Process Insights

EDM Surface Finish Sparks Niche at Lens Tool and Mould

With ever-increasing global competition and a shrinking manufacturing market, small job shops are under a lot of pressure. Many are thinking about their future and trying to define a specific niche where they believe they can succeed. Many are thinking strategically about their manufacturing processes. Canadian manufacturer Lens Tool and Mould of Windsor, Ontario, found its niche in high-quality EDM surface finish for specialty mold applications.

“My father founded the shop in 1965, focusing primarily on lens molds. He recognized that a successful business has to set itself apart with a specific expertise,” says Tamas Godinek, president of Lens Tool and Mould. “Carrying forward that mind-set, my first order of business in managing the shop was to increase our efficiency and determine our shop’s future specialty. An immediate observation was the need for fine EDM surface finish capabilities.”

In 2004, Lens Tool began extensive research on a variety of EDM technologies by visiting other shops and talking to local distributors. In speaking with Single Source Technologies, local distributor of Makino products, the company was introduced to a sinker EDM technology available from Makino known as HQSF (high-quality surface finish). This technology uses a semiconductive powder mixed into the dielectric fluid to produce superior EDM surface finish capabilities and tight rib machining in a significantly shorter time than conventional EDMs.

“During the process of investing in an internal EDM department, we realized that a Makino purchase would not only allow us to keep our work in-house and burn reliably unattended, but also provide a specialty EDM service that few other manufacturers offer,” says Godinek. “Makino’s reputation for quality and the uniqueness of their HQSF technology was intriguing enough for us to visit Makino’s EDM research and development center in Auburn Hills, Michigan, to run a few test burns and verify its capabilities. The HQSF technology’s accuracy and quality combined with Makino’s applications support led us to purchase an EDNC65S sinker EDM with a 32-position tool changer. This investment has single-handedly changed our business and given us an advantage in these specialty EDM applications.”

HQSF Additive Technology

For over 30 years, additives have been available for sinker EDM equipment to improve electrical conductivity for more consistent discharging and increased efficiency of energy transfer from the electrode to the workpiece. However, in the past, additives had serious limitations including health concerns, gravitational settling of particles, shortened fluid life span due to surface agent destruction and higher costs.

Makino’s HQSF overcomes these issues by using an environmentally safe powder called µSC. With a specific gravity of nearly zero, µSC is able to distribute itself more evenly throughout the dielectric fluid, accessing all surfaces of a mold cavity. These particles do not require the use of surface agents for proper particle separation, enabling them to remain unaffected by heat during the burn process. And while most competitive solutions require at least 15 to 20 grams per liter of fluid, Makino generally requires only one gram of µSC per liter.

HQSF technology requires little additional support compared to normal EDM procedures, and is compatible with most standard dielectric fluids and filters. Operator maintenance of the fluid mix is minimal, requiring a daily drop fill cycle to circulate the additive particulates and the occasional additive replenishment based on concentration measurements and the amount of machine usage. The EDNC65S’s magnetic conveyor system further reduces maintenance by separating metallic particles from the fluid to keep the fluid mix in good condition for up to 800 hours of machine time.

“With a history of little to no hands-on EDM experience and the complex inner workings of HQSF, we assumed there would be a difficult learning curve,” says Godinek. “In reality, the machine was easy to adjust to, and Makino’s training courses filled us in on every intricate detail of the machine’s features. Even after the training, Makino has always been available to provide us with valuable feedback to ensure we succeed with the absolute best EDM surface finish capabilities, accuracy and speed achievable.”

Attracting New Customers

Lens Tool’s investment and expertise quickly gained national recognition, attracting numerous customers from across North America.

“The most common requests we receive are applications for automotive speaker-grille molds featuring thousands of intricate core pins,” says Godinek. “What’s unique about these applications is the manufacturer’s inability to hand-polish within the crevices. This means that in order to produce a good mold, the cavities have to fill properly and the parts cannot stick in the molds. The tools must come out of the machine with perfect finishes.”

According to Lens Tool, the EDNC65S enables them to frequently produce surface finishes of up to 4 Rmax using standard graphite electrodes. On a recent powder-form punch produced using HQSF and copper electrodes, the company was able to achieve a mirror-like 2 Rmax surface finish, completely eliminating any need for manual finishing.

“The EDNC65S and HQSF allow us to produce unbeatable finishes when using high-grade graphite electrodes, while also providing high-quality finishes with standard-grade graphite electrodes that would normally require copper on a standard sinker EDM,” says Christopher Brooks, EDM leader of Lens Tool and Mould. “The additive has improved our efficiency in nearly all of the sinker EDM applications we’ve come across.”

Within the first two years of its investment, Lens Tool’s specialty EDM work had become 20 percent of its business. Today these applications comprise over half of its orders and show no signs of slowing down.

“We’re getting so many inquiries,” says Godinek. “We were recently approached by a potential customer who heard about our speaker-grille capabilities using HQSF from some friends in the industry. In previous tests, the manufacturer was unable to make it past the mold tryout stage due to sticking issues caused by poor finishes in the ribs. We produced the tool for them using their electrode with HQSF and passed the mold tryout stage with ease.

“There’s a lot of unnecessary work when tools with rough finishes are sent for injection. The sticking that ensues requires operators to manually peel the still-warm part from the cavity and continually spray the tool with a mold-release agent before the next shot can be processed. Additionally, these parts are at extreme risk of being scrapped due to warping or distortion. All in all, this situation causes adverse effects to cycle time, secondary assembly, finished part delivery and overall profit. It’s our mandatory goal to make sure these tools work without any hesitation.”

Burning Off Time

While the need for perfect finishes usually requires lengthy processing in EDM applications, the demand for shorter cycle times is a continual concern for all manufacturers. “Most customers are pleased to see the quality of the tools we produce using HQSF but are astounded when we’re able to rough and finish the job 20 to 30 percent faster,” says Godinek. “During one job bid, we went head to head with another EDM using the exact same electrodes from the customer. Both processes were started on the same day, but we were able to deliver the tool a day earlier with visibly better quality and finish.”

Generally, ram EDMs rely on ionization of the dielectric fluid between the electrode and workpiece until the electrical potential reaches a point at which the spark can develop through the conductive channel. This same activity occurs within HQSF technology. However, with HQSF technology, the additive particles increase the conductivity of the channel for a faster spark development and larger spark gap for graphite particles to exit the work zone.

Producing a 3 Rmax finish on conventional EDM with fine-grain graphite requires the electrode to be within 0.0003 inches of the workpiece; however, the average grain size of this premium-grade graphite is 0.000140 inches. With HQSF, the electrode can now be as far as 0.0005 inches from the workpiece. These requirements allow for a wider spark gap, enabling the 0.000140-inch grains of graphite to exit more freely. Better evacuation of debris from the spark gap provides for better, more homogenous, finer finishes over larger areas.

Reliable Unattended Machining

One of the key benefits to HQSF technology is its ability to use a single dielectric system, meaning roughing and finishing can be completed in the same solution. Alternative additives require all roughing operations to be performed using standard dielectric fluid, which then requires operators to maintain the machine by draining the standard fluid and transferring the additive fluid from a secondary reservoir for finishing operations. By using only a single tank, HQSF enables operators to automate the process for reduced labor costs and cycle time while increasing efficiency in other areas of the shop floor.

“The EDNC65S’s high-speed rib machining capabilities, positioning accuracy and automatic tool changer have also been critical to meeting competitive lead-times in many of our multi-cavity tools,” says Godinek. “While most of the shop operates through one shift a day, we frequently need to run our EDM applications unattended over nights and weekends sometimes using all 32 tool-changer positions.”

The EDNC65S is designed with a rigid machine structure composed of ball screws and guide-ways typically used in Makino’s milling machines. In addition, its set of automatic tool-change and adaptive controls provides Lens Tool with repeatable positioning accuracy and rib machining in the tenths.

“It doesn’t matter if we’re working with fine, intricate features or deep ribs, the EDNC65S always holds reliable tolerances,” says Brooks. “When I tell other operators that we’re performing unattended tool changes on speaker-grille applications, it blows their minds. And the best part is that I don’t even need to hand-polish the final tools because of its rib machining capibilities.”

“Depending on the size of the tool and how many cavities are required, we can usually knock out 10 to 30 percent in manual labor time and cost over a conventional EDM process,” says Godinek. “For some shops, 10 percent is their profit margin, meaning they could be achieving double the profit margin.”

The Specialty EDM “Go-to Guys”

Over recent years, Lens Tool has truly become an expert in specialty EDM applications. In 2008, Lens Tool decided to extend its EDM surface finish capabilities even further by investing in a high-performance wire EDM capable of rib machining tight-tolerance components such as pins, pockets, sub-inserts, broach pots and gears.

“We wanted to offer our current customers everything they would need under one roof while also appealing to new customers from a variety of markets,” says Godinek. “Our previous experience with Makino technology and service support made the purchase an easy decision. We bought a U53i wire EDM and have had the same quality and performance we’ve experienced out of the EDNC65S. As orders continue to rise for high-quality EDM surface finish capabilities, we’re also looking into a second Makino sinker EDM in the near future.

“Our investments in Makino EDM technology have had a dynamic impact on our business, setting us apart as the go-to guys for all specialty EDM applications. As more manufacturers approach us from across North America, we’re looking to expand our pipeline with additional investments in HQSF technology and uphold our reputation for competitive pricing, high quality and EDM expertise.”

Lens Tool and Mould
Windsor, Ontario
(519) 944-3111