Applications Programmable Automation Controllers Polaroid Focuses on Quality with CTC Polaroid uses CTC for motion control and system integration Application story index With the advent of digital photography, Polaroid had to rapidly adapt to changing markets. Five years ago, its Norwood, MA facility began a shift from manufacturing cameras to manufacturing lenses. In addition, Polaroid wanted to increase the quality and quantity of the lenses it made by automating more of its operations. Polaroid's Ted Parker, Principal Engineer, Bill McManus, Senior Electrical Engineer, and Bob Fischer, Senior Mechanical Engineer, ultimately designed an integrated motion control system that outputs 8000 variable focal point lens assemblies per day from a single station, and is a showcase installation for visitors from around the world. A CTC automation controller is the binding force that makes it all run smoothly. In the lens-making process, a "shot," a molded part that has eight or more lenses attached, is formed from acrylic, polycarbonate, or other polymer in a Shinwa injection molding machine. The finished shot is transferred to the lens de-gating and assembly area by a Wittmann robot. Once the shot is seated on an indexing table, the Dukane ultrasonic welder de-gates (separates by vibration) each lens from the shot. The lens drops into a nest on the indexing table, and, while all lenses are being de-gated, the robot moves out of the way and goes to get another shot. A second robot, a Sony 3CH robot comes in, picks up each lens from its nest, positions and snaps it securely into a housing (which is dispensed from a vibratory bowl track), and transfers the housing-lens assembly to a designated spot in a 40-well tray. When all wells in the tray are full, the Sony robot transfers the completed tray to a "done" stack, and a new, empty tray rises into position for the new batch of lens assemblies. To automate this process successfully, many different pieces of hardware had to communicate closely with each other to achieve the elegant synchronization that Polaroid needed (see inset below). Hardware tied together by CTC: Shinwa injection molding machine Two robots (Wittmann and Sony) Servo motor for the shot indexing table Servo motor for the Dukane welder positioning Two stepper motors for the elevators on which the trays rested V-bowl track for lens housing Vibratory bowl (V-Bowl) for lens housing orientation Flip-over mechanism for the housing/lens assembly All of this hardware had to be synchronized not only under normal conditions, but also under exceptional circumstances - what Bill euphemistically referred to as the "what-if's." What Polaroid was looking for was not just synchronization, but smart synchronization that could adapt to almost any situation that came up. If one machine stopped, all of the machines had to stop. If one machine slowed down to address an exceptional situation, the other machines had to adjust accordingly. "We have a lot of flags on this system," said Bill. To tie it all together, Polaroid chose CTC's rack style controller and Quickstep. "It's our favorite controller here," said Bill, who's been using CTC products for the last seven or eight years. One of the things that Ted and Bill liked best about the CTC was Quickstep. "We were looking for a higher level language. No ladder logic," said Bill. "Quickstep was the user-friendliest. It had multi-tasking rather than scanning [through the entire ladder logic sequence]." Unlike ladder logic, Quickstep's performance was maintained as Bob and Bill added more stations on. "We're using about half of Quickstep's multitasking capabilities now," said Bill, for a system that is fully operational. "We're monitoring 64 inputs and controlling 56 outputs." Another feature that Bill liked was Quickstep's modularity. "It lets you program and debug each station independently, then integrate." In this application, event timing was critical. Bill had to get ten different hardware elements to talk to each other and work together smoothly. With Quickstep, they got the application running with just 120 hours of programming, and then were able to tweak the response times quickly as they monitored the system under various conditions. For example, the CTC stops operations if the tray supply is empty or the track for dispensing lens housings is blocked. Another feature allows the operator to discard any number of the eight lenses, if there was a defect in the molding process. The CTC controller simply monitors the inputs from the cavity reject buttons that are located on the control panel. Alarms are relayed to a CTC display on the control panel, with diagnostic information on how to clear the alarm. A personal computer linked to the system has detailed system information for more sophisticated troubleshooting. According to Bill, "The CTC does 95% of the communication" for all of the different types of hardware. Before Polaroid automated the de-gating and lens assembly processes, each process needed one operator. Now a single operator can run not only the de-gator and lens assembly stations, but also another mold machine as well. CTC is proud to be part of Polaroid's success.

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