dept. of biomedical, industrial, & human factors engineering 1 work area design definition: the...
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Dept. of Biomedical, Industrial, & Human Factors Engineering 1
Work Area DesignDefinition: the design of the work area to accommodate workers while maximizing human effectivenessGeneral Requirements
Functional requirementsVisibility
Displays, controlsPresent data at right angle to line of sight to minimize visual parallax
Hearing requirementsBuzzersAlarms
Consider clearancesAccessEgressComfort and support for grasping and operating equipment/controls (e.g., tennis racket)
Reach and manipulationNormal (convenient sweep of arm) vs. maximum area (extending arm from shoulder)
Dept. of Biomedical, Industrial, & Human Factors Engineering 2
Work Area Design
General PrinciplesPopulation stereotypes
Operator expectancies – ensure they are not violated
Psychosocial factorsCleanly and orderliness of work setting
Environmental factorsHeatHumidityNoise
StandardizationSavings in training time
Design for the total systemDesign for maintainabilityAllow various work postures
Sitting, standing
Dept. of Biomedical, Industrial, & Human Factors Engineering 3
Workstation Design
Key is adjustabilityAdjustability is a key element of design – adjusting to the user, task allow you to obtain a good fit between the user and task
Key: usability will depend on the operator’s perception of resulting benefits
Adjustability approachesWorkplace adjustments
Cutouts can be used to minimize reach requirements and protrusion of chairs into aisles
vs.
Dept. of Biomedical, Industrial, & Human Factors Engineering 4
Workstation Design
Adjustability approachesWork surface height and inclination
Height
Angle of inclination
Dept. of Biomedical, Industrial, & Human Factors Engineering 5
Workstation DesignAdjustability approaches
Worker positionSeat heightChairs with rollers for horizonital adjustmentPlatforms – help change position in relation to work surfaceFootrests – resolve unsupported legs – must be adjustable to seat height
Work piece and tool adjustmentAdjust work piece via clamps, vises, jigsGravity bins to bring parts to within reach & reduce search timeLift tables
Work postureSeating – issues – visibility, clearances, less fatigue due to improved blood circulation, reduced static loadsStanding – experience greater physiological load, standing still for long periods leads to blood and body fluid accumulation in legs
Swelling, varicose veins
Dept. of Biomedical, Industrial, & Human Factors Engineering 6
Workstation Design
Based on: anthropometric data, behavioral patterns of people, and specific work requirementsStandards often arbitrary, unpractical
Developed by committees involving many partiesCan be politically motivated
Working heightsMust fit stature and type of workToo high: shoulder lifted, pain in the neck and shouldersToo low:back hunched, backacheStanding handwork
50-100 mm below elbowDelicate: 50-100 mm above elbow height, support elbowsManual work with tools, containers, and materials: 100-150 mm below elbowIf effortful work: 150-400 mm below elbow
Dept. of Biomedical, Industrial, & Human Factors Engineering 7
Workstation DesignWorking heights
How to accommodate different statures?Foot supportsRaise tableFully adjustable benchIf can’t adjust, accommodate tallest and provide platform
Work heights for sedentary workElbow height is general rule of thumb
Fine precision work: above elbowForceful or large motion: below elbow height
Conflict with providing adequate knee roomMeasured from floor to top of seated kneeConsiderations:
%tile to accommodateAmount of clearanceTable thicknessDistance from seat surface to table underside
Dept. of Biomedical, Industrial, & Human Factors Engineering 8
Workstation Design
Work heights for sedentary work (con’t)Office work
< 50% have upright posture
Common musculoskeletal complaints (% of 246 office workers surveyed)
57% back
29% knee and feet (short people)
24% neck and shoulders (desk heigh)
General recommendationsDesk height : 740-780 mm
Given seat adjustability and a foot rest
Seat below desk: 270-300 mm– Regardless of stature
– Natural trunk posture
Dept. of Biomedical, Industrial, & Human Factors Engineering 9
Workstation Design
Work heights for sedentary work (con’t)General recommendations (con’t)
Compensate for high work levelLift shoulders (trapezius)Adduct arm (deltoids)
Easier to accommodate tallest (desk height)Leg room
General rule of thumb: cross legs without difficulty– No drawers above legs– No thick edge to desk
Table thickness: 30 mmLeg space: 680 mm wide by 690 mm highDepth for stretching
– Knee: 600 mm– Foot: 800 mm
Keyboard tables– Working height is middle row of keys– Work height: elbow height– Adjustable from 600-700 mm
Dept. of Biomedical, Industrial, & Human Factors Engineering 10
Workstation Design
Sit/Stand workstationsRecommended physiologically and orthopaedicallyAlternates stressed and relaxed musclesVaries supplies of nutrients to the discSpecial considerations
Horizontal knee roomHeight of work area from seat and floorSeat adjustablility
Tilted tablesResearch comparing flat, 12 degree and 24 degree
Tilt had more erect postureTilt less electrical activityTilt subjectively preferred
Tilt for readingFlat for writingTradeoff of visual & postural advantages vs. ease of use
Dept. of Biomedical, Industrial, & Human Factors Engineering 11
Workstation designNeck and head posture
Hard to define since 7 jointsEstimate line along neck relative to verticle, horizontal, trunkEar-eye line (EEL): line from earhole to eyelid
Used to describe postureUsed to reference line of sight
Approximately 15 degree (to vertical) okChaffin: as angle increase, quicker to fatigueShould not be greater than 30 degrees for any time
Line of sightRepresented by line from pupil to visual targetIf head upright
Distant targets: along horizonital with eyeCloser target: more declinedReading: 45 degrees below EEL
General rule: preferred line of sight 10-15 degrees below horizontalDefines regular viewing cone of 30 degrees around preferred line of sight (15 degrees above, 15 degrees belowEEL should be less than or equal to 15 degrees relative to horizonResults apply to VDT work also
Dept. of Biomedical, Industrial, & Human Factors Engineering 12
Workstation designRoom to Grasp and Reach (see overheads)
Grasp/Reach envelope: sweep radius of arms with hand in grasping or reaching posture
Location of shoulder joint5th %ile measurements
Vertical Grasp – verticle plane in which you can take hold of things and move them around
Based on shoulder height of 5th % ile (closed hand arm length)Can occasionally extend by stretching shoulder, feet, and legs
Horizontal Grasp-horizontal plane in which you can take a hold of things and move over table topReach Height: vertical height reached with extended hand
Shelves, storage (consider shelf depth)