Rotating Curvilinear Tools for EDM of

Polygonal Shapes with Sharp Corners

Y. Ziada, P. KoshyMcMaster University, Canada

57th CIRP General Assembly, DresdenAugust 21, 2007

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

Flushing of the interelectrode gap is of critical importance in EDM processes, in regard to machining productivity and machined surface quality

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

Several techniques can be used to facilitate flushing in EDM

through-tool forced flow

jump EDM

jet flushing

horizontal EDM

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

Another approach to flushing is to induce a relative motion between the electrodes

ED-millingplanetary EDM

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

The present work involves kinematic aspects of rotating curvilinear tools for sinking cavities with sharp corners

rotating

sharp corners

toolscurvilinear

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

Reuleaux Triangle

s

1

23

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

Reuleaux Triangle is a curve of constant width that can rotate inside a square

s

s

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

Kinematics of a Reuleaux Triangle

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

For every revolution of the Reuleaux Triangle, the centroid traverses the orbit three times in the opposite direction

The swept area is 98.8% of that of the square

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

The area of a Reuleaux Triangle is 70.5% of that of the squareA circular tool for machining a similar corner will only be 4% of the area of the square

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

Replacing the complex orbit with a circular one facilitates implementation on a machine tool with a single servo-controlled axis, and entails a maximum profile deviation of only 0.003s

Figure 2: Performance of RT and conventional tools.

0 25 50 75 100 125

0

2

4

6

8

Vo

lum

e R

em

ove

d (

x 1

03m

m3)

Time (min)

RT tool (20 rpm)

Stationarytool

25 mm

(c)

(a) (b)

arcing

U 60 VI 72 Ati 42 sto 49 s

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

Reuleaux Triangle tools correspond to improved removal rates and better surface quality

Figure 2: Performance of RT and conventional tools.

0 25 50 75 100 125

0

2

4

6

8

Vo

lum

e R

em

ove

d (

x 1

03

mm

3)

Time (min)

RT tool (20 rpm)

Stationarytool

25 mm

(c)

(a) (b)

arcing

U 60 VI 72 Ati 42 sto 49 s

Stationary

Figure 2: Performance of RT and conventional tools.

0 25 50 75 100 125

0

2

4

6

8

Vo

lum

e R

em

ove

d (

x 1

03m

m3)

Time (min)

RT tool (20 rpm)

Stationarytool

25 mm

(c)

(a) (b)

arcing

U 60 VI 72 Ati 42 sto 49 s

RT

25 mm

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

Machining of a square with a sharp corner using Reuleaux Triangle tools involves modifications to tool shape and tool path

k = 1.93 for an included angle of 90 degrees

s ks s ksks

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

Modification to tool pathY

0.034

number of sides

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

Machining of a square with a sharp corner

Locus magnified 2X

10 mm

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

Extension of the concept to machine regular polygons

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

Machining of a hexagon

Locus magnified 2X

5 mm

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

Machining of a non-regular polygon

Locus magnified 2X

5 mm

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

Machining of a triangle

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Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

Conclusions

Innovative kinematic schemes motivated by the concept of Reuleaux Triangle for the seemingly impossible task of using rotating tools to sink polygonal shapes with sharp corners are presented

Application of the technology enhances gap flushing while maximizing the frontal machining area

Efforts are required to address tool wear issues resulting from the adverse geometric relative duty of Reuleaux Triangle tools

The work represents a significant advance towards exploiting the capabilities of CNC ram EDM

Rotating Curvilinear Tools for EDM of Polygonal Shapes with Sharp CornersY. Ziada, P. Koshy

57th CIRP General AssemblyDresden, Germany, August 21, 2007

For more information please see:

Y. Ziada, P. Koshy, Rotating curvilinear tools for EDM of polygonal shapes with sharp corners,

Annals of CIRP 56 (2007) 221-224.

or email:

koshy@mcmaster.ca