UPSC IES/ESE (Engineering Services) Manufacturing, Industrial and Measurement Engineering Syllabus

Define machinability and list the criteria used to judge it.

Machinability is the ease with which a material can be machined. Criteria: tool life, cutting forces/power consumed, surface finish achieved, chip form/disposal, and material removal rate.

What are the three primary functions of a cutting fluid?

Cooling (carry away heat, control temperature), lubrication (reduce friction at tool-chip and tool-work interfaces), and flushing away chips. It also improves surface finish and tool life and reduces forces.

Name the main mechanisms of tool wear.

Adhesion wear, abrasion wear, diffusion wear (high temperature), and oxidation/chemical wear. These produce flank wear (on the clearance face) and crater wear (on the rake face).

What is the difference between conventional and unconventional (non-traditional) machining?

Conventional machining removes material by direct mechanical contact of a harder tool. Unconventional machining uses other energy forms (electrical, thermal, chemical, mechanical erosion) without a hard tool harder than the work, suited to hard/brittle materials and complex shapes (e.g. EDM, ECM, LBM, USM).

In EDM, what is the material removal mechanism and what determines surface finish?

Material is removed by repeated electrical spark discharges (thermal erosion: melting and vaporization) between tool and workpiece in a dielectric. Surface finish improves with lower discharge energy (lower current/pulse on-time); rough cuts use high energy for high MRR.

Define additive manufacturing and name two common processes.

Additive manufacturing (3D printing) builds a part layer-by-layer directly from a CAD model by adding material. Examples: Fused Deposition Modeling (FDM), Stereolithography (SLA), Selective Laser Sintering (SLS), and Selective Laser Melting (SLM).

Distinguish between a limit, a tolerance, and an allowance in dimensional engineering.

Limits are the maximum and minimum permissible sizes of a part. Tolerance is the difference between the upper and lower limits (total permissible variation). Allowance is the intentional difference between the dimensions of mating parts (minimum clearance or maximum interference).

Define clearance fit, interference fit, and transition fit.

Clearance fit: hole is always larger than shaft (positive allowance, free movement). Interference fit: shaft is always larger than hole (always overlap, press fit). Transition fit: limits overlap so the fit may be either clearance or interference.

What is the basic principle of the hole-basis and shaft-basis systems of fits?

In the hole-basis system the hole size (lower deviation = 0, designated H) is kept constant and different shafts give different fits. In the shaft-basis system the shaft (upper deviation = 0, h) is constant and the hole is varied. Hole-basis is preferred (standard reamers/plug gauges).

State Taylor's principle of gauge design for GO and NO-GO gauges.

The GO gauge checks the maximum-material limit and should check all dimensions (size and form) simultaneously. The NO-GO gauge checks the minimum-material limit and should check only one dimension at a time.

What instrument measures angles using a graduated dial, and what is a sine bar used for?

A bevel protractor (vernier/optical) measures angles directly. A sine bar measures or sets angles indirectly using slip gauges: $\sin\theta = \dfrac{h}{L}$, where $h$ is the gauge-block height and $L$ the sine-bar length (roller centre distance).

How is the effective diameter of a screw thread measured, and name a method.

The effective (pitch) diameter is measured by the two-wire or three-wire method, in which wires of known diameter are placed in the thread grooves and the dimension over the wires is measured with a micrometer, then corrected by formula; or by a floating-carriage micrometer/optical projector.

What is the least count formula for a vernier instrument?

Least count $= $ (value of 1 main scale division) $-$ (value of 1 vernier scale division) $= \dfrac{\text{1 MSD}}{N}$, where $N$ is the number of vernier divisions. For a standard vernier caliper, LC $= 0.02\text{ mm}$.

How does an autocollimator measure small angular deviations?

An autocollimator projects a collimated beam onto a reflecting surface; the tilt of the surface displaces the reflected image, and the linear displacement of the image is proportional to twice the angular tilt, $d = 2f\theta$, where $f$ is focal length. It measures flatness, straightness, and small angles.

Define a transducer and distinguish active from passive transducers.

A transducer converts one form of energy (a physical quantity) into another, usually an electrical signal. Active (self-generating) transducers produce their own output energy (e.g. thermocouple, piezoelectric). Passive transducers require external excitation power (e.g. strain gauge, LVDT, RTD, capacitive).

How does an LVDT work and what is its key output characteristic?

A Linear Variable Differential Transformer has one primary and two secondary coils; movement of a ferromagnetic core changes the differential voltage. Output is linear with core displacement, with the null position at the centre and phase indicating direction. It is contactless, frictionless, with high resolution.

What is the working principle of a strain gauge and the gauge factor?

A strain gauge changes electrical resistance when strained: $\dfrac{\Delta R}{R} = G_{f}\,\varepsilon$, where the gauge factor $G_{f} = \dfrac{\Delta R/R}{\varepsilon}$ (about 2 for metallic gauges). Strain is measured via a Wheatstone bridge.

Distinguish between systematic (controllable) errors and random errors in measurement.

Systematic errors are repeatable and have a definite cause (calibration, environmental, loading, observer bias); they can be corrected. Random errors vary unpredictably about a mean (noise, friction, backlash) and are treated statistically; they cannot be eliminated, only reduced.

Define accuracy and precision, and explain how they differ.

Accuracy is closeness of a measured value to the true value (small systematic error). Precision is the repeatability/closeness of repeated measurements to one another (small random scatter). A measurement can be precise but not accurate, and vice versa.

What is calibration, and why is traceability important?

Calibration is comparing an instrument's readings against a known standard of higher accuracy to determine and correct errors. Traceability ensures the standard is linked through an unbroken chain of comparisons to a national/international primary standard, giving confidence in results.

How is the combined (overall) uncertainty obtained from independent component uncertainties?

Independent (random) uncertainties combine in quadrature (root-sum-of-squares): $u_{c} = \sqrt{u_{1}^{2} + u_{2}^{2} + \cdots + u_{n}^{2}}$. The expanded uncertainty is $U = k\,u_{c}$, with coverage factor $k$ (typically $k = 2$ for $\approx 95\%$ confidence).

What is the objective of work study, and what are its two main branches?

Work study improves productivity by examining and improving work methods and establishing time standards. Its two branches are method study (improving the method, reducing work content) and work measurement / time study (determining standard time for a task).

What is the difference between method study and time study?

Method study analyzes and improves the way work is done to eliminate waste and find the best method (uses charts: flow process, operation, two-handed). Time study (work measurement) determines the standard time a qualified worker needs to perform the established method at a defined pace.

Give the formula for standard time in time study.

Standard time $=$ Normal time $\times (1 + \text{Allowance fraction})$, where Normal time $=$ Observed time $\times \dfrac{\text{Rating}}{100}$. Allowances cover relaxation, personal needs, and delays.

What are the main functions of Production Planning and Control (PPC)?

Planning functions: forecasting, routing, scheduling, loading. Control functions: dispatching, expediting (follow-up/progressing), and corrective action. PPC ensures the right quantity is produced at the right time, quality, and cost.

Differentiate routing and scheduling in PPC.

Routing determines the path/sequence of operations and the machines/work centres a product passes through (the 'how' and 'where'). Scheduling fixes the timing—when each operation starts and finishes (the 'when').

What is exponential smoothing forecasting and its formula?

A weighted moving-average method giving more weight to recent data: $F_{t+1} = \alpha D_{t} + (1-\alpha)F_{t}$, where $F$ = forecast, $D$ = actual demand, and $\alpha$ is the smoothing constant ($0 \leq \alpha \leq 1$). Larger $\alpha$ responds faster to changes.

Derive the basic Economic Order Quantity (EOQ) and the relation between ordering and holding cost at the optimum.

$Q^{*} = \sqrt{\dfrac{2DC_{o}}{C_{h}}}$, where $D$ = annual demand, $C_{o}$ = ordering cost/order, $C_{h}$ = holding cost/unit/year. At the optimum, total ordering cost equals total holding cost, and total annual inventory cost $= \sqrt{2DC_{o}C_{h}}$.

What is the EOQ with finite replenishment (production/EPQ model) order quantity?

$Q^{*} = \sqrt{\dfrac{2DC_{o}}{C_{h}}}\sqrt{\dfrac{p}{p-d}}$, where $p$ = production rate and $d$ = demand (consumption) rate ($p > d$). The factor $\sqrt{p/(p-d)}$ makes the batch larger than the basic EOQ because stock builds up gradually.

Distinguish MRP from JIT as inventory/production philosophies.

MRP (Material Requirements Planning) is a push system that computes material needs from the master production schedule, BOM, and inventory records, planning orders in advance. JIT (Just-In-Time) is a pull system that produces/supplies items only as needed, minimizing inventory (ideal lot size = 1, zero waste).

In linear programming, what is the standard form and the role of slack/surplus variables?

Standard form maximizes/minimizes a linear objective subject to linear equality constraints with non-negative variables. A slack variable is added to a $\leq$ constraint and a surplus variable subtracted from a $\geq$ constraint to convert inequalities to equalities. The optimum lies at a corner (vertex) of the feasible region.

State the condition for a transportation problem to be balanced and the number of basic cells for a non-degenerate solution.

Balanced when total supply equals total demand: $\sum a_{i} = \sum b_{j}$. A non-degenerate basic feasible solution of an $m \times n$ problem has exactly $m + n - 1$ occupied (basic) cells; fewer indicates degeneracy.

For an M/M/1 queue, give the average number in the system and average waiting time in the system.

With utilization $\rho = \dfrac{\lambda}{\mu} < 1$: average number in system $L_{s} = \dfrac{\rho}{1-\rho} = \dfrac{\lambda}{\mu-\lambda}$, and average time in system $W_{s} = \dfrac{1}{\mu-\lambda}$, where $\lambda$ = arrival rate, $\mu$ = service rate. (Little's law: $L_{s} = \lambda W_{s}$.)