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23-Ind-A2 Analysis and Design of Work · December 2018

Question 4 of 7: Drill-Press Time Study, Uses of Time Standards, and the Stopwatch Study Procedure

Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)

Notes on this paper

National Exams — December 2018 — 17-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 charting, principles of motion economy, multiple-machine assignment, stopwatch time study, performance rating and allowances, predetermined time systems (MTM/MOST), work sampling, and job evaluation / wage-incentive systems.

Question 4: Drill-Press Time Study, Uses of Time Standards, and the Stopwatch Study Procedure (20 marks)

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.

Check — sub-part labelsThe marking-scheme table prints sub-parts (ii) and (iii) both labelled “(ii)”, and the question text labels them both “(iii)”; they are taken here in the question text's own (i)/(ii)/(iii) order.

(i) Normal Time and Standard Time for the Drill-Press Operation

Given.

Drill-press work elements
Work elementObserved time (min./pc.)Rating %
1. Load drill press0.25110
2. Drill hole (automatic power feed)0.15100
3. Check tolerance (go/no-go gauge)0.08115
4. Unload drill press0.20120

Allowances: 5% personal + 5% unavoidable delays + 5% fatigue.

Find. The normal time and standard time for the operation, in min./pc.

Approach. Normalize each element’s observed time by its own performance rating, sum the elements to obtain the cycle normal time, then apply the total allowance once to the summed normal time (the Niebel convention used consistently across this subject).

  1. Normal time per element. $NT_i=OT_i\times\text{Rating}_i$: $NT_1=0.25(1.10)=0.275$; $NT_2=0.15(1.00)=0.150$; $NT_3=0.08(1.15)=0.092$; $NT_4=0.20(1.20)=0.240$ min/pc.
  2. Cycle normal time. $NT=\sum NT_i=0.275+0.150+0.092+0.240=\boxed{0.757\text{ min/pc}}$.
  3. Total allowance. $A=5\%+5\%+5\%=15\%=0.15$.
  4. Standard time. $ST=NT(1+A)=0.757(1.15)=\boxed{0.8706\text{ min/pc}}$.
Check — assumption: element 3 (checking the last piece) is performed during the automatic machine cycle of element 2, so it overlaps element 2 in clock time. If the check is instead treated as fully absorbed within the 0.15-min machine cycle (it needs only 0.092 normal min, less than 0.150), the cycle normal time is $0.275+0.150+0.240=0.665$ min/pc and $ST=0.665(1.15)=0.7648$ min/pc. State whichever interpretation is used.
Question 4(i) — final results
QuantityValue
Normal time, $NT$0.757 min/pc
Total allowance, $A$15%
Standard time, $ST$0.8706 min/pc

(ii) Uses of Time Standards

A validated time standard is a foundational input used across essentially every operating function of the plant: (1) production planning and scheduling — determining machine and labour capacity, sequencing jobs, and setting realistic delivery-date commitments; (2) manpower and equipment planning — how many operators and machines a given volume requires, including the multiple-machine assignment decision of Question 3(i); (3) cost estimating and product costing — converting standard minutes into a labour-cost-per-unit for quoting and pricing; (4) wage-incentive rate setting and performance evaluation — comparing actual output to standard to calculate incentive pay (Question 7(iii)) and to evaluate operator performance fairly; (5) budgeting and standard-cost variance analysis — comparing actual labour cost to the standard-based budget to flag and investigate deviations; (6) evaluating alternative methods or equipment — a proposed method or machine can only be compared to the current one on a common, standard-time basis; and (7) line balancing — assigning work content evenly across stations on a line requires the standard time of every element to be known.

(iii) Steps in a Stopwatch Time Study

The classical stopwatch time-study procedure proceeds as an ordered sequence, each step depending on the one before it: (1) obtain and record background information about the operation, the operator, the machine, and the working conditions, and confirm the method is standardized and stable — a method that is not yet fixed should never be timed, since the resulting standard would describe a method that no longer exists once it changes; (2) divide the operation into elements at natural, easily identified break points (a distinct sound, a hand movement, a machine action) so each element can be timed and rated consistently from cycle to cycle; (3) determine the number of cycles to time, typically from a short preliminary study used to estimate variability, then applying a sample-size formula built around the desired accuracy and confidence level (the same statistical logic used for work-sampling accuracy in Question 6(iii)); (4) time and record each element (continuous or snap-back method) while simultaneously performance-rating the operator in real time against the analyst’s internal concept of a 100% normal pace; (5) compute the normal time for each element as observed time × rating, and sum to the cycle normal time (as done in part (i)); (6) apply the appropriate allowance for personal time, unavoidable delay and fatigue (part (i), Question 3(ii)) to obtain the standard time; and (7) review and finalize the standard — checking it against similar existing standards for consistency, documenting the method it describes, and issuing it for use, subject to the standards-maintenance discipline of re-timing whenever the method later changes.