of the tool, the cutting mechanisms switch from ploughing to shearing and vice versa. This paper introduces a time domain chatter model to investigate the effects of the ploughing and shearing mechanisms on stability. The model also considers the effects of process damping in micro milling, especially at low spindle speeds. Several experimental tests have been performed to validate the model.

Identification of Process Damping Coefficient Based on Material Constitutive Property

2014 ◽  
Author(s):  
Xiaoliang Jin
Keyword(s):  
Energy Dissipation ◽  
Flank Wear ◽  
Orthogonal Cutting ◽  
Element Model ◽  
Machining Process ◽  
Damping Coefficient ◽  
Chatter Stability ◽  
Workpiece Material ◽  
Process Damping ◽  
Constitutive Property

The contact between the tool flank wear land and wavy surface of workpiece causes energy dissipation which influences the tool vibration and chatter stability during a dynamic machining process. The process damping coefficient is affected by cutting conditions and constitutive property of workpiece material. This paper presents a finite element model of dynamic orthogonal cutting process with tool round edge and flank wear land. The process damping coefficient is identified based on the energy dissipation principle. The simulated results are experimentally validated.

Mechanics and Dynamics of Multifunctional Tools

2015 ◽  
Vol 137 (1) ◽  
Author(s):  
Min Wan ◽  
Zekai Murat Kilic ◽  
Yusuf Altintas
Keyword(s):  
Time Domain ◽  
Prediction Models ◽  
Chip Thickness ◽  
Combined Processes ◽  
Multiple Delays ◽  
Stability Prediction ◽  
Chatter Stability ◽  
Regenerative Effect ◽  
Hole Making ◽  
Chatter Stability Prediction

The mechanics and dynamics of the combined processes are presented for multifunctional tools, which can drill, bore, and chamfer holes in one operation. The oblique cutting forces on each cutting edge with varying geometry are modeled first, followed by their transformations to tangential, radial, and axial directions of the cutter. The regenerative effect of lateral and torsional/axial vibrations is considered in predicting the dynamic chip thickness with multiple delays due to distribution of cutting edges on the cutter body. The lateral and torsional/axial chatter stability of the complete hole making operation is predicted in semidiscrete time domain. The proposed static cutting force and chatter stability prediction models are experimentally proven for two different multifunctional tools in drilling Aluminum Al7050 and Steel AISI1045.

Automatic tool selection for milling operations Part 1: Cutting data generation

2000 ◽  
Vol 214 (4) ◽  
pp. 271-282 ◽  
Author(s):  
I D Carpenter ◽  
P G Maropoulos
Keyword(s):  
Tool Life ◽  
Chip Thickness ◽  
Minimum Cost ◽  
Optimization Criterion ◽  
Cnc Machining ◽  
Data Generation ◽  
Tool Selection ◽  
Workpiece Material ◽  
Milling Operations ◽  
Wide Range

The selection of tools and cutting data is a central activity in process planning and is often liable to an element of subjectivity. It is further complicated by the wide range of choice presented by the various operation types and the huge portfolio of cutters and inserts available from many different tool manufacturers. This paper describes a procedure to select consistently and efficiently tools for rough and finish milling operations performed on a computer numerical controlled (CNC) machining centre. A wide range of milling operations is considered, including faces, square shoulders, slots, T-slots, pockets, holes and profiles. An initial set of feasible tools is generated that satisfy the constraints of the tool type, the operation geometry, the insert geometry and carbide grade, the workpiece material and the machine tool capacity. Each tool consists of a holder and one or more indexable carbide inserts. Aggressive cutting data are generated for each feasible tool using a rapid search procedure in the permissible depth/width/feed space for good chip control. The cutting data are further refined by a set of technological constraints, which include tool life, surface finish, machine power and available spindle speeds and feeds. The overall cutting data optimization criterion is selected by the user from minimum cost, maximum production rate or predefined tool life. A new optimization criterion, called ‘harshness’, allows the user to influence the chip thickness that is achieved for any given cutter. Any feasible tools that fail to satisfy all the constraints and optimization criteria are discarded.

Robust chatter stability in micro-milling operations

CIRP Annals ◽  
2010 ◽  
Vol 59 (1) ◽  
pp. 391-394 ◽  
Author(s):  
S.S. Park ◽  
R. Rahnama
Keyword(s):  
Micro Milling ◽  
Chatter Stability ◽  
Milling Operations

Topography and Surface Roughness of Floor in Groove Micro Milling

2014 ◽  
Vol 30 (6) ◽  
pp. 667-678 ◽  
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.

Dynamics and Stability of Turn-Milling Operations With Varying Time Delay in Discrete Time Domain

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Alptunc Comak ◽  
Yusuf Altintas
Keyword(s):  
Time Domain ◽  
Chip Thickness ◽  
Body Motion ◽  
Depth Of Cut ◽  
Time Varying Delay ◽  
Milling Operations ◽  
Varying Time Delay ◽  
The Stability ◽  
Five Axis ◽  
Turn Milling

Turn-milling machines are widely used in industry because of their multifunctional capabilities in producing complex parts in one setup. Both milling cutter and workpiece rotate simultaneously while the machine travels in three Cartesian directions leading to five axis kinematics with complex chip generation mechanism. This paper presents a general mathematical model to predict the chip thickness, cutting force, and chatter stability of turn milling operations. The dynamic chip thickness is modeled by considering the rigid body motion, relative vibrations between the tool and workpiece, and cutter-workpiece engagement geometry. The dynamics of the process are governed by delayed differential equations by time periodic coefficients with a time varying delay contributed by two simultaneously rotating spindles and kinematics of the machine. The stability of the system has been solved in semidiscrete time domain as a function of depth of cut, feed, tool spindle speed, and workpiece speed. The stability model has been experimentally verified in turn milling of Aluminum alloy cut with a helical cylindrical end mill.

scholarly journals Mechanics and Dynamics of Serrated End Mills

Manufacturing ◽  
2002 ◽  
Author(s):  
S. Doruk Merdol ◽  
Yusuf Altintas
Keyword(s):  
Time Domain ◽  
Cutting Forces ◽  
Chip Thickness ◽  
Cutting Edge ◽  
Chatter Stability ◽  
Edge Point ◽  
Oblique Cutting ◽  
Edge Geometry ◽  
End Mills ◽  
Chatter Stability Lobes

Mechanics and dynamics of serrated milling cutters are presented in the article. The serrated flute design knots are fitted to a cubic spline, which is then projected on helical flutes. Cutting edge geometry at any point along the serrated flute is represented by its immersion angle and tangent vectors in radial, tangential and helix directions. The chip thickness removed by each cutting edge point is determined by using previously proposed exact kinematics of dynamic milling. The cutting forces are evaluated by orthogonal to oblique cutting mechanics transformation. The experimentally proven model is able to predict the cutting forces and chatter stability lobes in time domain.

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

2014 ◽  
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.

Analytical Chatter Stability of Milling With Rotating Cutter Dynamics at Process Damping Speeds

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
M. Eynian ◽  
Y. Altintas
Keyword(s):  
Chip Thickness ◽  
Prediction Method ◽  
Vibration Velocity ◽  
Chatter Stability ◽  
Process Damping ◽  
End Mills ◽  
Nyquist Stability ◽  
Matrix Differential ◽  
The Stability ◽  
Delay Matrix

This paper presents a chatter stability prediction method for milling flexible workpiece with end mills having asymmetric structural dynamics. The dynamic chip thickness regenerated by the vibrations of the rotating cutter and the fixed workpiece is transformed into the principle modal directions of the rotating tool. The process damping is modeled as a linear function of vibration velocity. The dynamics of the milling system is modeled by a time delay matrix differential equation with time varying directional factors and speed dependent elements. The periodic directional factors are averaged over a spindle period, and the stability of the resulting time invariant but speed dependent characteristic equation of the system is investigated using the Nyquist stability criterion. The stability model is verified with time domain numerical simulations and milling experiments.

Effect of Tool Condition on Cutting Mechanism in Micromilling

2019 ◽  
Author(s):  
Alwin Varghese ◽  
Vinay Kulkarni ◽  
Suhas S. Joshi
Keyword(s):  
Surface Finish ◽  
Micro Milling ◽  
Machining Parameters ◽  
Cutting Mechanism ◽  
Workpiece Material ◽  
Tool Condition ◽  
Force Signal ◽  
Surface Profiles ◽  
Cutting Mechanisms ◽  
Rapid Tool

Abstract Cutting mechanism in micromilling is governed by the tool condition along with the machining parameters and workpiece material properties. A rapid tool wear in micromilling often deteriorates the surface quality, which could be due to the occurrence of plowing. The effects of tool condition on the transition in cutting mechanisms from shearing to plowing have not been adequately addressed in micro milling. In this work, we attempt to correlate cutting mechanism with tool conditions, so that their influence on force and surface profiles are investigated. Micro milling experiments are performed to investigate these correlations. A fluctuation parameter has been defined to quantify the fluctuation in force signal. It is evident that as the feed varies from 0.2 μm/teeth to 5 μm/teeth, the fluctuation reduces and similar fluctuations are reflected on the generated surface also. The surfaces corresponding to lower force fluctuations has an Ra value less than 350 nm. As cutting edge radius increases, surface finish decreases. However, with chipping, new sharper cutting edges are formed which may improve the surface finish locally but contribute to the overall variation in the surface profiles.

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