Lamson & Sessions (Cleveland) produces thermoplastic conduit, enclosures, wiring outlet boxes and accessories for the electrical, construction, consumer, power and communications markets. It also makes large diameter pipe for the wastewater market. The company manufactures millions of injection-molded polyvinyl chloride (PVC) electrical wiring boxes and junction boxes each year.
To achieve approval from Underwriters Laboratories Inc. and the Canadian Standards Association, each box requires a seal to prevent water intrusion. For more than 20 years, cut foam gaskets with adhesive backing were manually applied to serve as a seal. But building boxes in 13 different sizes and increasing production challenged manual application.
For starters, the gaskets are too thick to correctly compress inside the boxes. This prevents sealing if box lids are slightly warped or “crowned.” Also manually installing gaskets is time-consuming and tedious, especially when creases or other irregularities slow down the process of removing the paper backing from the adhesive strip. And incorrectly installed or missing gaskets reduce quality and result in customer dissatisfaction. Finally, the cost of the foam gaskets had risen to nearly $500,000 per year, increasing operating expenses.
To eliminate the shortcomings of the manual operation, the company chose to convert the gasket sealing system from cut foam to a urethane form-in-place (FIP) gasket. Chemque (Indianapolis), a manufacturer of specialty, high-performance polymers, produces the material, which is less costly and offers a better seal than cut foam.
Lamson & Sessions also evaluated alternative methods to apply the material. It determined that robotic automation would provide the flexibility and precision required to meet production demands.
The company selected Radco Industries (Toledo, OH), a system integrator, to develop an automated system that would uniformly dispense the FIP gasket on the PVC electrical wiring boxes and junction boxes. The solution required consistency, precision and flexibility to accommodate the 13 different gasket sizes.
Radco suggested an automated dispensing system that incorporates an M-710iB/45 robot and an LR Mate 100iB robot from Fanuc Robotics (Rochester Hills, MI). The M-710iB/45 is paired with a two-component meter-mix dispensing system and dispenses the FIP gasket. This robot also has an extremely large work envelope without requiring significant floor space.
Once the FIP gasket is dispensed, the five-axis LR Mate 100iB robot, equipped with a vacuum end-of-arm tool, transfers the electrical boxes to an infrared curing oven. This automated process allows Lamson & Sessions to meet quality standards that could not be previously met.
Radco manufactured the curing oven with an automatic stainless steel link-belt conveyor. The 20-kilowatt infrared oven cures parts at 160 F and 100 percent humidity. Radiant panels provide the heat for curing.
Radco also specified a Camco three-station indexing dial system from Industrial Motion Control (Wheeling, IL) with a load station, gasket dispense station and automatic unload station.
An operator manually loads parts into the indexing dial system. A dedicated master plate locates each set of tooling. As parts are loaded, the system assigns and stores a unique signal for each of the 13 box sizes. Once tooling location is complete, the table indexes to begin the dispensing operation. A light curtain prevents operator intrusion until each job is complete.
The robot dispenses a bead of urethane foam around each part to form the FIP gasket. Dispensing rates depend on the mix of the material, the speed of the robot, and the size and features of each part. Dispense rates vary from 3 ips for the smallest part to 6 ips for the larger parts. The foam gaskets typically take 3 minutes to gel.
When all the gaskets are complete, the M-710iB/45 stops, and the table indexes to the unload position. The LR Mate 100iB transfers parts to the curing oven conveyor. The robot picks from one to six parts, 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.
The three stations—load, dispense and unload—function simultaneously. 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 streamlines the process.
Finished products leave the curing oven, sorted and prepared for shipment.
Payback for the system is estimated to be just 12 months. Radco engineers credit preplanning and conceptual design during the quoting stage to the system’s success and quick return on investment. Radco also performed extensive testing of the adhesive and the infrared and moisture curing mechanisms. The curing was a crucial part of the system engineering, because no one had previously taken freshly dispensed foamed urethane gaskets and dropped the parts into bulk storage bins.
According to George Foos, senior project engineer at Lamson & Sessions, the entire project was a success. “From initial construction to final testing, Radco accommodated our ‘on-the-fly’ changes. The changes proved to be painless and really enhanced the functionality and user friendliness of the system,” says Foos. “The system is well-conceived, innovative and durable. I’m sure this system will be running production 20 years from now,” adds Foos.
For more information on specialty polymers, call 317-291-9107 or visit www.chemque.com.
For more information on systems integration, call 800-283-0792 or visit www.radcoindustries.com.
For more information on indexing dial systems, call 847-459-5200 or visit www.camcoindex.com.
For more information on robotics, call 800-477-6268 or visit www.fanuc-robotics.com.