One EDM machine builder satisfies mould maker’s wide-ranging needs

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Mould making

C&M Mould Tools’ mould making projects range from simple moulds for large parts to ultra-precision moulds for contact lenses, the latter being a chief customer these days.

A recent contract for a very small automotive clip to be produced in an eight-cavity mould tool led to the company’s latest investment. Moth explains. “It is one of the reasons we purchased the new NX3 ONA machine, which replaced a previous-generation ONA EDM machine. We secured the new customer, and part of the work involved very fine sparking.”

Installed in early October 2011, the machine has not stopped running since it was commissioned, says Moth.

“The new machine uses graphite electrodes much more efficiently than the old machine,” he reports. Electrodes are produced in batches on a dedicated Mazak high-speed graphite-machining centre using diamond-coated cutting tools. “Graphite machining is much quicker,” says Moth. “We try to avoid using copper these days.”

Running the machines

EDM material supplier Erodex provides C&M with high-quality graphite and, as a one-stop-shop, equips the ONA NX3 with advanced EDM 244 dielectric fluid. With a high-performing oxidation inhibitor, the fluid offers a long operating lifetime, minimises corrosion and, because of its high dielectric strength, keeps mould-polishing time short. The fluid’s low viscosity allows rapid flushing at the point of cut and eliminates DC arcing because its high API gravity promotes rapid settling of particles into the filter.

An apprenticeship programme results in many trainees staying long-term with C&M Mould Tools, which has 14 highly skilled employees. Operators run several machines throughout the company, and just one person runs the EDM section, which comprises the NX3, two other ONA machines, a wire-cutting machine and the graphite-machining centre.

Before any mould tool requiring modification arrives at C&M, the graphite electrodes are already produced. “The tool needs to be in the press as long as possible,” says Moth, “because our customers run lean and do not carry stock. They mould parts as they are required, so we have to keep the downtime to a minimum. From the CAD data we can produce the insert with the modified details and then simply create a pocket and press the insert into the tool.”

See: ETMM to publish official daily newspaper at EuroMold 2012

C&M operators program CNC metal-cutting machines at CAM stations on the shop floor. However, graphite electrodes are programmed offline in the office. The CAM model of the electrode is sent to the ONA NC system so the operator can manipulate and examine it before machining commences. This additional visual check helps ensure that everything is correct before the start button is pressed.

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