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Qwestrum Engineering360 · Industrial & Production · Production Planning & Control

Shop Floor Control

Shop-floor control monitors and regulates execution so planned schedules convert into stable output.
Exam tip: keep SI units consistent end-to-end, write the governing relation symbolically before substituting, and sanity-check magnitude and sign.

Key formulas & points

Skim these first — then read the full notes below.

  • Dispatch lists prioritise queue at work centre
  • Andon signals abnormal conditions
  • Kanban limits WIP between stages

Topic details

Introduction

Real-time execution control is central in modern manufacturing systems. Groover highlights data visibility, while Chase links control policies with delivery reliability.

Key relations & formulas

Formulas (Indian textbook notation)

  • OEE=availability×performance×qualityOEE = availability \times performance \times quality

Formulas (Indian textbook notation)

  • throughput=completedunitstimethroughput = completed \frac{units}{time}

Formulas (Indian textbook notation)

  • WIPLittle:WIP=throughput×cycletimeWIP Little: WIP = throughput \times cycle time

Notation and sign conventions

Relation 1 —
OEE=availability×performance×qualityOEE = availability \times performance \times quality

Formulas (Indian textbook notation)

  • OEE=availability×performance×qualityOEE = availability \times performance \times quality
Write this relation with symbols exactly as in Martand Telsang Ppc — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.
Relation 2 —
throughput=completedunitstimethroughput = completed \frac{units}{time}

Formulas (Indian textbook notation)

  • throughput=completedunitstimethroughput = completed \frac{units}{time}
Write this relation with symbols exactly as in Martand Telsang Ppc — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.
Relation 3 —
WIPLittle:WIP=throughput×cycletimeWIP Little: WIP = throughput \times cycle time

Formulas (Indian textbook notation)

  • WIPLittle:WIP=throughput×cycletimeWIP Little: WIP = throughput \times cycle time
Write this relation with symbols exactly as in Martand Telsang Ppc — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.

Concept in depth

Key indicators include OEE, throughput, queue length, and WIP age. Dispatching rules and visual controls like Andon reduce response time to abnormalities. Kanban-based pull controls help cap WIP and expose bottlenecks early.

Assumptions and validity limits

State assumptions explicitly before using any relation for shop floor control — steady state, uniform properties, linear elastic material, ideal gas, incompressible flow, etc., as applicable.
Wrong assumptions invalidate the entire solution even when the formula is correct. In Production Planning viva and GATE descriptive questions, listing valid assumptions often earns separate marks.

Step-by-step problem approach

1. Read the question and list given data with SI units (common in Production Planning papers).
2. Draw a neat labelled diagram where applicable — examiners in Indian universities award diagram marks even when arithmetic slips.
3. Identify which relation from this topic applies to shop floor control.
4. Use equation 1:
OEE=availability×performance×qualityOEE = availability \times performance \times quality
.
5. Use equation 2:
throughput=completedunitstimethroughput = completed \frac{units}{time}
.
6. Substitute values, compute, and verify units and sign (direction).
7. State conclusion in one line — e.g. safe/unsafe, stable/unstable, feasible/infeasible.

Applications & exam relevance

Shop Floor Control appears in manufacturing plants. In Indian industrial curricula this topic is tested because it connects theory to MRP, scheduling, and capacity.
GATE and semester exams often combine shop floor control with earlier units — revise prerequisites before attempting mixed problems.
Industry interview panels sometimes ask: "Where did you use shop floor control?" — answer with a lab, mini-project, or plant visit example if possible.

Common mistakes in exams

Many students multiply OEE factors without converting percentages to decimals first. Another issue is quoting Little law without ensuring stable average conditions.

Quick revision checklist

Before attempting shop floor control problems, confirm you can:
1. Dispatch lists prioritise queue at work centre
2. Andon signals abnormal conditions
3. Kanban limits WIP between stages
Revise the solved examples in Martand Telsang Ppc — Standard reference and one previous-year GATE or university paper for this unit.

Worked examples

Try the problem first — open the solution when you are ready to check.

OEE computation

Problem

Availability = 0.90, performance = 0.85, quality = 0.96. Find OEE percentage.

Solution

OEE = 0.90 x 0.85 x 0.96 = 0.7344. Therefore OEE = 73.44%.

Conceptual check — Shop Floor Control

Problem

In a Production Planning semester or GATE paper you are asked: "State the main assumption, the governing relation, and one practical consequence of shop floor control." What should a complete answer include?

📖 Standard books (India)

  • Martand Telsang Ppc — Standard reference

    Read: Syllabus unit

    Referenced in Indian B.Tech syllabus

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