During the summer, I am consulting a company in lean manufacturing aspects. Currently I am working on creating “flow” in one of the assembly lines of the company. Yesterday, while finalizing the details of workstations in the assembly line, I was asked this question. Here are my two cents on this issue.
One of the most debated aspects of lean approach to assembly cell design is the requirement they be chair-free—that the assemblers stand rather than sit. In lean manufacturing the concept of standing workstation is popular. Given the choice between standing and sitting most people would prefer to sit.
There are numerous applications where standing is the preferred working posture, as opposed to sitting.
- Standing is preferred when the work area is too large. The maximum reach envelope when standing is significantly larger than the corresponding reach envelope when sitting. Have you ever seen a sitting workstation for checkout cashiers in stores like Wal-Mart? Do you ever cook on a sitting chair? Large work areas frequently are found in assembly environments, including auto assembly, packaging, welding, sheet metal, and paint lines. This also applies when the person works in more than one workspace to perform his/her job duties. In lean cells you want people to move frequently so that you can achieve “self-balancing” of the cell.
- Standing is preferred when the work surface obstruction does not allow the person to comfortably position his/her legs under the surface. This is often the case when working on a conveyor, using a workstation with a drawer located underneath the work surface or a wide front beam, or using specialized equipment.
- Ergonomics research shows that standing is recommended to maximize grip forces, and improve static or dynamic lifts. In general, more strength can be exerted while standing.
There is also an extensive lists of jobs that are most appropriately done standing, including construction workers, highway flaggers, medical personnel, painters, electricians, plumbers, loggers, firefighters, plant inspectors, and maintenance personnel.
Applications where seated workstation is preferred.
- Work that is highly dependent of fine motor functions—manual electronic assembly like soldering, writing, and sewing etc should be done at a seated workplace equipped with armrests.
- Work that require precise foot control movements.
Remember assembly and manufacturing line working requirements are different from the work requirements of office desks. The short term comfort of sitting does not translate to long-term well-being but instead leads to weight and back problems. In most of the manufacturing and assembly line scenario it is often un-ergonomic to perform your job while seated. From a strictly ergonomic standpoint sitting all the time is in fact no better than standing all the time.
So the rule of thumb…Use seated workstation only when fine motor skills are essential.
2 comments:
With these points in mind, it really depends on the nature of the work or task, gauging which position will give more focus, efficiency, and other requirements. More examples of tasks that are best executed while sitting are computer and manufacturing software operations, writing and drafting, etc. More intensive tasks require standing, on the other hand.
Waste reduction directly correlates with reduced energy consumption and carbon generation. Indeed, Lean work station that IT and energy costs can account for up to 60% of an organization's capital expenditures and 75% of operational expenditures. In this way, identification and streamlining of IT value streams supports the measurement and improvement of carbon footprints and other green metrics. For instance, implementation of Lean IT initiatives is likely to save energy through adoption of virtualization technology and data center consolidation.
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