Above: As the ram returns to home position, a sensor confirms the punch is clear of the laser beam which is then activated to precisely weld the piano wire to the tin disc through a narrow opening.

Pneumatic press technology combines stamping with in-die laser welding to eliminate manual step and raise throughput

April 2016 - Each of us has an internal body clock, a circadian rhythm that regulates our sleep patterns and other mental, physical and behavioral processes on a 24-hour cycle. NASA has conducted research on the space shuttle to observe the impact of time changes on the body’s circadian rhythms.

Aboard the International Space Station studies continue to examine the effects of space flight on the body and the brain. Part of that research has included use of Electro-Cap International’s EEG [electroencephalogram] electrode application technology. Affixed to a spandex-like cap, tin electrodes 0.470 in. in diameter and 0.045 in. thick measure, record and transmit the brain’s electrical activity to a computer for interpretation.

Electro-Cap was invented in Dallas in 1979 and patented in 1983 before the company was purchased and transplanted to Eaton, Ohio. Today the manufacturer produces more than 12,000 EEG caps a year and ships to 120 countries. Though other companies have tried to create facsimiles of the Electro-Cap, President Nelson Hardin says, “most have since gone out of business.” 

Increasing demand for the product prompted Electro-Cap to consider automating the manual punching operation it used to produce the tin discs. AIRAM Press Co. Ltd., located in nearby Covington, Ohio, designed and installed a production system that included a 3-ton pneumatic press with a 1.38-in. stroke, a maximum speed of 150 SPM, an uncoiler and controls in 2009. The press builder also engineered two progressive dies each with a cut-off for scrap. On part runs of 800 discs, the air-driven press system reduced processing time from eight hours to 30 minutes.

Voltage fluctuations

Electro-Cap has continued to capture larger market shares with its EEG caps and supplies and finds sales almost evenly divided between hospitals and research organizations. Product modifications have increased, too. The manufacturer can produce Electro-Caps with “as few as two electrodes and as many as 256 electrodes,” notes Hardin. “We make caps the size of tennis balls for premature babies and caps large enough to fit the biggest football player,” he says, adding that they also create caps for monkeys, sheep and other animals. “We produce and ship enough of our Electro-Gel to perform more than 6 million EEGs a year.”

Meticulous attention to detail follows each step of Electro-Cap’s supply chain. “We’ve been doing this for 28 years,” says Hardin. “We can’t make mistakes. Quality control is very strict here. We don’t spot check, we check every single piece.”

The caps are fabricated largely by precision hand work including until recently, a painstaking soldering process. After AIRAM engineers saw the solder work first hand, they began to brainstorm how to automate the step and improve part quality. 

The electrodes on standard Electro-Caps are positioned to the International 10-20 method of electrode placement.

“We were familiar with Electro-Cap’s supply stream and we had observed the labor-intensive work they were doing so we came up with a concept and pitched it to them,” says Vice President John Bornhorst.  

Using its established pneumatic press technology as a foundation, the press builder engineered its first air press system with in-die laser welding capability for the medical device manufacturer. “Laser welding, parts assembly and cut-off operations take place inside the press,” Bornhorst explains. “To support stamping and laser welding functions we had to design and build a multi-level, multi-station die, PLC control and two feedlines.”

The challenges were numerous. “Everything about this project was special,” says Bornhorst. “We first had to take into account that you are welding soft metal—a sliver of tin to tempered high-carbon steel piano wire—two alloys that are as far apart from each other as you can get.” Each metal required a different feed mechanism. “We had to construct a special reel for the wire feed and precisely orchestrate how both the wire and tin strip would be fed into the press,” Bornhorst notes.

Enclosed for safety

Use of a laser meant designing a press enclosure that met safety standards yet provided operators with easy access. “Laser safety was paramount,” says Laser Safety Technician Jim Nicodemus. “We had to address that during the design phase for the press because feeding of the tin and wire, stamping, laser welding and cut-off all had to take place inside the press in a completely enclosed space.”

The AIRAM pneumatic press stamps pure tin discs—a soft metal—and laser welds the tiny parts to high-carbon steel piano wire.

“We made it foolproof,” adds Bornhorst, referring to the sequence of the operation and the technology that supports it. “We have 6,000 presses in the field. We focus on engineering design and application because customers are looking for flexible systems that are also economical. We can custom design systems that cost much less than other press equipment on the market because we’re able to start with a proven press foundation.”

For Electro-Cap, a PLC control means it can use operators to run the system with minimal training. Once programmed, the press ram cycles downward to cut discs from a tin ribbon in the upper portion of the die before driving it to the die’s lower level. As the ram returns to home position, a sensor confirms the punch is clear of the laser beam. The laser is then activated to weld the piano wire to the tin disc. 

Once welding is complete, the wire feed cycles to reset the wire length for the next welded disc/wire assembly. Cylinders push the welded components into a cut-off area where the wire is positioned and held at a pre-determined length. Once the cut-off step cycles, the stamped, welded assembly is discharged into a parts container located beneath the press base. 

The system was installed in September 2015 with test runs completed in October. Parts production is underway. The system is able to process 10 stamped/welded assemblies a minute.

“Our biggest goal is to provide the best product available while keeping costs in line,” says Hardin. “This new stamping and in-die laser welding capability supports both objectives. We’ve experienced improved repeatability and minimal maintenance allows us to control operational costs. We expect to produce more than 300,000 electrodes annually with the AIRAM press.” FFJ