Belts vs. Live Roller Conveyors: When to Use Each
Belt conveyor and roller conveyor are both used to transport and/or accumulate products within a facility. With similar basic functionality, it may be difficult at times to determine which is the best selection to apply for a specific application. Both roller conveyors and belt conveyors can be utilized for sorting, assembly, inspection, picking and packing operations within manufacturing and distribution facilities; however, each have some specific performance advantages which should be understood for properly selecting for one’s specific need.
The basic differences
Looking at a live roller conveyor versus a belt, it’s easy to tell the difference between the two. A roller conveyor is comprised of rollers directly in contact with the conveyed products which support and transmit motion to the product. Rollers are typically constructed from steel tubing with low friction bearings in each end having a through-shaft for support the roller in the conveyor frame. Occasionally, these rollers may be constructed from composite materials for applying in corrosive or wash-down environments.
Rollers can be powered a number of ways:
- Belt-driven live roller conveyors use v-belts or flat conveyor belts supported with controlled pressure against the bottom of the rollers. Friction between the belt and roller causes the roller to turn when the belt is driven.
- Roll-to-roll driven conveyors utilize loops of chain from roller to roller in sequence so that when one roller is driven they all receive rotational power. Sprockets on rollers with loops of chain may also be substituted with Poly-V belts or simple elastic o’ring bands running in grooves in the rollers. The chain driven roll-to-roll drive type has the most positive drive of the roller conveyors and therefore is use for conveying heavier loads typically at slower speeds.
A belt conveyor is designed with a flat conveyor belt located on its conveying surface to directly support and move the product being conveyed. The belt is supported below by rollers, metal slider pans or plastic strips. The conveyor belt is power by a rotating cylindrical tube, or drive pulley, that spans the width of the belt and often coated with a high friction material called lagging. Belt conveyors can move a variety of products from normal cartons to fragile items, irregularly shaped or weighted items, to bags of materials. The belt conveyor is also a great option for inclines and declines as well as many other applications.
Applications for Live Roller Conveyors
Live rollers conveyors utilize low friction bearings to support the load being conveyed making them efficient in use of power required to convey cartons and totes over long distances.
Rollers may be spaced so accessories may be located below and extend up between the rollers to engage conveyed products and create a specific end result.
Package stops for traffic control points: Steel pins or blades can be manually or pneumatically raised between the rollers to create a physical stoppage of products. Packages may be stopped for traffic control, removal, quality inspection etc.
Diverting wheels: Wheels set at an angle to the direction of flow may be raised between the rollers to divert conveyed products off the conveyor onto another path of flow.
Lift bars: A bar or bars may be raised between the rollers to pick a conveyed product up for some secondary operation such as assembly and then lower back down for conveying on down the line. Another example may be a bar lifting a product and then rotating it before lowering it back down to convey it forward.
Rollers generally have a low coefficient of friction between their surface and the conveyed product. This allows employees to easily push products onto them or pull products off for picking, packing or simply loading from a side table. It also allows you to easily re-orient products sitting on rollers if needed. This type of equipment is ideal for utilizing when products will be side-merged onto a conveyor from another conveyor.
Rollers and roller conveyors may be easily constructed for specific load requirements. The most popular industry standard roller size for package conveyors is 1.9” in diameter. For heavier loads, including pallet loads, popular roller sizes are 2-1/2” or 3-1/2”in diameter. Rollers may be spaced at various distances in the conveyor to accommodate specific product requirements whether it be to meet weight or support requirements. 1.9” diameter rollers are most often spaced on 3” centers; however, with more ecommerce applications where products are smaller, a 2” spacing is growing in popularity. It is important to space rollers relative to the package length to keep a minimum of three rollers supporting a product.
One important factor when utilizing roller conveyors is the reality that products may not always travel at a fixed speed relative to other products. Heavy loads may travel slower than light loads and products that have uneven bottoms can potentially bounce and lose speed more than smooth bottom cartons. Keep in mind that bags of loose material will likely conform to the shape of the rollers and hinder prevent their ability to convey on rollers. In applications where accurately tracking cartons or maintaining gaps between cartons is important, a roller conveyor is not the best choice.
APPLICATIONS FOR BELT CONVEYORS
Belt conveyors provide full support and positive conveyance of products making it a great selection in many applications including:
Conveying irregular products: When a product has an abnormal weight distribution or doesn’t have a flat bottom surface for support, a belt conveyor will serve well for transporting the load.
Bagged products: Materials packaged in bags need the full support of a belt conveyor to conveyor well. Examples: Flour, dog or cat food, polybags used in ecommerce or parcel industry.
Conveying small product: As mentioned earlier, a product should be supported by 3 rollers at all times in order to convey well on a roller conveyor; if it is too small a fit the rule, a belted conveyor may be the best option.
Inclines and declines: To make sure products flow smoothly up an incline and down a decline, a belt conveyor is the best solution when fitted with a belt that grips the product. Inclining belt conveyors are best designed with rollers supporting the belt so the driving friction will be reduced, therefore keeping the horsepower requirements to a minimum. Declining belt conveyors may be best designed with a steel slider pan supporting the belt in lieu of rollers so the higher friction between the belt and the steel pan will prevent the products from trying to push the belt in a stopped condition. Even with the decline drive fitted with a brake motor to aid in preventing drift when stopped, the higher friction of the steel pan will extend the life of the motor brake.
High-speed scan tunnels: Belt conveyors with slider pans supporting the belt ads in keeping products stable while traveling through scan tunnels. This ensures that you get the most good scans possible.
Gapping and Tracking products: When accurately tracking a product’s position or maintaining set gaps is important, a belt conveyor is the right choice. All products, regardless of condition of bottom or weight, will travel at a constant speed when supported by a belt. For this reason, belt conveyors are almost always used for induction systems feeding sortation conveyors.
Belted conveyors and roller conveyors have many of the same functions, but knowing the differences between the two can save you time, money and a lot of frustration down the line. This is a general introduction to live roller conveyor and belted conveyor, but we’re always happy to talk more about your options.