23-Ind-A2 Analysis and Design of Work · May 2016
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — May 2016 — 98-Ind-A2 Analysis and Design of Work. Three-hour, closed-book exam (approved Casio/Sharp calculator only); any five of the seven questions constitute a complete paper and only the first five answered in the answer book are marked — all seven are solved below for completeness.
Reference texts: Niebel & Freivalds, Niebel’s Methods, Standards, and Work Design (13th ed.) — operations analysis and process/flow charting, motion economy, multiple-machine assignment, stopwatch time study, performance rating and allowances, predetermined time systems (MTM/MOST), work sampling, and wage-incentive and job-evaluation systems.
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
The classical Gilbreth/Barnes principles governing how the body itself should move fall into one connected group: (1) both hands should begin and complete their motions at the same time, so neither hand waits idle on the other; (2) both hands should not be idle at the same time except during a genuine rest pause; (3) motions of the arms should be made in opposite and symmetrical directions, simultaneously, since this is more natural to the body’s musculature and easier to coordinate than mismatched motions; (4) hand motions should be confined to the lowest classification with which the work can be performed satisfactorily — the principle expanded quantitatively in part (ii); (5) momentum should be employed to assist the worker wherever it helps carry a motion, and minimized (or absorbed by a jig, not the operator’s muscles) wherever it must be overcome; (6) smooth, continuous, curved motions are preferable to straight-line motions with sudden sharp changes in direction, because a direction reversal requires the moving mass to stop and re-accelerate; (7) ballistic (free-swinging) movements are faster, easier and more accurate than restricted or “controlled” movements, since a controlled movement fights antagonistic muscles throughout its path; (8) work should be arranged to permit an easy and natural rhythm, since a rhythmic cycle is both faster and less fatiguing than one with irregular pauses; and (9) eye fixations should be as few, and as close together, as possible, since each new eye fixation interrupts the motion pattern and adds time. Applied together, these principles are the reason a well-designed two-handed assembly cycle looks and feels different from an ad hoc one long before any stopwatch is involved.
Motions are classified by which body member acts as the pivot, and the classification runs from the smallest, fastest, least fatiguing pivot to the largest and most fatiguing:
| Class | Body members involved | Pivot point |
|---|---|---|
| 1 | Fingers only | Knuckle |
| 2 | Fingers and wrist | Wrist |
| 3 | Fingers, wrist and forearm | Elbow |
| 4 | Fingers, wrist, forearm and upper arm | Shoulder |
| 5 | Fingers, wrist, forearm, upper arm and torso | Trunk (twisting at the hips/waist) |
Each successively higher class recruits additional, heavier body segments to perform the same reach or move, and every added segment costs additional time to accelerate and decelerate and additional muscular effort to sustain — a Class 5 motion that twists the torso is measurably slower and more fatiguing than a Class 1 motion covering the same functional purpose. The principle is therefore to design the workplace — tool and material locations, control positions — so that every motion can be performed at the lowest classification that still accomplishes the work satisfactorily: place frequently used items within finger/wrist (Class 1–2) reach rather than forcing a shoulder- or trunk-level reach for something used every cycle. This is the direct link between motion classification and workplace layout: the “normal working area” commonly used in workstation design corresponds to a Class 3 sweep of the forearm pivoting at the elbow with the upper arm hanging naturally, while the larger “maximum working area” corresponds to a Class 4 sweep from the shoulder — a layout that keeps frequently handled material inside the normal area, rather than the maximum area or beyond it, is a direct, physical application of the lowest-classification principle.
Where micromotion study analyzes individual therbligs and motion classifications one at a time, the macroscopic (whole-workplace) approaches improve the station as a system: (1) workplace layout — arranging tools, materials and controls within the normal working area on both sides of the operator, in the sequence they are used, rather than optimizing one motion in isolation; (2) simultaneous, symmetrical two-handed work — designing the job so both hands work productively (and, where possible, in mirror-image motion) rather than one hand working while the other holds or waits; (3) mechanization of heavy, repetitive or hazardous elements — power feeds, conveyors, foot-operated clamps and fixtures that remove load from the hands entirely rather than merely shortening a manual motion; (4) workstation height, seating and posture design matched to the specific task and to anthropometric data, so the whole body — not just the hands — works efficiently; (5) environmental control — illumination, temperature, ventilation and noise, since these affect the whole workstation’s output rather than any single motion; and (6) work-rest scheduling and job rotation, spreading fatigue and monotony across the shift rather than trying to eliminate them motion by motion. These approaches are “macroscopic” precisely because they redesign the station as a whole rather than re-classifying one reach or move at a time, and they are normally applied first, with fine motion-economy analysis reserved for the specific elements that remain a bottleneck afterward.
