UNIT 2: WORK STUDY, METHOD STUDY, WORK MEASUREMENT & ERGONOMICS

I. FOUNDATIONS OF WORK STUDY

Work Study is a systematic examination of activities to make the best use of human and material resources for accomplishing specified tasks. It is the generic title for Method Study (improving the method) and Work Measurement (establishing standard time).

Objectives:

• Improve processes and methods.

• Establish standard times for tasks.

• Reduce unnecessary costs and waste.

• Improve working conditions and safety.

• Increase productivity and quality.

Scope: Applicable in manufacturing, services, offices, hospitals, etc., for any repetitive or non-repetitive activity.

Relationship: Method Study and Work Measurement are complementary. An improved method (Method Study) must be measured (Work Measurement) to set standards and plan production. Standardisation of the new method is a prerequisite for accurate time study.

[!TIP] Exam Focus: Questions often ask for the "Relevance in Modern Industry." Link it to lean manufacturing, waste reduction (Muda), and continuous improvement (Kaizen).

II. METHOD STUDY (MOTION STUDY)

A. Recording Techniques & Process Charts

Recording techniques are classified as:

1. Graphical: Charts, diagrams, flow diagrams.

2. Symbolic: Process charts using standard symbols (ASME/ISO).

3. Tabular: Tables for data collection.

4. Photographic: Still, video, or cine films.

Standard Process Chart Symbols (ASME/ISO):

Key Charts:

• Operation Process Chart (Outline/Flow Process Chart): Provides an overall view of the entire process sequence. Uses only Operation (O) and Inspection (I) symbols.

• Flow Process Chart (Material/Product Chart): Records the flow of a specific material/product through all stages (operations, inspections, moves, delays, storage). Uses all 5 basic symbols.

• Two-Hand Process Chart (Simultaneous Motion Chart): Records the activities of both hands (left/right) of an operator against a time scale. Used for detailed analysis of manual tasks.

• Multiple Activity Chart (Activity Chart): Records the activities of multiple operators and/or machines against a common time scale. Helps in balancing work and identifying idle time.

• SIMO Chart (Simultaneous Motion Chart for Multiple Operators): Combines multiple two-hand charts on a common time base for several operators/machines. Used for complex multi-operator/machine systems.

• Travel Chart (From-To Chart): A tabular record showing the number of trips between various departments/places. Used for planning material handling and plant layout.

• String Diagram: A scale drawing showing the path and distance travelled by a worker/material during a task. Used to analyse and minimise travel distance.

[!TIP] Exam Focus: Be prepared to sketch and distinguish between Operation vs. Flow Process Chart and Two-Hand vs. Activity/SIMO Chart. Know the utility (purpose) of each chart.

B. Motion Study & Principles of Motion Economy

Motion Study: Systematic recording and critical examination of the motions made by a worker or machine to achieve the most effective method.

Principles of Motion Economy (classified by Gilbreth):

1. Use of Body:

   • Use the lowest possible classification of muscle (fingers < wrist < arm < shoulder < body).

   • Use symmetrical motions for both hands, simultaneously and in opposite directions.

   • Use continuous, curved, and ballistic (momentum-assisted) motions instead of straight-line motions.

   • Minimise the number of motions.

2. Arrangement of Workplace:

   • Fix definite and constant places for all tools and materials.

   • Locate tools and materials in the order of use.

   • Use gravity feed bins and drop deliveries.

   • Provide adequate illumination and seating.

3. Design of Tools & Equipment:

   • Use jigs and fixtures to eliminate the need for holding.

   • Combine tools where possible.

   • Pre-position tools and materials.

   • Design tools to use the lowest possible muscle classification.

C. Micro-Motion Study & Advanced Techniques

Micro-Motion Study: Detailed analysis of an operation into its basic elements (Therbligs) using high-speed photography (cine film) at 1000+ frames per minute.

• Memo Motion Study: Uses a normal-speed movie camera (16-64 frames/sec) for longer-duration tasks. Useful for studying body movements and workflow over a complete cycle without the cost/complexity of micro-motion.

• Therbligs: 18 basic elemental motions (e.g., Search, Reach, Grasp, Move, Assemble, Use, Disassemble, Inspect, Position, Rest, etc.). Each has a symbol and a basic time value (in TMU - Time Measurement Units, 1 TMU = 0.00001 min). Used in PMTS like MTM.

D. Critical Analysis & Improvement

Critical Examination: A questioning technique applied to the recorded data using a checklist. Key questions for each element:

• Purpose? Why is it necessary?

• Place? Can it be done elsewhere?

• Sequence? Can the order be changed?

• Method? Can it be done better?

• Person? Is the right person doing it?

Development & Installation: Based on the critical examination, develop a new, improved method. Standardisation of this new method (tools, sequence, workplace layout) is essential before proceeding to Work Measurement to ensure reliable time data.

III. WORK MEASUREMENT

A. Objectives and Purpose

• To establish standard times for tasks.

• To compare worker efficiency (performance).

• To plan and schedule production (manpower & machine loading).

• To set realistic delivery dates and costs.

• To provide a basis for wage incentive schemes.

B. Techniques of Work Measurement

1. Time Study (Stopwatch Time Study): Direct observation and timing of a task using a stopwatch, with rating for performance.

2. Work Sampling (Activity Sampling): Statistical technique to estimate the proportion of time spent on various activities by taking random observations.

3. Predetermined Motion Time Systems (PMTS): Uses pre-determined time values for basic motions (Therbligs). E.g., MTM (Methods-Time Measurement), MODAPTS.

4. Standard Data: Using pre-established time values for similar elemental tasks from past studies.

5. Synthesis: Building up standard time from elemental data using standard data or PMTS values.

C. Time Study Procedure

1. Select the job, operator, and normal working conditions.

2. Record detailed data: element times, ratings, delays.

3. Evaluate performance using Performance Rating.

   • Objective Rating: Comparing to a defined standard pace.

   • Synthetic Rating: Using standard data for elements.

   • Pace Rating: Rating based on the operator's overall pace (e.g., 100% = normal pace).

4. Calculate Normal Time: Sum of (Observed Time × Rating Factor) for all productive elements.

5. Add Allowances to Normal Time to get Standard Time.

D. Calculations & Problem Solving

Key Relationships:

• Observed Time (OT): Raw time recorded for an element.

• Normal Time (NT): $$\displaystyle NT = \sum (\text{Observed Time} \times \text{Rating Factor}) $$

• Standard Time (ST): $$\displaystyle \boxed{ST = NT \times (1 + \text{Total Allowance Fraction})} $$

Allowances: Added to Normal Time to cover legitimate non-productive time.

• Personal Allowance: 3-5% (rest, personal needs).

• Fatigue Allowance: 0-10% (depending on work intensity, environment).

• Delay Allowance: For unavoidable delays (machine breakdown, material shortage).

• Policy Allowance: For company policy (e.g., union agreements).

Work Sampling Calculations:

• Proportion of Time (P): $$\displaystyle P = \frac{\text{Number of "working" observations}}{\text{Total observations}} $$

• Number of Observations (n) for desired accuracy: $$\displaystyle n = \frac{Z^2 \times P(1-P)}{E^2} $$

  • Z = Standard normal deviate (e.g., 1.96 for 95% confidence)

  • E = Desired precision (e.g., 0.05 for ±5%)

• Standard Time from Work Sampling:

  1. Find Total Available Time for the observed period.

  2. Effective Production Time = Total Available Time × P.

  3. Normal Time = (Effective Production Time / Number of Units Produced) × Rating Factor.

  4. Standard Time = Normal Time × (1 + Allowance).

[!TIP] Exam Focus: Problems on Standard Time calculation from Work Sampling data (like Jun 2025 Q) and Time Study data are very frequent. Always remember: Rating is applied to Observed Time to get Normal Time, and Allowance is added to Normal Time to get Standard Time.

E. Standard Data

• Definition: Pre-determined times for tasks or elements based on extensive historical studies.

• Advantages: Saves time & cost in new studies; ensures consistency; useful for planning and estimating.

• Applications: Estimating new jobs, setting piece rates, planning production, synthetic time study.

• Development: Requires a comprehensive database built from detailed time studies of various elemental tasks, classified by complexity.

IV. ERGONOMICS (HUMAN FACTORS ENGINEERING)

Definition: Scientific discipline concerned with understanding interactions among humans and other elements of a system, and the profession that applies theory, principles, data, and methods to design to optimise human well-being and overall system performance.

Objectives: Fit the job/task to the human (not vice-versa), improve safety, comfort, efficiency, and reduce fatigue/errors.

B. Man-Machine Systems

• Definition: A system where a human operator interacts with a machine (or process) to achieve a goal.

• Types:

  1. Semiautomatic: Human initiates, machine completes cycle (e.g., drilling).

  2. Automatic: Human monitors, machine operates (e.g., CNC machine).

  3. Serving: Human as a link between machines (e.g., assembly line).

  4. Decision-making: Human makes key decisions based on machine output (e.g., process control room).

• Analysis: Focuses on the Man-Machine Interface (controls & displays).

• Relative Capabilities:

  • Humans: Excellent pattern recognition, adaptability, judgement, learning, handling unexpected situations. Poor at sustained vigilance, rapid precise calculation, repetitive tasks.

  • Machines: Excellent at speed, power, precision, repetitive tasks, sustained vigilance. Poor at adaptability, judgement, handling unanticipated events.

C. Anthropometry

• Definition: Measurement of human body dimensions.

• Importance: Essential for designing workplaces, equipment, tools, and protective gear that fit the user population, preventing discomfort, injury, and inefficiency.

• Types:

  • Static: Body measurements in a static posture (e.g., standing height, arm reach).

  • Dynamic: Measurements during motion or in a working posture (e.g., reach envelope while seated).

• Factors Affecting Data: Sex, Age, Ethnicity, Nutrition, Socio-economic status, Posture.

• Application: Use percentiles (e.g., design for 5th percentile female to 95th percentile male reach). Design for adjustability where possible.

D. Sensory Information Processing & Display Design

Human Sensory Inputs: Visual (most common), Auditory, Tactual (touch), Olfactory, Gustatory. Selection depends on task demands and environment.

Coding: Assigning meaning to a display (e.g., colour, shape, sound, location). Good coding is intuitive and reduces memory load.

Visual Displays:

• Qualitative: Indicate condition (on/off, red/green). Use shape coding (circle, triangle) and colour coding (red=danger, green=normal).

• Quantitative: Indicate amount (speed, pressure, temperature). Use analog (dial, pointer) for trend detection; digital for precise reading.

• Design Guidelines for Effectiveness:

  • Location within normal field of view.

  • Appropriate size and brightness.

  • Minimise glare and reflection.

  • Use consistent coding.

  • Group related displays.

  • Provide clear scales and markers.

Tactual Displays:

• Characteristics: Used when vision is occupied or unavailable (e.g., vibration in steering wheel, Braille). Must be distinguishable by shape, texture, or location. Require active exploration.

• Design: Must be unambiguous, provide clear feedback, and be operable without visual attention.

E. Work Environment & Task Design

Work Environment Design:

• Lighting: Adequate illuminance, uniform distribution, minimal glare, appropriate colour rendering.

• Noise: Control at source, use hearing protection, design for auditory signals to be detectable.

• Temperature & Humidity: Maintain within comfort zone (approx. 20-25°C, 40-60% RH).

• Vibration: Isolate vibrating equipment, provide anti-vibration gloves/mats.

Task and Work Organisation Design:

• Job Rotation: Reduce monotony, balance workload, cross-train workers.

• Work-Rest Schedules: Based on task intensity (e.g., shorter work cycles for heavy work).

• Task Variety: Combine different types of tasks (mental/physical) to reduce fatigue.

• Human Factors in Work Study: Ensure method study recommendations consider human capabilities/limitations (e.g., avoid excessive reaching, twisting, or visual strain).

V. INTEGRATION & APPLICATIONS

Integration of 'Operation and Operator' (Balancing Man-Machine System)

The goal is to balance the work content so that neither the operator nor the machine is idle for significant periods. Achieved through:

• Method study to eliminate unnecessary motions.

• Multiple activity/SIMO charts to analyse and balance.

• Appropriate machine allocation and layout.

• Training operators for multi-machine operation.

Wage Incentive Plans (Output-Based)

• Objectives: Increase productivity, reward efficiency, improve morale, reduce labour cost per unit.

• Gantt's Task and Bonus Plan:

  • A standard time is set.

  • If worker completes job within standard time, they earn a high bonus (e.g., 125% of normal rate) on the entire job.

  • If they take longer, they only earn the normal hourly rate.

  • Effect: Strong incentive to beat the standard.

• Merrick's Multiple Piece Rate Plan:

  • Two piece rates: a higher rate for output above a standard level, and a lower rate for output below standard.

  • Unlike Halsey, worker always gets a piece rate, but it increases after the standard is met.

• Other Plans (for reference):

  • Halsey 50-50 Plan: Bonus = 50% of (Time Saved × Hourly Rate).

  • Rowan Plan: Bonus = (Time Saved / Standard Time) × Hourly Rate.

  • Emerson's Efficiency Plan: Bonus based on % efficiency above 66.67%.

Work Factor System

A PMTS that classifies motions into classes (A, B, C, D, E) based on the body part used and effort/distance involved. Each class has a predetermined time value. The total time for a task is the sum of the class values for all motions.

Method Time Measurement (MTM)

A widely used PMTS. It breaks down any manual operation into a sequence of basic motions (Therbligs). Each motion is classified into one of several MTM tables based on the body part and the distance/weight involved. Each table entry gives a time in TMU. Summing all TMU values gives the basic time for the method. It is highly accurate for method comparison and standard setting but requires extensive training.

[!TIP] Exam Focus: Be ready to explain Gantt's and Merrick's plans with their key features and differences. Know the basic concept of MTM/PMTS (pre-determined times for basic motions).