Mechanical Interview
Masterclass

Shift start par handover lena (pichli shift ke issues, pending jobs), manpower allocation, plan vs actual tracking har 2 ghante, quality issues par line par jaana, breakdown par maintenance ko coordinate karna, shift end par production report aur handover. Interview mein yeh routine confidently bol do — lagega ki aap plant dekh chuke ho.

OEE = Availability × Performance × Quality. Availability = actual run time ÷ planned time (breakdowns/changeover ka loss). Performance = actual output ÷ ideal output us time mein (slow running ka loss). Quality = good pieces ÷ total pieces (rejection ka loss). Example: 8 ghante ki shift mein 1 ghanta downtime (A=87.5%), ideal 500 piece ki jagah 420 bane (P=84%), 420 mein 10 reject (Q=97.6%) → OEE = 0.875 × 0.84 × 0.976 = 71.7%. World class ~85%. Yeh calculation likh kar dikhana aana chahiye.

Takt time = available time ÷ customer demand — customer ki chaal (har kitne second mein ek piece CHAHIYE). Cycle time = ek piece actually banne mein kitna time lagta hai — machine ki chaal. Lead time = order se delivery tak ka total time. Rule: cycle time ≤ takt time hona chahiye, warna demand miss hogi. Example: 8 hr (28800 sec) mein demand 400 pieces → takt = 72 sec/piece.

Assembly line ke sab stations par kaam barabar baantna taaki koi station bottleneck na bane aur koi idle na rahe. Method: har operation ka time study karo, bottleneck station identify karo, uske elements aage-peeche ke stations mein shift karo. Line efficiency = total task time ÷ (stations × cycle time). Practical example ready rakho.

Seiri (Sort — bekar cheezein hatao), Seiton (Set in order — har cheez ki fixed jagah, shadow boards), Seiso (Shine — safai + safai karte waqt inspection), Seiketsu (Standardize — pehle 3S ka standard banao, checklists), Shitsuke (Sustain — habit banao, audits). Sirf naam nahi — har S ka shop-floor example bolo: "Seiton matlab spanner ka shadow board taaki 10 second mein tool mile."

(1) Pehle containment — suspected lot hold karo taaki defect customer tak na jaaye. (2) Data — kaunsa defect, kaunsi machine/shift/operator/material lot se aa raha hai (stratification). (3) 4M change check karo — Man (naya operator?), Machine (tool wear, setting), Material (naya lot?), Method (process change hua?). (4) Root cause par countermeasure + standard update. Yeh 4M framework bolna production interview ka winning answer hai.

Kaizen = chhota continuous improvement, workers ke ideas se. Example: "operator ne fixture ki height 50mm badhai — bending kam hui, productivity 8% badhi." Poka-Yoke = mistake-proofing — galti ho hi na sake. Example: sensor jo part ulta rakhne par machine start hi nahi hone deta, ya asymmetric fixture jisme part sirf sahi orientation mein baithta hai.

QC (Quality Control) = product-focused, defect PAKADNA — inspection, testing, measurement. Reactive hai. QA (Quality Assurance) = process-focused, defect HONE SE ROKNA — systems, audits, SOPs, documentation. Proactive hai. Ek line: "QC product check karta hai, QA process ko pakka karta hai ki kharab product bane hi na." Yeh difference har quality interview ka pehla sawal hai.

Yeh table quality interview ka sabse pakka question hai — least count galat bola toh instant negative. Yaad kar lo:

(1) Check sheet — data collect karne ke liye (defect tally). (2) Pareto chart — 80/20: kaunse 2-3 defects 80% problem hain. (3) Fishbone (Ishikawa) — causes ko Man/Machine/Material/Method/Measurement/Environment mein baantna. (4) Histogram — data ka distribution/spread. (5) Scatter diagram — do variables ka relation (temp vs rejection). (6) Control chart — process time ke saath control mein hai ya nahi (UCL/LCL). (7) Flow chart / Stratification — process samajhna / data ko categories mein todna. Sequence bolo: "check sheet se data, Pareto se priority, fishbone se causes, control chart se monitoring" — poora quality cycle ek answer mein.

D1: Team banao. D2: Problem define karo (kya, kitna, kab se — data ke saath). D3: Containment — customer aur apne stock mein suspected material hold/sort karo, turant. D4: Root cause (5-Why/fishbone) — occurrence ka bhi aur detection ka bhi (nikla kyun + pakda kyun nahi). D5: Permanent corrective action choose karo. D6: Implement + validate karo. D7: Horizontal deployment — similar products/lines par bhi lagao, FMEA/control plan update. D8: Team ko recognize karo, close. D3 (containment) aur D4 ka do-part root cause — yeh dono bolna asli 8D samajh dikhata hai.

100% inspection har jagah possible/economical nahi — isliye lot mein se statistically sample check karte hain. IS 2500 / ANSI ASQ Z1.4 tables se lot size ke hisaab se sample size nikalta hai. AQL (Acceptance Quality Limit) = woh maximum defect percent jo process average ke roop mein acceptable hai — jaise AQL 1.0 par sample mein defects acceptance number tak hi allowed. Critical/major/minor defects ke alag AQL hote hain (jaise 0/1.0/2.5).

Non-Conformance Report — jab material/process requirement meet nahi karta. Flow: NCR raise → material quarantine (red tag/alag area) → disposition decide: rework, repair (concession se), use-as-is (customer/design approval par), ya reject/scrap → root cause + corrective action → closure with evidence. Disposition ke 4 options bolna documentation ki asli samajh dikhata hai.

Quality Management System ka international standard — customer focus, process approach, risk-based thinking, continual improvement (PDCA) par bana hai. Audit mein auditor documents vs actual practice compare karta hai — SOP kya kehta hai vs operator kya kar raha hai, records complete hain ya nahi, calibration valid hai ya nahi. Findings: major NC, minor NC, observation. "Main internal audits mein participate kar chuka hoon" bolna ho toh yeh flow pata hona chahiye.

MTBF (Mean Time Between Failures) = total running time ÷ number of failures — machine kitni der chalti hai fail hone se pehle (jitna ZYADA utna achha). MTTR (Mean Time To Repair) = total repair time ÷ number of repairs — average kitni der mein theek hoti hai (jitna KAM utna achha). Availability = MTBF ÷ (MTBF + MTTR). Example: mahine mein 720 hr mein 3 failures, total repair 6 hr → MTBF = 238 hr, MTTR = 2 hr, Availability = 99.2%.

Maintenance interview ka core question — yeh chart pakka kar lo:

Grease: jahan seal karna easy chahiye, low/medium speed, vertical shafts, maintenance interval lamba — most bearings. Oil: high speed, high temperature (heat carry karta hai), gearboxes, circulation systems. NLGI number grease ki consistency batata hai — 000 (fluid) se 6 (block) tak; industrial bearings mein commonly NLGI 2. Over-greasing bhi failure karati hai — churning se overheating; housing ka ~1/3 bharna rule hai.

(1) Vibration analysis — sabse powerful; unbalance (1×RPM), misalignment (2×RPM), bearing defects (high frequency), looseness sab alag signature dete hain. (2) Thermography — IR camera se hot spots (electrical joints, bearings, couplings). (3) Oil analysis — wear particles, viscosity, contamination se andar ki health. (4) Ultrasound — early bearing defects, air leaks, electrical arcing. (5) Motor current signature analysis. Ek real example ke saath bolo — "vibration spectrum mein bearing frequency dikhi, planned shutdown mein change kiya, breakdown bacha."

Gland packing: rope-type material stuffing box mein — sasta, lekin thoda leakage ZAROORI hai (cooling ke liye), shaft sleeve ghisti hai, power loss zyada. Mechanical seal: rotating + stationary lapped faces — near-zero leakage, kam friction, lekin costly aur dry-run se turant fail. Toxic/costly fluids mein mechanical seal must; water/slurry rough duty mein packing bhi chalti hai. Seal failure ke causes: dry running, misalignment, galat seal selection, vibration.

Criticality-based approach: (1) VED analysis — Vital (bina iske plant band — hamesha stock), Essential, Desirable. (2) Insurance spares — costly, lambi delivery, rarely fail (jaise bada gearbox) — management decision se stock. (3) Min-max levels lead time ke hisaab se, (4) standardization — bearings/belts ki variety kam karo, (5) CMMS mein consumption tracking. "Maine bearing varieties 48 se 31 ki, inventory ₹4 lakh kam hui" — aisa example ho toh sone pe suhaga.

Flow: (1) Sales/marketing se demand + pending orders lo, (2) capacity check — machine hours available vs required (efficiency factor ke saath), (3) material availability — stock + pipeline vs BOM requirement, (4) constraints dekho (maintenance shutdown, holidays, manpower), (5) machine-wise weekly/daily schedule banao, (6) daily plan-vs-actual review aur re-planning. Yeh 6-step flow bolo — PPC interview ka backbone yahi hai.

Material Requirement Planning — finished goods ke plan se raw material ki exact requirement nikalna. Inputs: Master Production Schedule (kya kitna banana hai), BOM (ek piece mein kya-kya lagta hai), inventory status (kitna hai + kitna aa raha hai). Output: kya kharidna hai, kitna, kab order karna hai (lead time minus karke). SAP/ERP mein MRP run yahi karta hai. Example ke saath: "500 pumps banane hain, har pump mein 2 bearing, stock 300, PO pipeline 200 → naya order 500 bearings, supplier lead time 30 din toh aaj se 30 din pehle order."

Reorder Level (ROL) = (average daily consumption × lead time) + safety stock. Safety stock demand aur lead time ki uncertainty ka buffer hai. Example: daily use 20 pcs, lead time 10 din, safety stock 100 → ROL = 300. Jaise hi stock 300 par aaye, order release. EOQ ka naam bhi le lo — ordering cost aur carrying cost ka balance point.

Woh station/machine jiski capacity sabse kam hai — poore plant ka output usi se decide hota hai (Theory of Constraints). Handle: (1) bottleneck ko kabhi idle mat hone do — uske aage buffer stock rakho, (2) uska changeover/downtime minimize karo, (3) uske pehle quality check lagao taaki bottleneck defective par time waste na kare, (4) possible ho toh us operation ko offload/outsource karo. "Ek ghanta bottleneck ka loss = poore plant ka ek ghanta" — yeh line TOC ki samajh dikhati hai.

(1) Reason-wise data banao — material shortage, capacity, quality hold, transport? Pareto lagao. (2) Sabse bade reason par action — material hai toh vendor follow-up system + safety stock review; capacity hai toh overtime/outsourcing + bottleneck fix. (3) Customer ko proactive communication — revised committed dates, chhupao mat. (4) OTIF (On Time In Full) % track karna shuru karo. Numbers wala answer: "OTIF 72% se 91% le gaye 3 mahine mein" — yeh PPC ki value hai.

Excel: VLOOKUP/XLOOKUP (codes se data milana), pivot tables (machine-wise/date-wise summary), conditional formatting (shortage red highlight), SUMIFS (plan vs actual). ERP/SAP basics: production order create/confirm, stock report (MB52 type), MRP run results, BOM display. Fresher ho toh bhi bolo "maine Excel mein plan-vs-actual tracker banaya hai" — PPC mein Excel hi asli hathiyar hai.

Yeh purchase interview ka sabse pakka question hai — 8 steps flow mein bolo:

Selection criteria: technical capability (machines, quality system), financial stability, capacity, location, existing customers, sample approval. Rating QCDS par: Quality (rejection PPM), Cost (rate competitiveness), Delivery (OTIF %), Service (response, flexibility) — weighted score, quarterly review. 90+ = A class, 75-90 = B, neeche wale ko improvement plan ya phase-out. Yeh QCDS framework bolte hi professional purchase person lagoge.

Preparation hi negotiation hai: (1) should-cost banao — raw material weight × rate + conversion + margin, (2) alternate vendor quotes saath rakho, (3) volume/annual contract ka leverage do, (4) sirf rate nahi — payment terms, freight, packaging, MOQ par bhi value nikalti hai. Vendor ad na maane toh: cost breakup maango (kahan zyada hai dikhega), long-term volume commitment offer karo, ya dual sourcing develop karo. Kabhi supply risk mein daal kar rate mat nichodo — "cheapest vendor jo time par de hi na, sabse mehenga hota hai."

Landed cost comparison mein GST samajhna zaroori hai: registered vendor se ITC milta hai toh basic rate compare karo; unregistered/composition vendor se ITC nahi milta — uska effective cost zyada. Inter-state par IGST, intra-state par CGST+SGST. E-way bill (₹50,000+ movement par), aur GRN ke against invoice ka GSTR-2B mein reflect hona — ITC tabhi milega. Itna GST knowledge purchase role ke liye kaafi hai.

ABC = value-based: A items (10% items, 70% value — tight control, low stock, frequent orders), B (20%/20%), C items (70% items, 10% value — bulk order, kam attention). VED = criticality-based: Vital (bina iske production band), Essential, Desirable. Dono ka matrix banakar policy banti hai — AV item (costly + vital) par sabse zyada focus. Stores/inventory interview mein yeh pakka aata hai.

Cost reduction = existing cost ghatana (rate ₹100 se ₹92 negotiate kiya — hard saving, P&L mein dikhti hai). Cost avoidance = future cost rokna (vendor 10% increase maang raha tha, 4% par settle — soft saving). Example ready rakho: "alternate vendor development se casting rate 7% kam kiya — annual saving ₹6 lakh" ya "packaging returnable bins mein shift ki — per-trip cost 60% kam." Purchase interview mein saving ka number sabse bada hathiyar hai.

First angle: object viewer aur plane ke BEECH mein — top view neeche banta hai, left view right mein (India/Europe — IS standard). Third angle: plane object aur viewer ke beech — top view upar hi banta hai (US standard). Symbol se pehchano: frustum of cone ka symbol title block mein hota hai. Interview mein symbol bana kar dikhana aana chahiye — pen-paper maang lo.

Design interview ka core — yeh 12 symbols ka chart yaad karo (ASME Y14.5 standard):

Teen types: Clearance fit (shaft hamesha hole se chhota — bearing par ghoomti shaft), Interference fit (shaft hamesha bada — press/shrink fit, gear on shaft), Transition fit (dono possible — location fits, dowels). H7/g6 padho: H = hole basis system (hole ka lower deviation zero), 7 = hole ka tolerance grade; g6 = shaft ka position (g = thoda neeche = clearance) aur grade 6. H7/g6 = precision clearance (sliding) fit; H7/p6 = interference. Hole basis kyun use karte hain? — Holes standard tools (drill/reamer) se bante hain, shaft ko adjust karna easy hai.

Framework: (1) Function — kya load (static/dynamic/impact), environment (corrosion, temperature)? (2) Properties required — strength, hardness, fatigue, weight. (3) Manufacturability — cast hoga, machine hoga, weld hoga? (4) Cost + availability. Example: shaft = EN8/EN19 (medium carbon, achhi fatigue strength, machinable); corrosive environment = SS304/316; wear surface = case hardened EN353 ya through-hardened EN31. Grade ke saath reason bolna hi design thinking hai.

Bending mein material ka bahar ka fiber stretch hota hai, andar ka compress — neutral axis par length same rehti hai. Flat blank ki length nikalne ke liye bend allowance add karte hain: BA = angle × (π/180) × (R + K×t), jahan K-factor (~0.33-0.5) neutral axis ki position hai. Baaki basics: minimum bend radius (usually ≥ material thickness), holes ko bend se door rakho (≥ 2t + R), grain direction ka dhyan. K-factor ka naam lete hi sheet-metal walon ki interview mein weight badh jaata hai.

Design For Manufacturing/Assembly — design aisi banao jo banane aur assemble karne mein sasti/easy ho. Principles: parts count kam karo, standard parts use karo, symmetric parts (orientation galti na ho), self-locating features, machining ke liye tool access socho, tolerances utne hi tight jitne functionally zaroori (har tight tolerance = cost). Example: "4 alag brackets ki jagah ek bent part design kiya — assembly time aadha, cost 30% kam." Design sirf CAD nahi, cost bhi hai — yeh attitude interviewer ko chahiye.

Flow: (1) Lead generation — references, exhibitions, IndiaMART/online, cold visits, (2) requirement understanding — application, specs, quantity, current supplier, (3) technical discussion/demo — fitment prove karo, (4) quotation, (5) negotiation — rate, payment terms, delivery, (6) PO closure, (7) order execution follow-up, (8) payment collection + repeat business. Sales sirf step 4-5 nahi hai — step 8 tak ownership hi achha sales engineer banati hai. B2B cycle lamba hota hai (weeks-months) — patience + follow-up discipline.

Item description + specs, quantity, unit rate, GST (extra ya inclusive — clearly), packing & forwarding, freight (FOR destination ya ex-works), payment terms (advance %, against delivery, credit days), delivery period, validity (usually 30 din), warranty/guarantee terms. Ex-works aur FOR ka difference pata hona chahiye — ex-works mein transport buyer ka, FOR destination mein aapka. Yeh commercial terms hi asli sales knowledge hai.

(1) Pehle poochho — kis product/spec se compare kar rahe hain? Aksar apples-to-oranges hota hai (material grade, warranty, scope alag). (2) Value bolo, price nahi — life zyada, rejection kam, service fast, total cost of ownership kam. (3) Reference do — "XYZ company 3 saal se le rahi hai isi rate par, unka rejection zero hai." (4) Phir bhi gap ho toh volume/terms ke against thoda adjust karo — lekin one-sided discount kabhi nahi, hamesha kuch ke badle kuch. Rate war mein jeet ke bhi haar hoti hai — yeh maturity interviewer sunna chahta hai.

Common terms: 100% advance, 30% advance + 70% against delivery, 30/60/90 days credit, LC (letter of credit — bade orders/exports mein), PDC. Payment atka: (1) polite structured follow-up — accounts + purchase dono ko, (2) statement of account bhejo, (3) next dispatch hold ka leverage (senior se aligned hokar), (4) personal visit — phone se zyada kaam karti hai, (5) relationship kharab kiye bina firmness. "Sales tab complete hoti hai jab payment aati hai" — yeh line bolo, har sales manager ka favourite sach hai.

(1) Mapping — us area ki target industries ki list (directory, GST data, IndiaMART, industrial estates), (2) segment karo — A/B/C potential ke hisaab se, (3) A-class par personal visits, existing customers se references, (4) local dealer/channel partner evaluate karo agar model hai, (5) 90-day plan banao — pehle 30 din mapping+meetings, 60 din trials/samples, 90 din pehle orders. Structured territory plan bolna fresher ko bhi experienced dikha deta hai.

B2B industrial mein: (1) IndiaMART/TradeIndia listings optimize — photos, specs, reviews, (2) Google My Business + website par product pages (log "manufacturer near me" search karte hain), (3) LinkedIn — purchase managers/plant heads se connect, company page par application posts, (4) WhatsApp Business catalog — enquiry handling fast, (5) exhibitions ka follow-up system. Marketing ka kaam quality enquiries lana hai, closing sales ka — dono ka funnel alag samajhna hi answer hai.

(1) Initiation — scope, feasibility, budget approval, (2) Planning — schedule (bar chart/MSP), resources, procurement plan, drawings, (3) Execution — civil, structural, equipment erection, piping, electrical, (4) Testing & Commissioning — cold trials, hot trials, performance test, (5) Handover — documentation, training, punch points closure, (6) Closure — final billing, lessons learned. Har stage ka ek deliverable bolo — planning ka schedule, commissioning ka performance test report.

(1) Foundation check — level, dimensions, anchor bolt positions drawing se verify (foundation release protocol), (2) equipment placement — crane plan ke saath, (3) leveling — machined surfaces par precision level se, shims/grouting se adjust, (4) alignment — driver-driven coupling alignment (dial/laser), (5) grouting — non-shrink grout, curing, (6) final alignment check grouting ke baad, (7) piping/electrical connections — kabhi bhi pipe ka load machine par mat aane do (pipe strain), (8) trial run. Pipe strain wala point bolo — real site walon ki pehchan hai.

Pre-commissioning: alignment records, lubrication charging, direction of rotation (decoupled), safety interlocks test, loop checking (instruments), flushing/blowing of lines. Cold/no-load trial: vibration, temperature, noise, current readings baseline. Load trials: step-wise load badhao, parameters log karo. Performance guarantee test: contract ke parameters (capacity, power consumption) prove karna. Punch list: A-category (safety/operation blocking — pehle close) aur B-category items. Yeh structured answer commissioning experience jaisa sound karta hai.

(1) Work order ke rates aur scope se compare, (2) measurement verification — joint measurement site par (MB/measurement sheet sign), (3) quantity WO ki BOQ limit ke andar hai ya extra item (extra ke liye approval chahiye), (4) deductions — advance recovery, retention (usually 5-10%), penalty agar delay LD clause mein hai, (5) GST/compliance documents (PF/ESIC challans labour contractors ke). Retention aur LD ka concept bolna projects ki commercial samajh dikhata hai.

(1) Work permit system — height work, hot work, confined space, electrical — bina permit kaam nahi, (2) height work: full body harness + lifeline + certified scaffolding (green tag), (3) lifting: crane capacity vs load chart, certified slings, rigger supervision, exclusion zone, (4) toolbox talk daily — aaj ka kaam + hazards, (5) PPE compliance + housekeeping. Ek line: "Schedule pressure mein bhi safety shortcut nahi — ek accident poora project peeche kar deta hai." Interviewer ko yahi attitude chahiye.

As-built drawings (jo actually bana — original se changes marked), O&M manuals, test certificates (material TCs, motor test reports, calibration certs), commissioning/performance test reports, spare parts list with recommended 2-year spares, warranty documents, training records, punch list closure evidence. "Documentation ke bina handover adhoora hai — operations wale isi se plant chalayenge" — project engineer ki maturity isi line mein hai.