Summer 1998

Pelco Tool & Mold Inc. and Micro-graph 4

Pelco was started in 1963 by Emil Peluso with a few machines in the basement of his home. His original business was machining graphite electrodes for Electrotools, the forerunner to Intech EDM.

The company grew to become a mold making shop, purchasing their first EDM machine in 1972. Mr Peluso retired and sold the company to three employees- Dick Truhlar, now President, Rob Suva, and Roger Wittersheim. Pelco now employs 30 mold makers, utilizing both wire-cut and sinking EDM, including a new CNC sinking machine with auto-matic tool changel The wire-cut machine is used primarily to manufacture precision graphite electrodes.

The company specializes in making 3-D plastic injection molds, and supplies tooling for intricate container caps, called "closures", which are used by major packaged goods manufacturers.

Although they use MG5 and some POCO graphite, their primary graphite grade for electrodes is Micro-graph 4 (MG4), which is used on 90% of their jobs. They have found it to be an excellent, cost effective general purpose graphite, with an excellent wear ratio and outstanding performance in no wear sinking applications. MG4 exhibits low wear on high amperage roughing operations, and yet can still hold details in finishing mode.

Following are some interesting examples of their work and how they effectively use EDM and MG4.

Arestor Bracket

Shown is an arrester bracket for insulators used in electrical transmission installations, the compression mold halves, and the M04 electrodes used to make the molds. Pelco uses two identical 0.015" undersize electrodes to rough and finish with orbiting for both. Roughing is done in 12 hours at a high amperage, no-wear setting; orbiting 0.005 " per side. The finish electrode orbits to final size and finish. After EDMing, the molds are chrome plated to 0.002" tolerance.


Seat Belt Cover and Toaster Base

The toaster base illustrates MG4's ability to create extensive ribbing and fine detail.

The 4-cavity seat belt cover mold is produced using 5 electrodes, orbiting a total of 0.015" per side in a rough milled cavity. The first electrode uses a 0.004" orbit in no wear mode. The finishing electrodes create the final, EDM textured finish.


Router Housing

These molds were a challenge to Pelco; they couldn't orbit the electrodes due to a concave bottom, and flushing was difficult due to depth and the intricate design. However, MG4 held the detail necessary and had an excellent wear ratio in this difficult job. The molds were stone polished and textured after EDMing.


"Closures"

These "closures", or container caps, are a speciality of Pelco Tool. The company builds models, from which they then tracer mill electrodes. The 24 cavity molds are EDMed on a CNC sinking machine with 16 position automatic tool changer.

Electrodes are typically 0.006" per side underside and can complete 8 cavities before needing to be replaced. Some roughing is accomplished using 20 amps and jet flushing, but the majority of the roughing is at 12 amps, with finishing at 3 amps.