First, the good news: A strong economy for the past several years has made for a job seeker''s paradise, at least in northern Kentucky -- opportunities are plentiful and workers can pick and choose employment. Next, the bad news: For employers in a strong economic region, openings are difficult to fill, turnovers wreak havoc on scheduling, and keeping good employees becomes more of a challenge. Such were conditions just over a year ago at the Florence, KY facility of the Battery Components Division (BCD) unit of Johnson Controls. But now, that''s all in the past -- at least in one area of the plant -- thanks to a series of 19 robotic material handling cells provided by specialty machine builder and systems integrator, Custom Machines, Inc. (Adrian, MI).
With more than a year on the job working 24/7, the cells have yet to miss a day, have not taken any vacation days, have not used their experience to seek another job, and with well over 99% uptime, have helped to keep production on an even schedule and have reduced overtime costs. In fact, according to Paul Buckethal, manager of engineering at the BCD facility, they have reduced costs to such a point that the 19 robotic cells will achieve their payoff mark in one more year (two years total).
"Importantly, the cost savings were achieved," Buckethal says, "without a single layoff and all of the employees we previously had doing this work were offered or trained for new positions in our organization. The cost reductions have resulted in lowering our overtime from having people stay over, come in early or working extra days, from reduced new-hire human resources costs, and from normal employee attrition through retirement or taking other jobs.
"Prior to the installation of the robotic cells, we had not been able to fully staff this area of the plant for more than three yearsto cover all shifts for the 7-day work week required over 40 people. Now, to fulfill our production requirements, only a single robotic technician is needed per shift to monitor the operations, enter programming data for part changeovers, and provide maintenance services if required."
For BCD, those production requirements are quite staggering. As part of North America''s largest automotive, marine/RV, and lawn/garden battery supplier for both OEMs and most major aftermarket retail brands, BCD and a sister plant in South Carolina are responsible for injection molding of battery components such as cases, tops, and vent caps. The components are then shipped to assembly plants where the plates, terminals, and acid are added.
Considering size variations along with different colors and terminal location options, the Florence facility molds over 200 varieties of battery cases, using 38 injection molding machines. Each machine can mold two battery cases per cycle; also, to provide an agile manufacturing mix, each is capable of running any one of the 200 or so battery cases, depending upon assembly operation requirements. After molding, the cases may be automatically routed via a conveyor line directly to the CMI-built robotic cells for offloading, or first sent to a hot stamping operation for brand name and/or logo identification, then transferred to the offloading stations where they are queued on the conveyor for removal and layering on pallets.
Each material handling cell provided by CMI consists of a 6-axis Nachi model SF-133 robot with its own controller, a dual-function end-effector adding a seventh, rotational axis, plus two sets of two roller conveyors/chain transfers. Each set of transfers (one set for every molding machine) has a conveyor that delivers empty pallets to the cell, and a chain transfer with 90o turn that shifts full pallets to an unload station by fork lift. In addition, CMI provided a full cage guarding structure with access openings for the incoming pallet conveyor. Other peripherals include sensors that monitor the numbers of battery cases awaiting removal on either of the two lines serviced by the cell, thus coordinating the robot''s actions as to which line needs offloading attention. The cells are also equipped with associated diagnostic and operational alarms, such as if a full pallet is not removed by a fork lift operator in a timely fashion.
In operation, the cell begins its offloading tasks with the entry of a program or palletizing pattern for each battery case configuration. Currently, this programming is done manually by the cell technician at each individual robot''s controller, although the controls are capable of networking to a single system control if required in the future. Once ''taught'' a palletizing routine, the controller''s memory can store that program for recall by way of a simple identification number, eliminating the need to reprogram with every changeover.
Once programmed, the cell takes over all offloading and palletizing functions for the battery cases from its two assigned molding lines. For example, as the molding machines and hot stampers begin production, an empty pallet will enter the loading zone. Depending upon the actual part and its palletizing pattern, the robot can retrieve a quick-connect end-effector (without removing its normal, battery case tooling) with vacuum cups specifically designed for picking up and placing a heavy paper liner on the pallet. Next, the robot returns the special end-effector to its storage rack, then waits for a signal from the sensors as to which of its two molding lines needs battery case removal. Even though there is only one robot, the programs for each line can run independently. If one line is down for changeover or is running at a slower pace than the adjacent line, the robotic cell, through various sensors, would service the line in operation or give priority to the faster of the two.
With the paper liner in place, the battery cases, again picked up using vacuum cups, are then placed on the pallet according to their programmed layout. For some cases, stacking requires that the parts be upside down, while others are placed right side up -- thus the need for the added, rotational axis. Once a layer is filled, the robot again retrieves the special sheet handling end-effector, places a second paper liner on top of the first layer of battery cases, then resumes part stacking. When the pallet is filled to the programmed limit, it is automatically transferred to the unload station, and the next empty pallet moves into position. During the process, the robotic cell has also been monitoring the second molding line, removing and stacking that line''s battery cases as required. Sensors continually monitor the level of paper liner to assure an adequate quantity is on hand.
On average, each material handling cell palletizes approximately 250 battery cases per hour for the two lines it services, but this can vary depending upon the parts being run and their cycle times.
The concept for these robot palletizing cells was developed by Buckethal and his engineering staff and, in fact, they first built a prototype unit for testing. Once satisfied with the viability of the concept, they turned the project of building the production units over to CMI. "Even though we (BCD) have over 25 years of experience working with robots in our facilities," notes Buckethal, "CMI''s expertise was instrumental to offering alternative equipment and design refinements, plus providing improvements and enhancements that have simplified the operation. And, since the installation, we''ve had exceptional uptime at 99.8%we''re down maybe a total of thirty minutes a day for all 19 cells. Most of the downtime that we do experience is to replace worn vacuum cups on the end-effectors," he continues.
"We actually purchased twenty of the cells, thinking one would be in reserve in case of emergencies. Thanks to the reliability of the CMI systems, we haven''t had to use it once, and now we''re hoping to squeeze in two additional molding lines.
"It''s a case where the robotic cells did not dramatically increase production, or vastly improve quality, nor did we save big by eliminating staff. But the savings and payback, through more efficient use of personnel, have proven to be well worth the effort," he concludes.