23-Ind-A2 Analysis and Design of Work · December 2013
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — December 2013 — 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. The source prints Question 3's second and third sub-parts both labelled “(iii)” (a typesetting slip); they are answered here in the marking-scheme order (i)/(ii)/(iii), 8/6/6 marks.
Reference texts: Niebel & Freivalds, Niebel’s Methods, Standards, and Work Design (13th ed.) — operations analysis, workplace/tool design and motion economy, stopwatch time study, performance rating and allowances, predetermined time systems (MTM/MOST), work sampling, 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.
Operations (or “operation”) analysis is the third step of the classical methods-engineering procedure — select the job, record the present method on a process or operation chart, then critically examine every recorded detail to find the most economical way of doing the necessary work before a new method is developed, installed and maintained. It is a systematic questioning discipline applied to each element of a job (what is done, why, where, when, by whom, and how) rather than an intuitive redesign, so that no productive possibility is overlooked and no unnecessary element survives simply because “it has always been done that way.”
Niebel groups the primary lines of questioning into a small set of recurring approaches, applied to every operation on the process chart: (1) purpose of the operation — can it be eliminated, combined with another, or simplified outright, since the cheapest and safest improvement is removing work entirely; (2) design of the part and its tolerances/specifications — is the accuracy demanded actually required by function, or does it needlessly inflate cost; (3) tolerances and specifications reviewed against functional need; (4) material used, including substitution for a cheaper or more workable stock; (5) manufacturing sequence and process, including whether a different process would combine steps; (6) setup and tooling, especially jigs, fixtures and combination tooling; (7) materials handling, minimizing distance, handling frequency and manual lifting; (8) plant layout, arranging workstations to shorten travel and eliminate backtracking; and (9) working conditions, since a poorly lit, noisy or fatiguing station degrades both quality and output. Every one of these approaches is applied to the SAME recorded operation, so operations analysis is best understood as a checklist walked methodically against the process chart rather than a single technique.
A human-machine (activity/multiple-activity) chart is a time-scaled chart that records, on parallel vertical bars against a common time axis, exactly what the operator is doing and what each machine under that operator’s charge is doing at every instant of a work cycle. Each bar is divided into blocks marking periods of productive work (operator servicing a machine, or a machine running automatically) and periods of idle/waiting time, so the analyst can see at a glance where the operator waits on a machine, where a machine waits on the operator, and where both are simultaneously busy.
The summary form condenses the same chart into one row per resource, each split into a “working” segment and an “idle” segment sized to scale, with the cycle time, total working time, total idle time and percentage utilization tabulated beneath — e.g. Operator: 4 min busy / 4 min idle (50% utilized); Machine 1 and Machine 2: 8 min busy / 0 min idle (100% utilized) each, over the 8-minute cycle shown above. The summary form is what actually drives a staffing decision, because it reduces the chart to the handful of numbers (idle minutes per resource per cycle) that determine whether adding a machine, adding an operator, or reassigning idle time to another task pays for itself.
Human-machine charts are used to: (1) determine how many machines can be economically assigned to one operator (the multiple-machine assignment problem solved quantitatively in Question 3(i)); (2) identify and quantify idle time in either the operator or the machine(s) so it can be filled with other useful work or eliminated by re-sequencing; (3) balance the workload between an operator and automatic equipment, or between two or more operators sharing a line; (4) justify capital decisions — whether purchasing an additional machine, a faster machine, or additional labour gives the better return; and (5) support incentive and cost-standard setting, since the chart makes the true cycle time (not just the busy time) visible.
The principles of motion economy that bear on equipment and tool design fall into three related groups: eliminate the need for the hand to do what a fixture or powered device can do, keep whatever the hand must still do as short and as symmetric as possible, and make the equipment fit the operator’s reach and grasp rather than the reverse.
Combine and pre-position tools. Where two or more tools are used in sequence, combine them into one (a combination screwdriver/wrench, a multi-station power tool) so the hand never has to release one tool to search for another; where combination is impossible, pre-position each tool in a fixed, easily reached location (often on a spring-loaded or gravity-return holder) so a “grasp” motion never turns into a “search” motion.
Replace manual holding with jigs, fixtures and clamps. Wherever a part must be held steady while it is worked on, a jig or fixture frees both of the operator’s hands for productive motions instead of one hand doing nothing but holding; foot-operated clamps, levers and switches similarly transfer holding or actuating work from the hands to the feet, which are otherwise idle during most bench and machine work.
Use gravity and mechanical advantage. Gravity-feed bins and chutes deliver parts to the point of use without a reach-and-carry motion, and gravity-drop delivery removes finished parts from the workstation the same way; levers, cranks and wheels should be sized and positioned to give the operator mechanical advantage rather than requiring raw muscular force, since force imposes a heavier fatigue allowance and slower, less consistent motion times.
Fit the equipment to the operator. Controls (levers, handwheels, pedals) should be located within the normal or, at worst, the maximum working area described by comfortable arm/leg reach so that repetitive motions stay short; handle shapes should distribute grip pressure over the largest practical surface area rather than concentrating it on a narrow edge; and where a choice exists between a manual and a mechanically or electrically powered tool for a repetitive high-force task, the powered tool both speeds the cycle and reduces the fatigue allowance the standard time must otherwise carry.
