Automation and robotics in manufacturing

In short

Automation means operating a manufacturing process with mechanical, electronic and computer systems in place of human effort and decision-making; an industrial robot is a reprogrammable, multifunctional manipulator that makes such automation flexible. The subject links process planning, material handling, control systems and economics, and is examined in GATE (Production and Industrial Engineering, section on manufacturing automation and robotics), in university papers on CAD/CAM, CIM and mechatronics, and in company tests. Indian employers hiring on it include Maruti Suzuki, Tata Motors, Mahindra, Bajaj Auto, Hero MotoCorp, Bosch, Siemens, ABB, KUKA, FANUC India, Yaskawa, Addverb, Rockwell, L&T, Godrej and Foxconn/Tata Electronics plants. Typical questions are numerical (cycle time, production rate, robot resolution, payback) plus definitional ones on robot configurations, sensors and safety standards.

Explained

Automation: definition, levels and types

• Automation - a technology by which a process is performed with minimum human assistance, using a power source, a programme of instructions and a control system (the three basic elements of any automated system).
• Control types: open-loop (no feedback, e.g. a stepper-driven table) and closed-loop/feedback (measured output compared with command, e.g. a CNC axis with an encoder).
• Levels of automation (device → machine → cell → plant → enterprise); each level adds its own controller and communication.
• Fixed (hard) automation: dedicated equipment, fixed sequence, very high rate, high investment, no flexibility - transfer lines, automatic assembly machines for a single product.
• Programmable automation: equipment can be reprogrammed for a new product - CNC machines, industrial robots; suits batch production.
• Flexible automation: an extension of programmable automation that changes over with no lost production time and can run a mix of parts - FMS.
• Mechanisation vs automation: mechanisation replaces muscle only; automation also replaces sensing, decision and control.
• USA principle (Groover) for approaching any automation project: Understand the existing process, Simplify it, then Automate - most failed projects automate waste.
• Ten strategies of automation and production systems: specialisation of operations, combined operations, simultaneous operations, integration of operations, increased flexibility, improved material handling and storage, on-line inspection, process control and optimisation, plant operations control, computer-integrated manufacturing.
• Reasons to automate: higher productivity, lower unit labour cost, reduced lead time, consistent quality, removal of humans from hazardous or ergonomically poor work, reduced in-process inventory.
• Limits: high capital cost, long payback for low volumes, need for skilled maintenance, inflexibility of hard automation, downtime risk when a line is fully coupled, retraining and industrial-relations issues.

Elements: sensors, actuators, controllers

• Sensors - analog (thermocouple, strain gauge, LVDT, load cell) and digital/discrete (limit switch, proximity switch, photoelectric sensor, encoder). Measured variable → signal → ADC → controller.
• Actuators: electric (servo motor - high accuracy and control; stepper motor - open-loop positioning; induction motor), hydraulic (very high force-to-size, stiff, used in heavy payload and press automation), pneumatic (cheap, fast, clean, but compressible so hard to position mid-stroke; used for grippers, clamps, pick-and-place).
• Resolution, accuracy, repeatability: resolution = smallest programmable increment; accuracy = ability to reach a commanded point in space; repeatability = spread on returning to the same taught point. Repeatability is normally much better than accuracy.
• Controllers: PLC (programmable logic controller) for discrete logic - ladder-logic rungs, inputs/outputs, timers, counters, scan cycle (input scan → programme execution → output scan); PID control for continuous variables; CNC for coordinated axis motion; SCADA/DCS for plant-wide supervision; HMI for the operator.
• Industrial networks: Modbus, PROFIBUS/PROFINET, EtherCAT, CAN, Ethernet/IP, and OPC-UA for machine-to-IT data.
• Transfer mechanisms in automated lines: walking beam, rotary indexing table (Geneva mechanism, ratchet-and-pawl, cam indexer), in-line powered conveyor; synchronous (indexing), asynchronous (power-and-free) and continuous transfer.

Industrial robots: anatomy, configurations, specifications

• Definition (ISO 8373): an automatically controlled, reprogrammable, multipurpose manipulator, programmable in three or more axes, either fixed in place or mobile. "Reprogrammable" and "multipurpose" are what separate a robot from hard automation.
• Anatomy: manipulator (links and joints) + end effector + actuators + sensors + controller + teach pendant. Joints are counted from the base: the arm-and-body (3 joints) sets position, the wrist (up to 3 joints - roll, pitch, yaw) sets orientation.
• Joint types: linear (L), orthogonal (O), rotational (R), twisting (T), revolving (V). Physically, joints are prismatic (P) or revolute (R).
• Configurations:
  • Cartesian / rectangular (PPP, gantry): three linear axes; rectangular work volume; best accuracy and stiffness; large floor area; used in gantry loading, 3-D printing, plasma cutting.
  • Cylindrical (RPP): rotating column + vertical and radial slides; cylindrical work volume; machine loading.
  • Spherical / polar (RRP): two rotary + one linear; spherical work volume.
  • Articulated / revolute (RRR, jointed-arm): all rotary; largest reach-to-footprint ratio and best obstacle avoidance; dominant in welding and painting.
  • SCARA (Selective Compliance Assembly Robot Arm): two vertical-axis rotary joints + a vertical slide; compliant in plane, stiff vertically; very fast small-part assembly and electronics.
  • Delta / parallel: three parallel arms from an overhead base; extremely fast light picking (food, pharma packaging).
• Degrees of freedom (DOF): number of independent motions; 6 DOF is the minimum to place a rigid body at any position and orientation inside the workspace; >6 is redundant (extra dexterity).
• Work volume (work envelope): the space the wrist end can reach, decided by configuration and link sizes - not the same as the space the end effector can usefully work in.
• Specifications to read off a datasheet: payload (kg, at the wrist, including the gripper), reach (mm), repeatability (±mm), number of axes, maximum axis speeds, protection class (IP), mounting (floor/ceiling/wall), controller type.
• Co-ordinate systems and transforms: world, base, tool (TCP - tool centre point) and joint co-ordinates. Forward kinematics - joint angles → TCP pose (unique). Inverse kinematics - desired pose → joint angles (may have multiple or no solutions; this is what the controller solves continuously). Jacobian relates joint rates to TCP velocity; it becomes singular at a singularity, where the robot loses a DOF and axis speeds blow up.

End effectors, sensing and vision

• Grippers: mechanical (two-/three-finger, parallel or angular), vacuum (suction cups - flat, clean, light sheet parts), magnetic (ferrous parts, fast, but residual magnetism), adhesive, expandable bladder, and multi-part/dual grippers to halve machine-loading time.
• Gripper force must allow for weight, acceleration and a factor of safety; for a friction gripper, required force depends on the coefficient of friction and the number of contacting surfaces.
• Tools as end effectors: spot-welding gun, MIG/TIG torch, paint spray gun, sealant dispenser, drill/spindle, deburring tool, screwdriver.
• Internal sensors: position (encoder, resolver, potentiometer), velocity (tachometer), current/torque - used for servo control.
• External sensors: tactile/touch, force-torque sensor at the wrist (assembly, polishing, cobot collision detection), proximity, range (laser, ultrasonic), and machine vision.
• Machine vision chain: illumination (back-light, dark-field, dome) → image acquisition → pre-processing → segmentation/thresholding → feature extraction → classification/decision → interface to the robot. Used for part presence, dimensional gauging, OCR of batch codes, bin picking and vision-guided pick-and-place; 2-D, 2.5-D and 3-D versions.
• Compliance devices: RCC (remote centre compliance) devices absorb small misalignment during peg-in-hole insertion.

Programming, integration and the modern factory

• Programming methods:
  1. Lead-through / teach-by-showing - the operator jogs the robot with a teach pendant and records points (powered lead-through) or physically guides the arm (manual lead-through, used for painting continuous paths).
  2. Textual/offline programming in a vendor language - FANUC KAREL/TP, ABB RAPID, KUKA KRL, Yaskawa INFORM, Universal Robots URScript.
  3. Offline simulation in RobotStudio, ROBOGUIDE, Process Simulate - programme on a CAD model, then download; little production lost.
  4. Learning/AI-based - demonstration plus force feedback; growing but not yet standard on production lines.
• Motion types: point-to-point (PTP, joint-interpolated), linear, circular, continuous path; via points, blending/cornering, speed and zone parameters.
• Programme structure: signals (DI/DO), waits and interlocks, loops, subroutines, frames/tool data, payload data, error handlers, home position.
• Applications by class: material handling (palletising, machine tending), processing (welding, painting, cutting, dispensing), assembly and inspection.
• Robot cell layouts: robot-centred cell, in-line cell, mobile cell; interlocked with the fence, light curtains and the PLC.
• FMS (flexible manufacturing system): CNC machines + automated material handling (AGV/conveyor/rail cart) + automated storage + a central computer; types - single machine cell, flexible manufacturing cell, full FMS; flexibility tested by part variety, changeover and routing capability.
• CIM joins design (CAD), process planning (CAPP), manufacturing (CAM/CNC/robots), quality (CAQ) and business systems (ERP/MES) on one data backbone.
• AS/RS and AGVs: automated storage and retrieval systems and automated guided vehicles (wire-guided, magnetic-tape, laser/natural-feature navigation); AMRs navigate freely with SLAM - widely deployed in Indian e-commerce and 3PL warehouses.
• Industry 4.0 layer: IIoT sensors, edge gateways, digital twin, predictive maintenance, additive manufacturing, AR-assisted service, and India's Samarth Udyog Bharat 4.0 demonstration centres; cobots (ISO/TS 15066) share space with people using power-and-force limiting, speed and separation monitoring, hand-guiding or safety-rated monitored stop.

Safety, standards and Indian practice

• ISO 10218-1 and -2 - safety requirements for industrial robots (robot itself, and the robot system/integration). ISO/TS 15066 covers collaborative operation and force limits. These are adopted in India as IS/ISO equivalents; check the current edition, since the ISO 10218 series was revised recently.
• Functional safety: IEC 61508 and IEC 62061 / ISO 13849-1 with performance levels (PL a-e) and safety integrity levels (SIL); emergency stop per IEC 60204-1 (stop categories 0, 1, 2).
• Safeguarding devices: perimeter fencing with interlocked gates, light curtains, safety laser scanners, pressure-sensitive mats, two-hand controls, enabling device on the teach pendant, muting and LOTO (lock-out tag-out) before entering an envelope.
• Risk assessment per ISO 12100 - identify hazards, estimate and evaluate risk, reduce by inherently safe design → safeguarding → information for use.
• Indian legal position: occupational safety and health for factories is now governed by the Occupational Safety, Health and Working Conditions Code, 2020, in force from 21 November 2025, which replaced the Factories Act, 1948 and several other Acts; state rules under the Code carry the detail on machine guarding, hazardous processes, safety officers and accident reporting. The Bureau of Indian Standards (BIS) publishes the Indian Standards; CE/BIS marking, electrical safety (IS/IEC 60204-1) and pressure-vessel rules apply to the cell's sub-systems. Quote a standard number only after checking the current edition - several older IS numbers have been withdrawn or renumbered.
• Automation-related schemes and bodies in India: PLI schemes for electronics and auto components (which drive robot installations), ARAI and ICAT for automotive validation, NSDC/ASDC and the Automation Industry Association (AIA) for skills. India's annual industrial robot installations have been rising and are of the order of a few thousand to around ten thousand units a year (IFR data; the exact figure changes every year, so quote the latest IFR World Robotics report rather than a remembered number), with automotive and electronics the largest users.

Key points

• Automation - running a process with minimal human assistance; needs power, a programme of instructions and a control system.
• Fixed vs programmable vs flexible - dedicated and fast; reprogrammable for batches; reprogrammable *with no changeover downtime*.
• USA principle - Understand, Simplify, then Automate; never automate an unsimplified process.
• Open vs closed loop - no feedback versus measured output compared with the command.
• Industrial robot (ISO 8373) - automatically controlled, reprogrammable, multipurpose manipulator with three or more programmable axes.
• DOF - independent motions; 6 DOF places a rigid body at any pose; arm-and-body positions, wrist orients.
• Configurations - Cartesian (stiff, accurate), cylindrical, polar, articulated (best reach per footprint), SCARA (fast planar assembly), delta (fastest light picking).
• Repeatability vs accuracy - repeatability (±0.02 to ±0.1 mm typical) is far better than absolute accuracy; datasheets quote repeatability.
• Work volume - reachable space of the wrist end; payload is quoted at the wrist and includes the gripper.
• Forward vs inverse kinematics - joints → pose (unique); pose → joints (multiple or no solution); singularities make joint speeds blow up.
• End effectors - mechanical, vacuum, magnetic grippers for handling; welding gun, torch, spray gun, spindle as tools.
• Programming - lead-through teaching, textual languages (RAPID, KRL, TP, URScript), and offline simulation with little production loss.
• Material handling automation - conveyors, AGVs/AMRs, AS/RS; synchronous, asynchronous and continuous transfer in automated lines.
• PLC - discrete controller running a cyclic scan of inputs, ladder logic and outputs; the backbone of cell interlocking.
• FMS and CIM - CNC + automated handling + central computer; CIM integrates CAD, CAPP, CAM, quality and ERP on one data backbone.
• Line reliability - the more serial stations with no buffers, the lower the line efficiency; buffers decouple breakdowns.
• Safety - ISO 10218-1/-2, ISO/TS 15066 for cobots, ISO 13849-1 performance levels; in India the OSH Code, 2020 (in force 21 November 2025) replaced the Factories Act, 1948.
• Justification - payback, NPV and robots-per-10,000-employees (robot density) are the usual economic measures.

Formulas and examples

Example 1 - production rate of an automated line with breakdowns. A 10-station synchronous transfer line has a station service time of 0.5 min, transfer time 6 s, and on average one breakdown every 20 cycles with mean downtime 8 min.

• Tr = 6 s = 0.1 min → Tc = 0.5 + 0.1 = 0.6 min; ideal Rc = 60/0.6 = 100 parts/h.
• F = 1/20 = 0.05 breakdowns/cycle → F·Td = 0.05 × 8 = 0.4 min.
• Tp = 0.6 + 0.4 = 1.0 min → Rp = 60/1.0 = 60 parts/h.
• Line efficiency E = 0.6/1.0 = 60%; downtime proportion D = 0.4/1.0 = 40%.
• If material is ₹120/piece, line cost rate ₹15/min and tooling ₹5/piece: Cpc = 120 + 15 × 1.0 + 5 = ₹140 per piece. Raising E to 80% (Tp = 0.75 min) gives Cpc = 120 + 11.25 + 5 = ₹136.25, i.e. ₹3.75/piece saved - ₹11.25 lakh a year at 3,00,000 pieces.

Example 2 - robot resolution, accuracy and repeatability. A robot's linear axis has a 1.0 m stroke controlled by a 12-bit register; mechanical errors give a ±0.05 mm spread (taken as 3σ).

• Addressable points = 2¹² = 4096, so increments = 4095. CR1 = 1000/4095 = 0.2442 mm.
• Spatial resolution ≈ CR1 + 0.05 ≈ 0.294 mm (worst case).
• Accuracy ≈ CR1/2 + mechanical error = 0.1221 + 0.05 = 0.172 mm.
• Repeatability = ±0.05 mm - independent of the register size, which is why a datasheet quotes repeatability, not accuracy.
• With a 16-bit register: CR1 = 1000/65535 = 0.01526 mm, accuracy ≈ 0.0076 + 0.05 = 0.058 mm - now limited by mechanics, not electronics.

Example 3 - gripper sizing and payload check. A 4 kg steel plate is lifted vertically by a two-pad friction gripper (μ = 0.3, two gripping surfaces), maximum robot acceleration 5 m/s², factor of safety 2.

• Fg = (4 × (9.81 + 5) × 2)/(0.3 × 2) = (4 × 14.81 × 2)/0.6 = 118.48/0.6 = 197.5 N total clamping force (≈98.7 N per pad).
• With a 1.5 kg gripper, the wrist payload = 4 + 1.5 = 5.5 kg, so a 6 kg-payload robot is marginal at full speed; a 10 kg robot (e.g. a small articulated arm) is the safe choice because rated payload falls with wrist offset and acceleration.

Example 4 - economic justification of a welding robot. A robot cell costs ₹45 lakh installed and replaces two welders per shift on two shifts (4 operators) at ₹3.6 lakh/year each; rework falls by ₹4 lakh/year; power, maintenance, consumables and spares cost ₹6 lakh/year.

• Annual saving = (4 × 3.6) + 4 − 6 = 14.4 + 4 − 6 = ₹12.4 lakh/year.
• Simple payback = 45/12.4 = 3.63 years.
• At a 12% discount rate over 8 years, the annuity factor is 4.968, so PV of savings = 12.4 × 4.968 = ₹61.6 lakh → NPV = 61.6 − 45 = +₹16.6 lakh, so the project is viable even though payback exceeds three years.

Example 5 - cycle time with a dual gripper on machine loading. A CNC turning cell has machining time 90 s, load 8 s, unload 7 s, and robot travel between machine and bin 5 s each way.

• Single gripper: the machine waits while the robot unloads, travels, drops, picks, returns and loads → non-machining time = 7 + 5 + 5 + 8 = 25 s → cycle = 90 + 25 = 115 s → 31.3 parts/h.
• Dual gripper (fresh part already held): unload + index + load at the machine = 7 + 2 + 8 = 17 s; travel happens while the machine cuts → cycle = 90 + 17 = 107 s → 33.6 parts/h, a 7.5% gain for the cost of one extra gripper.

Where it is used

• Automotive - spot-welding and sealant robot lines at Maruti Suzuki (Manesar, Gurgaon), Tata Motors, Mahindra, Hyundai Chennai, Bajaj and TVS: body shops run almost entirely on articulated robots with welding guns, plus robot paint booths.
• Electronics and appliances - SCARA and delta robots for SMT handling, screwing, dispensing and testing in Noida, Sriperumbudur and Hosur plants (Dixon, Foxconn, Tata Electronics); machine vision for solder and cosmetic inspection.
• Pharma, food and FMCG - delta pick-and-place, robotic palletising and case packing at Sun Pharma, Cipla, Nestlé, ITC and Amul lines; serialisation and vision-based code verification.
• Warehousing and logistics - AMRs, sorters and AS/RS from Addverb, GreyOrange and Grey Matters in Flipkart, Amazon, DMart and 3PL warehouses.
• Heavy and process industry - robotic ladle handling and casting at foundries, robotic deslagging at steel plants (Tata Steel, JSW), CNC-FMS cells at Godrej, L&T and BHEL.
• Job roles - automation engineer, robot programmer, controls/PLC engineer, manufacturing or industrial engineer (cycle time and line balancing), maintenance and reliability engineer, systems integrator, applications engineer at ABB/FANUC/KUKA/Yaskawa and at SIs like Difacto, Hi-Tech Robotic Systemz and Rapid Robotics.

Interview questions

• Q: What makes a machine a robot rather than just automation? A: It is reprogrammable and multipurpose - the same manipulator can be given a new programme and a new end effector for a different task, which fixed automation cannot.
• Q: Why is repeatability quoted on datasheets instead of accuracy? A: Repeatability is a measurable statistical spread (±3σ) around a taught point and is what matters for a programme that returns to taught positions; absolute accuracy depends on calibration, payload, temperature and link tolerances and is far worse.
• Q: Why are six degrees of freedom considered the minimum for a general-purpose robot? A: A rigid body in space needs three translations and three rotations, so three arm-and-body joints position the wrist and three wrist joints orient the tool.
• Q: What is a singularity and why does it matter? A: A pose where the Jacobian loses rank and the robot cannot move the TCP in some direction; nearby, joint speeds required become very large, so the controller faults or the path slows - programmes are planned to avoid it.
• Q: Which robot configuration would you pick for fast assembly of small parts on a flat pallet, and why? A: A SCARA - it is compliant in the horizontal plane and stiff vertically, with very short cycle times for planar pick-place-insert motions.
• Q: How do you decide between a servo motor and a pneumatic cylinder for a motion? A: Servo when you need programmable positions, controlled speed and feedback; pneumatics when it is a fast, cheap, fixed two-position stroke, since air is compressible and cannot be held accurately mid-stroke.
• Q: A 10-station line has 95% availability per station and no buffers. What happens to output? A: Availability multiplies, so line availability is 0.95¹⁰ ≈ 60% - serial coupling destroys output, which is why buffers or station redundancy are added.
• Q: What is the USA principle? A: Understand the existing process, Simplify it, then Automate - automating an unsimplified process locks waste into capital equipment.
• Q: How does a cobot work safely without a fence? A: Through risk assessment under ISO 10218 and ISO/TS 15066 using power-and-force limiting, speed and separation monitoring, hand-guiding or safety-rated monitored stop - a fenceless cell still needs a documented risk assessment, not just a cobot.
• Q: What is the difference between an AGV and an AMR? A: An AGV follows a fixed guide path (wire, magnetic tape or reflector-based) and stops at obstacles; an AMR maps and localises itself (SLAM) and re-routes dynamically.
• Q: Why does offline programming matter commercially? A: The programme is built and verified on a CAD model in simulation, so the line loses little or no production during changeover and reachability problems surface before installation.
• Q: Where would you refuse to use a robot? A: Where volumes are too low for payback, where the part or fixture varies unpredictably without sensing, or where a simplified manual or low-cost mechanised method meets the rate at a fraction of the cost.

Common mistakes

• Confusing accuracy, repeatability and resolution, or dividing the axis stroke by 2ⁿ instead of (2ⁿ − 1) when finding control resolution.
• Forgetting the gripper mass (and the wrist offset and acceleration) when checking payload, so the "6 kg robot" cannot actually carry a 5.5 kg load at speed.
• Using ideal cycle time Tc instead of Tp when asked for actual production rate, cost per piece or number of machines needed.
• Calling programmable automation "flexible" - flexibility requires changeover with no production loss and a mixed part flow.
• Assuming closed-loop control everywhere; stepper-driven and pneumatic axes are often open-loop and lose position silently.
• Treating a cobot as automatically safe, or omitting risk assessment, interlocks, light curtains and LOTO from a cell design answer.
• Quoting the Factories Act, 1948 for machine-guarding duties - the OSH Code, 2020 has been in force since 21 November 2025; and quoting robot-density or installation figures from memory instead of the latest IFR report.

Related topics

CNC machines and part programming · Computer-integrated manufacturing and FMS · Mechatronics, sensors and PLC control · Material handling and plant layout · Production planning and control · Metrology and quality inspection