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

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
W. B. Ferry ◽  
Y. Altintas
Keyword(s):  
Cutting Forces ◽  
Orthogonal Cutting ◽  
Cutting Tools ◽  
Chip Thickness ◽  
Friction Angle ◽  
Flank Milling ◽  
Cutting Force Prediction ◽  
Jet Engine ◽  
End Mills ◽  
Five Axis

This work is the first of a two part paper on cutting force prediction and feed optimization for the five-axis flank milling of jet engine impellers. 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 angular motion 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 forces are shown to be in reasonable agreement with those collected during a roughing operation on a prototype integrally bladed rotor.

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).

Cutter-Workpiece Engagement Calculations by Parallel Slicing for Five-Axis Flank Milling of Jet Engine Impellers

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
W. Ferry ◽  
D. Yip-Hoi
Keyword(s):  
Cutting Forces ◽  
Solid Modeling ◽  
Boundary Representation ◽  
Flank Milling ◽  
Jet Engine ◽  
Current Configuration ◽  
End Mills ◽  
Machining Operations ◽  
Intersection Curves ◽  
Five Axis

Cutter-workpiece engagement maps, or cutting flute entry/exit locations as a function of height, are a requirement for prediction of cutting forces on the tool and workpiece in machining operations such as milling. This paper presents a new method of calculating tool-part intersection maps for the five-axis flank milling of jet engine impellers with tapered ball-end mills. The parallel slicing method (PSM) is a semi-discrete solid modeling technique written in C++ using the ACIS boundary representation solid modeling environment. The tool swept envelope is generated and intersected with the workpiece to obtain the removal volume. It is also subtracted from the workpiece to obtain the finished part. The removal volume is sliced into a number of parallel planes along a given axis, and the intersection curves between each tool move and plane are determined analytically. The swept area between successive tool positions is generated using the common tangent lines between intersection curves, and then removed from the workpiece. This deletes the material cut between tool moves, ensuring correct engagement conditions. Finally, the intersection curves are compared to the planar slices of the updated part, resulting in a series of arcs. The end points of these arcs are joined with linear segments to form the engagement polygon that is used to calculate the engagement maps. Using this method, cutter-workpiece engagement maps are generated for a five-axis flank milling toolpath on a prototype integrally bladed rotor with a tapered ball-end mill. These maps are compared to those obtained from a benchmark cutter-workpiece engagement extraction method, which employs a fast, z-buffer technique. Overall, the PSM appears to obtain more accurate engagement zones, which should result in more accurate prediction of cutting forces. With the method’s current configuration, however, the calculation time is longer.

Influence of Reground Tool Sharpness on Micro-Cutting Process

2010 ◽  
Vol 37-38 ◽  
pp. 550-553
Author(s):  
Xin Li Tian ◽  
Zhao Li ◽  
Xiu Jian Tang ◽  
Fang Guo ◽  
Ai Bing Yu
Keyword(s):  
Cutting Forces ◽  
Orthogonal Cutting ◽  
Cutting Tools ◽  
Chip Thickness ◽  
Cutting Edge ◽  
Cutting Process ◽  
Micro Cutting ◽  
Temperature Distributions ◽  
Edge Radius ◽  
1045 Steel

Tool edge radius has obvious influences on micro-cutting process. It considers the ratio of the cutting edge radius and the uncut chip thickness as the relative tool sharpness (RST). FEM simulations of orthogonal cutting processes were studied with dynamics explicit ALE method. AISI 1045 steel was chosen for workpiece, and cemented carbide was chosen for cutting tool. Sixteen cutting edges with different RTS values were chosen for analysis. Cutting forces and temperature distributions were calculated for carbide cutting tools with these RTS values. Cutting edge with a small RTS obtains large cutting forces. Ploughing force tend to sharply increase when the RTS of the cutting edge is small. Cutting edge with a reasonable RTS reduces the heat generation and presents reasonable temperature distributions, which is beneficial to cutting life. The force and temperature distributions demonstrate that there is a reasonable RTS range for the cutting edge.

Cutter-Workpiece Engagement Calculations by Parallel Slicing for Five-Axis Flank Milling of Jet Engine Impellers

2007 ◽  
Author(s):  
W. Ferry ◽  
D. Yip-Hoi
Keyword(s):  
Application Programming Interface ◽  
Solid Modeling ◽  
Flank Milling ◽  
Workpiece Material ◽  
Jet Engine ◽  
End Mills ◽  
Slicing Method ◽  
Machining Operations ◽  
Intersection Curves ◽  
Five Axis

Cutter-workpiece engagement maps, or cutting flute entry/exit locations as a function of height, are a requirement for prediction of cutting-forces on the tool and workpiece in machining operations such as milling. This paper presents a new method of calculating tool-part intersection maps for five-axis flank milling of jet engine impellers with tapered ball-end mills. It is called the parallel slicing method (PSM) and is a semi-discrete solid modeling technique written in C++ using the ACIS B-rep solid modeling environment. Although it is tailored towards five-axis flank milling, it can also be applied to both planar and multi-axis milling processes. The tool swept envelope is generated and intersected with the workpiece to obtain the removal volume. The removal volume is then sliced into a number of parallel planes along a given axis and the intersection curves with the tool and each plane are determined analytically. The swept area between the intersection curves of successive tool moves is calculated by solving for the area enclosed by the tangent lines. This area is removed from the workpiece material, which deletes the material cut between tool moves. Finally, the intersection curves are compared with the planar slices of the updated part, which results in a series of arcs. The end points of these arcs are joined with linear segments to form the engagement polygon which is used to calculate the engagement maps. Using this method, cutter-workpiece engagement maps are generated for a five-axis flank milling toolpath on a prototype integrally bladed rotor (IBR) with a tapered ball-end mill. These maps are compared with those obtained from a benchmark cutter-workpiece engagement calculation method – the Manufacturing Automation Laboratory’s Virtual Machining Interface (MAL-VMI). The MAL-VMI uses an application programming interface (API) in a commercial NC verification software package to obtain cutter-part intersections through a fast, z-buffer technique. Overall, the parallel slicing method appears to obtain more accurate engagement zones than those given by the MAL-VMI, although the calculation time is longer.

scholarly journals Analytical modelling of cutting forces in near-orthogonal cutting of titanium alloy Ti6Al4V

2014 ◽  
Vol 229 (6) ◽  
pp. 1122-1133 ◽  
Author(s):  
Yun Chen ◽  
Huaizhong Li ◽  
Jun Wang
Keyword(s):  
Titanium Alloy ◽  
Cutting Forces ◽  
Chemical Reactivity ◽  
Orthogonal Cutting ◽  
Chip Thickness ◽  
Analytical Modelling ◽  
Shear Instability ◽  
Published Data ◽  
Machining Processes ◽  
Titanium Alloy Ti6al4v

Titanium and its alloys are difficult to machine due to their high chemical reactivity with tool materials and low thermal conductivity. Chip segmentation caused by the thermoplastic instability is always observed in titanium machining processes, which leads to varied cutting forces and chip thickness, etc. This paper presents an analytical modelling approach for cutting forces in near-orthogonal cutting of titanium alloy Ti6Al4V. The catastrophic shear instability in the primary shear plane is assumed as a semi-static process. An analytical approach is used to evaluate chip thicknesses and forces in the near-orthogonal cutting process. The shear flow stress of the material is modelled by using the Johnson–Cook constitutive material law where the strain hardening, strain rate sensitivity and thermal softening behaviours are coupled. The thermal equations with non-uniform heat partitions along the tool–chip interface are solved by a finite difference method. The model prediction is verified with experimental data, where a good agreement in terms of the average cutting forces and chip thickness is shown. A comparison of the predicted temperatures with published data obtained by using the finite element method is also presented.

Virtual Five-Axis Flank Milling of Jet Engine Impellers—Part II: Feed Rate Optimization of Five-Axis Flank Milling

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
W. B. Ferry ◽  
Y. Altintas
Keyword(s):  
Feed Rate ◽  
Tool Path ◽  
Fixed Time ◽  
Flank Milling ◽  
Tool Deflection ◽  
Jet Engine ◽  
Root Finding ◽  
Five Axis ◽  
Feed Rate Optimization ◽  
Chip Load

This paper presents process optimization for the five-axis flank milling of jet engine impellers based on the mechanics model explained in Part I. The process is optimized by varying the feed automatically as the tool-workpiece engagements, i.e., the process, vary along the tool path. The feed is adjusted by limiting feed-dependent peak outputs to a set of user-defined constraints. The constraints are the tool shank bending stress, tool deflection, maximum chip load (to avoid edge chipping), and the torque limit of the machine. The linear and angular feeds of the tool are optimized by two different methods—a multiconstraint based virtual adaptive control of the process and a nonlinear root-finding algorithm. The five-axis milling process is simulated in a virtual environment, and the resulting process outputs are stored at each position along the tool path. The process is recursively fitted to a first-order process with a time-varying gain and a fixed time constant, and a simple proportional-integral controller is adaptively tuned to operate the machine at threshold levels by manipulating the feed rate. As an alternative to the virtual adaptive process control, the feed rate is optimized by a nonlinear root-finding algorithm. The virtual cutting process is modeled as a black box function of feed and the optimum feed is solved for iteratively, respecting tool stress, tool deflection, torque, and chip load constraints. Both methods are shown to produce almost identical optimized feed rate profiles for the roughing tool path discussed in Paper I. The new feed rate profiles are shown to considerably reduce the cycle time of the impeller while avoiding process faults that may damage the part or the machine.

Mechanics and Dynamics of Hard Turning Process

2004 ◽  
Author(s):  
Kivilcim Buyukhatipoglu ◽  
Ismail Lazoglu ◽  
Hubert Kratz ◽  
Fritz Klocke
Keyword(s):  
Cutting Forces ◽  
Hard Turning ◽  
Prediction Models ◽  
Orthogonal Cutting ◽  
Cutting Tools ◽  
Temperature Fields ◽  
Turning Process ◽  
Cycle Times ◽  
High Productivity ◽  
Recent Developments

In precision machining, due to the recent developments on the cutting tools, machine tool structural rigidity and improved CNC controllers, hard turning is an emerging process as an alternative to some of the grinding processes by providing reductions in costs and cycle-times. In industrial environments, hard turning is established for geometry features of parts with low to medium requirements on part quality. Better and deeper understanding of cutting forces, stresses and temperature fields, temperature gradients created during the machining are very critical for achieving highest quality products and high productivity in feasible cycle times. In order to enlarge the capability profile of the hard turning process, this paper introduces to prediction models of mechanical and thermal loads during turning of 51CrV4 with hardness of 68 HRC by CBN tool. The shear flow stress, shear and friction angles are determined from the orthogonal cutting tests. Cutting force coefficients are determined from orthogonal to oblique transformations. Cutting forces and surface profiles are predicted and compared with experimental measurements.

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.

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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