We are planning to create a 2 or 3 station workspace cell for a sewing operation. The stations will be within a cell. Looking at a "U" shaped configuration (for 3 stations); a side by side (90 degree configuration for 2 stations) or a back to back configuration (for 2 stations). My questions: how large an AREA do we use for each configuration workspace knowing that one operator will walk from station to station within the cell? How do we determine this space requirement? Does anyone have any sources or ideas. We are set on workstation heights, lighting, reaches, etc but we want to provide enough space for the worker to feel comfortable and not cramped but also save floor space. Thanks.Eric B. Michael, OT, M.S. IH
In my experience if the cell layout is too tight then the operator will twist at the torso and lean to reach rather than take a step to square up to a workstation. I have known some people who use the "five foot" rule where the dimensions of the inside of the cell are no less than five feet. The purpose of this is to force the operator to take a step and turn rather than leaning and twisting. Personally, I believe a lot depends on your cycle time and work content at each station. I have had U-cells that were as little as three feet of space that worked well, but the cycle was a minute long and there was some stationary standing at each station during assembly. I have had other stations with shorter cycles (15-20 sec) where operators did simple loads and unloads and complained of getting dizzy from walking in circles. These stations fared better at about 5 feet distance in the walk pattern. For 90 degree workstations with short cycles, operators will often want the machines close together and try to pull in a chair. We have been successful in some cases in designing workstations that allow the operator to sit and swivel at these type of stations (7-8 sec cycle, small parts, close reaches, knee room cleared out under machines). Human nature is to sacrifice the biomechanical to reduce energy expenditure. In other words, I will twist, bend or reach before I will move my body because of the energy required to do so. Another thing to consider is the effect on knees and hips from side stepping and pivoting. We had many complaints regarding this issue when we went from lines to cells, especially for the shorter cycle cells with tighter layouts. We experimented with different floor materials so operators could more easily slide their feet and pivot. Rubber or gritty mats resutled in more knee strain. For dry areas smooth mats like those used in a barber shop seemed to work better than textured mats like ergomat that our operators often flipped over to the smooth side.
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