New Life for Conveyors
By using modular conveyors, assemblers ensure their investment can evolve along with changing production needs.
In his 1984 novel, The Unbearable Lightness of Being, Czech intellectual Milan Kundera took the philosophical position that, because each of us has only one life to live, decisions, ultimately, do not matter. But, as any production engineer worth his salt knows, that's a bunch of hooey.
Decisions do matter-a lot. This is especially true when allocating resources or making capital investments in a new facility or production line. On the one hand, to over-invest, or overbuild a process means you've wasted money. On the other, if a particular process or system can't handle future production needs, you may find yourself building the thing all over again a couple of years down the road.
Luckily, when dealing with small- to mid-sized and even some larger components, production engineers have the option of implementing any one of the recent generation of nonsynchronous modular conveyors. In a sense, these provide engineers with "take backs" of the kind that would never be allowed on a school playground. They also allow a production line to evolve with market demand. Conveyors can be upgraded, enlarged, downsized or even rebuilt from the floor up. Generally, these changes require just a handful of simple tools. No longer is a conveyor system set in stone.
For example, Quickdraw Conveyor Systems' products were specifically designed for use in automation processes. Their low-profile, open-center, slip-roller design can easily be integrated with a variety of automation processes. The company's lineup includes the standard MR series and the heavy-duty HD series. In both cases, the conveyors come in self-contained sections measuring from 6 to 60 inches for the MR and up to 120 inches for the HD.
Each conveyor section includes its own motor to power a series of slip rollers. These rollers, in turn, move the workpieces via configurable pallets. In some cases-for example, if the product is flat and square, like a data-tape assembly-products can be transported directly by the rollers. But, in the majority of cases, workpieces are fixtured to a pallet.
The conveyors feature a twin-rail, open-center design, and are available in both fixed and adjustable widths. Because of their low-profile design, the conveyors are easy to integrate with robotic cells and other automated modules. According to Quickdraw chief technology officer Dave Helgerson, joining two separate conveyor sections is as easy as lining them up end-to-end and attaching connector plates. Helgerson adds that over the past 9 years, he has had some customers reuse their conveyor components in as many as three different lines.
To build up a complete system, a manufacturer simply combines various standardized components, including leg sets; pallet pushers, which transfer pallets from one lane to another; diverters; elevators; and lift and locate docks, which locate pallets within 0.0035 inch for precise operations. Depending on the size of the job and the familiarity of the customer with its products, Quickdraw technicians may be on hand to help install the various components at a customer's production facility. Or the customer may elect to do the work on his own.
Because each of these components is fully modular, they can be easily reconfigured as production needs change. In fact, it's not unusual for customers to install a Quickdraw system with the intent of scaling up the line in the future. Helgerson recalls one customer that was doing electronics assembly using expensive automatic wire bonders. The customer started production with just enough wire bonders to meet initial demand, then added three more wire bonders to the line 8 months later.
As an added benefit, because the conveyor sections are fully self-contained, they can be sent off to different machine builders so that the systems can be tested in-house before they are shipped to the customer's manufacturing facility. The result is a system that has already been debugged and calibrated, so that it is truly plug-and-play.
Similar in concept are sectional belt conveyors built by companies like SmartMove Conveyors (Fall River, MA). In the case of the SmartMove line, preassembled conveyor sections can be run independently, or linked together, so that they run off a single drive. The conveyors can be mounted on interchangeable legs or simply placed on a tabletop. They are also available on casters, so employees can easily roll them from place to place, depending on production needs.
Another manufacturer using this type of approach is Montech LLC (Huntersville, NC), which offers what it calls its TB, KTB and GTB belt conveyors. These conveyors are all based on a standard chassis that can be trimmed to size to accommodate various production needs.
These systems can all be used either with Montech's own motors and belts, or with motors and belts from a locally sourced supplier. This can not only save manufacturers money, it helps systems integrators meet pressing deadlines. Often, integrators don't know where all the components are going until the last minute. By having various Montech conveyor parts in stock, a systems integrator can begin assembling the basic framework as soon as the layout is finalized. Motors and belts, which aren't attached until the basic framework is assembled, can then be installed when they arrive from the supplier.
For those looking for more complex conveyor systems, Montech also offers its LTE system. This is basically the TB belt conveyor equipped with components like turning modules, fixturing modules and diverters. Then there is the company's Montrac system. This turns the entire conveyor concept on its head by having a series of independent, powered shuttles convey various workpiece pallets over a fixed track.
Like its more conventional brethren, the track sections that make up a Montrac system are highly modular, so a system can be upgraded or reconfigured as production needs change. Reconfiguring a system is made especially easy, because each track section comes complete with its own I/O. Programming is done directly through the different track sections, which communicate with the various shuttles as they pass overhead, streamlining the process of producing multiple products on a single line. It is this kind of flexibility--the ability to easily accommodate multiple products within a single system--that manufacturers are often searching for in today's build-to-order production environment.
Another approach to modular conveyors is based on the concept of extruded aluminum framing. Specifically, the profiles include slots that accept various belts, chains and accessories, in addition to the basic nuts and bolts used to join the frame pieces themselves. Accessories and components are all standardized, so that they will be infinitely interchangeable.
For example, FlexLink Systems Inc. (Allentown, PA), one of the pioneers in this area of modular conveyors, manufactures and markets a wide range of systems used in everything from the aerospace sector to the electronics industry. These include the XT line of module-based twin-rail, or twin-track, conveyors and the "X" series of single-chain conveyors. The latter includes the XK line to handle heavier loads, like those found in the automotive industry.
Similarly, Automation & Modular Components Inc. (AMC, Davisburg, MI) manufactures a variety of conveyors, including the Modu-Flex 83 single-track chain system, and a number of different iterations of the company's twin-rail Modu-Con line.
For its part, Bosch Rexroth Corp. (Buchanan, MI) offers the TS1, TSplus and TS4plus, a line of twin-rail conveyors that can accommodate everything from lightweight medical assemblies to workpieces weighing over 500 pounds. The company also manufactures various single-chain conveyors as part of its VarioFlow line.
When looking at these kinds of systems, one of the first things an assembler has to decide is whether to go with a twin-rail or single-chain system. Twin-rail systems carry individual workpiece pallets on parallel belts, flat-top chain or accumulation-roller chain. Whatever the medium, they rely on friction to carry each pallet forward, with the belt or chain simply sliding under the pallet whenever it comes in contact with a stop. They offer stability, which can be important if a workpiece has a high center of gravity. They also allow access to a workpiece from directly below.
Single-rail chain systems, on the other hand, employ a single strand of flat-top chain which can be used to convey a pallet or to directly support the workpiece. While these systems don't offer the same inherent stability as their parallel-rail counterparts, they can be equipped with guide rails to keep product in position. Different types of chain also come with cleats or friction strips to help transport products up inclines. Single-chain conveyors have an advantage in that they are less expensive and less complicated to install. They are also capable of making sharp turns, a plus in settings where space is an issue.
According to Kevin Gingerich, director of marketing services at Bosch Rexroth, the ultimate deciding factor is precision. A single-chain system like his company's VarioFlow is very good at moving product, but doesn't offer the same precision that can be obtained with a dual-rail approach. The reason for this is that, in a twin-rail system, the locating station can actually engage the pallet from below with the help of precisely positioned locating pins. This kind of precision simply isn't possible when engaging a pallet from the sides, as is necessary when using a single chain.
In either case, conveyor manufacturers offer a host of accessories to facilitate routing, pacing and the presentation of workpieces to both automated cells and manual workstations. These include everything from simple guides and connecting plates to pallet stops, pneumatic elevators, electric elevators, crossovers, turntables, accelerators, transfers, and modules that will lift and rotate each workpiece pallet 90 degrees or 180 degrees.
In addition to being able to swap out flat-top chain styles with a single-chain system-say, from a smooth chain to one with cleats-it is also possible to switch out the transfer medium with many dual-rail systems.
For example, in the case of AMC's Modu-Con series, the basic aluminum extrusion, or track, is the same whether a customer is using belts or chain. The only difference is the type of wear guide pressed into the extrusion's upper groove. To change out the transfer medium, all you need to do is change the guide.
The result is an investment in equipment that can last far beyond its initial use. For example, FlexLink has had customers who have been able to reuse 95 percent of the components from one application in another.
Dick Shore, president at AMC, says his experience has been much the same. "We have equipment that has been in the field for some 15 years, and customers are just now asking for replacement of wear items," he says. "There's a myth that aluminum extruded conveyors do not hold up as well. But, this just isn't true."
Gingerich agrees that the ability to produce multiple products on a single system is many manufacturers' ideal, citing a recent study showing that for a majority of assemblers, this is what they really have in mind when they think of "flexible" manufacturing. He notes this is an area in which a pallet-based system excels, because a variety of fixtures can all be transported over the same medium, so long as they are supported by the same kinds of pallets.
In terms of the types of products that lend themselves to these kinds of systems, Shore says it runs the gamut, from lightweight medical syringes to 1,000-pound axle and power train assemblies. The same goes for the type of assembly process. Extrusion-based modular conveyors can be used with robots and in fully automated systems, in manual assembly environments, or in processes that combine the two. Again, there are a host of accessories that serve to present, stabilize and, if necessary, precisely locate each workpiece for processing. Components also serve to support both the pallet and workpiece in the event a process calls for in-line pressing.
According to Shore, his customers in the electronics and medical device industries tend to be the ones that reconfigure their conveyors the most aggressively, often planning their initial lines with an eye toward future expansion. Shore says manufacturers in the automotive sector tend to stick with their initial configurations. But, they will still take advantage of a system's modularity to tweak a system or maybe add stations.
Finally, there is the DynaCon concept from Dynamic Conveyor Corp. (Muskegon, MI). Originally created to serve the injection molding industry, each DynaCon conveyor is made up of standardized sections that, literally, snap together, and are then secured in place with nuts and bolts. In addition to curves and inclined sections, these lightweight all-plastic conveyors are available with caster-equipped stands, so they can be easily rolled from place to place, depending on production needs.
"In some cases, a single system will be [regularly] used in two or three parts of a plant," says company President, Jill Batka. "Our customers' investments last a lot longer...They no longer have old parts collecting in a conveyor ‘bone yard.'"
Batka says she has had a number of cases in which manufacturers have taken advantage of her products' flexibility to overcome glitches in initial design. She remembers one case, in particular, when a company CEO demanded that operators "replace" a brand-new DynaCon conveyor because it was not performing the way he had envisioned. Instead, workers simply pulled the conveyor apart and rebuilt it in accordance with the boss' wishes. A little while later, the boss was back, pleased with the results and asking workers where they'd found the "new conveyor." Talk about second chances!