Barcodes combined with radio-frequency identification tags support just-in-time automotive-parts manufacturing.
By Joseph Hallett, Contributing Editor
In the automotive industry, product-liability precautions and manufacturing efficiency require accurate identification and tracking of seats and airbags installed in new automobiles. For example, seats for Toyota minivans are produced by Total Interior Systems-America (TISA) at its plant in Princeton, IN, about three miles from Toyota’s final assembly plant. Under Toyota’s just-in-time system, or Kanban, material flow must be tightly coordinated between suppliers such as TISA and the final vehicle-assembly line.
TISA systems manager Dee DeMuth says, “Labels drive our production.” Kanban labels carry barcoded information about each seat, and reusable radio-frequency identification (RFID) tags provide a method for keeping seats for each vehicle together as they move on pallets through various stages of assembly and quality inspection within TISA’s facility (see Fig. 1).
As parts are taken for use in seat assemblies, information is sent back to TISA’s information system, supplied by enterprise-resource-planning (ERP) software specialist Glovia, a Fujitsu subsidiary, creating demand for additional parts. The Kanban process is designed to let the assembly process proceed smoothly, while minimizing the quantity of in-process material.
The SMS Group, with expertise in shop-floor data collection, joined with Glovia to develop TISA’s integrated shop-floor automation system. The system supplies data to the manufacturer’s ERP system for product tracking and reporting and contributes to each vehicle’s permanent record.
SYSTEM OVERVIEW
Toyota’s minivan can be constructed with seating for seven or eight passengers, depending upon the model, by installing configurations of seven different individual seats. Toyota triggers the seat-manufacturing process by broadcasting its requirements via a dedicated wide-area network to TISA’s material-requirements-planning (MRP) database server. TISA then responds by printing a unique set of Kanban labels for each vehicle, with one label for each seat. These labels carry information that is used in the manufacturing process, including a sequence number to identify the vehicle and details such as upholstery, trim, and seating configuration.
Completed seats travel on pallets whose movement along conveyors is tracked by RFID tags and fixed readers. A customized version of SMS’ CORE shop-floor data-collection system (SFDC) software controls the acquisition and validation of scanned data from barcode labels and RFID tags. It interfaces with the Glovia MRP database system, which deals with inventory and the flow of materials used by TISA. Toyota’s ERP system communicates with the Glovia system in setting up requirements and monitoring the flow of finished goods (see Fig. 2).
While the SMS CORE system was written in C++, customization of the user interface and screens uses Virtual Basic. “Most of the SFDC was custom,” says SMS technology chief Jeff Gottschalk. “We had to design and develop new transactions and the associated functionality.”
An SMS toolkit called CORE Builder created data fields, data entry screens, and menus, controlling navigation in the screen, validating the data entered, and responding to function key presses. A test mode allows the user to verify that the code is working correctly before installation in the production environment.
The data-collection system is operated from the TISA terminal, a PC running Windows 2000 (see Fig. 3). Administrative and troubleshooting functions also can be performed from a laptop computer connected to the network, where it can see the server or look at the various scanners on the floor. “The beauty of SMS CORE is that it can start and stop processes,” according to TISA’s DeMuth. “It provides a lot of good visual tools.”
SCANNING
“We supply three rows of seats on two pallets per vehicle,” says DeMuth. Seat types are front right and left (FR), second row right and left for seven passengers (RR1) or right, center, left for eight passenger (RR1 and CTR), and third row (RR2), which consists of 60/40 right and left seats that fold into the floor. Seats are assembled on two lines, each feeding the shipping conveyor. After initial assembly is complete, seats are automatically brought together in groups according to the Kanban labels. At the ends of the lines, seats are stack-loaded on shipping pallets. Each pallet contains an RFID tag that lists detailed information for all of the seats on that pallet.
Kanban labels are produced by Intermec 3400 printers on basic wax/resin and paper label stock. Paper tags and adhesive labels are printed for each of the four types of seat positions. Each has a unique layout, carrying part numbers, seat position, and manufacturing sequence numbers, using barcode Code 39 format (see Fig. 4).
TISA uses both fixed and portable (hand) scanners to read the barcoded labels at various places on the manufacturing floor. Intermec 2425 and 2435 hand scanners employ wireless connections over an 802.11b local-area network. HHP (Welch Allyn) 3800 Image Scanners and Computerwise TSD3 proximity card readers are used at fixed locations, wired to Computerwise ET215 Ethernet data-collection terminals.
Both scanners and workers have to be able to read the labels, tag stock, and paper, according to Gottschalk. “Scanners need to ensure that the label scanned was a Kanban label and not a pack of cigarettes,” he says.
Each seat has been preassigned to a particular vehicle as designated by the Kanban sequence. To track tthe seats, Kanban cards are scanned using hand-held scanners. Data flows via an 802.11b wireless network to the SMS server. At position 1 the data are used to pull seat covers and other materials from inventory for delivery to the beginning of each production line. If an airbag is needed, the serial number and other information are recorded.
Intermec 3400 thermal transfer printers print two serial-number labels at the airbag-scanning station. One is attached to the seat and other to the Kanban label. As the seats reach the ends of their assembly lines, their barcoded labels are read by hand-held scanners at positions 2, 3, and 4.
PALLET TRACKING
Radio-frequency identification was a requirement from the beginning of system design. This relatively new technology was seen as an improvement over barcoded stickers that would reduce confusion and lower the possibility of errors. Since data are stored electronically in flash memory, the tag can be rewritten each time that the pallet reappears. “The pallet is the only item that uses RFID,” says Gottschalk. “It’s easy to recover costs since the tags are reused.”
A standard Omron v700-series, 125-kHz RFID tag-about the size of a US quarter-is mounted in each pallet in a special cavity. Mounting is straightforward, according to Gottschalk, although there initially was a problem getting signals through the shielding of steel rollers in the conveyors (see Fig. 5). “We had to space the antennas away from metal brackets. Read range is normally 20 to 25 cm, but we get only about 13 to 15 cm.”
Seats flow down two assembly lines, reaching a shipping conveyor where they are loaded on pallets in sets corresponding to an established sequence for one specific vehicle. Two pallets are required to carry a full set of seats for a seven- or eight-passenger vehicle.
The flow of pallets is monitored by reading the RFID tags with Omron series V70 reader/writers, V700-CD2D-V2 controllers, and V700-H01 antennas; records are kept of the progress of each pallet. “Wherever there’s an RFID reader/writer, we log what happens at that location,” says Gottschalk. “The tags are rewritten when the pallets come back from TMMI, at the end of the production lines, and sometimes at the rework area due to a substitution from safety stock when the sequence number needs updating on the RFID tag. All other RFID points are read only.”
At the end of the first seat-assembly line, a loader places two front (FR) seats on a pallet. Then the pallet moves to its next position where rear (RR2) seats are stacked and the pallet’s RFID tag is written. Another Omron RFID reader verifies that front and rear seats are in the correct sequence and order. Then the order of pallets is reversed, and loads two-levels high are set up for loading the truck so that unloading will be in the correct sequence.
A combination of modular software design with the latest label-reading equipment made it possible to get TISA’s system up and running in just a few months from a cold start. Further improvements in the systemof reworked seats will be helped by building on existing SMS and Glovia software systems.
Company Info
Adaptive Micro Systems, Milwaukee, WI, USA www.adaptivedisplays.com
Computerwise, Olathe, KS, USA www.computerwise.com
Glovia International, El Segundo, CA, USA www.glovia.com
HHP (Welch Allyn), Skaneateles Falls, NY, USA www.hhp.com
Intermec, Everett, WA, USA www.intermec.com
Moxa Technologies, City of Industry, CA USA www.moxaUSA.com
Omron, Schaumburg, IL, USA www.omron.com
The SMS Group, Sidney, OH, USA www.thesmsgroup.com
