4 new ways AGVs & carts support automotive

Driverless, battery-powered automatic guided vehicles (AGVs) and automatic guided carts (AGCs) have long been deployed at automotive original equipment manufacturer (OEM) facilities as a means to eliminate forklifts and the inherent potential safety risks they pose to personnel and products.

“Automotive manufacturers want to get rid of manual fork trucks in the production areas because they can be the most dangerous piece of equipment in the plant,” says Greg Pachuta, sales manager at JBT Corp. “Safety is often one form of justification for the investment in an AGV system.”

Initially deployed to deliver components and kitted parts to assembly workers lineside at the point of vehicle assembly, automakers have now further expanded the use of these autonomous vehicles elsewhere in their plants. The practice not only extends the “fork-free” safety mandate, but also supports greater flexibility within operations as OEMs now build multiple vehicle models on the same line—and offer an ever-expanding selection of customization options to customers.

Further, AGV and AGC installations have trickled down from OEMs to their suppliers. Now, Tier 1, 2 and 3 sub-assembly and component manufacturers who supply the automotive OEMs are installing these systems in their own facilities, and reaping the same benefits, explains Terry Shaw, operations manager at Murata Machinery USA. “Most of our AGV systems are installed at the supplier level,” he says.

A variety of AGV and AGC styles support the need for manufacturing flexibility, adds Shaw. “Fork-based AGVs are generally larger units that hold larger capacities. Their forks handle and transport loads, typically short distances, and the latest models can now reach heights of 24 feet to interface with four- to five-level high storage rack,” he says.

Tugger-style AGVs and AGCs pull one or more carts along behind them in a train across longer distances. And, single-unit AGVs and AGCs can be customized with different mechanical transfer unit attachments, including roller conveyor, chain conveyors and lifters. These add-ons support ergonomics, making it easier for a worker to access the transported item or move it to or from the vehicle.

The experts Modern spoke with for this article outlined four ways automatic vehicles can support operational flexibility and safety best practices at automotive manufacturing facilities.

1. Vehicle and component assembly flexibility
Instead of only delivering parts and components to a permanent overhead or in-floor conveyor-based assembly line, some of the newest automotive manufacturing plants are using AGVs as the base upon which a car body or component assembly travels during assembly, says Noel Dehne, vice president of automotive sales for Daifuku America Corp.

“OEMs are creating a continuous build line based on AGVs and AGCs,” Dehne explains. “Advances in the vehicles’ drive systems and electronics create the torque required for a continuously moving production line traveling at a slower speed that maintains accurate spacing between the parts.”

Should production rates increase or decrease, it’s much easier to make adjustments to the automatic vehicle line than to a permanent conveyor installation without a huge capital expenditure, adds Dehne. “Further, using this concept, it’s very easy to pull a job out on the spot if a manufacturing flaw is observed at any point during production—not just during designated quality control areas.”

2. Human-free access to secondary manufacturing and buffer storage areas
Manufacturers are also adding fleets of AGVs and AGCs to secondary manufacturing and assembly processes outside of the main assembly line, such as in body shop areas, says Keith Soderlund, vice president of sales of Creform.

“AGCs are ideal for feeding and removing the finished parts from robotic stamping and welding stations,” he says. “This eliminates the need for personnel to enter the robot’s safety cage zone, which requires a shutdown for safety. Instead, the vehicles can automatically enter secured work cells to remove carts of finished components and replace them with empty carts without interfering with the robot’s operation.”

For example, says Soderlund, an AGC can pull an empty cart into a work cell, disengage its connection pin, then travel to a full cart of welded doors, engage that cart and exit the cell. From there, the AGC travels directly to the assembly line where it disengages from the full cart, reconnects to an empty cart and returns to the robotic welding cell to repeat the exchange process.
Although automatic vehicles have traditionally been used to facilitate horizontal movement of items, more automotive manufacturing operations are deploying fork-style AGVs that can access work-in-process items stored vertically.

“Automotive OEMs are all about keeping their production lines up and running as much as possible, so they’ve started looking at adding secondary buffer storage areas closer to the production line to hold additional stock,” says Scott Hinke, director of North American sales for AGVs at Dematic. “Products come from one sub-assembly area and head into a smaller buffer storage zone prior to being needed at the next work cell.”

“The AGVs provide more flexibility in a facility’s overall work piece movement and workflow design,” adds Bryan Knott, global product manager for Dematic AGVs. “They’re no longer limited to linear movement from work cell to work cell. Instead they allow manufacturers to automate storage without tethering an AGV to a single aisle—they provide both horizontal transportation and vertical storage at the same time.”

At the supplier level, these buffer zones (also called supermarkets), store small parts in totes on flow rack. Personnel stationed there build kits by hand of unique components to support mixed product assembly. When the kits are complete, tugger-style AGVs can pull carts of kits to another production destination for further assembly steps.

“Kit part delivery to the appropriate station improves the picking efficiency of a line worker and keeps the most skilled production employees working on the line,” adds Soderlund.

“Meanwhile, less skilled employees can be used to assemble the kits. By adding the AGVs to synchronize the delivery of subassemblies and parts, personnel can be deployed to value-added tasks.”

3. Various cart forms support various functions
The carts pulled by tugger-style AGVs and AGCs have also been enhanced to support flexible manufacturing, says Larry Tyler, vice president of sales and marketing at K-Tec.

“Carts are used to bring out raw materials as needed for assembly, as well as finished goods transfer. They’re also being used on the warehousing side of an assembly operation for picking of kitted parts and tooling and transfer to both lineside and buffer storage,” he says.

One of the newest cart trends being applied in automotive manufacturing is the use of mother/daughter carts. These two-part systems include a larger mother cart that corrals several smaller daughter carts inside it. The smaller carts can be easily separated from the mother without dismantling the train.

“These cart systems offer flexibility in sequencing, improvements in ergonomics, and the systems can be designed so that the daughter carts can be fairly low cost, while the mother carts can be more expensive—because they need far fewer of them,” Tyler says. “You might have 10 mothers and 200 daughters.”

Further, the daughter carts often ride on a common base with customized, bolt-on upper sections. The upper cart sections are customized to hold one or more parts without any packaging or dunnage. “If the part changes, you just bolt on a new upper, but the cart system still supports that need for flexibility.”

4. Virtually limitless navigation and travel flexibility
The variety of navigation options also makes implementing AGC and AGVs in automotive OEM and supplier facilities an easier decision. Magnetic tape-guided systems are the least expensive and require no damage to an existing floor surface, as they simply adhere (as opposed to magnetic bars embedded in the floor). In laser-guided navigation systems, reflective tape is placed on columns, walls or the ceiling at regular intervals along a path.

On-board laser detection interacts with the reflective tape and communicates the angle of the intersected laser beam back to the control software to determine location. Gyroscope systems for inertial navigation detect waypoint transponders embedded in the vehicle path for validation of the vehicle’s position. Camera- or vision-based systems read stickers, such as bar codes adhered to the floor, allowing the vehicle to communicate its location back to the control software to verify that it’s on the correct path.

The development of a completely autonomous navigation system, which uses a virtual map of the facility paired with vision systems and navigational algorithms, is on the horizon. Taken together, the vehicles’ on-board controllers use all these information inputs to enable the vehicle to make travel adjustments—based on fixed (or moving) obstructions—while remaining in motion, says Dematic’s Knott.

“Although it’s not here yet, these systems will allow the vehicle to follow a virtual, preferred traffic lane, yet still be able to deviate intuitively from that to avoid as many obstacles as possible,” he says. “There’s been a lot of interest in this from the automotive industry because it could potentially add another 10% to 15% movement efficiency with less teaching time than laser- or magnet-based systems and minimal infrastructure and commissioning.”

Further, advances in vehicle control software allows for flexibility in path programming, adds Murata’s Shaw. “If you want to run different production routes on Tuesday and Thursday, you can pre-program the vehicles to travel different paths, allowing you to use the same AGV to support different processes depending on the day,” he says.

Safety systems, including laser- or vision-based technologies, reduce the risk of collisions and enable faster running speeds, says JBT’s Pachuta. “In the old days we used mechanical bumpers that actually had to make contact with an object to trigger a stop,” he says. “Now the vehicles include solid-state laser bumpers that can be programmed with different, adjustable sensor fields. That allows users to have their vehicles travel faster across longer distances.”

With the newest sensors, the vehicles can travel faster because they can detect an object further away from the sensor. That means the faster a vehicle travels, the further the distance the safety sensor can be programmed to cover, Pachuta says. Depending on the distance between the object and the vehicle, the vehicle can be commanded to slow down gradually or abruptly stop.

Companies mentioned in this article
• Creform
• Daifuku America Corp.
• Dematic
• JBT Corp.
• K-Tec
• Murata Machinery USA