Roller Conveyor & Gravity Roller Conveyor Systems
A roller conveyor carries boxes, pallets and unit loads on a line of spinning or free-running rollers. It is a different machine from a belt conveyor — and from the conveyor rollers (idlers) that support a belt. Here is how to tell them apart and when each wins.
A roller conveyor transports unit loads — cartons, totes, pallets — on a bed of rotating cylinders. Unlike a conveyor roller (the idler that passively supports a belt), the rollers in a roller conveyor are the conveying surface itself. A gravity roller conveyor has free-spinning rollers set on a slight decline so loads roll by hand or slope; a powered version drives the rollers with a belt, chain or line shaft.
Gravity vs powered roller conveyor
- Gravity roller conveyor — no power, lowest cost, ideal for declines, accumulation and manual lines. Great for sturdy, flat-bottomed loads.
- Powered roller conveyor — rollers driven individually or in zones; handles accumulation, merges and controlled sorting. Used in packaging and distribution.
- Line-shaft / belt-driven — a single shaft or drive belt turns every roller; simple and robust for straight runs.
When to use a roller conveyor
Choose rollers when you move discrete, rigid items rather than loose bulk. Roller conveyors excel at cartons, totes and pallets in warehouses and packaging; a belt conveyor with troughing idlers is the right tool for coal, ore and aggregate. Mixed operations often run both: belt for bulk in, rollers for packed-out cases.
Gravity roller conveyor: design rules
A gravity roller conveyor is the cheapest way to move a carton — no motor, no controls, no power bill. It works because a flat-bottomed, rigid load rolls down even a shallow decline, and it is set by three numbers: slope, roller pitch and roller diameter.
- Slope. Run a gravity roller conveyor at roughly 2 to 5 percent (about 1.5 to 2 degrees) — around 20 to 50 mm of fall per metre. Below about 1.5 percent a loaded carton stalls; above about 6 percent it accelerates and can overrun the end stop. Heavier loads need less slope; light or soft-bottomed loads need more.
- Roller pitch (spacing). Space the rollers so the smallest load always rests on at least three of them — practically, pitch no more than one third of the shortest load length. Closer pitch means smoother travel and less roller load; wider pitch means lower cost and less rolling resistance to overcome.
- Roller diameter and wall. 50 mm, 60 mm and 76 mm steel rollers cover most gravity roller conveyor duty; go up a size when loads are heavy or the span between frame rails is long, because roller deflection under load is what stalls a carton.
- Guard rails and end stops. Fit side guides to keep skewed cartons on track, and a fixed or sprung end stop — plus a brake roller on any decline over about 5 percent — so loads do not shoot off the end of the line.
A gravity roller conveyor is also the standard way to bridge between two powered lines: gravity for accumulation and manual pick faces, powered wherever the product has to climb or hold a controlled rate.
Powered roller conveyor drives
A powered roller conveyor turns every roller instead of only the load's own momentum. There are four common drive methods, and the choice decides how fine the accumulation control is:
- Round-belt (O-ring) drive — a single line shaft or drive roller turns the rest through elastomer O-belts. Simple and cheap, used on straight runs and light accumulation.
- Chain-driven — sprockets on the roller ends carry torque along the line. Robust, high-torque, suits pallets and heavy totes.
- Line-shaft — one powered shaft under the bed drives each roller by a tangential belt. Quiet, easy to zone, and the classic accumulation conveyor.
- Motorised (MDR / 24 V) rollers — a motor inside each roller shell, switched electronically. Zero-pressure accumulation, quiet running and easy re-zoning, at a higher cost per roller.
The roller shell, shaft and bearings in a powered roller conveyor are the same components we build for belt conveyors — HDPE/UHMWPE rollers, polyurethane rollers and the sealed TK bearing housing — so one plant can standardise spares across both machine types.
Roller materials and spacing
Rollers are steel, polyurethane, nylon or plastic (HDPE/UHMWPE) — the same materials as belt-idler shells. Spacing is set by the smallest load: rollers must be close enough that a carton always rests on three. For belt-conveyor support the equivalent choice is carrying idlers and self-aligning idlers, which cradle the belt the same way rollers cradle a box.
Integrating rollers with belt conveyors
At transfer points a roller conveyor often meets a belt line: rollers for accumulation and sortation, belt for the long bulk haul. Both share the same shaft, seal and bearing platform — the TK bearing housing that sets service life — so a plant can standardise spares across roller beds and belt pulleys alike.
Related HBXM components
Frequently asked questions
What is a roller conveyor?
A roller conveyor moves unit loads — cartons, totes, pallets — on a bed of rotating rollers. It is distinct from a belt conveyor (which uses a continuous belt) and from a conveyor roller / idler (the passive support under a belt).
What is the difference between gravity and powered roller conveyor?
A gravity roller conveyor has free-spinning rollers on a slope or pushed by hand — no power, lowest cost. A powered roller conveyor drives the rollers (belt, chain or line shaft) for accumulation, merging and controlled transport.
When should I use a roller conveyor instead of a belt conveyor?
Use rollers for discrete, rigid items like boxes and pallets in warehouses and packaging. Use a belt conveyor with troughing idlers for loose bulk such as coal, ore and aggregate. Many sites run both, with rollers for packed-out cases and belts for bulk.
What are roller conveyor rollers made of?
The same materials as belt-idler shells: steel, polyurethane, nylon or HDPE/UHMWPE, chosen for load, abrasion and corrosion. Spacing is set so the smallest load always rests on at least three rollers.
What slope should a gravity roller conveyor have?
About 2 to 5 percent — roughly 20 to 50 mm of fall per metre, or 1.5 to 2 degrees. Under about 1.5 percent a loaded carton stalls and needs a push; over about 6 percent it accelerates and needs a brake roller and a sturdy end stop. Heavier loads need less slope than light or soft-bottomed ones.
How are powered roller conveyors driven?
Four common ways: round-belt (O-ring) drive from one line shaft, chain drive on sprockets for high torque, a line-shaft under the bed driving each roller tangentially, and motorised (MDR / 24 V) rollers with a motor inside each shell for zero-pressure accumulation. MDR gives the finest zoning at the highest cost per roller.
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