Mechanical Engineering 2022 Paper I 50 marks Discuss

Q8

Q8. (a) (i) Discuss the mechanism of material removal in ultrasonic machining. (10 marks) (ii) What are the different parameters affecting the material removal rate in ultrasonic machining ? Show the variation of material removal rate with respect to these parameters using suitable schematic. (b) (i) Discuss the ABC, VED and SDE classification of inventory items. (10 marks) (ii) A plastic moulding company provides the following details of various products in terms of annual demand and unit cost. Classify the products in A, B and C categories. (10 marks) | Item Code # | Annual Demand | Cost/Unit (₹) | |-------------|---------------|---------------| | XA-101 | 400 | 4.00 | | XA-102 | 300 | 5.00 | | XA-103 | 120 | 3.00 | | XA-104 | 80 | 2.00 | | XA-105 | 50 | 2.50 | | XA-106 | 40 | 1.50 | | XA-107 | 20 | 2.20 | | XA-108 | 15 | 32.00 | | XA-109 | 8 | 51.80 | | XA-110 | 6 | 42.00 | | XA-111 | 5 | 3.00 | (c) Discuss the various steps used in sourcing of a product or service. Also, mention the name of the factors influencing the sourcing decision. (10 marks)

हिंदी में प्रश्न पढ़ें

Q8. (a) (i) पराश्रव्य मशीन में पदार्थ पृथक्करण की क्रियाविधि की विवेचना कीजिए । (ii) पराश्रव्य मशीन में पदार्थ पृथक्करण दर को प्रभावित करने वाले कौन-से विभिन्न प्राचल हैं ? समुचित व्यवस्था आरेख द्वारा इन प्राचलों के सापेक्ष पदार्थ पृथक्करण दर में परिवर्तन को दर्शाइए । (b) (i) सामग्री-सूची मदों के ABC, VED व SDE वर्गीकरण की विवेचना कीजिए । (ii) एक प्लास्टिक संचकन (मोल्डिंग) कम्पनी विभिन्न उत्पादों के निम्नलिखित विवरण वार्षिक माँग व इकाई लागत के पदों में देती है । उत्पादों को A, B व C श्रेणी में वर्गीकृत कीजिए । | आइटम कोड # | वार्षिक माँग | लागत/इकाई (₹) | |------------|-------------|--------------| | XA-101 | 400 | 4·00 | | XA-102 | 300 | 5·00 | | XA-103 | 120 | 3·00 | | XA-104 | 80 | 2·00 | | XA-105 | 50 | 2·50 | | XA-106 | 40 | 1·50 | | XA-107 | 20 | 2·20 | | XA-108 | 15 | 32·00 | | XA-109 | 8 | 51·80 | | XA-110 | 6 | 42·00 | | XA-111 | 5 | 3·00 | (c) एक उत्पाद अथवा सेवा को प्राप्त करने (सोर्सिंग) के लिए विभिन्न पदों की विवेचना कीजिए । उत्पाद अथवा सेवा को प्राप्त करने (सोर्सिंग) के लिए निर्णय को प्रभावित करने वाले कारकों का नामोल्लेख भी कीजिए ।

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Directive word: Discuss

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How this answer will be evaluated

Approach

Discuss the material removal mechanism in USM with emphasis on cavitation, hammering and erosion effects; for part (b) explain ABC/VED/SDE classifications with clear criteria and perform the ABC analysis calculation showing cumulative percentage steps; for part (c) outline the sourcing process from need identification to supplier relationship management. Allocate approximately 25% time to (a)(i)-(ii), 35% to (b)(i)-(ii) due to numerical work, and 25% to (c), reserving 15% for diagrams and review.

Key points expected

  • (a)(i) Material removal via three mechanisms: direct hammering by abrasive particles, cavitation-induced erosion, and chemical action at tool-work interface; frequency 15-30 kHz, amplitude 10-50 μm
  • (a)(ii) Parameters: amplitude, frequency, static feed force, abrasive grit size, concentration, slurry viscosity; MRR ∝ (amplitude)^0.5, ∝ (frequency), ∝ (grit size) up to optimum, then decreases
  • (b)(i) ABC by annual consumption value (70-20-10 rule), VED by criticality (Vital-Essential-Desirable), SDE by availability (Scarce-Difficult-Easy); applications in Indian manufacturing context
  • (b)(ii) Calculate annual consumption value (Demand × Cost), rank descending, compute cumulative percentage: A items (top 70-80% value), B (next 15-25%), C (remaining 5-10%)
  • (c) Sourcing steps: specification, supplier identification, RFQ/bidding, evaluation (technical-commercial), negotiation, contract, performance monitoring; factors: cost, quality, delivery, reliability, geopolitical risk, Make-in-India policy alignment

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness25%10Accurately describes all three USM material removal mechanisms with correct physics; precisely defines ABC/VED/SDE criteria with distinct applications; correctly identifies 7-8 sourcing steps with logical sequencing; no conceptual confusion between inventory classification systems.Covers hammering and cavitation in USM but misses chemical action; defines ABC correctly but VED/SDE definitions vague or swapped; lists 4-5 sourcing steps with minor sequencing errors.Confuses USM with EDM or ECM mechanisms; cannot distinguish ABC from VED/SDE; sourcing steps jumbled or omitted; fundamental conceptual errors in multiple sub-parts.
Numerical accuracy20%8All annual consumption values correct (XA-108: ₹480, XA-109: ₹414.40, XA-101: ₹1600, etc.); proper ranking; cumulative percentages calculated with A: XA-101, XA-108, XA-109 (~70%), B: XA-102, XA-103, C: remainder; clear tabular presentation.Most consumption values correct but 1-2 calculation errors; ranking approximately correct but boundary between A/B or B/C slightly misplaced; cumulative percentages shown but arithmetic slips.Major calculation errors in consumption values; incorrect ranking methodology (uses demand or cost alone); no cumulative percentage analysis; ABC classification arbitrary.
Diagram quality20%8USM setup diagram with transducer, horn, tool, abrasive slurry, workpiece clearly labelled; schematic graphs showing MRR vs amplitude (increasing), vs grit size (peaking), vs frequency (linear); ABC Pareto curve with proper axes and 70-20-10 zones marked.USM diagram present but missing key components (e.g., no horn or slurry pump); MRR trends described verbally or one schematic drawn; ABC shown as simple table without Pareto visualization.No diagrams despite explicit requirement for 'suitable schematic'; poorly labelled sketches; diagrams contradict textual explanation; missing entirely for USM parameter variations.
Step-by-step derivation20%8ABC analysis shown in complete tabular format: Item → Annual Demand → Unit Cost → Annual Consumption Value → Rank → Cumulative % → Category; each computational step visible; sourcing process as numbered flowchart with decision gates.ABC calculation steps present but condensed (jumps to final ranking); some intermediate values implied not shown; sourcing as bullet points without clear workflow logic.No derivation shown—final ABC categories stated without calculation; sourcing as random list without process logic; impossible to trace how conclusions reached.
Practical interpretation15%6USM applications: machining glass, ceramics, carbides for ISRO components, dies; ABC implications for Indian SMEs' working capital; VED for hospital/pharma inventory; sourcing factors linked to Atmanirbhar Bharat, supply chain resilience post-COVID, China-plus-one strategy.Generic USM applications mentioned (glass, ceramics); ABC linked to 'control' without specific Indian context; sourcing factors listed without policy or strategic framing.No practical interpretation; answer remains purely theoretical; no connection to Indian manufacturing context, MSME challenges, or contemporary supply chain issues.

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