In a move to upgrade stamping operations, DaimlerChrysler Corp. has installed a system for handling sheet-metal blanks that controls pneumatics over an Ethernet/IP network.
It is reportedly the first such system in North America.
The pneumatics are incorporated into destackers built for the automaker by High Production Technology Co. (HPT), Napoleon, Ohio. Destackers clean and shuttle blanks into machines that stamp out body panels and interior structural parts. Pneumatics work together with electromechanical actuators to move and position parts. For instance, air knives help separate individual blanks from a stack, then gantry-mounted suction cups lift them onto a conveyor. The conveyor carries the blanks through a washer, where they are squeegeed top and bottom, then on to centering stations that align them with stamping dies. Finally, the blanks are fed to the first stamping station. This all takes close synchronization to ensure efficiency.
Bosch Rexroth 261 Series manifolds control the pneumatics. The ISO 5599-2-type manifolds use Ethernet/IP as a fieldbus to reduce costs, simplify the network, and increase productivity, says Joe Mitory, stamping project manager at DaimlerChrysler.
Ethernet/IP uses the existing top-level control and information protocols of DeviceNet/Control-Net and TCP/IP for network and transport layers. Ethernet/IP offers the means to carry DeviceNet information over highspeed Ethernet.
The allure of Ethernet stems from three factors: performance, compatibility, and cost, says Jay Finn, applications engineer at HPT. While traditional fieldbuses have progressed from kilobit to megabit speeds, Ethernet is still an order of magnitude faster — 10 or 100 Mbytes/sec on the factory floor, explains Finn. That's increasingly important as stamping equipment gets more sophisticated to handle a wider range of blank sizes, materials, weights, and shapes, as well as meet demands for shorter cycle times. Equally important, switched Ethernet does away with collisions that made the technology nondeterministic.
Ethernet also lets Daimler-Chrysler integrate factory-level operations with its higher-level office network, offering advantages in processing real-time information and making off-site monitoring feasible. And thanks to widespread availability, Ethernet devices cost significantly less than their fieldbus counterparts. Thus, Ethernet offers an extremely attractive price-to-performance ratio, says Finn.
According to Bosch Rexroth officials, Ethernet/IP interfaces are now common on PLCs, servocontrols, and the like. But they have been slow to appear in pneumatic devices. One reason is that PLCs are inherently " intelligent." Traditional pneumatics differ in that control is centralized and little, if any, intelligence is distributed outward to individual components.
But intelligent pneumatics can simplify designs while improving capabilities and reliability. One example on the HPT machine is its built-in diagnostics. Ethernet's high speed and data capacity let the 261 Series manifold's Drive & Diagnostic Link (DDL) continuously monitor supply-voltage tolerances on each valve's electronics and solenoids. It also watches for solenoid faults and electrical short circuits.
DDL often recognizes problems well in advance of failures, permitting predictive maintenance. For instance, it can spot low voltages, indicators of potential power-supply problems, and detect a rise in current draw that warns of impending valve-coil breakdown. DDL also means faster testing and commissioning, with fewer glitches, says DaimlerChrysler's Mitory. And, if problems occur, they are easier to trace and remedy.
According to Mitory, "Diagnosticcapabilities are always important and, as systems become more complex, we need higher levels of self-diagnostics." Simplicity begets reliability, and improved diagnostics eliminate surprises.
The pneumatics work in tandem with servocontrolled Bosch Rexroth IndraDyn L linear and MKD rotary motors, combining for more than 50 axes of control on the HPT units. Destackers currently run 22 different parts, mostly oddshaped blanks that measure up to 96 66 in. They can run two unattached blanks simultaneously and handle up to 32 stampings/min.