Located on the shores of the St. Lawrence River in Québec, Aluminerie de Bécancour is an aluminum smelter that produces 400,000 metric tons of aluminum annually in the form of rolling ingots, T-ingots (pure and alloyed), and billets. The ISO: 2000 and 14001 certified Aluminerie de Bécancour smelter, which is part of Alcoa Canada Primary Metals (ACPM), has been up and running since 1986.
Running most of the time, that is. Once or twice a day, production was interrupted by pieces of metal falling onto the line during a crushing process. To detect this “felted debris,” Aluminerie de Bécancour recently installed a BOA integrated vision system from Teledyne DALSA (Waterloo, Canada). The BOA has significantly reduced production downtime and damage caused to equipment on the line.
A Crushing ProblemSmelting is an electrolytic reduction process that transforms the white powdery material-called “alumina”-that is produced from bauxite into aluminum. Alumina is dissolved in a cryolite bath inside large, carbon-lined cells called pots. When a powerful electric current is passed through the bath, aluminum metal separates from the chemical solution and is siphoned off.
After 21 days, the anode through which the current enters the pot reaches the end of its life. A crusher removes the used carbon attached to the anode frame. As crushing occurs, steel parts from the anode’s frame can fall on the conveyor and eventually damage equipment further down the process line. This can lead to costly equipment repair and replacement as well as production downtime.
Engineers at Aluminerie de Bécancour considered various ways to address this problem. Photoelectric sensors were considered but ultimately rejected because of the quantity of sensors that would be needed to perform the inspection. Due to product variations, machine vision was determined to be the simplest solution to the problem. Working with Groupe Rotalec, a distributor of high technology industrial automation products, product identification systems, and mill products for over 30 years, Aluminerie de Bécancour engineers selected a Teledyne DALSA BOA 640x480 monochrome camera.
Getting-and Communicating-the Big PictureThe BOA is a fully integrated machine vision system in an ultra compact, designed for industry enclosure. Contained entirely within a tiny (44 x 44 x 44 millimeter) industrial IP67 housing, the BOA is packaged complete with application software which contains a comprehensive library of tools and functions that can be readily applied to a wide range of manufacturing tasks. The software is embedded within the device and is set up through an intuitive web browser interface.
At Aluminerie de Bécancour, every product is inspected by comparing three images. One BOA detects the anode’s frame geometry before the anode gets crushed. Using the same configuration, another camera detects the anode’s frame geometry after crushing. A “fail” occurs if one of the three images indicates that the geometry changed during crushing.
According to engineers at Group Rotalec, one major advantage of using the BOAs is the ease with which they and other operators can program and re-program the application.
“Because the process is pretty slow at only two parts per minute, we were triggering every 100 milliseconds, waiting for the perfect positions to apply the analysis tools,” says Alexandre Dargis, Ing. Jr. vision application engineer at Groupe Rotalec. “We overwrite all of our tool’s results using the BOA software’s custom scripting functionality. This scripting functionality allows us to write the communication I/Os whenever the picture is the one we’re looking for.”
Since much of the equipment on the line is original to the plant, there was no way to communicate through Ethernet. As a result, Groupe Rotalec used digital outputs from the expansion I/O breakout board (eight inputs and 10 outputs) to communicate with the PLC.
Rush DeliveryAnother advantage of using the BOA in this application was Teledyne DALSA’s ability to deliver product quickly.
“This was a rush job for us: we had two weeks to complete the entire project, from sizing to installation, due to nonstandard parts coming into our system,” says Dargis. “All of our requested products were in stock at Teledyne DALSA’s plant, including camera, lens, cable, expended I/O breakout board, and IP67 accessories.”
Dargis attributes the success of the BOA in this application primarily to Teledyne DALSA’s rapid response in delivering product, the scripting portion of the BOA, and the availability of the appropriate BOA hardware.
“The BOA is a simple and effective camera that meets Aluminerie de Bécancour’s inspection requirements,” Dargis says.
Since the BOA solution was installed at Aluminerie de Bécancour, the company has experienced no downtime as a result of falling debris, and engineers are currently reviewing additional areas that would benefit from BOA vision system installations.