Golf car manufacturer uses sophisticated fastening tools to error-proof assembly.
It happens every year on every golf course in America. Some goof has a few too many and drives his golf car into a pond, a tree or another golf car. There may be a "loose nut" behind the wheel, but there won't be a loose fastener anywhere else-not if the engineers at Club Car Inc. in Augusta, GA, have anything to say about it.
The company goes to great lengths to ensure that every nut, bolt and screw is tightened correctly on every golf car, all-terrain vehicle (ATV) and utility vehicle that rolls off its assembly lines. "If a mistake is made on the assembly line, it's never the operator's fault. It's our fault for not making the system error-proof," asserts Club Car manufacturing engineer Gerald Skelton.
There are four assembly lines at the plant: one for the company's DS line of standard golf cars, one for ATVs, one for utility and transport vehicles, and one for the Precedent, Club Car's new state-of-the-art golf car. All totaled, the plant outputs nearly 800 vehicles per day.
Nowhere is the attention to detail greater than on the line for the Precedent. "It's the Cadillac of golf cars," boasts Skelton.
When designing the Precedent, Club Car engineers wanted a vehicle that excelled on the golf course, yet was also easy to manufacture. To that end, the Precedent has 60 percent fewer parts than the previous model. Fewer parts means faster assembly, fewer opportunities for error, and less inventory to track.
"One of our objectives was to get rid of as many parts...and operations as possible," says Skelton. "We wanted the car to be leaner and less labor-intensive, while at the same time, improving quality through the process."
That goal is also reflected in the car's body and chassis. The body is molded from Surlyn Reflections from DuPont. The material has a glossy, impact-resistant surface, obviating the need for painting or clear-coating. The chassis consists of an automotive ladder-style aluminum frame and two sections of fiber-reinforced composite that have been bonded together under high pressure to create a single structure. This design has twice the torsional rigidity of the old frame, and it protects the car's wiring, brake and pedal systems from corrosion and debris. "It gives the Precedent a sports car feel," says Skelton.
A subsidiary of the Ingersoll-Rand Inc., Club Car employs a mix of electric and pneumatic tools from another IR business unit, Ingersoll-Rand Tools. "We were using Ingersoll-Rand tools long before Ingersoll-Rand bought us," Skelton says.
"One thing that IR does really well is work together," says Skelton. "In fact, there are financial incentives for the divisions to cooperate with each other."
Often, this interdivision collaboration leads directly to product innovations. For example, Club Car worked closely with the power tools division to develop a sophisticated multispindle fastening system for attaching the wheels on golf cars. The system automatically determines whether a steel wheel or an aluminum wheel is being assembled, and adjusts the tightening strategy accordingly. "Now, [Productivity Solutions] has a new product it can sell to other manufacturers," says Skelton.
On most assembly lines at Club Car, computer-controlled DC electric tools are primarily used on critical assemblies, such as the steering wheel, wheel lugs, axles and transmission. "If we started having problems in the field with a joint fastened by an air tool, we would switch to an electric tool," says Skelton.
On the Precedent line, however, electric tools predominate. The accuracy, control and record-keeping ability of the tools make them essential for assembling a high-end product like the Precedent, says Skelton.
The heart of the Precedent assembly line is a tow-line conveyor from SI Production and Assembly Systems. Tow-line conveyors are configured in a loop and can be installed in new or existing facilities. The tow-line, a chain, moves continuously and rides in a track approximately 3 inches below the floor. The loop can range in length from several hundred feet to several thousand feet.
Heavy-duty wheeled carriers are attached to the chain in fixed increments. When a carrier arrives at an assembly station, it releases the chain and stops, temporarily, while the operators do their jobs. When the operators are finished, the carrier regrips the chain and moves to the next station.
Affixed to each carrier is a radio frequency identification (RFID) tag. When a new golf car frame is loaded onto the carrier, its serial number is recorded on the tag. As the carrier pulls into each station on the line, the tag transmits assembly instructions for that specific golf car, such as torque requirements and what parts to install. This is critical, because both gas- and electric-powered versions of the Precedent are built on the same line. When the carrier leaves, the tag receives data confirming that all the processes for that station have been accomplished successfully.
"A carrier is not allowed to leave a station until everything is right," says Skelton.
If threaded fasteners will be installed at a station, the RFID system tells the controller what bolts to install, how many there are, and how they should be tightened. This information is displayed on the controller's screen and on a flat-screen monitor above the work area. If four bolts need to be tightened, four circles are displayed on the screen. As each bolt is fastened to the correct torque and angle, a circle turns green. If a bolt is fastened incorrectly, the circle turns red, and the station won't release the car until the problem has been rectified.
At the same time, the controller records the torque and angle data for each bolt, as well as the date and time the bolts were fastened, and who and what fastened them. This information is tied to the specific golf car through its serial number. Such data can be useful if, for example, a particular joint begins failing in the field, Skelton explains. Club Car engineers can go back in the record to see if there was a problem with that joint during assembly.
Of course, Club Car engineers need not wait for problems to occur in the field before using the data gathered by the tools. By examining aggregate fastening data on a daily, weekly or monthly basis, they can monitor the stability of the assembly process. A drift in the data could indicate that some tools need maintenance, a batch of fasteners is substandard, or a tightening strategy needs to be tweaked.
Accessories are added to the golf car near the end of the line. Greens keepers can order golf cars with numerous options, including coolers, ball washers, sand bottles and rake holders. A flat-panel monitor at the station displays the options to be installed in the car. As assemblers retrieve each item from line-side storage areas, they scan a bar code identifying the product. This ensures that the right items are installed in the right cars, and it tells the inventory management system that a part has been used.
Here too, electric tools of various sizes dangle from ergonomic balancers. "Are these critical joints? No," Skelton admits. "In this case, we're using the tools for their ability to tell us that the right tool was used for the right job. If the operator picks up the wrong tool to install an accessory, he won't get a ‘good' signal from the tool."
The utility vehicle assembly line is another area of the plant where electric tools are heavily used. As with the plant's other assembly lines, the tools are mostly used for critical joints. However, the programmability of the tools is particularly useful on the utility line because of the large number of model variations produced on the line. One tool can tighten several different fasteners. And because the controller can automatically configure the tool for a particular application, there's less chance of the operator tightening a bolt to the wrong specification.
To limit the amount of welding used to assemble the Precedent, fasteners are used to attach various components to the chassis. However, Club Car engineers did not want to tap holes in the parts during fabrication, and then worry about the holes matching up later on the assembly line. Nor did they want to perform separate drilling operations on the assembly line.
TEKS self-drilling fasteners from ITW Shakeproof solved the problem. This screw drills its own hole in thin sheet metal, heavier gauge metals and nonmetallic materials. Once the hole is drilled, the fastener taps the hole in the same way as thread-forming or thread-cutting screws do in predrilled holes.
Although the screws save a fabrication step, they must be installed at just the right speed and pressure. "Operators cannot install these fasteners by hand," explains Skelton. "It takes so much pressure and so much time, it would wear them out. We tried it for a while when we were building prototypes, and it was murderous."
Weber Screwdriving Systems Inc. provided five semiautomatic screwdriving systems to handle the job. Some stations have four spindles fixtured together, so four fasteners are installed simultaneously. Other stations have a single spindle mounted to an X-Y-Z positioning system, which installs a fastener at multiple locations.
When a carrier arrives at a screwdriving station, the operator activates the machine. The spindles come down, install the fasteners, and retract. If the right number of fasteners are installed, and if all are installed at the correct torque, the controller allows the operator to release the carrier to the next station.
The application was challenging, because the speed and pressure requirements at each station were slightly different, says Skelton. Some fasteners were going through steel into aluminum. Others were driving through composite into aluminum, and others were drilling through composite into steel.
Lean manufacturing principles are evident throughout the plant. Club Car doesn't build anything to stock. Everything assembled at the plant has been ordered by a customer. Indeed, on the Precedent line, most finished cars go straight into trailers for delivery. Color-coded tape is applied to racks, containers and the floor itself to indicate where parts and equipment should be kept. Welding and fabricating operations have been organized into lean cells.
Some components, such as wheels, batteries, gas tanks, wire harnesses and plastic body panels, are outsourced and delivered to the plant in the correct sequence, on a just-in-time basis. Other components, such as frames and axles, are assembled at the plant on lines of their own. Either way, a kanban system tells suppliers when to replenish parts.
By embracing lean manufacturing, Club Car was able to remove a lot of warehousing space. That space became the assembly line for the Precedent. "We keep only what we need for the day," says Skelton. "Parts come in and head straight for the line."
Most of the plant's 1,100 workers have been there 5 to 10 years. Because the staffing level on each line depends on how many orders the plant receives for each model, cross-training is essential. On the Precedent line, for example, operators at one station know how to do the tasks at the two stations in front and behind their own. "We have a lot of people who know the whole process," says Skelton.
In a unique program, Club Car often sends assemblers and engineers to visit customers. "We can preach quality, but it means a lot more when they hear it from the customer," says Mike Snyder, production administrator at the plant. "They won't feel pride in their product just because I tell them to."
Ergonomics is a critical concern at the plant. On the Precedent line, for example, the conveyor carriers were designed so that operators can accomplish their tasks at a comfortable height. Lift-assist devices are used to handle any part that weighs more than 25 pounds-or less if the task is particularly repetitive. "Safety is our No. 1 concern," insists Skelton. "Quality is No. 2. Productivity is No. 3."