Bright future for AGV's
There are two diverse paths for the future of AGV's extremely simple and inexpensive, or complicated or sophisticated.
Several decades ago automated guided vehicles (AGVs) were being heralded as the saviour for automotive OEMs material handling requirements. Plants such as Ford's Cologne facility, with its legions of AGVs, were to be the flagship for future factories, but that utopian vision has fallen some way short of the reality. Not that AGVs are scarce among the global automotive manufacturing facilities, but their use is less universal than the earlier hype or than the AGV vendors would have had us believe.
Today, typical AGV applications in the automotive industry include automated raw material delivery, automated work in process movements between manufacturing cells, and finished goods transport. AGVs link shipping/receiving, warehousing, and production with just-in-time part deliveries that minimise line-side storage requirements. They can also help create the fork-free manufacturing environment, which many plants in the automotive industry are seeking.
But why do OEMs use AGVs given that they operate at half the speed of traditional fork lift trucks and are more expensive to purchase? It would seem a tough sell but Pascal Milliot, general manager of body assembly engineering department at Renault, explains it succinctly: "We increasingly use AGVs in order to gain room along the assembly lines."
Sometimes the real reason for using AGVs can get lost in the drive for technology and, according to Mark Sharp, director/plant manager at Nissan's US facilities, that real reason is making the job easier.
"I think there is a financial upside to greater application in body assembly," he says. "The goal was not AGV application; that was strictly a tool to support the ultimate goal to make the job easier for the end-user, the body assembly technician, and the individual putting parts into the vehicle. How do we do that? I think we look at that as we look at processes. Changing processes, changing part supplier, and the application of AGVs does support that but that is not our ultimate goal to just bring AGVs to the process."
One of the major players in AGVs is FMC Technologies, and Greg Pachuta of the Pennsylvania, US-based supplier argues that AGV use has not diminished. "True, the use of AGVs now is definitely on a case-by-case basis; nobody is doing an entire plant," he says. "However, I don't think that it has died down but it has stayed steady.
"They are used in all different fashions now. Before, it was strictly material handling, moving parts from a shipping dock to the assembly line. Now they are actually used in place of the assembly line. They have smaller AGVs that form part of the assembly line of the seats or part of the assembly of an axle. That was a trend many years ago and now they are doing that again, but with very inexpensive AGVs.
"In effect it is replacing a conveying system. They are much more flexible than putting a full conveyor in the middle of a plant. This way, they just have a piece of magnetic strip tape that they use for guidance that is very easy to pick up and move somewhere else."
This is a function often seen in operations like engine marriage with chassis such as at BMW Liepzig and Volvo in Gent. Units on AGVs can be delivered in sequence ready to marry to the chassis that is moving along the production line on an overhead conveyor.
Rick Youngblood, plant manager truck trim and chassis at Nissan Smyrna, is among the manufacturers in North America who have seen a changing market for AGVs. "Actually, I think this is growing," he explains. "I think that initially it was a novel idea that gained a lot of allies just because it was a novel idea. Going forward we have to be very selective and very careful about what type of applications that we put AGVs in. By that, I mean that there are different types of AGVs on the market available to us.
"Some of those are simple magnetic-guided vehicles that just follow the track that you embed in the floor. Others have decision-making capabilities and are powerful enough to travel large or different distances and make stops based on the need of a particular part. I think as we move forward and try to become much more competitive in the market place, there is definitely a market out there and a segment of our operations that those fit. There were also probably some areas in the past that we and maybe other manufacturers have tried to use those in, that didn't work out so well. I think that is a normal trial and error in the growth process."
In the early days of AGVs the magnetic-guided vehicles were less flexible, requiring wires buried under the floor, but by using magnetic tape the current breed can tick all the flexibility boxes.
"Actually, the magnetic-guided vehicles are more flexible because what we call a dumb AGV doesn't have a great deal of programming," Youngblood continues. "It basically follows a magnetic tape and that tape comes in a roll just like standard masking tape. It is very flexible; it is a matter of just pulling the tape up and moving it to another area of the plant. So it is probably more flexible than the smart AGVs, which have decision making capabilities, but it is surely a function of what is available in the programme itself rather than the flexibility."
Speed is a recognised downside of AGVs but as Pachuta explains this is more than compensated for in other areas. "AGVs will run at probably half of the speed of a manual fork truck," he says. "They run at about 6mph and AGVs run about 3mph. So we typically need more vehicles than you would with manual fork trucks. We are able to compensate for that if the plants operate in more than one shift. So we need twice as many vehicles but then we break even in a two-shift operation. There are really major benefits if it is a three-shift operation."
AGVs can broadly be divided into two groups - dumb and intelligent. The dumb - or more politically correct 'unintelligent' - AGVs are basically simple systems. "These are used more for moving short distances, moving at a very slow speed, moving very light weight parts and they also could be used in the assembly," Pachuta says.
Then there is the more traditional, more heavy-duty or industrial AGVs, that are used for material handling, taking parts to the assembly line and parts from one process to another.
A trend that Pachuta is witnessing in other sectors, and something that the automotive industry is paying great attention to, is the automatic unloading of truck trailers.
"As a truck pulls up, we will automatically unload the whole trailer and deliver it out to the assembly line," he explains.
"The control system picks up the information from the trailer as it pulls up and has the right AGVs waiting at the dock, and the vehicle can be automatically unloaded and the parts or assemblies moved to holding areas or delivered lineside.
"I don't know of any in the automotive industry at the moment, but other industries are using this method and the automotive industry is definitely looking at it now. Most of them are dedicated docks where it is always the same part all of the time.
"We already have systems where parts, like engines, are never touched by a manual fork truck," Pachuta says. "They automatically come off an automatic truck-unloading system, not an AGV system, onto a conveyor inside the plant and we pick up the load and take it straight to the line and bring the empty racks back to the conveyor system where they are pushed back into the trailer."
The control system of an AGV is the intersection controller that does traffic control. It also gives the vehicles destinations and tells them where to go next. "From that you have complete tracking of where the vehicles are at all times," Pachuta says. "You can monitor what is happening, how many loads have been moved a day, and what their battery level is. There is complete monitoring of the system through the system control. Typically computer controlled and then from the computer we talk to the vehicles through radio technology.
"Usually there is an interface to transfer information back and forth, but it is not very complicated. The plants always want to keep track of what is happening, so they want messages back and forth to say if the system is operational or non-operational. They may also want to pass information between one supplier, or from the supplier of the parts to the AGV system and so on."
The system usually operates much in the same way a traditional Kanban system would: this time instead of the red or green lights, flags or markers that an operative would use under a manual system, the operator can push a button to say that he is out of parts or it can be an automatic signal. "Most of it is regulated by the operator and in most cases he pushes a button to say 'I am out of parts, can you bring me another one'."Pachuta says.
At Nissan in Smyrna, AGVs are predominantly used in final assembly. "We are using them in the assembly portion of the building rather than in the body assembly area, and we use those particularly where we have sequenced delivery of parts to the line," John Davenport, department manager for body assembly, explains. "We are also using them in several applications where we are kitting - sending a kit of parts to the line to eliminate the walk to a supply rack or something like that where we will have a block kit of parts that accompany the vehicle through its process and has everything that a particular line would need to add to that vehicle."
Despite all the advantages of flexibility, the prime reason behind the adoption of AGVs is safety, as Pachuta confirms.
"In many companies safety is the key feature," he says. "The auto companies in the US and, I am sure, all over the world are doing studies of the cost of manual fork trucks and the lack of safety associated with dealing with them. AGVs have a stellar record for safety with all the electronic emergency bumpers that they have on board, they can sense things and stop if somebody walks in their way. So safety is the key issue.
"I am sure that there is still some push to reduce the cost of manual labour, so that helps.
"Then there is the flexibility of the AGVs; they can be laser guided so you can move the vehicle past anywhere that you want."
As for future technologies for AGVs, the automatic truck unloading that we touched on earlier is the next big wave that is hopefully going to revolutionise the market.
"Being able to automatically unload truck trailers and deliver parts to the assembly line," Pachuta says. "The technology of being able to determine where the trailer is and automatically have the vehicles sense
the trailer and adjust properly so that it can automatically unload it is definitely going to be a big advantage."
Pachuta says that there are two diverse paths that vendors are treading - simple and complex. "There are two extremes," he explains. "One is to make them extremely simple and inexpensive so they can use them in many different fashions. Then there is the other issue of making them more complicated or sophisticated, where you are able to use them for something more than manual fork truck drivers have done in the past."