Manual Tasks -- Cut-Off Machine

IR, age 31, was found dead with his neck lacerated. A gas powered "circular saw" was found running next to a wood deck that had been partially dismantled. There was blood splattered on the deck, ground, and wall. The Chief Medical Examiner reported finding abrasions over the left elbow, left hand, left wrist, and right elbow in addition to the neck injuries. Upon inspection of the cut-off machine, it was observed to have a toothed circular blade. The blade guard was pushed back and wedged so as to expose more of the blade than the design specified. The manufacturer had provided a warning in the accompanying instructional manual that a toothed blade should not be used with this product.

HF Issue: I was retained by defense to determine whether the wedged blade guard contributed to the accident.

HF Investigation: Information obtained included, but was not limited to: obtaining an exemplar cut-off machine; the autopsy report with attached photographs; results of the police investigation including photographs of the scene; product operation manual; and all depositions and statements.

HF Analysis: A model of the cut-off machine was created in Knowledge Revolution's Working Model 2D. The model of the circular blade was made to revolve at a simulated speed that corresponded to what was specified in the manual.

A model of IR was generated in the same computer application. A systematic evaluation of different postures was conducted. The primary consideration was "best fit" with the pattern of injury reported in the autopsy report. Once IR's probable posture was identified, guarding was examined.

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