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A Study of Fixture Layout and Clamping Force for a Ti-6Al-4V Disk in a Vertical Turning Lathe Numerically Controlled Machine
Maureen Fang Sept 17, 2009
Overview
Vertical Turning Lathe (VTL) Machine
Fixture-Disk Assembly Cutting Forces Finite Element Models in ANSYS Initial Fixture Layout Deflections within Disk Questions
Vertical Turning Lathe (VTL) Machine
Machine Table/
Worktable
Numerically Controlled Unit
Tool Head
Fixture-Disk Assembly
Clamp
Plate
DiskInner Diameter=0.457m (18 in)Outer Diameter=0.508m (20 in)Height=0.0508m (2 in)
Locator
Machining an Outer Diameter
Cutting Tool
Cutting Forces Orientations
Cutting Forces Calculation Flow Diagram
Tool Geometries
Machining Parameters
Input Variables
Normal Shear Angle
Chip Compression Ratio=1.2
Cutting Constants
Cutting Forces Formulas
Cutting Forces (Fr, Ft, Ff)
Formulas and assumptions from
Manufacturing Automation By Y.
Altintas
Normal rake angle
Matlab Codes
Input Variables Tool Geometry Machining
Parameters
Cutting Forces Results are
generated by Matlab codes for both oblique and orthogonal cutting
Orthogonal cutting has only two cutting forces components
Tangential force is the dominate component.
Cutting Forces using Feedrate=0.178mm/rev or 0.007 in/rev
0.0
50.0
100.0
150.0
200.0
250.0
300.0
0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700
Depth of cut (mm)
Cu
ttin
g F
orc
es (
N)
Ft, Tangential Ff, feed Fr, radial Ft. Tangential_Orthogonal Ff, feed_Orthogonal
Tangential Force
Orthogonal Cutting
Finite Element Model in ANSYS
Number of elements 32000
Number of Nodes 38720
Degree of Freedom per Node 6
Type of Elements Brick
Material of Workpiece
Ti-6Al-4V
Modulus of Elasticity 110 GPa
Poisson Ratio 0.34
Clamps, Locators, and Cutting Forces applied to Initial Fixture Layout
Cutting Forces Orientations Magnitude(N)Fr, radial -x 10Ft, Tangential -y 736Ff, feed -z 275
Cutting Speed
Feed Rate,
h
Depth of Cut,
bm/min mm/rev mm
Finish 60 0.178 0.635
Type of Cut
• Locators are constraint in 3 axis
• Clamping Force = 1500N
Deflections within a Finish Cut
Top
Bottom
Middle
1.40E-05
1.45E-05
1.50E-05
1.55E-05
1.60E-05
1.65E-05
1.70E-05
1.75E-05
1.80E-05
1.85E-05
1.90E-05
Location of cutting forces (node position)
Dis
pla
ce
me
nt
ve
cto
r s
um
(m
)
The “U” shape curve presents the magnitude of deflection changes as the cutting tool travels from the top to the bottom surface of the disk.
The displacement vector sum is largest at the top.
The subsequent models will have the cutting forces applied at the top surface.
Key Locations to Represent a Dynamic Machining Process
ANSYS model is static analysis of a dynamic process. Therefore, selected cases are used to represent snap shots of the overall machining process.
Point A, B, and C are key locations of disk where cutting forces have been applied, as disk rotates.
Displacement vector sum
6.00E-06
8.00E-06
1.00E-05
1.20E-05
1.40E-05
-50 -40 -30 -20 -10 0 10 20 30 40 50
Circumferential location of one clamp and locator w ith respect to cutting forces (degree)
Disp
lace
men
t (m
)
Displacement Vector Sum
A
B
C
Displacement components
0.00E+00
1.00E-06
2.00E-06
3.00E-06
4.00E-06
5.00E-06
6.00E-06
7.00E-06
8.00E-06
9.00E-06
1.00E-05
-50 -40 -30 -20 -10 0 10 20 30 40 50
Circumferential location of one clamp and locator w ith respect to cutting forces (degree)
Dis
plac
emen
t (m
)
maximum x-component Displacement Absolute minimum y-component Displacement Absolute minimum z-component Displacement
Displacement Components Z-component = axial direction
Y-component = circumferential direction
Clamp and locator is aligned with cutting forces at Key Location “B”
X-component = radial direction
Contour Plots from ANSYS
Questions
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