Follow the magnetic tape to automatic guided assembly

In this installment of What Works, a John Deere plant consolidates three product lines into one.

In a move to streamline its lawn tractor assembly plant in Horicon, Wisconsin, John Deere (www.deere.com) decided in the fall of 2004 to consolidate its three separate product lines into a single, common component platform line.

John Deere has been a part of the Horicon community since 1911. From horse-drawn grain drills to the latest in lawn-care equipment and utility vehicles, Horicon Works has built a reputation for manufacturing durable and reliable products for generations.

The local population comes with a strong work ethic, and employees take great pride in their jobs. On the assembly lines at the Horicon Works John Deere delivers Select Series riding lawn tractors and Gator Utility Vehicles.

The additional costs of maintenance prompted Deere analysts to investigate new technology as an alternative.

From the stamping of each steel mower deck and frame to the robotic welding done at Horicon Works, John Deere abides by the highest quality assurance standards as a symbol the town and its residents. Even a former mayor of Horicon had worked at John Deere. The first thing visitors see when they drive into town is a John Deere sign.

John Deere is one of the oldest industrial companies in the United States and has a high level of sophistication in the selection and implementation of material handling systems throughout its facilities, having installed a variety of equipment over the years, including roller conveyors, automatic guided vehicles (AGVs), and power and free systems.

The Deere team responsible for evaluating conveyors for use in the Horicon plant put together a matrix that compared the benefits and liabilities of various different systems, considering cost and delivery along with improved workforce ergonomics requirements. After reviewing the option, it selected the SmartCart from Jervis B. Webb (www.jervisbwebb.com).

Prior to implementing the SmartCart, Horicon’s production area had been using a fleet of more than 50 wire-guided AGVs to manufacture several generations of John Deere lawn tractors for about 20 years. Because the AGVs had exceeded their normal useful lives, the additional costs of maintenance prompted Deere analysts to investigate new technology as an alternative.

To see the technology in action, Deere management paid two visits to a JCI automotive interiors facility in Whitby, Ontario, which had several SmartCart lines running. They were impressed by the flexibility of the units, which are guided by removable magnetic tape affixed to the floor. Given the configuration of some of Deere’s production lines, which had to accommodate L-shaped lines, right-angle corners, pallet returns, Smart Cart seemed a viable solution.

The flexibility of SmartCart’s magnetic tape overcame layout obstacles dramatically, says Dave Werkheiser, manufacturing engineer at Horicon. “The advantage of being able to just pick up the magnetic tape and change the layout in a matter of minutes allows us to change an entire line over a weekend,” he explains.

John Deere is one of the oldest industrial companies in the United States and has a high level of sophistication in the selection and implementation of material handling systems throughout its facilities, having installed a variety of equipment over the years, including roller conveyors, automatic guided vehicles (AGVs), and power and free systems.In February 2005, Deere ordered a single unit to test as a first step in receiving design approval to implement a production changeover at Horicon. Later, six additional carts were added to the prototype build and 56 more AGCs joined the mix during the summer. By the fall, final approval and acceptance testing had to take place before full production was undertaken. This included functional safety testing, component repair procedures and the setting up of in-line and off-line charging stations.

When the SmartCart line installation was finally optimized and completed with 76 carts, other AGC features helped to streamline the Deere production line. Unlike the earlier AGVs that had trunnions to rotate the tractor bodies for access, the company mandated top-down assembly for ergonomic reasons. The SmartCart’s hydraulic lift capabilities made it possible for operators to tailor the cart height for individual operations, raising or lowering the tractor bodies to the proper height for optimum assembly operations. For the most part, all the ergonomic concerns were addressed, says Werkheiser.

As with any automation process, during the initial commissioning and debug phase, a number of unexpected issues, including transponder signal misses, speed encoder problems, optical tracking blocking, and sticking buttons, had to be addressed. All glitches were resolved with the help of Webb engineers.

Another concern was the assembly throughput, which planners desired to peg at a 9-sec index between operations to achieve daily production shift volume targets. However, the distance between stations and the length of the carts, along with the suggested optical blocking distance between carts, made this difficult to achieve, but Werkheiser believes the SmartCarts will eventually reach their goals.

In addition to the cart’s flexibility in making line modifications and ease of installation, Deere found further savings with SmartCart battery recharging times by employing a short, in-line automatic “opportunity charge” during every production cycle.

Since the AGCs have been in operation, management from other Deere plants have visited Horicon to observe the units in action. “These things have piqued interest throughout the company,” says Werkheiser. “Many of the plants are looking for alternative solutions for their material handling systems, including those in our agricultural division.”

Read more What Works case histories

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