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Kohler Excels at Manufacturing Small Gas Engines

Reliability in the field starts with quality on the assembly line.

June 3, 2014
Trans

Small gas engines are the lifeblood of the outdoor power equipment industry. They run all sorts of commercial and consumer devices, ranging from lawnmowers and generators to power washers and portable welders.

Wherever there’s hard-working machinery cutting grass, blowing leaves or chomping up debris, chances are good that it’s powered by a Kohler engine. It’s the same Kohler Co. that is a leading manufacturer of kitchen and bath products, such as bathtubs, showers, sinks, toilets and faucets. The company also makes tile, cabinets and furniture.

Kohler Engines is a division of the Kohler Power Group, which produces a wide variety of devices, including generators for commercial, industrial, marine and residential applications. Kohler’s gasoline, natural gas and propane powered engines are popular with many leading manufacturers of outdoor power equipment. Its OEM customers include Ariens, Craftsman, Cub Cadet, Deere, Exmark, Lincoln Electric, Miller Electric, MTD, Scag, Toro and Walker.

The company’s flagship plant is in Kohler, WI. It’s located on a large manufacturing campus that includes a foundry and factories that produce all sorts of plumbing fixtures. The 460,000-square-foot facility specializes in high-mix, low-volume engines like the Command PRO, which is widely used in commercial equipment, such as zero-turn mowers, ride-on mowers and wide-area walk-behind mowers.

A sister plant in Hattiesburg, MS, produces low-mix, high-volume engines. The 16-year-old facility assembles several different engine models, such as the Courage, a popular workhorse found primarily in consumer riding mowers, and two new models, the 7000 Series and the Confidant. Kohler’s engine division also operates plants in China and India, while a subsidiary in Italy specializes in diesel engines.

Proud Heritage

Kohler Co. is one of America's oldest and largest privately held manufacturers. It traces its roots to 1873. That’s when an Austrian immigrant named John Kohler purchased his father-in-law’s foundry. The company produced farm implements, such as cast-iron and steel plows, in addition to castings and ornamental pieces for local furniture manufacturers.

One day back in 1883, Kohler decided to add feet to a livestock watering trough and turn it into a bathtub. Within four years, enameled cast-iron sinks and bathtubs accounted for 70 percent of Kohler’s sales. The company became a full-line plumbing manufacturer in 1926, when it opened a factory to mass-produce faucets and other brass fittings.

Kohler has long been a pioneer in product design and innovation. One of its big breakthroughs was a one-piece bathtub with built-in apron in 1911. A few years later, Kohler engineers developed a way to produce identical pastel colors on both vitreous china and cast-iron fixtures, which revolutionized bathroom and kitchen design.

In 1920, Kohler entered the power systems market when it produced the world’s first engine-driven electric generator. The rugged device was a big hit with farmers in the days before the advent of line electricity.

After World War II, Kohler diversified into small gas engines to meet growing demand for outdoor power equipment. By 1963, the company was supplying engines for nearly half the lawn and garden tractors built in the United States.

In the mid-1980s, Kohler engineers developed the industry’s first overhead camshaft small engine, which was quieter, more fuel efficient and more environmentally friendly than traditional side-valve engines. The next wave of small engine technology was unveiled in 2000 with a line of liquid-cooled products. The next-generation engines were based on technology used in large off-road equipment.

Kohler is also known for its unique family approach to business. In 1913, it established a planned community that was modeled after European garden communities and American company towns, such as Hershey, PA, and Pullman, IL.

Kohler Village featured single- and two-family homes, a school, a village hall and a dormitory for unmarried workers. A prominent landscape architecture firm was hired to design a bucolic setting just outside the factory walls. Today, the community continues to thrive with winding, tree-lined streets, attractive homes and numerous parks.

And, Kohler still prides itself on the design and craftsmanship of its products. Whether it’s a luxurious whirlpool tub or a 25-hp gas engine, all products must pass the approval of Herbert Kohler Jr., chairman of the board and CEO of the company that his grandfather started 141 years ago. In fact, Kohler has designed more than 200 new products himself.

Strong Demand

Demand for power lawn and garden equipment depends heavily on the housing market and the weather. According to the Freedonia Group Inc., the market will grow 4 percent annually between now and 2017, reaching $11 billion. Demand for commercial mowers will be driven by landscaping services and recreational activities, such as golf.

Turf and grounds equipment will record the most rapid market gains during the next three years, stimulated primarily by an expansion in the number and average size of landscaping firms. The Freedonia Group predicts that higher landscaper revenues will also be the primary driver for increased commercial sales of power lawn and garden equipment, as firms hire additional employees and invest in new equipment to capitalize on growth opportunities.

In addition to requesting alternative-fueled equipment, the marketplace has been demanding lighter duty commercial mowers that retain heavy-duty engines.

“There’s been a gradual replenishment of equipment, as people continue to recover from the recession,” says Kris Kiser, president and CEO of the Outdoor Power Equipment Institute. “Today’s machines are much cleaner and more efficient than in the past. We’re especially seeing growing demand for propane-powered equipment on the commercial side.”

That’s good news for assemblers at Kohler Engines who build products known for high-power performance, durability, reliability and efficiency. “Consistent power is the defining characteristic of all our products, which are proven to go from zero to full load with only a market-leading 10 percent drop in rpm,” claims Brian Melka, vice president of Kohler Engines Americas.

“Commercial landscapers depend on their mowers and engines for their livelihoods,” adds Melka. “Down time is not an option. Because cutting conditions won’t always be advantageous, Kohler engineers focus on designing products with an optimized governor system that can respond with peak performance even when confronting thick, wet grass.”

Green Technology

One of the biggest challenges facing the outdoor power equipment industry in recent years has been increasingly stringent environmental requirements for exhaust gases. “It requires us to do things differently,” says Melka. “Our challenge is how to meet all the emissions requirements in the most cost-effective way. We’re tackling that through innovation, such as electronic fuel injection (EFI) control systems.”

Kohler’s flagship plant serves as its center of excellence for EFI technology, which the company pioneered in the mid-1990s. “Our next-generation closed-loop EFI system, which is the most efficient fuel-injection system available in the small engine market, was unveiled four years ago,” says Melka.

The Kohler Command PRO EFI engine provides optimal fuel efficiency and reduces emissions. The engine is popular with commercial mower manufacturers that want to offer their customers faster starts, smoother operation and greater efficiency.

“What makes these engines unique is an oxygen sensor that analyzes the air and fuel mixture in the muffler,” explains Melka. “If the oxygen level strays from the ideal air-fuel mixture, the sensor triggers adjustments to the amount of fuel injected into the system. Only Kohler EFI engines close the loop between the air-fuel intake and the exhaust output to provide a constant stream of critical feedback, which helps deliver optimal fuel efficiency and other benefits.”

Because of the increased demand for engines that run on alternative fuels, Kohler recently expanded its EFI offering to include propane and flex-fuel models. Melka believes that all engines for outdoor power equipment will eventually move to an EFI system, due to the performance benefits the technology provides and increased emissions requirements.

“Our operational organization has had to constantly evolve to support these new products,” Melka points out. “Back in the days when everything we produced was carbureted, it was an entirely mechanical assembly process. Now, we’ve introduced a lot more electrical components. This has required us to retrain operators and make changes in areas such as material handling.”

Assembly Challenges

Outdoor power equipment comes in many shapes and sizes, so Kohler makes engines in multiple configurations to meet different customer needs. Each of the company’s plants is dedicated to a different family of engines. Assemblers at the Kohler, WI, plant build the Command PRO EFI and the Command PRO Twin Cylinder, which are available in sizes ranging from 19- to 37-hp.

“This is our highest mix and most complex plant, where we have the most number of product specifications” notes Melka. “We produce several hundred more SKUs in Kohler than at our Hattiesburg plant. We are targeted toward the higher end, commercial market, where there’s a lot more customization of the product to meet customer needs. As a result, we rely on both manual and automated operations on the plant floor.”

“There’s tremendous variation within our SKUs; most assembly is build to order,” notes Dave Mauer, vice president of operations. “We produce both air- and water-cooled engines, which each react differently from an emissions perspective. We also assemble both gaseous-fueled (propane and natural gas) and gasoline-powered engines in the plant.

“On top of building a variety of engines for different marketplaces, our operators have to contend with many architectural differences,” adds Mauer. “For instance, we produce engines with both vertical and horizontal driveshafts.”

Kohler engines are also equipped with many features that appeal to commercial landscapers, such as a heavy-duty cyclonic air cleaner that traps grass and other fine contaminants to help maximize power and engine life. Other options include recoil or electric starters, different types of carburetors and throttles, and large-capacity air, fuel and oil filters.

Most of the engines on the Kohler assembly line look alike on the outside. But, inside, they’re quite different. Due to all the variations required by customers, the assembly line averages 10 to 12 changeovers per shift. “We have gone as high as 25 changeovers, especially during our peak season, which occurs in the fall and winter,” says Jim Nussberger, production manager for assembly and finishing.

“With the wide range of specs within eachengine, one of our biggest challenges is cross training our employees so they understand all the variations,” adds Nussberger. “The wiring harness changes on some of our engines can be very labor intensive, especially when we get into the EFI options.

“Some of the setups for the throttle bodies are labor intensive, depending on what spec we’re building,” adds Nussberger. “We often have to move people in and out of those production areas.”

Some components, such as engine block castings, are made by suppliers. “However, highly engineered components and parts that require complex steps, such as engine blocks, are machined in-house; we buy the castings from external suppliers,” says Nicholas Devine, production manager for Wisconsin machining. Plastic parts for the external shrouding are also supplied by third parties.

Key components required to assemble all engines include camshafts, crankcases, connecting rods, cylinder heads, flywheels, pistons and valve covers. More variation occurs when it comes to attaching components such as air cleaners, air filters, blower housings, manifolds, oil filters, starters, throttles and wiring harnesses.

“Manifolds and fuel rail systems are a couple of the most challenging components to assemble, because they require both mechanical and electronic components,” says Nussberger.

Mechanical fastening is widely used on the assembly line. Engines are assembled with studs, screws and bolts, in addition to some press-fits. A wide variety of pneumatic, DC electric and battery tools are used throughout the plant.

“Our fastening strategy depends on the type of joint,” says Nussberger. “If it’s a critical joint, we use DC electric tools to provide feedback to operators.”

Several robots are used in the plant to apply liquid adhesive to help seal the case and the closure plate together. Robots also attach cylinder heads and are used for some material handling applications in the machine shop.

The 54-year-old Kohler Engines plant operates three separate assembly lines. “Each one is a little bit different,” says Nussberger “They’re arranged specific to product families.” One line is linear and another is laid out in a traditional race track configuration.”

The third assembly line is horseshoe-shaped, with engines manually pushed on carts. But, that process is being replaced by a new assembly line set up in a section of the plant that formerly served as a stock area.

The new line’s pallet-based conveyor system uses RFID technology for traceability. Another key feature is that it allows operators to work on both sides of the line. The more open layout also accommodates for more line-side storage and point-of-use delivery.

 “The ability to deliver materials to inside and outside portions of the line will improve flow,” says Mauer. “We believe that some of our greatest opportunities for improvement moving forward involve how we move and store parts. Our long-term goal is to eliminate forklift transportation within the plant.” 

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