Mechanical Engineering Experts Evaluate Fatal Injury Caused by Runaway Machinery

    Mechanical Engineering Expert WitnessThis case involves a female employee of a large contract manufacturing firm who suffered fatal injuries while on the job. On the date of the incident in question, the woman was reviewing the programming of several CNC lathes and milling machines in her capacity as a managing engineer. The woman was in the process of inspecting an active lathe when the work-piece began to rotate at an unusually high rate. The woman was looking at the work-piece through the safety window when the work-piece disintegrated, shooting chunks of metal at a very high speed. One of the chunks of metal was able to pierce the safety screen, at which point it struck the woman in the head, killing her instantly. It was alleged that the CNC machine malfunctioned, due to the fact that the work-piece was able to spin at such a high rate of speed, and the fact that the safety screen failed to prevent the woman’s fatal injuries.

    Question(s) For Expert Witness

    • 1. Do you have extensive experience with computer numerical control machines?
    • 2. What is your experience working with similar machines?
    • 3. Have you worked on cases involving CNC machinery malfunctioning?

    Expert Witness Response E-008230

    I have worked with N/C equipment, including lathes and many types of manufacturing machinery as a forensic engineer with multiple different firms. In conjunction with other experts on N/C, I have had cause to examine the actual N/C program code for similar machines to determine cause for accidents, or just to improve production techniques. I have done several N/C failures in recent years, mostly due to lightning strikes and power related issues. There are a number of areas where failure could have occurred: The first may have been in the N/C programming itself, setting the wrong speed for an operation. Second, there are mechanical/electrical failures that did not keep the spindle speed at the specified RPM, such as feedback circuits. Third, mechanical failures could have caused the chuck to eject the piece. Finally, since most N/C operations can be manually overridden, there is always the possibility of operator error. A number of people including factory employees, N/C service and maintenance personnel, and others would have to be interviewed to obtain the full story.

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