| "We discovered people don't sharpen their knives enough. Now they're being trained to do so more." Manager of Safety & Environ. (The Turkey Store Company) Chris Henderson |
At The Turkey Store Company in Barron, Wisconsin -- one of the nation's largest poultry processing plants -- the knife is king. When it comes to making precision cuts with both agility and speed, no high-been able to compete with this versatile hand tool, which each worker uses to make about 15,000 cuts per shift.
Because of the knife's importance to this industry, it has been the subject of numerous ergonomics studies. Some have focused on shape and design while others have examined related factors such as cutting table height and angles. However, until very recently, little had been known about how knife sharpness affects operator exertion. And considering the prevalence of carpal tunnel syndrome and other upper limb injuries among meat and poultry handlers, such a study was greatly needed, says Chris Henderson, manager of safety and environment at The Turkey Store.
With a proper knife-sharpening schedule, workers in poultry processing plants can reduce the risk of carpal tunnel syndrome.
|
Enter the UW-Madison Industrial Ergonomics Research Group, led by Professor Robert G. Radwin. In the summer of 1997, Richard Szabo, one of Radwin's graduate students, was assigned to an internship at The Turkey Store's northwest Wisconsin plant as part of his master's degree thesis project. While working with Henderson in the safety department, he discovered a knife sharpness tester that had been built by a former employee for a college class. "I thought that it would be interesting to redesign this tester to perform sharpness measurements on knives that have been used to process 10 pieces, 100 pieces and so on," he says. "That started me thinking about a number of experiments that I could run, given the ability to measure knife sharpness. Force-of-exertion testing was the most interesting in terms of ergonomics."
With guidance from Henderson and Radwin, Szabo began what is now a baseline study for future researchers. "We wanted to come up with a scientific method of determining how frequently the operators should sharpen their knives," explains Szabo, who over the course of four months observed and videotaped eight volunteer employees from the white meat cleaning department. Two jobs were examined: skin extraction (a low-force procedure) and removal of gristle and top fat (a higher-force task).
Why is it so important to determine an ideal knife-sharpening schedule? On the positive side, says Radwin, a freshly sharpened knife means the worker doesn't have to exert as much force. It also makes a cleaner slice, improving the quality of the product. On the flip side, he notes, knife sharpening is an activity that industrial engineers would call "a non-value-adding operation" since it takes the employee away from the job at hand. "Therefore it is important to sharpen the knife frequently enough, but not too frequently so as to reduce productivity."
As for employee health, "you need to keep the knives sharp to prevent injuries to hands and arms," says Radwin. "By reducing the amount of force required, you reduce fatigue and make the operators more productive. Poultry processing is hand-intensive work. Unless you are careful, it has all of the hazards that can lead to repetitive motion disorders that these companies want to avoid."
Szabo says that all of the experiments took some time just to set up since they had to be done while the employees were actually processing the turkey. "I would ask employees to switch knives for X number of pieces processed, re-sharpen for X number of swipes, or just ask them about their job and how knife sharpness influences it." He used the modified knife sharpness tester to determine the dulling effect each sequence had on the knives.
In the end, the study showed that to reduce the target surface area cut by the knife by 30 percent, it took 57 cutting cycles of the high-force jobs and 125 cutting cycles of the low-force tasks. While this dulling effect may seem dramatic on paper, it's probably not immediately noticeable to the people performing the work, says Henderson. "It's not uncommon for someone to cut 30 birds without sharpening a knife even though five is ideal." However, adds Szabo, "The cumulative damage that can occur because of increased force due to re-sharpening every 30 birds instead of five can be dramatic."
"In the past, we never had a way to quantify knife sharpness," says Henderson. "But with information from this study, a least 250 people who rotate each day through these jobs will benefit. Some changes are being implemented at our plant. We discovered that people don't sharpen their knives enough. Now they are being trained to do so more."
This is a win-win situation, with each side gaining valuable information, says Henderson of his company's project with the College of Engineering. "In this case, the study confirmed for us that fairly frequent knife sharpening is necessary."
--By Paul Bauman--
| For further information, please contact: |
Robert G. Radwin, 608/263-6596
bmechair@engr.wisc.edu
Copyright 1999 The Board of Regents of the University of Wisconsin System
Content by perspective@engr.wisc.edu
Markup by webmaster@engr.wisc.edu
Date last modified: Wednesday, 03-Mar-1999 12:00:00 CST
Date created: 03-Mar-1999
