For decades wire cutting has been synonymous with the efficient, high-precision machining of electrically conductive materials. Machine manufacturers regularly introduce innovative refinements such as automatic wire threading and the tubular shaft motor. However, no less important for cost-effective eroding processes are suitable software solutions. Only with highly evolved software is it possible to make efficient use of a wire EDM system’s hardware.
Wire EDM systems operate with extreme precision, with tolerances of a few thousandths of a millimetre. They generate outstanding finishes, operate with high process security and create the ideal conditions for unsupervised machining for long periods – advantages marginally offset by the longer machining times. What is obvious is that manufacturers of tools and moulds need cost-effective systems. And this is where wire-cutting machines with intelligent software come into their own.
As a leader in the wire EDM market, Mitsuibishi EDM never stops looking for ways to innovate. A perfect example: The new cylindrical-drive technology of Mitsuibishi EDM’s MV series wire EDM machines. The round magnetic shaft of the linear shaft motor creates a 360 degree magnetic flux for a revolutionary non-contact design.
Another example is the company’s partnership with a software firm that has been concentrating entirely on wire EDM for almost 30 years – DCAM GmbH. Managing Director Jens Franke is convinced that: “For companies that don’t constantly use their machines and only cut the simplest contours with them, the software solutions supplied by the machine manufacturer are sufficient. But the more complex the task, the more difficult it becomes to operate profitably with bottom-of-the-range CAM solutions.” DCAM has therefore developed an ingenious CAM solution that delivers a number of advantages.
DCAMCUT and Mitsubishi EDM cover areas such as less programming effort thanks to templates, deviations are programming errors, new 4-axis clearing process, code generated directly, finding the most cost-effective solution and training at the machine in an effort to provide users with a tool that is easy and quick to programme even for complex workpieces and one that ensures maximum process security and permits unsupervised machining over long periods.
Fiber optics improve EDM spark monitoring, wire life
During wire electrical discharge machining (EDM) operations, effective spark monitoring is essential to ensure process control, maximise wire life and prevent wire breakage. In working to improve the capabilities of its wire machines to best monitor the state of the electrical discharges between the wire and workpiece, Mitsubishi EDM ran into an unexpected problem: The electrical signals feeding back to the control were too slow for the monitoring system to make timely, necessary adjustments to on/off time and current on its new machines to maintain consistent sparks.
One design goal for those new machines was to reduce wire wear. “Previous generations of the company’s machines had stronger sparks discharged at a lower frequency, which can be hard on the wire because of the relatively high voltage required,” said Mike Bystrek, applications manager for MC Machinery, a subsidiary of Mitsubishi Corp that sells and services Mitsubishi EDM units and other equipment in the US during an interview published in Modern Machine Shop.
“The new machines can produce a higher number sparks per second with less intensity, which means we needed to improve our monitoring to differentiate between ‘good’ sparks and short circuits to maintain a uniform curve along the wire.”
The “curve” Mr Bystrek is referring to is the combined shape of the electrical arcs that form between the wire electrode and the workpiece. A wire produces more uniform electrical arcs when there are fewer short circuits that would increase wire wear and possibly create surface defects. To maintain uniform electrical arcs, the company needed to improve its spark-monitoring capabilities, but found that its older controls were not able to keep up with the pace of the new machines.
The crux of the challenge was simple: Electrical discharge machining relies on, well, electrical discharges. During operation, the spark travels from the wire electrode to the workpiece at roughly the same speed as the electrical signals moving through the wires of the monitoring system. However, the distance between the wire electrode and workpiece is far shorter than the distance between the spark and the control. This means that the control is processing out-of-date information because it receives the electrical signals well after each spark has completed, diminishing the machine’s ability to maintain uniform sparks. To solve this problem, the company developed the M800 series control, which uses fibre optic cables to increase data processing speed for its wire EDM units.
The solution is simple, but effective. While electrical wires are limited by the speed of electricity, fibre optic cables send data through light pulses that travel roughly 100 times faster than electrons through wires. By upgrading to “light speed,” the M800 is able to measure 128 000 sparks per second, a fourfold improvement over the company’s older controls. This enables the EDM unit to better maintain uniform spark output, reducing wear on the wire and decreasing the voltage required. Less wear on the wire translates to a slower spool and longer wire life, a cost saver for the user. According to the company, the new series of M800-equipped EDM units reduce wire usage by as much as 60 per cent compared to previous models.
The M800 comes standard with the MV1200R, MV2400R, MV1200S and MV2400S series of wire EDM units. The control’s new screen design puts spark monitoring information alongside machine progress and status, emphasising its importance. In addition to fibre optic signal transmission, the company has added other features to the M800, which include:
Legacy mode: This capability enables users to switch operating interfaces from the M800 to the M700 interface so that users who are familiar and comfortable with the older control can benefit from the M800’s features without having to learn a new interface
Onboard programming macros: This function is said to enable users to more easily programme common shapes by selecting the desired shape and inputing its dimensions.
Programme suspension: Operators can pause a job when another more urgent job must be processed and pick up from that paused state once completed.
Operational checklists: Setup personnel are said to be able to more easily set machining tasks in a specific order, and they have the option to gate tasks so that they must be completed in that exact order.
Mitsubishi EDM has enjoyed a long and established heritage, originally formed in 1959 to provide the latest technological products and solutions to the manufacturing industry.
Since the early days, the company has been synonymous with innovation and advancement, and renowned for offering the highest quality products.
Today, Mitsubishi EDM supply world leading Wire EDM, die sinking and high speed milling machines. Offering a full range of services, ranging from sales through to training and after-care, providing total solutions to a wide range of industries, including aerospace, engineering, medical, marine, mould and die.
Mitsubishi EDM’s range of machines offer the latest game-changing technology and deliver new levels of precision, performance and accuracy. This includes the fastest wire cutting EDM machine in the world, along with the highest precision, high speed EDM die sinking and start hole drilling systems, featuring lights out automation systems.
Mitsubishi EDM are represented in South Africa by WD Hearn Machine Tools. For further information contact them on TEL: 021 534 5351 or visit www.wdhearn.co.za