Material handling principles and equipment

Why it matters

Moving material adds cost but no value, yet in most plants it takes a large share of manufacturing cost, floor space and lead time, and it causes many injuries. Choosing the right handling method and equipment, and sizing the fleet correctly, is part of every layout decision.

Key ideas

Material handling is the movement, storage, protection and control of materials throughout manufacturing, warehousing and distribution. The aim is the right material, in the right amount, at the right place and time, in the right condition and orientation, at the right cost (the "seven rights"). The best handling is no handling: first reduce moves through layout and method, then mechanise the moves that remain.

The ten principles of material handling (Material Handling Institute / College-Industry Council)

1. Planning: define needs, performance objectives and functional specifications first.
2. Standardisation: standardise methods, equipment, controls and software where possible, without losing needed flexibility.
3. Work: minimise handling work (flow × distance): eliminate, combine, shorten moves.
4. Ergonomic: fit handling to human capabilities; avoid manual lifting, twisting and repetitive strain.
5. Unit load: move material in standard unit loads (pallets, totes, containers) rather than piece by piece.
6. Space utilisation: use the full cubic space, including height, while keeping aisles clear.
7. System: integrate handling with receiving, inspection, storage, production, packing and shipping as one system.
8. Automation: automate where it improves responsiveness, consistency and cost (conveyors, AGVs, AS/RS, robots).
9. Environmental: consider energy use and environmental impact.
10. Life-cycle cost: judge equipment on total cost over its life (purchase, installation, operation, maintenance, disposal), not purchase price alone.

Equipment classes

• Conveyors: continuous movement over a fixed path; belt, roller (gravity or powered), chain, slat, screw, overhead trolley, tow-line. Good for high, steady volume between fixed points; inflexible and may block aisles.
• Industrial trucks: variable path, intermittent moves; hand trucks, pallet jacks, forklift trucks (counterbalanced, reach), tractor-trailer trains, and automated guided vehicles (AGVs), which follow wires, tape, lasers or maps under computer control.
• Cranes and hoists: lifting and moving heavy loads within a limited area; electric overhead travelling (bridge) cranes, gantry cranes, jib cranes, hoists. They use overhead space and keep the floor free.
• Positioning and unit-load equipment: lift tables, manipulators, industrial robots, pallets, skids, containers.
• Storage: pallet racks, flow racks, mezzanines, automated storage and retrieval systems (AS/RS), carousels.
• Identification and control: bar codes, RFID, warehouse management systems.

Selection factors: material (size, weight, shape, fragility, hazard), move (distance, frequency, path, flow rate, fixed or variable route), method (unit load or bulk, manual or automated), building (floor loading, ceiling height, aisle width, columns) and cost (life-cycle). Fixed path, high volume suggests conveyors; variable path, moderate volume suggests trucks or AGVs; heavy loads in a bay suggest cranes.

Formulas

Handling work = Σ f_ij × d_ij (load-m per period)

Conveyor flow rate R_f = v_c / s_p

• v_c = conveyor speed (m/s); s_p = centre spacing of parts (m); R_f in parts/s.

Transit time on conveyor T = L / v_c; parts on conveyor = L / s_p

• L = conveyor length (m).

Vehicle delivery cycle time T_c = T_L + L_d / v_c + T_U + L_e / v_c

• T_L, T_U = load and unload time (min); L_d = loaded (delivery) distance, L_e = empty return distance (m); v_c = vehicle speed (m/min).

Workload WL = R_f × T_c (min of vehicle time per hour)

• R_f = deliveries per hour.

Available time per vehicle AT = 60 × A × T_f × E_w (min/h)

• A = availability, T_f = traffic factor, E_w = worker efficiency (for manual trucks); use those given.

Number of vehicles n = WL / AT, rounded up

Worked examples

Example 1 (standard). A belt conveyor 75 m long runs at 0.5 m/s, carrying cartons spaced 1.25 m apart. Find the flow rate, the transit time and the number of cartons on the belt.

1. R_f = 0.5 / 1.25 = 0.4 cartons/s = 1,440 cartons/h.
2. T = 75 / 0.5 = 150 s.
3. Cartons on the belt = 75 / 1.25 = 60.

Example 2 (GATE level). An AGV system must make 40 deliveries per hour. Average loaded distance 120 m, average empty return 90 m, vehicle speed 50 m/min, load and unload 0.5 min each. Traffic factor 0.85 (availability taken as 1). How many AGVs are needed?

1. T_c = 0.5 + 120/50 + 0.5 + 90/50 = 0.5 + 2.4 + 0.5 + 1.8 = 5.2 min.
2. WL = 40 × 5.2 = 208 min/h.
3. AT = 60 × 0.85 = 51 min/h per AGV.
4. n = 208 / 51 = 4.08, round up: 5 AGVs.

With 4.08 needed, it is worth checking whether a shorter empty-travel route or faster transfer could bring the requirement to 4 vehicles before buying the fifth.

Common mistakes

• Forgetting the empty return trip in the vehicle cycle.
• Rounding the number of vehicles or trucks down.
• Mixing units: speeds in m/s with distances in m and times in min.
• Calling a conveyor flexible; it serves a fixed path. AGVs and trucks serve variable paths.
• Choosing equipment on purchase price instead of life-cycle cost.

For GATE PI

Expect one-mark questions on the principles of material handling, matching equipment to situations (fixed vs variable path, heavy lifts, unit loads), and NAT questions on conveyor flow rate, transit time, vehicle cycle time and fleet size. Practise the vehicle cycle formula with consistent units.

Quick check

1. A conveyor runs at 20 m/min with parts every 0.8 m. Parts per hour?
2. Which principle says to judge equipment by total cost over its life?
3. Which equipment suits heavy loads moved within a single bay?
4. Workload 150 min/h, available 50 min/h per vehicle. Vehicles needed?

Answers: 1. 20/0.8 × 60 = 1,500 parts/h; 2. Life-cycle cost; 3. An overhead (EOT) crane; 4. 3.