Updated August 2019 || Conveyors are automated tracks that move bulk material or discrete products from one area to another. They’re the backbone of myriad material-handling applications to improve efficiency and throughput.
Recent advances in materials, controls, and modular subcomponents have spurred new large conveyors for bulk material transport, miniature conveyors for discrete sorting, and everything in between.
Just about any product made of metal, food, cosmetics, medical supplies, plastics, or boxes move on a conveyor during manufacture. No wonder that conveyors come in all shapes and sizes, from belt widths of less than two inches (for moving extremely small parts) to several feet wide for transferring bulk substances. Once viewed as an afterthought, conveyors have become an integral component in myriad automated facilities and applications.
2. Dorner’s Hartland, Wis. location became ISO 9001:2015 certified earlier this year. Conveyor-fabrication image courtesy Dorner
3. Activated Roller Belt (ARB) conveyor technology from Intralox is based on modular plastic belting with in-belt actuation to move discrete products laterally across the conveyor. It is suitable for quick on-the-fly tasks related to product merging, sorting, and switching.
4. This is another conveyor from mk North America with a food-grade fabric belt.
5. Motion Index Drives Stainless Steel Precision Link Indexing setups exceed requirements for washdown common in food-processing facilities. Heavy corrosive chemicals in such settings would corrode standard steel components. Click to enlarge.
Factors to consider when selecting a conveyor
To select a conveyor, first answer these questions about the application.
1. What types of product is the application moving? Conveyors for material handling of bulk product are more rugged than those for moving discrete product. In contrast, the latter often requires conveyors that can advance product with more precision.
2. How does surrounding equipment interact with the product riding on the conveyor? Conveyor class 1 includes material-handling uses in which the conveyor serves as an artery to transport bulk or discrete product in a steady stream (with little interaction along the way). Class 2 includes conveyors that act as bridges to take product from one location or machine to another. Class 3 includes conveyors that take materials into or out of machines or stations; class 4 includes conveyors that run right through machinery without break.
The first two classes generally prioritize ruggedness or throughput. The last two classes need positioning and (in many cases) custom workpiece pucks to steady product while machines perform work on the product pieces.
3. What is the maximum weight of the product being moved?
4. Does the conveyor need to operate at a certain speed?
5. Does the application require the conveyor system to have inclines, declines or curves? Look for conveyor features that secure or enclose material or product onto the conveyor.
6. Will moisture be present in the application? Does the application need to be sanitary? Look for rugged or washdown-ready conveyors with open frames.
Conveyor choices for discrete-product transport
Most conveyors in light to medium-duty discrete-transport applications use belt that’s wrapped around two or more pulleys. A motor powers the pulleys that in turn engage the conveyor belt. Styles and materials abound to meet specific applications.
Some belts are low friction so product can slide a bit for accumulation. In contrast, high-friction belts have more grip to better hold products to the belt. Engineers can design such conveyors to meet exact application specifications. Here are some options.
Magnetic conveyors are built with ceramic magnets for applications that need parts to adhere to the belt during processing, or for jobs that require elevation changes. The designer can specify higher magnet strength for use in inverted applications. In contrast, metal-free conveyors have Delrin bedplates (instead of the traditional steel bedplate) under sections where metal-scanning equipment checks product—usually food—for metal shavings. (Delrin is an inflexible polymer that works as a tough, heat-resistant metal substitute.) This lets a device check passing product without getting false readings.
Case in point: The CAMCO iQue conveyor is based off a programmable linear drive for independent control of magnetically propelled cars in forward or reverse at varying speeds and in batch or asynchronous sequences. Such conveying designs are increasingly common.
Pivot conveyors mount to a pivot base to swing out of the way when workers need to walk through the line. Interlock switches and a timer let the conveyor clear before the gate opens. Some controls can resume product flow automatically resume after the conveyor returns to the inline position.
Servo drives accurately start and stop belt conveyors to provide precise part location. They also let engineers control acceleration and deceleration, so are most suitable for conveyors used in assembly operations. Manufacturers mount encoders to a conveyor’s drive shaft to sense shaft rotation or count pulley revolutions for accurate control of the belt in feeding or indexing applications.
Single-drive multi-belt conveyors serve two or more lanes of product for the sake of efficiency. Here, two or more conveyors run off a single gearmotor on a common drive shaft or coupled shafts. In some arrangements, the belts even mount to a single conveyor frame. For more information on this and the topic of conveyor efficiency, read the related article: How to reduce energy use of conveyor systems.
Timing-belt conveyors use toothed belts that engage synchronous drive pulleys while serving as the conveyor surface as well. These provide excellent belt-movement control for accurate part or fixture positioning.
Vacuum conveyors work with a perforated belt that draws air through grooves in the conveyor bedplate to hold light or flimsy parts on inclines or during especially fast transport.
Side note on conveyor choices for bulk material handling
Traditional options for large bulk conveyors include belt, cleated-belt, screw, roller-pin, and chain conveyors. But no matter the subtype, conveyors for bulk material handling are increasingly custom. For example, natural-gas extraction needs machinery to transport frack sand. Here, belt conveyors with cleats are common … and now, new compounds, cleat profiles, and endless-construction options extend life. More specifically, newer synthetic rubbers, aramids, ethylene-propylene-diene-monomer M-class (EPDM) rubbers, and EPM, and woven-basalt layers help such conveyors last longer.
The way engineers specify these large conveyors is also changing. First of all, basic manufacturing processes are slowly incorporating job-specific subcomponents, so users can order equipment tailored to the applications at hand. Second of all, consolidation in North American conveyor distribution plus more value-added services means there’s more installation and maintenance support than ever for end users. Finally, online design tools now let engineers design subcomponents and even record conveyor condition in the field, for easy-than-ever maintenance scheduling.
Maintaining conveyor systems of all types
Once conveying equipment is up and running, it’s imperative it keeps operating well. It doesn’t do anyone any good to have equipment worth hundreds of thousands of dollars sitting idle because the conveyor that feeds it product is down for maintenance. Establishing an ongoing preventive maintenance program for conveyors is one way to trim downtime by catching potential problems before they shut down an entire line.
First consider how much the conveyors operate. Conveyors that run more frequently need more service. So inventory all facility conveyors and log key information, including the make and model of all conveyor parts and their dimensions, motor types, and bearing serial numbers where applicable. Then log all maintenance and schedule future inspections, recording the manufacturers’ phone numbers. There’s no right or wrong way to create an inventory database; it can be as simple or extensive as the facilities manager wants it to be. The purpose is to get control of the conveyor fleet and it for improved performance and uptime.
Another key tenet of a preventive maintenance program is to make a bench stock of common replacement parts for the conveyors.Keep wear items such as rollers, belts, and bearings on hand. After operating conveyors for a while, operators come to know what other parts may require additional maintenance; keep extra stock of those items as well.
For belt conveyors, a general rule is to keep at least two replacement belts on hand. If personnel sees frayed or ripped belt, replace it immediately.
Although belt swaps interrupt production, ignoring signs of wear puts the conveyor at risk of failure during production, which in turn can damage surrounding (often expensive) machinery. Some conveyor manufacturers even offer kits that include common replacement parts for an easy and time-saving way to stock repair parts.
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