How to ensure wire EDM upkeep

Some telltale signs that a wire EDM system requires maintenance include decreased machine performance, issues with speeds, and excessive wire breakage. Phuchit/iStock/Getty Images Plus

Wire electrical discharge machining (EDM) has advanced and become commonplace on the shop floor. This is partly because it has become easier to use and provides significant productivity gains through reduced cycle time, increased accuracy, and high surface finish capabilities.

Today’s wire EDM machines can produce micromachined parts with details so tiny that they are almost invisible at first glance.

However, these machines tend to be highly susceptible to poor performance because of maintenance neglect, which negates the benefits of this precision process.

“You will start to see decreased machine performance, issues with speeds, and excessive wire breakage,” said Mike Bystrek, national wire EDM product and application manager, MC Machinery, Elk Grove Village, Ill. “These signs will signal that some maintenance is required. However, there are certain things that you can do on a regular basis to ensure your machine is running at peak performance and throughput.”

Manufacturers that use EDM, especially those in production environments, often have a good understanding of what’s necessary to keep their machines running well, and they have a dedicated person who ensures the machines are maintained.

Some shops, especially those with high-mix/low-volume production environments, may not have the resources or knowledge to ensure proper machine upkeep.

In these situations, machine owners should reach out to the OEMs, who can provide proper maintenance guides or training to help develop in-house skills. Shop owners wanting to outsource this task can invest in preventive maintenance (PM) programs offered by OEMs or other service providers, where a trained professional performs PM at various intervals throughout the year or life cycle of the machine.

Wire EDM uses dielectric water, which is essential for proper machining processing.

“The dielectric water flushes out the cut surface where the material is being melted,” said Scott Gaal, operations and consumable sales manager, Sodick, Schaumburg, Ill. “That water is recirculated into a supply tank and filtered out and returned into the tank. There is a lot that goes into ensuring this is maintained. If this is not done properly, you might see pitting on the workpiece because you will have particulate in the water with a secondary discharge.”

For the most part, the wire EDM process is inherently dirty, especially depending on the material being cut. Filtration is essential to purify the water and remove debris.

Shops that perform a visual inspection before machining can ensure that all components are in good working order. Sodick

When the main water filters are depleted, most machines will signal that a change is needed. Some high-production shops may be able to better predict filter replacement intervals, but for the most part, it fluctuates based on the type of work, workpiece material, and other factors.

The filter system on a wire EDM system is essential to controlling the amount and size of particles and debris that can exist and be circulated through the flushing system during machining.

“It’s important to use the proper filtration media to collect the particles of dirt that are going inside the supply tank,” said Gaal. “There are different kinds of grades of filters. You can get 20-, 10-, 5-, and 3-µm filters to filter the water properly.”

Using a higher-micron filter will capture the larger particles, but some of the smaller particles will still get through. They tend to be cheaper, and because they only capture larger particles, but they won’t deplete as quickly.

“In the end, you're not doing yourself any favours because you're just putting more wear and tear in the end on that machine,” said Gaal. “It doesn't happen overnight, but over a period of time, when that doctor bill comes, it's going to be a big one.”

Deionization resin (di-resin) controls the conductivity of the water within the machine. If the water conductivity is not controlled or maintained to a certain level, the process will become unstable.

Many machines will signal when resin needs to be replaced. Tools such as conductivity probes require cleaning to ensure that they can attain accurate readings.

“Very clean water, like city water, does not have a lot of minerals in it,” said Gaal. “The resin bed should last a long time. However, if you are working in rural areas or pumping water from a well, it could have a high mineral content, meaning that the resin will deplete much faster. This is something to keep in mind.”

Manufacturers that use wire EDM should know that general maintenance practices, regardless of machine brand or model, are generally the same. Certain things should be checked and maintained in the short term, whether daily or weekly.

“Do a visual inspection before you actually start machining and make sure the upper and lower head assembly, where the wire is fed through, and the plastic nozzle that jets the water are fully intact and there are no missing or scratched pieces,” said Gaal.

A carbide power feeder should be indexed for wear (wear area circled in blue) every 80 to 100 hours based on application and wire size. MC Machinery

Water flow is essential for the precision process to work efficiently. The plastic nozzles are the machine's sacrificial components and often are inexpensive to replace. However, if they are not checked regularly, broken or damaged nozzles can cause wire breaks and other issues.

Wire guides, whether diamond or sapphire, need to be indexed after a certain number of operational hours. They are in both the upper and lower heads and are used to align and locate the wire within the machine.

“We use flat-plate carbide power feeders,” said Bystrek. “The feeder is where the wire rides along, and it’s what is putting energy to the wire. As usage of the machine increases, the feeders wear, and they need to be indexed every so many hours. It’s important to rotate the power feeders every so many hours. It is as simple as popping open a lever mechanism and moving it over with a scale tool that is provided. It gives you a new index of power.”

Carbide contacts need to be indexed 80 to 100 hours based on the application and wire size, which requires an operator to stop the machine briefly. This helps ensure that the flow of electricity can move from one head to the next.

Cleaning the machine each day, when it is not in use, is a great way to maintain the components of this somewhat dirty process.

“If you're not running the machine, rinse out the work tank and wash away any loose material and wipe down any surface so that particulates don’t dry or adhere to the sides of the tank or any work surfaces and leave them gritty,” said Bystrek. “A simple wash hose on the machine can be used to wash everything down periodically to reduce overall maintenance. General cleaning is one of the most overlooked items of wire EDM maintenance.”

There are several different maintenance checks that need to be performed at longer intervals.

The filter media needs to be checked every 250 operational hours. How quickly the filter depletes will depend on the material being cut, but it is not unheard of for some shops to get upwards of 1,000 hours out of a filter, while others only 100 hours. For example, a shop that cuts aluminum will experience clogged filtration media much faster than a shop that cuts tool steel. An awareness of what is being run on the machine and the frequency of challenging jobs will help manufacturers be proactive about filter changes.

The same goes for the resin. Maintenance is done on an as-needed basis.

Semi-annually or every 2,000 operational hours, the experts recommend that shops remove and inspect the guides with an optical comparator or similar tool to ensure that the size of the hole remains concentric and isn’t wearing in one direction.

“Today, diamond guides, power feeders, rollers, and even wire can be purchased from third-party vendors,” said Bystrek. “In most cases they work, but you will not always get the same performance or life as using OEM consumable components. Keeping a closer eye on these parts is advisable.”

Shops also should monitor the air filter media for the fans and intake area.

EDM systems perform best in controlled environments, but that’s not realistic for most shops, explained Gaal. They are often found by milling and grinding machines, meaning that the oil and coolant often reaches the machine and can cause serious problems. While filter material is inexpensive, it can lead to very expensive problems if it is not changed regularly.

Air filtration media for the cabinet needs to be checked based on the environmental conditions and is something that is often overlooked.

Associate Editor Lindsay Luminoso can be reached at [email protected].

MC Machinery, www.mcmachinery.com

Sodick, sodick.com