Roller Conveyor

What is a Roller Conveyor

A roller conveyor is a unit-load handling device that transports discrete objects, boxes, totes, trays, drums, crates and pallets, along a series of parallel rollers mounted at fixed centres between two frame rails. Each roller is a tube spinning on an axle through two end bearings. Unlike a belt conveyor, which carries product on a continuous surface and handles loose bulk or small items, a roller conveyor needs a rigid, flat-bottomed load that can bridge at least three rollers. This is the defining boundary of the category: a roller conveyor moves parcels and pallets, not powder or gravel.

Mechanically every roller conveyor reduces to four elements. First, the rollers, which are the load-bearing rolling elements, defined by tube diameter, wall thickness, length, axle size and bearing class. Second, the frame, usually formed-steel channel or structural channel that sets the between-frame width and resists the distributed load. Third, the supports, floor stands or ceiling hangers that fix elevation and pitch. Fourth, in powered versions, the drive, a chain, belt, lineshaft or built-in roller motor that turns the rollers. The interplay of these four elements, not any single roller spec, determines what a given conveyor can carry and how fast.

The roller conveyor is one of the oldest powered-handling formats in industry. Free-spinning roller decks were used to move heavy goods through nineteenth-century foundries and warehouses, and the gravity roller section remains essentially unchanged in principle. The live roller conveyor matured through the twentieth century: chain driven live roller (CDLR) beds carried heavy castings and pallets, belt driven live roller (BDLR) units brought quieter carton handling, and the lineshaft conveyor introduced slip-clutch accumulation. The most recent shift, from roughly the 2000s, is the motor driven roller (MDR): a brushless DC gearmotor built inside the roller itself, turning the conveyor into a string of independently controlled, low-voltage zones.

In scale terms roller conveyors span an enormous range. A portable flexible gravity conveyor may carry a few kilograms per roller and stretch across a loading dock, while a heavy chain-driven pallet line carries several hundred kilograms per roller and thousands of kilograms per section. Speeds run from a slow hand-fed gravity transfer to powered lines around 0.05 to 1 metre per second (about 10 to 200 feet per minute) for unit handling, with high-rate sortation feeds running faster still. No single roller conveyor covers this whole envelope; engineering selection means mapping the real load and throughput onto the correct type and roller class.

Four engineering questions decide the design: how heavy and how large is the load, how fast and how continuous is the flow, does product need to accumulate without damage, and what controls and power are available. These four shape every later choice of drive, roller, frame and pitch. The chapters that follow work through them in order, starting with the most consequential branch point, gravity versus powered.

Gravity and Powered Types

The first selection decision is whether the conveyor is non-powered (gravity) or powered (live roller). This single choice fixes cost, controllability and the rest of the specification. The ANSI/CEMA unit-handling standards formalise the split: CEMA 401 covers non-powered roller conveyors, while CEMA 404, 406 and 407 cover the powered live-roller families. The table below maps the principal types, their drive, typical load class and where each fits.

Gravity roller conveyors have freely spinning rollers and no drive. Product moves either by an operator pushing it along a level run or by a gentle decline that lets the load roll under its own weight. They are the cheapest format, need no electricity and no controls, and are ideal for short transfers, pack and inspect stations and dock loading. The practical limitation is control: speed builds with slope and weight, so a long decline can accelerate a load to an unsafe discharge velocity unless the grade is stepped or a brake roller is added. The companion format, the skatewheel conveyor, replaces tube rollers with rows of small wheels on common axles, giving very low rolling resistance for light cartons and flexible expandable sections, but it cannot carry heavy or small-footprint loads.

Powered (live roller) conveyors drive every load-carrying roller, so the conveyor runs at a controlled speed on the level, climbs gentle inclines, and integrates with sensors and a PLC. Power is delivered four ways, by belt, chain, lineshaft or built-in motor, and that drive choice, covered in Chapter 3, is the heart of live-roller selection. The reasons to pay for power are metered throughput, reliable accumulation, long horizontal runs and automation. A useful rule: choose gravity when an operator is present and the run is short, and choose powered when throughput must be predictable, product must accumulate without contact, or the line is too long to push by hand.

Geometry adds a second dimension to the type map. Straight sections handle the bulk of any layout, but curves, 30, 45 and 90 degree turns, demand tapered rollers whose diameter is larger at the outer radius than the inner radius, so the load surface speed stays matched to the adjacent straight sections and the product holds its orientation through the bend. Spurs, merges and transfers add or remove product from the main line, and a spiral or incline section changes elevation. Each geometric element carries its own roller and drive constraints, which is why a full system is specified section by section rather than as one uniform conveyor.

Live Roller Drive Technologies

Within powered roller conveyors, four drive technologies dominate: chain driven live roller (CDLR), belt driven live roller (BDLR), lineshaft, and motor driven roller (MDR). Each balances load capacity, noise, maintenance, accumulation behaviour and controls differently, and each maps to a CEMA standard. There is no universally best drive; the right one follows from load weight and the accumulation requirement. The table compares the four on the metrics that decide a project.

Chain driven live roller (CDLR) fits a sprocket to each roller end and links neighbouring rollers with short roller chains, so torque passes positively from roller to roller with no slip. This makes CDLR the heavy-duty standard for pallets, drums, grid containers and automotive components, with per-roller capacity commonly in the range of about 150 to 700 kg and section totals in the thousands of kilograms. The positive drive is its strength and its constraint: because rollers cannot slip, plain CDLR does not accumulate on its own, and engineered accumulation requires clutch packs or brake-meter-belt zones. Chains also need guarding and periodic lubrication, raising maintenance relative to belt and motor drives. Roll-to-roll (RTR) single-chain and continuous-chain variants trade flexibility against load.

Belt driven live roller (BDLR) presses a flat belt against the underside of the carrying rollers from below; friction between belt and roller turns each roller. Because the drive is friction rather than a positive link, a load held stationary on the bed lets the rollers slip beneath it, giving inherent low-pressure accumulation without external controls. BDLR runs quietly, has few moving parts and low maintenance, and suits cartons and totes in the light-to-medium class, roughly up to 50 to 90 kg. Its limits are heavy loads, where belt friction cannot transmit enough torque, and high-temperature or oily environments that degrade the belt. Curved BDLR sections use 2.5 inch tapered rollers to keep load orientation through 30, 45 and 90 degree turns.

Lineshaft conveyors run a single rotating shaft beneath the rollers, with one spool per roller and an elastic polyurethane O-band looped from each spool to its roller. Because the spools sit slightly loose on the shaft, they act as friction clutches: under back pressure the band slips and the roller stalls while the rest of the line keeps moving, delivering quiet low-pressure accumulation. Lineshaft is a light-duty format, typically up to around 50 kg, well suited to cartons and totes where quiet operation, low energy use and flexible layout matter. Band wear and shaft alignment are the main service items.

Motor driven roller (MDR), also called a 24 V or 48 V motorized-roller conveyor, builds a brushless DC gearmotor inside selected rollers; each motorized roller then drives the idle rollers in its zone through O-band or poly-vee belts. A representative product, the Interroll RollerDrive EC5000, is a 50 mm (1.9 inch) tube available in 24 V and 48 V, in 20, 35 and 50 watt classes, with a nominal torque near 0.89 Nm at an 18 to 1 gear ratio, IP54 sealing and a 0 to 40 degree Celsius standard ambient range. MDR is the format behind most modern e-commerce and zoned-accumulation lines: each zone runs only when a sensor calls it, which cuts energy and noise, it brakes with energy recovery, it carries no central shaft or exposed chain, and it delivers native zero-pressure accumulation under PLC control. Typical unit-handling speeds span about 0.05 to 1 metre per second (10 to 200 feet per minute).

Roller Construction and Materials

The roller is the heart of the conveyor, and its construction, tube diameter, wall thickness, axle, bearing and surface, sets the load, speed and environment the conveyor can serve. A roller is a metal or plastic tube closed at each end by a bearing housing through which a fixed axle passes; the load presses on the tube, the tube spins on the bearings, and the axle locks into the frame. Getting the roller class wrong is the most common cause of premature wear, noise and dropped capacity.

Tube diameter follows the load. Light totes and cartons use 1.4 inch (35.8 mm) and the very common 1.9 inch (48.6 mm) rollers; medium unit loads step up to 1.9 inch and 2.5 inch (60.3 mm); heavy pallets, drums and steel stock use 2.5 inch and 3.5 inch (89 mm) tubes. Wall thickness scales with duty: light PVC and steel rollers start around 1.4 to 1.65 mm, general-duty steel runs near 2 to 3 mm, and heavy CDLR tubes reach 3.5 to 5 mm or more. The axle, commonly 11 mm hex through to 20 mm and larger, carries the load into the frame and resists deflection, while the bearing class, from non-precision through semi-precision to ABEC-rated precision bearings, sets the speed ceiling and the noise: precision bearings suit lines up to around 180 metres per minute (600 feet per minute), semi-precision suit moderate speeds, and non-precision suit slow manual decks.

Tube material and surface set the environment and product fit. Plain and galvanized steel is the general-duty default, strong and economical, with galvanizing adding corrosion resistance. Stainless steel (304 or 316) withstands washdown, humidity and corrosive media and is the standard for food, beverage and pharmaceutical lines. Aluminium is light and suits portable or wet light-duty units. A PVC, rubber or polyurethane sleeve over the tube adds grip, dampens noise and protects fragile product; polyurethane lagging operates roughly from minus 62 to plus 93 degrees Celsius (minus 80 to plus 200 degrees Fahrenheit). The table below is a quick reference for matching material to duty.

Two construction details deserve attention at selection. First, driven rollers in BDLR, lineshaft and MDR systems carry extra features, grooves for O-bands or poly-vee belts, or sprockets for chain, so the roller part number differs from a plain gravity roller and must match the drive. Second, the frame and roller share the load path: a strong roller in a weak frame, or rollers spaced too far apart, fails regardless of tube rating. The next chapter turns to the numeric parameters, including pitch and capacity, that tie roller, frame and load together.

Key Specification Parameters

Reading a roller conveyor datasheet means weighing the parameters that actually govern selection. Many sheets list a dozen dimensions, but eight drive the decision: load capacity, roller pitch, between-frame width, roller diameter and wall, conveyor speed, slope (for gravity), frame rating, and drive and controls. Each is explained below.

Load capacity is set by the weakest of three links: the roller tube and bearing rating, the roller pitch, and the frame. Per-roller capacity runs from a few kilograms on light 1.4 mm rollers to several hundred kilograms on heavy steel CDLR rollers. The frame caps the distributed load per section, often in the thousands of kilograms for a 5 inch structural-channel section supported on close centres. Always read per-roller, per-section and per-support figures together rather than quoting a single number.

Roller pitch, the centre-to-centre roller spacing, is the most misunderstood parameter. The governing rule is that at least three rollers, ideally more, must support the load at all times, so pitch should be no greater than one third of the shortest product dimension. Too coarse a pitch lets a load drop between rollers, stall or tip; too fine a pitch wastes rollers and cost. Between-frame (BF) width is the clear roller length between frame rails and must exceed the widest product by a margin so loads do not bind. These two geometric parameters, set before any drive choice, often decide whether a conveyor works at all.

Conveyor speed matters for powered units: unit-handling lines typically run about 0.05 to 1 metre per second (10 to 200 feet per minute), with sortation feeds higher, and the bearing class must suit the speed. Slope is the gravity-conveyor equivalent: a starting grade of roughly 3.5 to 4.5 inches of drop per 10 feet (about 1.7 to 2.2 degrees), trimmed for load weight, with heavier loads needing less grade. Roller diameter and wall tie back to Chapter 4 and set the load and speed envelope.

Frame and supports turn roller capacity into a real installation. Frame channel depth (commonly 4 to 6 inches structural), support spacing (often 1.5 to 3 metre centres) and mounting (floor stands or ceiling hangers) determine the distributed load the section actually carries and the elevation and pitch it holds. Drive and controls close the specification for powered units:

• Drive type: chain (CDLR), belt (BDLR), lineshaft, or built-in motor (MDR), each with its own load, noise and accumulation profile.
• Voltage and power: MDR rollers use 24 V or 48 V DC at 20 to 50 watt classes; central-motor drives use standard three-phase gearmotors.
• Accumulation grade: none, low-pressure, or zero-pressure (ZPA), set by drive type and zone controls.
• Controls interface: photo-eyes, zone control cards, PLC or fieldbus integration for powered and sortation lines.
• Environment rating: ingress protection (for example IP54 on MDR rollers) and ambient temperature window, such as the 0 to 40 degree Celsius standard range of typical motorized rollers.

Two parameters are routinely under-specified and cause field problems: roller pitch (set against the smallest, not the average, product) and frame support spacing (which silently caps the section load). Confirm both against the supplier's roller load curve and frame rating, not a headline capacity figure.

Selection Decision Factors

To turn the preceding chapters into a real order, follow the decision sequence below. Most selection mistakes come not from one wrong number but from deciding the drive or roller before the load and geometry are fixed. These eight steps double as an RFQ template.

1. Load profile: Establish the heaviest and lightest, largest and smallest loads, their weight, footprint and base condition (rigid, flat, or needing a carrier). The smallest, lightest load usually sets pitch and slope; the heaviest sets roller class and frame.
2. Gravity or powered: Choose gravity for short, attended, low-throughput transfers; choose powered for metered throughput, long runs, inclines or accumulation. This branch fixes most of the rest of the spec.
3. Drive technology: For powered units pick CDLR for heavy positive drive, BDLR for quiet medium-duty with low-pressure accumulation, lineshaft for light quiet accumulation, or MDR for zoned zero-pressure lines under PLC control (Chapter 3).
4. Roller and pitch: Select tube diameter, wall and bearing class for the load and speed, then set roller pitch no greater than one third of the shortest product dimension so at least three rollers always carry the load (Chapters 4 and 5).
5. Geometry and width: Lay out straights, curves (tapered rollers), spurs, merges and elevation changes; set between-frame width with clearance over the widest product.
6. Materials and environment: Match tube material and surface to the duty and corrosion environment, steel for general duty, stainless for washdown, sleeves for grip and noise, and confirm the ingress and temperature rating.
7. Accumulation and controls: Define the accumulation grade (none, low-pressure, zero-pressure) and the controls, photo-eyes, zone cards, PLC or fieldbus, that the throughput plan needs.
8. Standards and total cost: Confirm the applicable CEMA class (401 / 404 / 406 / 407) or BS 2567, CE marking under the Machinery Directive for powered systems, then weigh purchase price against energy, maintenance (chain lube versus motor zones), spares and downtime over the conveyor's life.

One often-overlooked dimension is serviceability and integration: roller and motor spare-part availability, the standardisation of roller lengths and bearings, the openness of the zone-control and PLC interface, and local support for commissioning and repair. A conveyor that is cheaper to buy but uses non-standard rollers or a closed control protocol can cost far more across a 10 to 15 year service life. Established suppliers across the category include Interroll and Rulmeca for rollers and RollerDrives, Dematic, Honeywell Intelligrated, Daifuku and TGW for integrated systems, and Omni Metalcraft, Hytrol, Ashland Conveyor and Rolcon for standard sections and replacement rollers, all of which publish the roller load curves, frame ratings and CEMA classes a buyer should verify before ordering.