The influence of knife dullness on poultry processing operator exertions and the effectiveness of periodic knife steeling.

A novel procedure is described to establish knife steeling schedules for poultry and meat- processing operations based on increased force due to knife dullness from repetitive use to minimize operator exertions and physical stress associated with work-related musculoskeletal disorders. Knife dullness was quantified using a novel apparatus described in this article that measures the area cut by a knife into a carrageenan gel target for a controlled dynamic load at the knife handle. Two meat-cleaning jobs in a poultry-processing plant were studied. One job required significantly more force and a greater number of cuts than the other. Eight experienced operators participated in the study. Four freshly ground and honed knives were randomly used by each operator for 4, 45, 75, or 125 cutting cycles, measured for dullness and reconditioned by the operator using a steel sharpening rod. An empirical model for knife dulling and reconditioning was developed, and the corresponding increase in force was predicted for various cutting and reconditioning frequencies. The model showed that it took 57 and 125 cutting cycles for the high- and low-force jobs, respectively, to achieve a similar reduction in target surface area of 30%. This reduction in target surface area corresponded to a similar percentage increase in force needed for the same cut in carrageenan gel as compared to a freshly honed knife as measured using strain gages. This method may be used in meat processing plants for determining effective reconditioning schedules that reduce operator exertions with minimum effect on quality and productivity.