Conveyors: Belt or Roller?
It's a matter of load, situation and function
Belt and roller powered conveyors are specified for a variety of reasons within a given conveyor system. The reasons almost always come down to load characteristics and functionality. Both can be used in transportation, sortation, and accumulation applications. This article delves into the differences and the specific advantages each conveyor type offers.
When should you use a belt system?
- For products that can’t be conveyed on rollers. That’s typically loads like bags, envelopes, small parts, components, fabric and cartons with irregular bottoms. Anything that can’t travel on rollers is a candidate for belt conveying. Belts are much more forgiving on poor loads than rollers, which can drop small items or allow them to tilt between rollers.
- When you convey vertically. Incline conveyors are usually belt applications because rollers don’t grip the load, which can cause slippage or sliding. See more: Inclines vs. Spirals for Vertical
- For machine integration. Many machine integrations, such as packaging equipment, scanners, diverts, and others need control of the load’s orientation to function correctly. Belts don’t allow the load to shift or rotate since they grip the surface. The consistent speed and positioning for belts make them ideal for scan tunnels, where stability is critical for accurate reads.
- For pre-sortation applications. When you need to gap and/or track loads heading toward sortation, belts are ideal. Belts control the product better and work best in these applications. If your system has a curve leading to a sort area, and you must gap or track the load, belts are a good solution.
- For material versatility. Belt curves can be built with a variety of materials, ranging from rubber to high-grit to other specialized and materials that can be easily cleaned. You can specify a large variety of belt types to fit your needs.
- Gapping applications. When setting precise gaps between loads is critical, belt conveyors excel. Because belts support 100% of the load bottom (weight and surface area don’t matter), everything travels at a constant rate.
What about belt curves?
Curves allow systems to effectively use space by letting you redirect product direction at critical points. Many curve applications are based on rollers, but there are situations where belt curves are preferable. When is a belt curve your best option? The main reason you’d specify a belt curve is usually the same one you would use to specify a belt conveyor rather than a roller: belts can handle different load types of loads and control them better than rollers. When a product’s position and orientation are critical, belt conveyors are a better solution. Loads slip less and stay where you need them to on a belt. Belted curves are typically more specialized and expensive than roller curves.
More importantly, even for loads that don’t have issues with fragility, alignment is critical. You may need to align your products for a scanner, scale, taper, or other machinery. Belts let you keep the product exactly where you want it, in the direction you want it.
When to use roller conveyors
Accessories and add-ons
Rollers can accommodate accessories like pins, package stops, pop-up rollers, blades and other options to help stop and precisely control the load. Some possibilities include:
- Lift bars, which fit between rollers and raise/lower the load at need.
- Under-roller scanners.
- Diverts, wheels and pop-up rollers.
Rollers control the load less precisely than belts but offer more types, configurations, and accessories. When a tote or carton is conveyed on rollers, it can move across the rollers and bump the guardrails. For most products, the impacts are minor and don’t cause issues, but for some more fragile loads, you need finer control provided by belt conveyors.
Ease of human interaction
Above: order pickers can easily slide totes loaded with books conveyed on a roller system at Educational Development Corporation
Rollers are easier to deal with when people must push, pull, remove, rotate, and interact with the load. Due to their low coefficient of friction, it’s much easier for a person to slide a tote across rollers than a belt. This is why picking and packing applications are frequently specified with roller conveyors. When you have side-by-side lines that merge loads, roller is the ideal conveyor, whether that’s done by people or mechanical pushers.
Rollers move at inconsistent speeds
Load characteristics may affect the rate of speed an item moves on a roller conveyor. Heavier, larger loads may move slower than light ones on rollers. This may or may not be important to your application, but keep it in mind if constant flow is desired.
Heavy, difficult loads
Most pallet and pipe conveyors tend to be roller systems, due to high capacities. These high-duty loads tend to be better suited for roller systems, although there are specific cases where they are best conveyed by belt.
Your needs, application, load, and system will eventually determine the type of conveyor needed. In many cases, belts and rollers are used at different points within a conveyor system for maximum control and efficient flow. We are always available to assist with the specification and design process.
Scott Stone is Cisco-Eagle's Marketing Director with three decades of experience in material handling, warehousing and industrial operations. He writes on automation, warehousing, safety, manufacturing and other areas of concern for industrial operations.