Conveyors in Manufacturing: Special but Simple

March 1, 2011
Modular, operator-friendly conveyor systems are helping manufacturers make better use of production space and handle an ever-broadening array of product shapes and sizes.

There’s a golden rule material handling managers must live by when running conveyor through their manufacturing operations: “The best move is the shortest.”

The link from one process to the next needs to be efficient and that means the shortest distance. In manufacturing, that link may be horizontal or vertical—and ergonomic as well. That often calls for more specialized conveyor than is used in a distribution center or warehouse. The specialization could be related to load size or the way the load is positioned or how it is buffered. Even a standard load footprint, such as a tote or a pallet load, may have to be tilted, adjusted or elevated once it reaches a work cell.

Whether delivering goods to people or robots, space efficiency and consistent workflow are vital. That’s why conveyor manufacturers put a lot of R&D into interfacing with buffers and sequencing systems, according to Ken Ruehrdanz, market development manager for Dematic Corp., a producer of material handling solutions.

Efficiency in the Air

“As you go from one work cell to the next, the rates might not be a one-to-one flow, so in manufacturing you often need to use buffers to stage product between the processes,” Ruehrdanz notes. “Conveyor has to interface effectively with these buffers, and that means using lifts to elevate product above the factory floor. Going overhead is a trend because you want to use the space effectively. Even if it’s a low-height building, there may be 10 or 20 feet overhead that could still be used as a buffer, so your conveyor system has to effectively interface to these buffer subsystems. We’re not talking about some 80 to 100 ft high storage buffer, just three to four layers of product in a 15-foot area.”

Dematic has installed such systems for electronics manufacturers, which commonly buffer items such as sensors and controls above a work area. For example, the Siemens Electronics manufacturing plant in Amberg, Germany, makes 50,000 electronic control devices. The heart of the system is a conveyor circuit located above the production lines, connecting these lines to each other. Standard loads are buffered in two logical warehouse areas. These are located at different positions, so their feeder speeds to the production line also differ. The line buffers are above production and each has one or two Dematic Multishuttle vehicles serving storage bins and supply trays to automated line palletizers.

“Many existing buildings have enough height to do this kind of thing, and it’s space that’s typically not very effectively used,” Ruehrdanz says. “You can add this buffer without having to punch a hole in the roof or even take up valuable floor space. You can’t put a miniload AS/RS overhead in a factory.”

Ross Halket, director of automated systems for Schaefer Systems International, a manufacturer and integrator of material handling automation, agrees that the ceiling is a good place for conveyors in a plant. That leaves clear space on the floor for expansion. That was the concept behind their Auto Cruiser, a rail-guided unit load transporter designed to fill an application gap between lift trucks and conventional conveyor systems. The system’s light weight means it can be hung on the ceiling without worry that the building’s structural strength will be compromised. Halket believes this concept may be getting more attention from U.S.-based manufacturers who want to adopt lean practices.

“Appliance manufacturers want to be as lean as possible,” he says. “So they’re working on alternatives to line-side supply, and doing right-piece, right-time. One of our clients is doing put-to-light to improve accuracy [on the line]. And when you see robotics come into play in a lights-out system, the contingency plan for that design is to make sure everything’s taken care of—with more conveyor. A big energy bite can be taken out of manufacturing with energy efficient equipment. Our equipment goes to sleep when not in use.”

User Control for Better Fit

Another trend Halket sees making its way to the U.S. from Europe is reducing conveyor by raising the level of software control of specialized equipment in a more compact area.

Chris Glenn, director of product technology at Hytrol Conveyor Co., Inc., a manufacturer of conveyor systems and components, says he is involved in more sophisticated development projects as a result of the drive toward lean manufacturing. Many of his projects are managed from Hytrol’s Technology Center, where concepts are tested and equipment is put through its paces. The new modularity of controls and hardware makes it easier to meet conveying challenges brought about by constantly evolving packaging trends.

“Manufacturers say they’re moving more and more away from conveyability because their product will change so much, but we find that if the footprint stays the same in one direction or the other our EZLogic conveyor can digest changes in length,” Glenn says. “One of our biggest customers for whom we did our highest throughput system was a food manufacturer. It’s all about conveyability for companies like this, as their product sizes shrink down to as little as 6 inches by 6 inches.”

Gregg Goodner, president of Hytrol, adds that along with conveyability, the interface with workers on the line is important from an ergonomic perspective. He cites a window manufacturer to illustrate his point. The system incorporates “window flippers” for better work positioning on the line.

“They wanted to tilt the windows at a 45 degree angle so employees could work on them more easily,” he explains. “The windows move down to another workstation, and are rotated 180 degrees so people can work on the bottom half of the window first, then on the top half. We made that rotating device. We’ve also done mattress flippers so we could convey mattresses through production.”

Better Buffer Control

With all the marketing-driven packaging changes happening in the food and beverage industries, conveyors used in today’s most modern production facilities offer a glimpse of material handling best practices. In keeping with the less-is-more philosophy mentioned earlier, there’s a closer coupling of end-of-line palletizing to packers. The long lengths of accumulation conveyor typical in such operations a decade ago have been cut in half. The type of conveyor is changing, too.

“It used to be zero pressure type accumulation conveyors were used extensively, and it was thought that the more you put in the better,” says Bryan Boyce, product manager for Intelligrated, a provider of material handling automation. “Now it’s used in key areas for short bursts of accumulation buffering. That means less conveyor and fewer controls. Additionally, the conveyor accumulation is generally operated by air, and with a 24 volt DC motor on top of it to run the smart zone control, you can reduce energy consumption as well.”

He adds that to make better use of vertical space, spiral type lifts are an efficient alternative to engineering long runs of inclined conveyor. Package downsizing is driving that, too. It has made the degree of incline drop lower and lower, necessitating those longer runs.

“It used to be you could do 20 degrees,” Boyce says. “Now the packaging is driving companies to be in the five to 10 degree range. When you have to get up as high as you need to, that’s a long run of conveyor. Sometimes it even forces you to do back-to-back because you can’t do it in a single incline, so that’s why we’re seeing more use of spiral lifts.”

Modularity Meets Energy Efficiency

Packaging trends are also driving programmability trends in production conveyors. Zone control and localized I/O are reducing the number of photo eyes deployed in a system, and robots are increasingly being controlled by PLCs instead of the proprietary controls their vendors provided. That also creates an easy interface between the robotic arm and the conveyor for overall system control.

Under that modularity umbrella, those photo eyes are now pre-wired plug-and- play modules, to be deployed when and where needed along with localized motor controls. Large centralized control cabinets are going the way of large, energy-sucking motors. The new Energy Independence and Security Act (EISA) passed late last year by the federal government is driving the use of high efficiency motors.

“The use of variable frequency drive controllers for running conveyors at the speeds required for whatever packaging you’re running was accepted first in manufacturing, and now federal law requiring energy efficient motors will help drive it in warehousing and distribution,” Boyce predicts. “There’s also more attention being paid to motor driven roller conveyor in manufacturing, which was already somewhat accepted in various areas in warehousing and distribution.”

Conveying Trends

This all means faster conveyor system implementations, starting at the conveyor OEM’s factory where as many of the customer’s specifications will be pre-wired and pre-mounted. Hytrol’s Gregg Goodner adds another prediction: All this modularity and flexibility will drive a trend toward leasing through third-party logistics providers (3PLs).

“The end user can avoid capital outlay by leasing,” he says. “Some of the 3PLs we’ve worked with have bought the equipment, bought or leased the facility and managed the people. The only cost to the end user becomes some leasing arrangement with that 3PL. They don’t have the capital investment in the equipment or the facility. These agreements are ranging anywhere between three to 10 years. This could happen in manufacturing as well, although it’s somewhat easier to run a distribution operation than manufacturing.”

With flexibility growing on both the equipment and the service sides, material handling managers who have been putting off a system investment have a good reason to take a fresh look at these new conveyor options.