Small to big, conveyors get job-specific features

Today’s conveyors perform better than ever thanks to material advances and modular designs tailored to applications. That’s true of miniature conveyors for discrete product sorting, extra-large conveyors for bulk material-handling operations, and everything in between.

Discrete medical, pharmaceutical and assembly applications use the most miniature conveyors, but until the last decade or so, most such conveyors had frames made in-house. Traditional conveyors also have overdesigned bearings and frames, often to ensure safe operation. But the trend today is toward leaner operations that run right-sized systems. The problem is that customizing right-sized conveyors is sometimes hard because the manufacturer must account for the handling and orientation of parts during movement, as well as the application environment.

Small conveyors not just smaller

Consider medical and pharmaceutical product handling: Parts are often small, light and fragile, so are difficult to handle and orient—and must move between conveyors in one processing area to the next. “North American manufacturers shied away from these applications mainly due to the amount of research and development required to make suitable conveyors,” said Mike Hosch, director of engineering at Dorner Manufacturing. That’s because conveyors to move and handle tiny medical and pharmaceutical products need miniature bearings with long lives; small drives with high strength and durability; short belts with consistent fabrication; and effective use of product space.

“Some such miniature conveyors have end rollers reduced to 5⁄8 in. so they fit into tight machine spaces and transfer products as small as 7⁄8-in. in diameter when installers position them end-to-end with other conveyor sections,” said Hosch. Here, the conveyor frame fully encapsulates the bearing housings. That way, end users can also put the conveyors side-by-side and get them nearly flush with only a 1⁄4-in. gap from belt edge to belt edge.

Low-profile miniature conveyors necessitate specialty actuation, and the trend is toward pinch drives. “Typical belt conveyors run under high tension to give the drive roller enough traction to drive the belt, but that necessitates oversized bearings and conveyor rollers. We use pinch drives to let conveyors run with almost no belt tension,” explained Hosch. A conveyor uses two pinch-drive mechanisms, each spring loaded against the drive roller—so the belt can run in either direction under just enough tension to keep the belt flat. The pinch drives force the conveyor belt against the drive roller to give it driving traction without tension. Without the need for high tension, the belt lays flatter, which is essential for keeping lightweight components upright.

“The medical, pharmaceutical and assembling industries have always needed miniature conveyors, but didn’t have many options available to them. That’s changing now as some manufacturers are investing in research into miniature conveyors,” said Hosch.

Increasingly stringent standards for food and drug processing are spurring other conveyor-design changes. Case in point: Engineers from Hudson-Sharp, a Green Bay builder of machines that make plastic bags and re-sealable pouches, recently put a Dorner 3200 Series conveyor into their post-applied slider. This machine adds reusable closures to the tops of large-format pouches. Such closures are common on small wrappers, but there’s a growing market for machines that apply sliders to bags as tall as 36 in.

First, stacks of pouches go on a Dorner 3200 Series conveyor. Then an overhead vacuum-transfer assembly picks them off for processing. Multiple pouch stacks go on the conveyor for picking; the conveyor then indexes them toward the picker for continuous product flow. One catch: The pouches have a slick plastic finish, so Hudson-Sharp engineers need a conveyor belt with a high coefficient of friction to avoid slippage. Initially, Dorner sent Hudson-Sharp a selection of belts for testing. “Dorner sent us several types of friction belting, so we could pick the one that works best for the plastic we move,” said Kristina Vogt, project engineer at Hudson-Sharp. “All the belt options helped eliminate guesswork [so we knew] we specified the right belt ahead of time.” It takes about 16 weeks from time of order to machine installation.

Large conveyors withstand rough material-handling tasks

At the other end of the conveyor size spectrum, larger conveyor installations for material handling (versus discrete motion tasks) are also going custom. Two markets spurring innovation are agriculture and oil and gas.
Consider natural-gas extraction, which needs machinery to transport frack sand. Many operators use conveyors with cleated belts that run fast over long lengths, even though they quickly wear out without special belt profiles and compounds. But now there’s a trend toward material-handling belts with cutting-edge compounds, custom cleat profiles and endless construction to extend conveyor life.

Synthetic rubbers, ethylene-propylene-diene-monomer M-class rubber, or EPDM rubber, and aramids to make conveyor belts are not new materials, but some manufacturers are switching from EPDM for EPM because it processes better and performs as well or better than EPDM in service. “Plus the woven basalt layer in some belts is something that wasn’t used before. This material is better than fiberglass, what we used to use to prevent hot materials from burning completely though belts,” said Lee Brammer, key account manager for the Conveyor Belt Group, ContiTech North America. Belts made of the company’s EPDM also carry hot materials, even to 600° F for the newest version, and splice better than other options, according to Brammer. Such belts protect strength members from hot materials with a cooling layer that reduces heat transfer and a basalt layer that prevents burn-through.

Industry changes for process conveyors

Even the way engineers specify large conveyors is changing. That’s thanks to three trends.
1. Basic processes of manufacturing conveyor belting has been the same for years, but there’s a trend toward new materials and application-specific equipment so users can specify belts to order. Brammer cites his company’s specialty compounding and vulcanizing presses (including DOBA double-banded continuous presses in a facility in Northeim, Germany) as sources for application-specific materials.
2. Recent years have consolidated North American conveyor distribution (so national and international corporations have displaced small independent businesses) even while OEMs and operations engineers now expect value-added services from their distributors—including belt installation, splicing and conveyor maintenance.
3. There are more online conveyor-design tools than ever. “Like most companies, we’ve made efforts to be more active online,” said Brammer. His company offers distributor partners and end users online materials and services. These include an online purchasing site that sells splicing materials and a database and mobile application to simplify field surveys and let users track belt performance and forecast replacements. Online training tools are in the works, and distributors will soon get access.