7 fresh ways to think about AGVs
Using automatic guided carts (AGCs) as continuously moving assembly lines at an automotive assembly plant offers flexibility in operations.
September 01, 2012 - MMH Editorial
Unfortunately, for the next few decades it was the bane of the materials handling family. It was expensive (costing $100,000+ per unit), inflexible (could only go one fixed path using wires), not very smart (drop a pallet in its path and it stops) and had a bit of a weight problem (heavy batteries with hefty platforms). It was relegated to menial tasks mostly in manufacturing, carrying loads or towing carts from Point A to Point B.
As a value proposition to displace human beings, yesterday’s AGVs had a long way to go. “Human beings are the most sophisticated robots the world has ever seen,” says Bill Torrens, director of ADAM Systems Group for RMT Robotics. “If you really want to displace the labor associated with a human being, you’ve got to mimic its operational capability.”
So AGV suppliers changed their focus, gearing their development emphasis on characteristics of robotics that would best duplicate the functionality of human activity. Over the past decade, everything from batteries, circuit boards, traffic management software and sensors not only became more intelligent and reliable, but also significantly less expensive. The vehicle underwent a few makeovers—and added a few acronyms. (Read story: Equipment 101: AGV Basics)
One version has it stripped down to a light duty platform, guided by more flexible, easy-to-change, magnetic tape on the floor. This version, christened automatic guided carts (AGCs), now costs as low as $15,000 per unit and is able to carry loads up to 6,000 pounds.
There were simultaneous new developments in navigation and guidance. Gone are wires: In their place are lasers, inertial guidance and vision-based systems using everything from reflectors, targets and magnets to bar codes in its immediate environment to keep the vehicle within its designated path. The latest versions are “learning” the natural features of the facility to literally “free” themselves from any fixed path with random origins to random destinations, with no tape or targets required. They’re called autonomous mobile robots (AMRs).
Whether you call it an AGV, AGC, AMR or robot, today’s “driverless vehicle” has been creating quite a buzz in the materials handling industry. The flexibility, affordability and easier-to-use controls has this system venturing beyond simple tow and carry applications to critical tasks in both manufacturing and distribution.
Here’s a look at seven ways AGVs are being deployed today to reduce labor and promote safety and ergonomics, while minimizing product and equipment damage.
1. To replace conveyors in continuously moving assembly lines.
When most people envision assembly lines, they think of conveyors transporting product from station to station. But Palo Alto-based electric car manufacturer Tesla uses tape-guided AGCs (Daifuku Webb) in a continuously moving assembly line in place of traditional conveyors. Low-profile AGCs carrying the main chassis are sequenced so they move at a particular distance apart. Seats, consoles and bumpers are installed as AGCs transport this work-in-process car down the assembly line.
Carts like these are also being used to assemble riding lawn mowers at John Deere. “In John Deere’s case, the AGC is equipped with a scissor lift which it can raise to work underneath or lower to add parts on top,” says Sarah Carlson, Daifuku Webb’s marketing director and this year’s chair of the AGVS Industry Group for the Material Handling Industry of America (MHIA).
According to Carlson, AGCs in assembly lines offer flexibility. “If production needs to increase by 30%, it can simply increase the number of carts by 30%.” Changing an AGC assembly line can be done in a matter of hours as opposed to weeks when revamping a conveyor assembly line. Where do AGCs not make sense? “If the product has to enter harsh environments such as ovens or paint facilities, then you need to use conveyors,” she adds.
2. For lineside delivery of parts
Many operations are creating kits and pre-assembling components in another part of the plant and delivering these kits and components directly to the assembly line, also known as lineside delivery. “Now we are delivering on demand,” says RMT Robotics’ Torrens. “An AMR goes to the kitting area, retrieves only what it wants, when it wants, in the quantities that it wants and delivers it to the line.“
A similar system involves a customer-designed kitting cart towed by a tape-guided AGV system, showing up at the correct time, at the correct spot on the assembly line with the correct inventory sequenced for production. “It’s all positioned conveniently for the production associate to access,” says Keith A. Soderlund, vice president of sales for Creform. “This leads to gains in production efficiency as well as ergonomic enhancements with a properly designed cart.”
3. As a personal assistant and a runner
Torrens takes the concept of lineside delivery a step further with a mobile robot that acts as a personal assistant to the assembler. As the worker is assembling Part A at Location 1, the robot is already moving Part 2 to Location 2. “The total assembly time in the work cell was previously 14 minutes,” says Torrens. “By using a mobile robot, the cycle time decreased to 10 minutes—a more than 20% reduction.” He dubs this the “repositioning of the value of labor,” letting robots be in an assistive role so that humans can do the more sophisticated tasks of assembly.
He cites another example at a steel plant where sample billets of steel need to be collected by lab technicians from various production lines and brought for testing to a QA laboratory 650 feet away. “Lab technicians cost a lot of money and collecting samples is not what they are paid to do. A robot does the grunt work of collecting and delivering samples, so that the technicians can concentrate on what they were hired to do.”
4. To connect islands of automation
Many operations are still pushing carts or driving lift trucks to and from sophisticated machine cells. However, in one application, carts and lift trucks have been replaced with a system that uses inertial guidance—a tape-free, target-free AGC (Savant Automation) that transports unstable loads of tall, narrow, cartons of paper from a robotic palletizer to a stretch wrapper. “We use a variable drive on the AGC’s deck to slowly accelerate and decelerate the transfer so that the load doesn’t tip over,” says Garry Koff, Savant’s president. “Once it’s on the vehicle, we take it to the stretch wrapper, where it gets wrapped.”
According to Koff, tape-free, target-free AGCs are especially suited for automatically moving material through high-traffic main aisles notorious for wearing down magnetic tape. “These vehicles are slightly more expensive but money is saved with installation and with no tape to maintain.”
5. For storage and retrieval applications
Unmanned reach trucks and turret trucks (Dematic) can automatically store and retrieve pallets in both narrow aisle and very narrow aisle (VNA) racking configurations. Systems like this can offer three benefits: labor reduction, safer operations and reduced product/equipment damage, says Scott Hinke, vice president and general manager for Dematic’s AGV business. He calls this type of technology: “automating the conventional.”
This application can be retrofitted into existing rack configurations with very little infrastructure changes, adds Mats Herrstromer, global product manager for AGVs. Essentially, the vehicle replaces a fixed crane in a traditional automated storage and retrieval system (AS/RS). He adds that in VNA applications where aisles can go as low as 68 inches, the traffic management system ensures that two vehicles don’t get stuck in non-passing aisles. “We know exactly where each vehicle is at all times. We’re managing vehicle traffic and priorities of moves at the same time,” Herrstromer says.
6. Use for picking
Increasingly, automatic guided vehicles are not a standalone solution; they are working in conjunction with other technologies or as one component in an overall process. One example involves the use of an automatic lift truck in a traditional pick-to-pallet operation.
In a typical process, an order selector drives a walkie rider into a pick zone and then gets on and off the truck to pick cartons to a pallet. When all the items in that zone have been picked, or the pallet is complete, the order selector drives the truck to the next zone or task location.
In the revamped process, the order selector doesn’t have to get on and off the truck to complete picking tasks in the pick zone. Instead, the order selector receives picking instructions using voice pick technology and picks to a pallet on a walkie rider equipment with AGV controls. The lift truck automatically moves with the order selector through pick locations. Travel distance is reduced and productivity is increased by up to 100%.
Those gains are the result of reducing or eliminating the amount of time spent on unproductive activities such as: taking the completed pallets to the stretch wrapper, transporting the wrapped pallet to staging, and retrieving the next set of empty pallets. “With this solution, the picker remains in the pick aisle to concentrate on the task at hand and not on driving the vehicle,” explains Dematic’s Hinke. “The AGV automatically transports full and empty pallets.”
7. For automatic truck loading (and unloading)
Historically, AGVs’ area of work in a plant or distribution center was limited to tasks taking place between the loading and receiving docks. Lift trucks still loaded and unloaded trailers. That is changing, thanks to automatic truck loading technology, or ATL, according to Mark Longacre, marketing manager for JBT Corp. “It’s beyond a beta site installation,” says Longacre. He points out that JBT has 60 ATL vehicles in the field and that other suppliers also have implementations up and running. “Trailer unloading is starting to pick up too, although it’s a lot more difficult because the jostling of the load during transport causing pallets to be slightly askew and more difficult to pick up.”
While automatic trailer loading is typically justified based on labor savings, Longacre notes that users appreciate that it improves safety and reduced product and equipment damage at a busy dock.
Companies mentioned in this article
Daifuku Webb: http://www.daifukuwebb.com
RMT Robotics: http://www.adamrobot.com
Savant Automation: http://www.agvsystems.com