- SPECIAL REPORTS
Progressive Machine and Design (PMD, Victor, NY) was called in to create a new manufacturing system integrating error-proofing in all steps, from manual kitting operations to pressing and assembly operations to final testing. The system also checks each finished differential for a wide range of performance characteristics, including torque, gear-train backlash, and operating speeds and directions. All testing is performed under real-life loading applications using a dynamometer.
Shortly after this system went on-line, Hilliard contracted PMD to build another system capable of assembling three different differential models on a single line. Again, in-line process verification systems represent an integral part of the system, starting with a manual assembly and vision inspect station.
At each assembly station, all process information is recorded on an RFID tag from Escort Memory Systems (Scotts Valley, CA), which is attached to the pallet carrying the assembly. At the final assembly station, the system creates a unique serial number for each part, which is then printed on a label that is attached to the case. Both the part number and all process data are transferred to an upper-level control system, which is further updated during final inspection and can be referenced in case of problems in the field.
Historically, the manual assembly of each differential's roller cage, which includes installing a number of different H-clips and roller bearings, had been a persistent source of manufacturing error. To help solve this problem, PMD built an automated insertion machine, which loads the rollers into each assembly. Although an operator still manually loads all the H-clips-the task proved too costly to automate-a vision inspection system employing a DVT 510M camera from Cognex Corp. (Natick, MA) checks to see that all components are in place before a Lexan sleeve is loaded around the roller cage. This loading of the transfer sleeve is a signal to the operators that the roller cage is a passed unit.
All pressing operations on the line are monitored using high-impedance load cells from Kistler Instrument Corp. (Amherst, NY) connected to in-line charge amplifiers, with 0- to 10-Volt DC tied to analog input cards in the PLC. Limits for each press force operation are set via machine interface to within 0.01 pound.
At each station, assemblies are checked for parts presence, assuring that only passed subassemblies and all components are loaded before being released. At one point in the line an M16iB six-axis robot from Fanuc Robotics America Inc. (Rochester Hills, MI) is used to manipulate each differential through a series of press and part loading operations that were ergonomically stressful for operators. As each part is fed, pressed or driven, and torqued, a battery of sensors ensures that the process is proceeding correctly. The robot employs an RJ3iB controller with DeviceNet communications.
For more on automated assembly systems, call 585-924-5250, visit www.pmdautomation.com or eInquiry 3.
For more on machine vision inspection, call 508-650-3000, visit www.cognex.com or eInquiry 4.
For more on robotics, call 800-47-ROBOT, visit www.fanucrobotics.com or e-Inquiry 5.
For more on process monitoring, call 888-547-8537, visit www.kistler.com or eInquiry 6.
For more on RFID systems, call 800-626-3993, visit www.ems-rfid.com or eInquiry 7.