Lamson & Sessions (Cleveland) produces thermoplastic conduit, enclosures, wiring outlet boxes and accessories for the electrical, construction, consumer, power and communications markets. Among its specific products, the company manufactures millions of injection-molded PVC electrical wiring boxes and junction boxes per year.
To obtain approval from Underwriters Laboratories and the Canadian Standards Association, each box requires a gasket seal to prevent water intrusion. For more than 20 years, the company used die-cut foam gaskets with adhesive backing to perform the sealing operation. But with 13 different box sizes and an increasing production schedule, the manual application of the gaskets became increasingly unwieldy and expensive. Variation in the size of the gaskets could also result in poor seals.
To eliminate these problems, Lamson & Sessions decided to change over to a form-in-place (FIP) gasket technique, using robotics to ensure consistency and precision. The company selected the system integration company Radco Industries (Toledo, OH) to design the line. Radco incorporated a pair of FANUC (Rochester Hills, MI) robots into the system: a FANUC LR Mate 100iB and a FANUC M-710iB/45. The latter is paired with a two-component meter-mix dispensing system, with triple servomotor portioning and mixing. It is also equipped with HandingTool application-specific software to guide it while dispensing the FIP gasket.
The LR Mate 100iB robot is equipped with a quick-change, vacuum-based, end-of-arm tool, to transfer the electrical boxes to an infrared curing oven. This small, five-axis robot is often used in laboratory applications. In this case, it was programmed to handle the parts as gently as possible to avoid disturbing the integrity of the dispensed gasket.
Other system components include a 20-kilowat, infrared oven with an automatic stainless steel link belt conveyor and a three-station indexing dial from Camco (Wheeling, IL).
When gasketing, an operator manually loads parts into fixtures on the indexing dial. The fixtures are made of ultra high molecular weight polyethylene, a tough material with a chemical resistant surface. As parts are loaded, the system assigns and stores a unique signal for each of the 13 box sizes. A light curtain prevents operator injury.
The robot dispenses a bead of urethane foam around each part to form the FIP gasket. Bead rates depend on the mix of the material, the speed of the robot and the size and features of each part, such as corners and a "ramped blend" that occurs at the start and finish of each gasket. Dispense rates vary from 3 ips for the smallest parts to 6 ips for the larger parts. The foam gaskets typically take 3 minutes to gel.
Upon completion of all of the gaskets, the M-710iB/45 stops, and the table indexes to the unload position where the LR Mate 100iB transfers the parts to the curing oven conveyor. The robot picks from one to six parts at a time depending on weight and dispense cycle time. The curing oven conveyor has a variable speed drive to maximize throughput regardless of the amount of parts being unloaded.
All three stations function simultaneously-load-dispense-unload. Unload time is always less than dispense time, which makes throughput dependant on dispense speed. Average processing time is 4 seconds per part.
The curing oven reaches the correct temperature and humidity level before dispensing begins. A temperature indicator, which is tied into the control system, signals the robot to begin dispensing when the oven is ready. Automatic temperature gauging helps streamline the entire process. Finished products exit the curing oven into storage bins, where they are sorted and prepared for shipment.
Since the system was installed, Lamson & Sessions estimates it paid for itself in about 12 months. The company also experienced an increase in product quality, and now has the flexibility to easily process new product models.
"From initial construction to final testing, Radco Industries accommodated our on-the-fly changes," says George Foos, senior project engineer at Lamson & Sessions. "The changes proved to be painless and really enhanced the functionality and user friendliness of the system. The system is well conceived and innovative. It's highly durable, as in ‘built like a tank.' I'm sure this system will be running production 20 years from now."
For more information on systems integration, call 800-283-0792 or visit www.radcoindustries.com.
For more information on indexing dials, call 800-645-5207 or visit www.camcoindex.com.
For more information on robots call 800-477-6268 or visit www.fanucrobotics.com.