AGVs and Software Keep Deere Running
To keep up with orders while building the variety oftractors John Deere markets, flexibility had to be a key part of its newassembly system, its handling devices, and even its workforce.
byTom Andel, chief editor
Tractorsare almost as unique as people at John Deere. In an era where customer serviceis a critical competitive advantage, that makes automated manufacturing a must.Nowhere is that more evident than at John Deere’s Augusta, Georgia,plant, located in nearby Grovetown.
Toachieve the level of service performance this plant required, Deere invested$23 million in plant expansion, including an automatic guided vehicle (AGV)system, smart tools, 106 workstations and a new 188,000-square-foot assemblyfacility.
BillTasch, manufacturing engineer at the plant, anticipates the day when a virtual“birth certificate” will be created for each model.
“TheManufacturing Execution System [MES] we’ll be implementing will [keep arecord of] the serial number, the P.O. number, the torques on all the criticalfasteners and error proofing checks to ensure the right parts were put on theright models,” he says. “We already have a good track record forwarranty claims, but the goal is to reduce those claims and improve customersatisfaction. Anything that hurts our customer satisfaction index we’lladdress by putting some automated check in our assembly process.”
MES takes time
Asimportant as the MES will be to this Deere plant’s quality record, thecompany isn’t rushing into implementation. It will be online toward theend of 2002. Why wait so long? Success requires the building of a foundation,which Deere is doing by automating this plant a step at a time — startingwith its tractor assembly line, which is now up to speed with AGVs from AGVProducts Inc. (www.agvproducts.com)
TheMES, from ICE Automation Group Inc., (www.ice-automationgroup.com) will beinterfaced with the business software to define all the correct part numbersfor 1,300 different configurations. That takes quite a bit of time. Theinformation system (IS) people must first concern themselves with therelationship between these configurations and the individual component parts.They also have to understand how the part number structures work. That requirescommunication with the plant floor people and, as Jim Smith, owner of ICEAutomation, told MHM, that’s not always an easy connection to make.
“TheIS department and the plant floor people don’t talk real well, but theyboth hold important pieces that form the heart of an MES system,” hesays. “The MES has to transmit what’s happening on the floor up tothe business system and vice versa. If an AGV doesn’t have the propercomponents, the MES alerts the operator and lets him know what’s there,what should be there and holds the AGV until it has the proper equipment onit.”
Bill Tasch offers an example of the component complexityinvolved: “A joystick will be different depending on whether it goes intoa narrow cab tractor, a platform or a straddle model. Today, one assemblystation might have to carry 28 different kinds of joysticks to get ready forany type of tractor that comes down. Our model mix makes it complicated.”
AGVs carry product and data
Rightnow this Deere plant is mastering the complexities of flow manufacturing byautomating the assembly line for its 5000 Series tractors. Information flow isas important as product flow in this developing environment.
“Theprocess needs to operate in a fully integrated and networked assemblysystem,” says Chip LaPole, project manager at the plant. “We chose‘smart’ automatic guided vehicles [AGVs with onboard computers]that are precisely routed through assembly steps and mesh with cross-trainedoperators using ‘smart’ tools in workstations. The result is a‘smart’ device network.”
AGVProducts, based in Charlotte, North Carolina, supplied the 62 AGVs forming thework platforms upon which work-in-process (WIP) tractors ride. The wire-guidedvehicles are part of a quarter-mile-long assembly line with 106 workstations.Each AGV can carry 7,200 pounds gross weight and is outfitted with one of threecustom fixtures, depending upon whether it carries a tractor chassis, engine ortransmission.
Thethree-wheeled AGVs have a forward steer/drive wheel and two fixed rear wheels.A 48-volt battery system powers separate steer and drive motors. An onboard,microprocessor-based system called TRACE 2000 controls each vehicle andcommunicates by radio signals with a base control unit. For most routingoperations at Deere, the vehicles travel at a speed of approximately 40 ft/min.
As anadded safety measure, the AGVs are equipped with a mechanical bumper, infraredobject-detection sensors, audible and visual warning devices, aloss-of-guidance braking function, emergency stop pushbuttons, and anauto/manual key switch. If needed, the AGVs can be operated manually by handcontrol devices that enable an operator to control speed, direction (forward orreverse) and steering.
Speeding along a “race track”
Thereare nearly 3,500 steps in the assembly process for the 5000 Series tractors,but the job can be completed in less than four hours. The 5000 Series workforceis educated in flow manufacturing methodologies and cross-trained forflexibility in a non-traditional approach.
“Theassembly line is laid out much like a ‘racetrack’,” explainsLaPole. “The racetrack has two spur or feeder lines for engine andtransmission assembly. Six AGVs work the engine line, six more on thetransmission line. The remaining 50 AGVs loop around the main racetrack line.The AGVs then mesh with cross-trained operators equipped with smart tools inworkstations.”
Whysmart tools? The most common warranty claims on tractors are for fuel andhydraulic leaks. Deere is addressing this problem through fuel system designand tools that apply just the right torque to secure components.
“Clickerwrenches let workers know that fittings are torqued correctly,” saysTasch. “They even count the number of fasteners and tell you what theirtorques were.”
Information means quality control
Deereoperations managers follow the progress of work in process (WIP) on computermonitors. Assembly operators get their tractor build instructions and qualitycontrol information from the computer system via touchscreen monitorspositioned throughout the plant. System software uses radio frequencycommunication to directly interact with the AGVs’ onboard computers andtransceivers to precisely control and track AGV movements.
LaPoleadds, “Full network implementation will ensure that the AGV will not movefrom a specific assembly station until the work is complete and verified. Thecontrol system will then process quality control parameters to guaranteeacceptance. Also, the ‘smart’ AGV stops only at assembly stations wherework is required on the specific tractor carried aboard that AGV. The vehiclewill bypass stations where no assembly is needed.
Dependingon the specific tractor under assembly and its options, there is widevariability in the labor performed on each vehicle. For example, twice as manylabor hours can be spent on a high-option tractor as compared to the hoursspent on a basic model. Therefore, variable routing with smart AGVs isimportant in juggling production scheduling. That’s what makes the buildingof a network so important — down to the proper use of the smart tools.
“Thesmart tools are interfaced with AGVs,” Tasch notes. “The AGVwon’t move to the next station until the smart tool provides a signalthat it reached the proper torque on all the critical fasteners. We’llalso have a bar code system to check for the proper part numbers.”
Theoperator scans the menu of critical parts twice. The first time lets themanufacturing planning system know that a tractor is being built. It alsoallows plant personnel to track process times at every station. It gives themprocess statistics to see how different build sequences for the different modelmixes affect assembly throughput.
“Ifwe have a model that takes more time than usual and we see a problem at astation, we can go back and look at the data and see what tractors wereassembled that caused that problem,” Tasch explains.
Building a future
Deere’ssuppliers will also play a bigger part in the plant information loop. Forexample, the plant’s tire supplier — located a mile away — islinked to plant operations so it can see the build sequence. When an operatorscans the build sheet, that will send a signal to the tire supplier. Thisensures that the right tires get put on the right tractors.
Futureplant expansion projects are possible, and will take several directions. Butfor now, Deere’s Augusta, Georgia, plant is looking forward to runningwith less inventory and fewer line-down situations. MHM