The proportional revolution

DN Staff

June 24, 1996

10 Min Read
The proportional revolution

Rochester Hills, MI--The scene at Detroit's Metro Airport was pure Hollywood: Thirty executives, cramped in an airport conference room waiting for the unveiling of a revolutionary new product. The executives, mostly from the giant global motion-control firm of Vickers, had flown in from around the world. They watched expectantly as two men laid a hydraulic valve on a table at the center of the room.

The men, who came from a tiny, nine- person firm called Microhydraulics Inc., launched into an explanation of the valve's characteristics: It was smaller, sleeker, faster, more accurate, and more repeatable than any proportional valve that Vickers had ever built. In short, it represented a revolution in hydraulic valve technology.

For such an innovative product to come from outside the boundaries of the mainstream industry, however, was rare. But on this chilly day in March 1995, the two outsiders made believers out of the high-powered corporate crowd.

Vickers management saw the technology and immediately began planning to introduce it into their product line. Vickers' Executive Vice President John Weber declared his intention to rally the technical forces behind the new valve--and introduce it in a scant 90 days. His message: "Do what-ever you have to do to bring this product to market," recalls Nick Matten, director of valve engineering at Vickers' Havant, England, facility.

The fruits of Vickers' subsequent labors, known as the Discovery Series KV Proportional Directional Valve, reached the market late in 1995. But not before the company had virtually remade itself and its engineering culture. In the process, its engineers questioned almost everything they'd learned about valve design in the last two decades.

They adopted new product-development techniques. And they introduced a valve that could change the face of hydraulic motion control. Says Charles Wall, marketing manager for Vickers in the Americas, "This proportional valve will take all but the very high-end servo-valve applications off the market."

'Out-of-the-box' thinking. The odyssey of the KV Valve began years earlier, when Canadian inventor George Kadlicko began to assemble new concepts for hydraulic valve technology. Kadlicko, a machine designer, believed that hydraulic valve technology often was woefully inefficient. Over a period of years, he worked at developing new hydraulic techniques to improve on those inefficiencies.

During occasional meetings with Vickers sales representatives, from whom he bought components, Kadlicko expressed some of his ideas. After several years of hearing about these ideas, Vickers management travelled to Mississauga, Ontario, in July 1994 to meet with the machine designer.

There, Vickers managers looked at a cartridge-style valve that Kadlicko had designed. They also expressed some of their own desires for future products, particularly in the area of valve performance and packaging.

Based on that meeting and others, Vickers management began to formulate a plan to dramatically advance the state-of-the-art in hydraulic valve technology. As a result of extensive surveys, they knew there was a market for a valve that offered servo-type performance, without all the disadvantages of servo technology. In particular, they wanted to eliminate the high cost and maintenance problems associated with the intricate mechanisms of conventional servo valves.

Vickers wasn't the first company to conjure up such ideas. Engineers have long toyed with the idea of improving on servo technology, but their efforts typically come up short in the area of performance. Proportional valves were invented as an alternative to servos. They traditionally traded lower manufacturing costs for lower performance in terms of bandwidth, deadband, and hysteresis.

Kadlicko's concepts offered hope, but they hadn't yet reached the product stage. So Vickers executives hit on the idea of giving Kadlicko 30 days to package his concepts in a valve that would offer all the features they sought: high bandwidth, low hysteresis, no deadband, ruggedness, serviceability, and low cost. In short, they asked Kadlicko to do what the industry had failed to do for nearly two decades.

For Vickers, the entire process was a step removed from the normal hum of day-to-day operations. The company's executives referred to it as "out-of-the-box" thinking--a whole new way of approaching not only the product, but the process. "They were trying to find a way to nurture our ideas, and bring them into their organization, without killing the golden goose," Kadlicko says. "They were very careful not to 'Vicker-ize' us."

Design competition. At the same time, Vickers managers called on the company's engineers to build--in the same 30-day time span--a product that addressed the same issues. They expressed it to the engineers as a winner-take-all design competition, with the Vickers engineers going head-to-head against Kadlicko's team from Microhydraulics.

For Vickers engineers, the design competition proved to be a form of culture shock. Working in a large corporation, most had grown accustomed to designing evolutionary products. Now, however, they were forced to design a revolutionary project--and to finish it in just 30 days.

"The first thing they did was ask for more time," says Fred Phillips, director of advanced technology for Vickers. "Next, they argued about who should be on the team. Ultimately, almost four weeks were spent just getting organized."

Phillips insists that their performance was not the fault of the engineers. Rather, he says, corporate culture was the culprit. Product design had slowly grown into a committee-based process, where engineers hesitated to make decisions. The company's engineering ranks hesitated to take risks. "This is a large company," he explains. "And large companies tend to be asset managers. There's a tendency to breed an environment where you make modifications to existing technology."

At Microhydraulics, meanwhile, engineers had finished the prototype in the assigned four weeks. Kadlicko, along with the company's vice president, Greville Hampson, flew to Detroit, where they unveiled it to critical acclaim in the airport conference room.

Best of both worlds. The key to Kadlicko's concept then, as now, involved the use of a "hydraulic position follower." The follower consists of a small pilot spool contained within a main spool. When a small amount of electrical current is applied to the pilot spool, it moves. Specially designed porting within the assembly then induces a pressure imbalance, causing the main spool to move to the same position as the pilot spool. "It has to move to the same spot to reestablish its pressure balance," explains Phillips. This technique enables the valve's main spool to move to its desired position, without the need for large electrical currents.

As a result, the Discovery KV Valve falls in a category somewhere between conventional proportional valves and servos. Unlike conventional proportional valves, which use electrical currents of 1.5A to 3.2A for force amplification, the KV employs only about 0.4A of current. "You don't need a lot of current to make this valve work," Phillips says. "It takes advantage of the power density of hydraulics."

But the KV valve accomplishes that hydraulic amplification without using the intricate passageways that servo valves typically employ. The hydraulic follower concept enables it to attain servo-like performance with orifices about 40 times the size of those in servo valves. That makes the KV less susceptible to the effects of lightly contaminated oil. This eliminates the need for "clean and calibrate" procedures, which often plague servo valves.

What's more, the low inertia of the pilot spool contributes to higher bandwidth. Frequency response exceeds 100 Hz for small signals. And the design of the main spool, which fits within a fixed sleeve, eliminates many manufacturing problems. Therefore, the KV solves problems that typically plague proportional valves.

Ninety-day goal. For Vickers engineers, however, the acceptance of Kadlicko's design concepts were just the beginning. The KV product team now had 90 days in which to produce drawings, build prototypes, test parts, develop the product for manufacturing, and write the technical information, sales support literature, and catalogs.

Product team members, uncomfortable with the new approach, complained that time would be too short and the process too expensive. Management refused to accept excuses. They encouraged team members to make decisions on their own, buy whatever equipment was necessary, and "don't ask permission, just do it."

Engineers started the development process in CAD, doing all of the design drawings in Pro/ENGINEER from Parametric Technology Corp., Waltham, MA. Geometric models were then transferred to ANSYS Pro/FEA from ANSYS, Pittsburgh, for structural finite element analysis. Later, engineers also transferred the software models to Rampant, a computational fluid dynamics program, from Fluent Inc., Lebanon, NH, which checked pressure drops and flow dynamics within the valve. Finally, software models were fed to a local company that used stereolithography techniques to create physical models of the parts.

Vickers engineers relied heavily on software modeling as an early warning system for impending problems. Physical lab tests were used only for confirmation, rather than discovery of potential problems. By operating this way, engineers accomplished more work in parallel.

Soon after the first prototypes were built, the team began to run into problems. With only two weeks left before the 90-day deadline, castings for the valve failed endurance tests.

The problems baffled the engineers, who had been using an aluminum casting for the valve body since the outset of the design. Kadlicko, a strong-willed and opinionated entrepreneur, had insisted that aluminum would be sufficiently strong and offer weight advantages. And, indeed, all of the finite element models and burst tests proved him right. But, in the endurance tests, the valve lasted only 700,000 cycles, instead of the required 10 million.

So, with the deadline drawing near, the team tried a different grade of aluminum. It, too, failed. They altered the geometry. Again, it failed. Each time, the failure involved deformation of the aluminum body. Finally, with the deadline already past, they switched to a cast-iron body, which easily passed the endurance tests.

For the valve team, it was a critical learning experience. "Experience should have told us much earlier that deformation in aluminum would have been a problem at 5,000 psi," Phillips says. "But we were specifically involved with Microhydraulics so as not to have our paradigms. As a result, we didn't follow our own gut instincts."

The endurance problems set the project back several weeks, temporarily causing the team to lose sight of its goal, slipping back into a more traditional mode and forgetting to work in parallel. It wasn't until mid-1995, when the company set a special date for a "Discovery Show" to introduce its new line of products, that the sense of urgency returned.

Still, the team ran into another problem days before the rollout. Management even considered scrapping the introduction of the entire product line. Vickers engineers at Havant frantically exchanged drawings and prototypes with Microhydraulics engineers in Mississauga before resolving the problem with minor alterations to the valve's passages only two days before the show convened.

December rollout. Unveiling of the valve at Vickers' Discovery Show in Orlando last December marked the introduction of a revolutionary technology, say Vickers executives. "All of this was done by re-thinking the hydromechanical and electromechanical aspects of amplification," notes Wall. "Servo valves use a lot of hydromechanical gain; proportional valves use a lot of electromechanical gain. The combination designed into this valve gives us the best of both worlds."

For Vickers, the unveiling of the valve also marks the beginning of a new culture. Since launching the KV valve program, the company staged a similar competition for the design of a mobile proportional valve, which its engineers won. The message trickling down to the staff, Wall says, is that the firm is not risk averse. What's more, team members now feel confident that they can develop new products in 90 days.

"We truly believe this is the right way to develop a product," Wall says.

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