Workstation Design A. H. Mehrparvar, MD Occupational Medicine department Yazd University of Medical Sciences

Tools/Methods of Workstation Design Anthropometry Design Guidelines Design Tools There are several methods available for employees to use to setup workstations. Here are three areas that your workers can use for this purpose.

آنتروپومتری (Anthropometry) Anthropos: انسان Metrin: اندازه گیری یا سنجش اندازه گیری ابعاد بدن انسان

هدف ارگونومی طراحی ایستگاه یا پست کاری متناسب با ویژگیهای فیزیکی و روانی کارگر

عدم رعایت اصول ارگونومیک در طراحی ایستگاه کاری ایجاد وضعیتهای بدنی نامناسب هنگام کار ایجاد بیماری

آنتروپومتری تفاوت بین دو جنس: مردها درشتتر از زنها تفاوت در نژادهای مختلف: نژاد آمریکایی در برابر آسیای جنوب شرق تفاوت در سنین مختلف

People Are Different Age Differences Height Differences

صدکها بیان ابعاد آنتروپومتریک بر اساس صدکها صدک پنجاهم، صدک پنجم و صدک نودوپنجم صدک پنجم: 5٪ جمعیت کوچکتر از آن (= میانگین – 65/1 انحراف معیار) صدک پنجاهم = 50٪ جمعیت کوچکتر و 50٪ بزرگتر از آن (= میانگین) صدک نود و پنجم= 5٪ جمعیت بزرگتر از آن (= میانگین + 65/1 انحراف معیار)

بین صدک پنجم زنها و صدک نودوپنجم مردها طراحی ارگونومیک بر اساس صدکها طراحی تمامی ابزارها، تجهیزات و وسایل برای گستره ای ازجمعیت بین صدک پنجم زنها و صدک نودوپنجم مردها

شعار آنتروپومتری وسایل و تجهیزات در حد دسترسی کوچکترین فرد قرار داشته باشند و با بزرگترین فرد تطبیق داشته باشند.

Acceptable/Unacceptable Work Positions The concept that we are trying to reinforce here is that work needs to be in front of the employee. We need to design tasks in this manner. Reaching behind the body or working with the upper arm raised should be avoided.

Effect of Workstation Design on Posture In this slide you can see the effects of work station design on posture. If this were a task where a person was placing chicken parts in totes or removing products from a conveyor you could see the impact of orientation and height. Totes placed too high can cause poor hand and wrist postures. If it is too high it can also cause poor arm postures as well.

Reach/Work Envelopes These pictures show reaches for employees. The first picture shows the overhead shot of a worker at a work station. It defines acceptable reaches and work zones for people. The next shot shows the side view for a seated person. It shows the acceptable reaches for a person who has to grasp an object. You will notice that both pictures express the reaches in arcs.

Optimal Work Zone Here is another diagram that shows you the ideal work zone on a table or work surface. This is where most work should be done while in a seated posture.

Work Surface Heights These two diagrams show the ranges for work station heights for both seated and standing work. As you will notice the heights vary based on the type of task being performed.

Work Surface Heights Here is another example of work surface height guidelines. You can find these type of guidelines in several textbooks or other references. Activity 2 How tall should you make an offline rework station? It involves some fairly detailed cuts to salvage as much breast meat as possible. If workers are working out of totes, where would you locate them so that they are easy to reach.

Issues in Workstation Design Avoid static loads and fixed work postures Reduce cumulative trauma disorders risks Work height at ~50 mm below elbow Give employee an adjustable chair Use feet as well as hands Use gravity, don't oppose it Use two-handed motions rather than one-handed

Pivot motions about the elbow Use the preferred hand Keep arm motions in the normal work area Let the small woman reach; let the large man fit

Goals of Workplace Design and Layout Maximize performance and minimize hazards: Minimize postural stress and fatigue (e.g. due to static loading) --- risk factor for work-related injury Provide reach capability Anthropometry Minimize motion times and error rates Work measurement

Often a major task of ergonomists Strong relationship between productivity of a workers and their comfort Primary objective: accommodate the worker An uncomfortable workplace results in increased energy demands, fatigue, decreased worker performance, and occupational injuries

General considerations Clearances, reaches, and manipulations (conserve momentum, use gravity when you can) Visual and auditory demands Environmental (noise, lighting, temperature, vibration) and organizational factors (such as contact with workers, supervisory control) Posture changes

Workstation Types Sit Needed items can be reached, assessed, and handled within the seated workplace Items handled are approximately 6” above and 16” in front of the worker No large forces, no weights greater than 10lbs Fine assembly, data entry, etc.

Stand No proper knee clearance Object weight >10lbs Frequent high, low, or extended reaches Frequent movement between stations Requires downward forces Optimal height of the hands Elbow-light assembly, writing, packing Waist-downward and sideward forces

Sit/Stand Repetitive operations Multiple tasks are performed but are of sufficient duration that benefit from sitting Design in postural flexibility

Benefits of sitting over standing Delays the onset of fatigue (weight is taken off the legs, lower energy requirements, lower cardio-respiratory demands, avoid unnatural body postures) More stability in the task Allows for the use of foot controls Pitfalls of prolonged sitting Negative effects on the curvature of the spine Disruption of body functions (blood flow, breathing, etc.) Weakened abdominal muscles

Adjusting the workplace Why is it important? People vary in size and capability, accommodate individual comfort and usability, provides for possibility in changes in posture How do you do it? Adjust the workstation Layout, Location (ht), Orientation Adjust the person Chair, Footrests, Armrests Adjust the work piece Jigs, clamps Adjust the tools Design the size, weight, material, use tool balancers

Use preferred hand for reach and grasp motions Dominant hand is 10% faster for reaching and more accurate Dominant hand/arm is about 5-10% stronger About 10% are left hand dominant Preferred hand should be used for dangerous or critical work Allow for change-off to non-dominant hand for non-critical work, thus proving rest and recovery