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metal shell is a further problem. For epoxy materials,

thermal disengagement could distort the copper shell, thus

it is to be applied after the back filling process. This causes

problems too. The most common procedure is to preheat

the copper shell and use a low melting alloy material as

backfiller, and then to remove the mandrel by heating.

Even if the above is taken into account, the uneven copper

shell thickness causes premature wear to this kind of

electrode too.

In addition to the above problems, the ‘stair stepping’

problem must be considered for complex electrodes.

Experimental investigations have shown that under strict

conditions simple shaped metal shell electrodes can com-

pared to conventional electrodes. Also, electroformed

electrodes seem to have better performance on rough EDM

and electroplated ones on finishing applications.

The potential of using other RP techniques to produce

RT electrodes has been investigated too. Even though some

of them give faster prototypes than SLA, the dimensional

accuracy and surface roughness of these processes are not

appropriate for EDM. Nevertheless, if these processes are

chosen to be used for RT electrode fabrication, some

modifications of the above-mentioned procedures mustbe

made. For example in this case it is better to apply the first

metallization by brushing or spraying.

Soft tooling of RP patterns could also be an alternative

to produce more than one similar electrode for sequential

EDM.

On the other hand, direct metal electrodes whichare

produced by RP techniques [3,55–59] demonstrate the

same disadvantages; poor surface roughness and dimen-

sional accuracy.

DLMS and IMLS seem to give the most accuratepro-

totypes. Thus, these techniques were tested for metal tools

and final parts.

Simple shaped electrodes were fabricated and tested in

several EDM applications such as roughing, semi-roughing

and finishing.

The results have been disappointing until now for

industrial production of RT electrodes. But investigations

of MMC selective laser sintering electrodes were promis-

ing indicating that if the RP part final quality is improved

then MMC electrodes will give a better EDM performance.

DMLS also promises better material powder systems that

will overcome porosity and uncontrolled shrinkage issues.

Until now infiltration or electroplating of copper on RP

metal parts has not given the appropriate quality for

industrial use either.

Finally, cast made electrodes do not meet the specifi-

cations of EDM yet. The development of an appropriate S/

W, which will manipulate an STL file of an RP pattern for

EDM use, is needed. This S/W will incorporate features

like scaling, cutting, joining, etc., of the STLpart taking

into account the EDM specifications. Also, it must produce

the technological program for CNC finishing automati-

cally. These programs will be useful for other RT electrode

methods too.

Although variations of RT electrodes were developed

and research was performed extensively, until now the

results of RT electrode performance have shown that they

do not meet the desirable standards for use as an alternative

to conventional CNC or high speed machining (HSM)

milling electrodes.

RP techniques need improvement and redesign as

manufacturing processes rather than as prototyping pro-

cesses. Also, the mechanical properties of RP available

materials must be investigated more extensively and the

material systems must be expanded.

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