Lear Corporation's seating plant in Montgomery, Alabama is driven by just-in-time delivery. At peak production, Lear builds approximately 1,000 seat sets per day or 73 sets per hour in 56 distinct combinations of colors and options for the Hyundai Sonata sedan and Santa Fe SUV.
To help this 94,000-square-foot, four assembly line plant stay on time it receives an estimate each day of which seat models it will need to build for Hyundai's scheduled production. About two hours before the seats need to be installed into the cars, Lear receives a live broadcast of the exact production sequence and seat model requirements from Hyundai.
Production efficiency is built into the plant’s material handling operations. The seats are assembled on pallets with fixtures that can rotate and tilt for worker accessibility, providing an ergonomically sound procedure that improves efficiency. The assembly lines use a non-synchronous looping conveyor system, with an automated, timed release at each workstation that can be overridden by the operator when necessary.
Assuring Quality Assembly
The entire assembly process is managed by a PC-based quality assurance system (Integrated Systems Design) that improves overall seat quality by monitoring the seat assembly and sequencing process. The quality assurance system is interlocked to the conveyor system to prevent seat movement before each assembly and inspection step is properly completed at a particular workstation.
Read-only RFID tags index the conveyor system's product tracking. RFID antennas located at each quality assurance station read RFID chips embedded in the seat build fixtures. The quality assurance system electronically displays instructions at critical workstations working in conjunction with the RFID system to provide positive seat identification and data tracking. Once a "work complete" message appears on the workstation display screen, operators can release the part they're working on and allow it to move to the next process.
The system allows Lear operators to simultaneously assemble several different types of seats on the same production line. Build sequence numbers and specific work instructions for each seat are displayed at the assembly line workstations. Critical data, such as torque and angle, are recorded and associated with each seat build sequence number and maintained for years, along with each seat's build record/birth certificate.
Tracking Quality and Delivery Parameters
As the seats move down the assembly conveyors, the quality assurance system receives various tool, equipment and operator inputs and determines whether a seat assembly or component is a "pass" or "fail." This information is used to route defective seats to a repair station, provide notification of defects found at inspection to the operation that caused the defect and provide a means for tracking internal defects. The quality assurance system automatically sends information to Lear's ERP system at several points in the assembly process. That information is used to trigger other events in the system and transfer data associated with each seat.
After a set of seats is assembled and placed on a shipping pallet at the Lear plant, they're wrapped in a plastic bag and bar code labeled. The seats are then transferred to the shipping area and prepared for delivery to the customer. A mid-load automated storage and retrieval system (AS/RS) determines where to store the seats based on the bar code. The system also selects and retrieves seats in the order they're to be shipped, based upon the live broadcast from the Hyundai plant.
Because the seats are moved exclusively by an automated system from Hyundai's receiving dock to the assembly line, Lear software directs the AS/RS to sequence each truck load of seat sets in reverse broadcast order prior to loading. This ensures that they'll be delivered in the correct sequence to the assembly line precisely when the appropriate vehicle reaches the seat install locations.
Passive read-write RFID tags are also used in the outbound shipping sequence control system. A chip is mounted to the rear of each of Lear's fleet of conveyorized semitrailers. RFID antennas are located on Lear's shipping dock and Hyundai's receiving dock. Each semitrailer holds 54 seat pallets, which are automatically loaded onto a truck in less than one minute by a shipping conveyor system. When a truck is loaded, trailer sequence information is written to the trailer's RFID chip. The chip's information is then checked to ensure that the write was successful. The sequence control system won't allow the trailer's dock lock to be unlocked unless the correct data has been written successfully to the chip.
When the trailer is backed into Hyundai's dock, the RF chip on the semitrailer is read. If the trailer sequence information is correct, the Hyundai conveyor control system allows workers to initiate the trailer unload sequence. If the trailer sequence information is incorrect, an alarm horn and beacon are activated, and Hyundai employees are prevented from unloading the truck until the correct trailer is in place at the dock.
Handling Return Pallets
The pallets on which the seats are shipped to Hyundai return to the Lear facility in stacks on dedicated conveyorized delivery trailers. The driver connects the trailer conveyor to the in-plant conveyor system via an umbilical cable plugged into a receptacle adjacent to the exterior dock door. He then initiates the trailer unload cycle. The stacks of empty pallets are automatically conveyed to an installed mezzanine level where they're staged until needed.
Lear prides itself on achieving 100 percent on-time delivery to the Hyundai plant. Their new material handling equipment and quality assurance system are an integral part of ensuring they maintain their record.
Ed Romaine is chief marketing officer of Integrated Systems Design (www.ISDDD.com), a manufacturer, systems consultant, designer and integrator for warehouse, manufacturing, distribution, wholesale, life sciences, institutions and retail organizations in North America.