“Production processes had been kaizened and were nearly as efficient as they could be, but conveyance of parts and sub-assemblies had not been as closely scrutinized. AGVs in the TMMK Body Weld department have provided fertile ground for cost savings.”
That’s Paul Stafford, Toyota Motor Manufacturing Kentucky (TMMK) production engineer and automated guided vehicles (AGV) project lead, talking about how they’ve made cycle time reductions, efficiency improvements and saved costs in the department by improving the material-handling operations. Given that the Georgetown plant produces some 500,000 vehicles annually (Camry, Camry Hybrid, Avalon, and Venza), every improvement matters.
How They Did It
Being Toyota, they looked at what they had, then set about to improve it, not simply replace it. Stafford’s team worked with several technology and equipment partners on the processes for transporting stamped parts to the robotic welding stations in the Body Weld department. AutoGuide Systems (autoguideagvs.com
) retrofitted 22 24-volt, AC-drive industrial tow tractors—converting the standard industrial truck into an AGV. The industrial trucks were produced by sister company Toyota Material Handling U.S.A. (TMHU; toyotaforklift.com
). “Adding automation to an industrial truck provides built-in durability and readily available replacement parts. It also enables fast service from a local dealer and a lower starting price point,” says Tim Meyer, AGV product manager for TMHU.
AutoGuide equipped the 10,000 lb.-capacity tow tractors with obstacle and guidance sensors, radio frequency modems, radio frequency identification (RFID) tag readers, and other technology. A touch-screen programmable logic controller interface allows for programming on the plant floor. An operator can step on an AGV, allowing it to be run manually when the automation needs to be overridden.
As with the development of any new technology, there were kinks.
The AGVs tow up to five racks of parts stretching 45 ft. long to the robotic welding cells, a 1,900-ft. round trip. (Because the Georgetown plant has been in operation for more than 20 years, the distances between manufacturing processes aren’t as close as they are in newer Toyota facilities.) One consequence of the longer travel distances is that the interaction between AGVs and other traffic can be high. Which can result in accidents.
Stafford explains: “Some of the optical sensors that were used for safety control had limited range—a field of view of 130º—which created blind spots, particularly in corners. We discovered that in the intersections where we had an AGV coming in at an angle, there were collisions.” An average of three collisions per shift took employees 90 minutes per week to clear. To combat this, Stafford’s team changed the optical sensor to a laser scanner that has 240º field of view, but this still didn’t assure that there wouldn’t be collisions. What they needed was traffic-control software.
Enter Industrial Concepts Incorporated (ICI; ici-ky.com
). ICI worked with the AGV implementation team to develop custom traffic control technology. The Automated Vehicle Intersection Navigational Utility (AVINU) system monitors the activity of each AGV and reports its location and performance, which can be checked on any authorized PC in the facility. The system also monitors battery charge, assigns available AGVs to loads and regulates traffic at AGV intersections.
As the AGVs travel, they read their location from RFID tags embedded in the floor, which trigger certain instructions. When they arrive at an intersection, they’re programmed to stop and check for other traffic.
The use of AGV parts delivery reduces operator walk time and floor-space requirements. For example, a Toyota team member previously followed a 16-stop process, picking up parts from flow racks, loading the robots and picking up the next part. Moving between the parts dollies towed by the AGV and the load stations reduced the number of stops to nine, and reduced the average cycle time by 35 seconds. That adds up to a savings of 317 days per year. Additionally, floor space savings from eliminating flow racks and pallets averaged almost 37 ft.2 per process.
Another benefit of the AGVs is lower labor requirements. In total, the introduction of AGVs in TMMK Body Weld allowed the department to move 42 people to higher value-added jobs. Stafford stresses that no employees lost their jobs because of the AGV implementation.
The Body Weld department is currently using 22 of the AGVs, of which 18 are running regularly on nine routes. Through the implementation of the AGVs, TMMK is seeing about $1 million in annual savings. 1.8 million parts are being handled annually in Body Weld. Not surprisingly, Stafford says the team is looking at more areas that could benefit.