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. The system has significantly reduced production downtime and damage caused to equipment on the line.

A Crushing Problem

Smelting 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. This harsh environment included falling steel parts as well as the byproducts of the smelting process in the air, and made the inspection process especially difficult.
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 BOA 640x480 monochrome camera.

Getting-and Communicating-the Big Picture

The BOA is a fully integrated machine vision system in an ultra compact, designed for industry enclosure. Contained entirely within in a tiny (44 x 44 x 44 mm) industrial IP67 housing, it 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 system 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 2 parts per minute, we were triggering every 100ms, waiting for the perfect positions to apply the analysis tools," said 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 (8 inputs & 10 outputs) to communicate with the PLC.

BOA Equipped to Handle Special Environments

The smart camera was engineered specifically to handle special environments. It is equipped with a lens cover that is IP67 compliant which means it can operate in harsh, wash-down environments without needing additional protective enclosures. It's protective lens cover prevents tampering or accidental movement of the lens.
The smart camera also contains no moving parts and will continue to operate in 50°C ambient temperatures. The camera can be directly attached to a robotic arm and moved continuously in any orientation, and its tiny package allows it to be easily installed in most industrial environments. Finally, the cameras include embedded processing which allows them to operate autonomously in noisy environments, or other conditions without having to have an operator involved.

Rush Delivery

Another advantage of using the BOA in this application was the quick delivery.
"This was a rush job for us: we had two weeks to complete the entire project, from sizing to installation, due to non-standard parts coming into our system, "said 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 camera in this application primarily to the rapid response in delivering product, the scripting portion of the camera, and the availability of the appropriate hardware.
"The BOA is a simple and effective camera that meets Aluminerie de Bécancour's inspection requirements," Dargis said.
Since the vision system was installed at Aluminerie de Bécancour in November of 2011, the company has experienced no downtime as a result of falling debris, and engineers are currently reviewing additional areas that would benefit from the vision system installations.