Optimising EDM spark impulses shortens cycles 40%

An integrated system for optimizing the duration of EDM spark erosion impulses promises to shorten cycle times by up to 40% and reduce graphite electrode wear.

In the die-sinking branch of electrical discharge machining (EDM), graphite electrodes are now state of the art, and that is for good reason.

OPS-Ingersoll Funkenerosion, whilst taking notice of this trend, has developed a spark erosion optimization technology called 'multipulsePro' to enable users of its die-sinking machines to increase their machining productivity.

The technology has the potential to reduce machining time with graphite electrodes by as much as 40% and to reduce costs up to 50%.

OPS-Ingersoll die-sinking EDM machines equipped with multipulsePro - these can now be any of the company's machines that bear the designation 'Performance', which can easily be upgraded - provide the benefit of an optimized cycle through both hardware and software enhancements.

The technology improves process-monitoring hardware by not only monitoring but controlling the erosion process.

In the area of software, it enhances the function of regularly checking the current machine status.

What this means in practical terms is that the discharge speed will increase and electrode wear will decrease when multipulsePro is operating.

* Technical advances - multipulsePro is not simply an add-on solution but rather a complete technological adjustment and optimization, that is made evident by the catalogue of advantages the system introduces for the user.

First and foremost, it brings a clear reduction in the response time of the process-monitoring function.

Before the development of this technology, process monitoring involved the system responding to an observation of each electrical-discharge pulse once a statistical interpretation had been completed.

When discharges were determined to be degrading, among the reactions of the system would be a switching off of the discharge generator.

This resulted in processing intermissions of much greater duration than is the case with multipulsePro.

The new OPS-Ingersoll technology analyses each discharge pulse as it occurs and reacts before the pulse concludes.

Time also is a factor with regard to electrode wear behaviour.

The longer the duration of the impulse, the less rapidly the tool wears out.

But it is not possible to lengthen the pulse arbitrarily.

In practice, the power occasionally has to be reduced, for example, for the final processing step.

Process-related circumstances additionally may sometimes restrict adjustment of the time of the discharge pulse.

However, control by multipulsePro results in noticeably less electrode wear because of the synchronization of its process monitoring with the length of the spark impulses and flushing parameters.

Precision tool and die shops producing filigree (complex and delicate) geometries in graphite are the clear beneficiaries of this.

* Functional improvements - besides these technical innovations, the system is characterized by functional advancements.

An example is provided by the rinse system.

Full flushing recedes into the background more and more, with higher speeds and greater removal rates resulting in a consistent gap and a stable process, flushing the interval becomes more desirable and more common.

The rinsing technique continued to be improved by the engineers at OPS-Ingersoll.

The speeds became variable and the entire ram strategy changed with respect to the path and the jump-down time, which is now up to 0.25s.

This is especially important for eroding graphite, because high speeds are necessary to enable large jump movements.

This erosion technology has met the test of 10m/min travel speed.

Now, efforts are under way to find a means of making 20m/min practical.

To avoid having these elevated ram speeds become disadvantageous at shallow depths, the jump distances will be preset for the necessary depth from the control programme.

Furthermore, the area for very high discharge speeds was extended, since there is no risk when these are implemented upon any surface.

OPS-Ingersoll machines were formerly excellent for forming smaller ribs, but now they cover a far wider application spectrum.

During company tests, travel speeds of 1, 3, and 10m/min were used.

In the case of a slot geometry having a surface of up to 100mm2 in cross section, the highest speed used heretofore was 10m/min.

However, with the help of the newly developed technology, a cross-sectional surface of 250mm2 can now be machined at the same speed.

With the improved process monitoring of multipulsePro, a higher duty cycle of pulses can be attained-that is, the periods of electrical discharge relative to the length of pauses increase dramatically with multipulsePro.

The greatest advantages will accrue to users with critical manufacturing processes or workpiece cross-sectional surfaces as small as 1mm2.

Shop-floor tests conducted by OPS-Ingersoll with multipulsePro resulted in time savings of 17-40% for sparking jobs involving difficult electrodes.

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