In an automotive assembly plant, it’s all about keeping the line moving. In 1913, Ford’s Model T rolled off the assembly line in about 93 minutes. These days, manufacturers are rolling out vehicles at a rate of about a car a minute.
To keep pace with these revved up rates, every step of the process must be lean and efficient, including the delivery of parts to the assembly line, or lineside delivery. This means getting the right parts and components to the right operator at the right time with the right equipment.
The assembly line work areas are shrinking as companies work to lean down operations. Gone are the days of storing days worth of just-in-case product, today companies are storing hours worth of product and making deliveries just-in-time and just-in-sequence for the next vehicle cruising down the line.
But it’s not just when the inventory is presented that matters, it’s also the what and how that makes lineside delivery an important part of the manufacturing process. For example, rather than individual parts being delivered to the line, more kits and assemblies are being presented to the operator’s workstation. These kits, often housed in totes, give workers the parts and tools necessary to complete the specific components they are building, while assemblies, like dashboards, are complete units delivered lineside ready for installation.
“In the old days there were 6,000 to 7,000 pieces that had to be assembled on the line,” explains Tom Meyers, national sales manager for Muratec. “Now you may have 200 to 300 assemblies that go to the line ready to be incorporated into the car. This has saved the auto industry a lot of money and brought up the quality because you can test the assembly along the way before it’s put into the car.”
Different assembly strategies mean different lineside delivery strategies and technologies. Here’s a look the best practices of lineside delivery and how equipment like manual carts, smart carts, automatic guided vehicles, autonomous mobile robots and overhead handling equipment are being implemented.
Manually operated carts
While the trend in the materials handling sector, including the automotive industry, is toward automation, manual movement can still be a best practice for some operations. “Lean operations have the same goal: Invest less capital and come up with simpler solutions,” explains John Neumann, president of K-Tec. “Carts bring material flow to lean manufacturing, but the challenge to suppliers is to come up with new ways to be effective.”
Because end users want customized solutions, there are hundreds of cart design options available. In one example, carts with rotating decks can be individually equipped with stainless steel uppers, like pop-up shelves, to allow more parts to be moved on the cart. The horizontal shelves are stocked with parts and delivered to the workstation in the right sequence. As the operator selects parts from the shelf, the deck can be rotated to allow quick and easy access, without excessive reaching. When the operator has unloaded the top shelf, the shelf springs up into a vertical position so the operator can access the stock on the next shelf.
This simple solution works well for a number of reasons. According to Neumann, manual carts make it easy to quickly locate and pick up the right parts ergonomically. Additionally, he says, “The operator on the line doesn’t have to do anything other than the operation, meaning no searching for parts, making decisions about the right tools to use, or unpacking parts and removing packaging materials from the workstation. And, if a big plant wants to change a line, you can move a cart in 10 minutes for free.”
While manual carts offer an inexpensive, flexible way to transport parts, there are limitations. To avoid worker injuries, an operation has to apply specific guidelines of gender, height and weight to determine the ergonomics and safety of usage.
AGC and AGV spell flexibility
Moving from manual to powered lineside delivery solutions, smart carts, or automatic guided carts (AGCs), are capable of moving loads up to 6,000 pounds. Guided by magnetic tape on the floor, they allow users to change the guide path quickly and easily.
“AGCs are popular for lineside delivery because they are extremely flexible,” explains Noel Dehne, vice president of automotive for Daifuku Webb. “These systems improve the process by automating it and by providing flexibility that other forms of automation cannot. They are also easy to install and scalable, enabling users to simply add more carts to increase throughput.”
In some cases, AGCs, or tugger systems, pull trailers that can be customized to transport kits, pre-assembled components and virtually any car parts from storage to the line. They can also be equipped with customized carriers to move specific parts. By simply changing the customized carrier, different parts can be moved to the assembly line.
“One day the AGC can move fascias, but if the company needed to move steering wheels a new carrier could be designed and still be moved by the cart,” Dehne explains.
AGCs can also be equipped with other devices such as scissor lifts that can raise and lower the load for improved ergonomics when delivering the product to the operator at the workstation.
Like AGCs, automatic guided vehicles (AGVs) can also be introduced to the lean manufacturing process without the need for plant modifications and are flexible enough to adapt to an operation’s changing business needs. Battery-powered and computer-controlled, AGVs also have defined paths and are effective solutions for moving materials on repetitive, pre-determined routes.
Both AGCs and AGVs can redistribute workers in your plant to value-added positions, improve safety and material tracking, and reduce labor costs. These automated materials handling systems reduce lift truck traffic, increase plant safety and improve the quality of the build because workers don’t have to walk to the storage area and make selection decisions, explains Neville Croft, executive vice president of Transbotics.
When the AGV arrives lineside with its delivery, there’s a handshake of sorts, explains Croft. The exchange of information validates that the AGV has arrived in the right place with the right material and initiates the process and activates controllers, motors, lifts and other electro-mechanical devices that complete the delivery.
Autonomous mobile robots
Traditional AGCs and AGVs work well in repetitive applications that move from point A to point B. However, they are not autonomous, meaning they are tethered to their guidance systems and travel on a fixed path. Autonomous mobile robotic solutions, however, can navigate and maneuver around objects—moving or stationary—independently from a random origin to a random destination.
This capability is especially important in a manufacturing area where things are moving randomly. Bill Torrens, director of sales and marketing at RMT Robotics, describes the manufacturing environment as “organized chaos” and explains that autonomous mobile robots “have the flexibility to move within that labyrinth. Using a solution that has the flexibility of an autonomous mobile robot, you can change the game.”
Torrens explains that you can change the location of a kitting area without creating the challenge of transporting parts to the line. The advantage of dynamic layout means space efficiency and optimized productivity.
But don’t think of these robots are a replacement for workers. “Robotic solutions don’t eliminate people, they amplify throughput at a workstation,” Torrens says. “Think of it as the technology lending a helping hand to increase performance, not to replace people. If you could realize a 20% improvement, that would be huge. Imagine the profit you could glean if you build one more car per hour.”
Leading automotive manufacturers are using materials handling equipment to lend a helping hand when it comes to how the parts are delivered to the line and presented to the worker. Delivering parts to workers ergonomically, or in the golden zone, means they don’t have to reach and strain, and can focus more easily on the task at hand so the part goes into vehicle with precision.
“Cost savings, process improvement and increased productivity within a plant stem from changes in technology. Automotive manufacturers are always looking for materials handling solutions that improve safety and ergonomics,” explains Michael Paisley, controller of the Dearborn Mid-West Conveyor Company.
One example of delivering work to the operator in the golden zone is with an overhead rotational carrier. It holds the suspended car body upright then rotates it 90 degrees, one way or another. Its rotating capability enables the worker to safely access specific areas of car without reaching and bending. “The carrier rotates the car sideways so the worker can look straight at it to work on it,” explains Paisley.
Another overhead handling solution is a monorail system. Electric and quiet, some monorails can handle loads of up to 250 pounds, while others can move and handle the entire car. Ergonomically speaking, explains Muratec’s Meyers, “it’s better to drop down to the height needed rather than lift up to the height needed.”