Machine Vision Gives Meat a Safety Inspection
Brent D. Johnson
Following the epidemic of mad cow disease that struck the UK and the recent outbreaks of foot-and-mouth disease in Europe, the meatpacking industry is looking for improved methods of screening and tracking animals during processing.
A machine vision system that enables the inspection and identification of individual animals is boosting production in a meatpacking plant and making the meat safer for consumers.
Quality Meat Packers, a slaughterhouse in Toronto, was searching for a way to track hogs throughout the disassembly process so that they could record the health and fat content of each. Slaughterhouses are paid for the quality of their product, making it important from a monetary standpoint -- as well as from a sanitary one -- to individuate the carcasses.
ATR Systems Inc. was hired to work with the meatpacking company to develop a system that could withstand acid baths and extreme temperatures while reliably monitoring as many as 20 hogs per minute on a moving trolley.
Previously, the packing company had used point solutions that were not integrated. For example, hogs are usually tattooed for identification. On the assembly line, an autopsy is performed, during which the animals are rigorously inspected for disease and defects. They go through a series of baths, a burner removes hair, and they are eviscerated. During this process, the identification marks can disappear, making tracking unreliable or even impossible.
Marked with codes
Richard Neidart, ATR's president, happened to make a sales call to a company that was using abrasive water-jet cutters. He was impressed by the way the water jets could cut cleanly into metal, and he asked if they could cut into the metal hooks, called gambrels, that are used to suspend the hogs by their legs.
The company was able to cut a three-character alphanumeric code using 25 of the most reliable characters, yielding 15,625 unique IDs. The MVS 8110 machine vision platform from Cognex Corp. reads the ID codes. ATR says that this system is more reliable than bar coding and that it can withstand the environmental conditions better than radio frequency identification. The font is readable by humans, so the workers can identify the animals easily, which isn't possible with other systems.
The hogs go to six stations that monitor each stage of the process, collecting codes indicating disease and demerits, weight, fat and meat yield and other critical information. The 8110 can support four cameras firing simultaneously at 40 frames per second and connects to PCs, cameras and sensor probes via the Ethernet. This level of integration is important because it results in a real-time process where information from previous inspection stations can be viewed and can signal problems with animals coming down the line. The system can read at a 60° angle to allow for the swinging motion of the hog as it moves on the trolley. The 8110 has 32 MB of onboard image memory. This large image buffer allows high data rate transmission through the PCI bus without losing images -- an important consideration for high-speed production lines. In addition, the 8110's PatMax object location software, also from Cognex, works well under ambient light conditions. This is significant because the cameras are buried in a sealed environment to protect them from temperature, humidity and dirt.
With the new system in place, Quality Meat Packers predicts that it will increase its production from 5400 hogs per day to approximately 7700.
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