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Reliability has more impact on machine throughput and productivity than on pure cutting speed. The very nature of the wire EDM and the systems required to control the (wire) cutting tool is critical to machine performance. Higher flushing pressures and premium wires (electrodes) all have had an impact on machine performance and cutting speeds. Faster machining rates result in the need for stiffer, more rigid machine structures and tooling.

The type of wire also will impact overall cost and performance. Standard brass wires are used more than any other wire type by a large-up to 80 percent-margin. When using standard 0.010" O brass wire you can expect a consistent, reliable wire EDM cutting speed of approximately eighteen to twenty inch}/hour. Unfortunately, the EDM process creates minute chips and debris that can adversely affect the reliability of this transport system. For this reason, a wire EDM machine requires much more maintenance than virtually any other conventional machine tool.

Premium coated wires offer enhanced performance for certain types of applications, overall operating costs caused by higher-wear parts and consumables including contacts, filters, resin and guides all will have an impact on the bottom line. Coated wires will machine faster than uncoated brass. The outer coating melts rapidly cooling the wire and increasing the size of the spark gap, providing better flushing. Some wires may provide a better finish than brass. Knowing which wire to use for your particular application will help to make you profitable.

It is important to match the correct tool with the application. It is just as important to prevent throwing your money away. Obviously, the earning capacity of a CNC machine tool is more valuable than a few dollars worth of wire, unless of course the wire is simply being wasted. Depending upon the wire being used, the few dollars an hour can translate into thousands of dollars a year.

In addition, the complexity of the wire transport system and automatic wire threader (AWT) both have a direct impact on performance. Since the wire used in the wire EDM is small and flexible, no more than two times larger (0.008" to 0.010") than a human hair, threading reliably over long periods of time without extensive maintenance has been perceived as a problem. However, the most important feature of a wire EDM machine, in terms of real profitability to the end user, is the AWT-a reliable AWT system can add many hours of available machine time every week, month and year. The AWT makes it possible to schedule work more efficiently on the wire EDM machine based upon the importance rather than the length-time-of cut. Most AWTs use a high-pressure water jet as the main wire transport system between the upper and lower guides. The entire transport system must be maintained according to the manufacturer's recommendations. Wire guide types, the complexity of the jet, the cutting system, drive pulleys and tensioning all have an impact on reliability and performance.

(Source: Machining Variables Influencing High-Performance Wire EDM)

Due to the electro-mechanical nature of wire EDM machines, there are several items in normal operation that routinely wear and require cleaning and/or replacement. If certain machine components are not properly cared for, machining speeds and accuracies will rapidly decay.

The most important reason to properly schedule and perform this routine wire EDM maintenance is to ensure consistent and repeatable machining results for the aforementioned machine traits of speed, accuracy and surface finish. This level of maintenance also prevents machine failure and unexpected machine downtime.

There are several wire EDM machine tool manufacturers, and there are some significant differences in the machine design of each. But the importance and type of basic items that need to be maintained on all wire EDMs are very similar. When planning and scheduling wire EDM machine maintenance, required actions can be grouped into short interval and long interval items.

Short interval items vary in occurrence from weekly to monthly.

1. Automatic Wire Threading System
2. Power Contacts
3. Belts and Rollers
4. Brake/Clutch Roller
5. Wire Guides
6. Wire Alignment
7. Wire Collection Box
8. Machine Seals
9. General Cleaning

Long interval items vary from bi-monthly to yearly.

1. Machine Filters
2. De-ionization Resin
3. Water Level
4. Belts, Rollers and Pulleys
5. Wire Choppers
6. Cabinet Filters
7. Machine Seals
8. Machine Floats
9. Water Reservoir
10. Machine Lubrication

Good cleaning habits and care of a wire EDM machine is highly recommended. Regular and systematic cleaning of the machine also can extend the life of some consumable items.

(Source: Maintaining a Wire EDM Machine)

In the machine tool world, the sinker EDM is like a military tank, and in many mold shops the oldest CNC machine in use is often a sinker EDM. They have few moving parts and a very robust electrical system that allow them to continue to make good parts for a long time. This makes it difficult for a company to justify the cost of upgrading technology. In the end, however, even the best-kept machine reaches a point where performance, throughput, accuracy and quality concerns tip the scales toward purchasing new equipment, and advancements in sinker EDM technology can help justify a new machine.

Modern mold shops have become more competitive by having fewer people run more equipment, and today’s EDMs are easier to run. New controls are more menu-driven and allow operators to become quickly proficient at machine operation. Being able to manipulate settings for the correct surface area, flushing and undersize is important for achieving good results, and the modern EDM allows operators to create custom settings by filling out a menu-driven form, making it much easier to achieve those great results. 

Improved jump speeds and ease of operation are factors that moldmakers can easily observe, but the best improvements in modern EDMs are under the hood, in the areas of electronics, processing speed, and waveform creation and adjustment. The best way to determine if it is time to upgrade your EDM to the newest technology is to offer a supplier your most common and challenging cuts and see how the new technology performs.

(Source: Justifying an EDM Upgrade)