Charmilles E110-D10 - Influence of the Type of Dielectric Fluid; Influence of the Graphite Grade

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The

electrode

wear

is

also

affected

by

renewal

of

the

dielectrid

fluid:

When

working

with

graphite

electrodes

it

is

best

to

provide

for

abundant

renewal

of

the

dielectrid

fluid,

thus,

the

machining

area

is

less

en-

dangered

by

pollution

with

consequent

reduction

of

the

risk

of

formation

of

short-circuits

or

sustained

arc

discharges

and

the

electrode

wear

is

also

slightly

decreased.

With

copper

electrodes,

however,

the

behaviour

is

different:

the

wear

ratio

increases

considerably

with

increasing

renewal

of

the

dielectric

fluid.

It

is

best,

therefore,

to

work

with

very

low

pressures

or

under

pulsed

injection

conditions

in

order

to

increase

the

life

of

the

electrodes.

The

removal

rate

decreases

slightly

as

flushing

is

decreased,

but

this

defect

receives

considerable

compensation

in

many

cases

where

the

wear

on

the

electrode

has

to

be

taken

into

consideration

(shaped

electrodes,

accurate

roughing

without

wear

on

the

electrodes,

etc.).

Pulsing

the

dielectric

feed

is

recommended

even

for

lateral

flushing

as

the

wear

of

copper

electrodes

can

be

severely

restricted,

for

certain

roughing

settings.

In

cases

where

the

electrode

wear

is

not

important,

it

is

best

to

work

with

abundant

renewal

of

the

dielectric

fluid

as

this

leads

to

increased

removal

rate.

2.

Influence

of

the

type

of

dielectric

fluid.

If

a

dielectric

fluid

other

than

Mentor

28

1s

used,

the

values

such

as

surface

finish,

sparking

gaps

and

influence

limits,

can

be

directly

related

with

the

removal

rate

resulting

from

use

of

said

fluid.

If

the

ratio

of

machining

rates

is

of

=

rate

with

oil

X

rate

with

Mentor

28

then

the

values

of

rugosity

as

well

as

those

of

sparking

gaps

and

influence

limits

are

to

be

multiplied

by

Vf

3.

Influence

of

the

graphite

grade.

The

only

differences

encountered

between

different

grades

of

graphite

will

be

the

amount

of

wear

and

the

arc

striking

ability.

The

graphite

used

is

Type

Ellor

9

manufactured

by

Carbone

Lorraine,

it

has

the

following

characteristics:

density:

tensile

strength:

resistivity:

1.8gr/cm3

700

kg/cm2

1500

f n

em.

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