Modular designs carry the future
While speed, noise, and quality continue to be major areas of importance in the design and installation of conveying systems used in factories, flexibility is the feature most sought by today's manufacturing facilities.
By David Maloney -- Modern Materials Handling, 9/1/1999
Conveyors have always been an integral part of manufacturing operations, especially heavy manufacturing. Power-and-free and tow line designs have a long history of moving work-in-process such as cars, trucks, and steel.But in recent years, the real area of growth is in light manufacturing, especially final assembly. As the high tech industries have grown at a rapid rate, they have generated strong demand for lighter duty conveyors for assembly applications.
Modular conveyor designs are a significant part of this mix. As product cycles continue to shrink, companies need conveyor systems that can be easily adapted to these shifts, and modular conveyors fill the bill quite nicely.
In addition, conveyor users are highly interested in systems that offer quiet operation, have minimal maintenance requirements, and have a history of high uptime rates.
Nothing ever stays the same
Heavy manufacturing was the heartbeat of the American economy for many years. But in the past two decades, much of our basic manufacturing has moved overseas, and what remains is increasingly assembly oriented.
Conveyor manufacturers have had to adapt to these changes as well. To meet this marketplace, manufacturers have developed more sophisticated conveyors that allow for flexible manufacturing. Power-and-free conveyors, especially inverted models, remain a favorite for their ability to divert products to workstations and then back again to the main assembly line. The story on pg. 36 of this issue details the recent installation of an inverted power-and-free system at car manufacturer NUMMI.
Meanwhile, light manufacturing is turning to assembly conveyors that can divert materials, such as electronic components, to pre-determined workstations. An example is the Tektronix facility in Oregon featured on pg. 49 of last month's MMH.
Other conveyor types used widely in manufacturing are similar to those found in warehouses and distribution centers. These include gravity, powered roller, belt, and slat conveyors. See the art panel in this article for capsule descriptions of eight leading types of conveyors used widely in manufacturing.
"Ultimately, it is the needs of the manufacturer that determine the type of conveyor used," says Tom Carbott of the trade association Material Handling Industry. "A lot will depend on the speed, weight, and flexibility desired."
The Lego design
Regardless of conveyor type, most customers today seek flexibility in their systems.
"Modularity of conveyors continues to be a characteristic required by the end-user community," says Carbott.
"As little as five years ago, conveyors were looked at as disposable," he says. Once a system was installed, it was believed it would stay in place forever. It would die with its belts on, so to speak.
But just as companies have been forced to adapt their manufacturing processes, so have their materials handling needs changed. Modular systems have been the answer.
One conveyor manufacturer describes modulars as "big Lego sets" that can be built to meet the exact needs of customers. One such system was recently reconfigured over the course of a weekend.
In addition to trimming installation time significantly, modular systems are typically 40 to 60% less costly to install than non-modular designs. Their plug-and-play electronics make field wiring easier too. Many have Windows-based control systems that can easily tie into other factory management systems. More and more of such systems are being controlled from PC's rather than programmable controllers, a trend that will only increase in the future say experts.
Overall maintenance is also easier with modular designs. A defective unit can be unbolted and a new section inserted within 15 minutes on most popular systems, reducing not only costs but downtime.
Modular systems also hold their value longer, since they are re-usable as the needs of a facility change. One manufacturer described it as "buying a Mercedes". You may pay a little more initially for modular hardware, but it has a longer useful life, and, as a result, greater long-term value for the customer.
Many of today's modular design users are component manufacturers who sell products to finished good producers.
Parallel to the rise of modularity is a decline in users' tolerance for delays between ordering a conveyor and its installation. This, in turn, has placed pressure on conveyor makers to build units that have fewer parts and simpler designs. Systems that used to take up to a year to design now have to be ready within four to six months. Installations that might have once been allotted a month, now must be ready within two weeks.
Conveyor companies report that customers now expect to receive engineered products as fast as they once received stock items. Gone too are the days when companies allowed for a certain amount of time to "work out the bugs." Systems are expected to work perfectly out of the box.
Conveyor manufacturers today not only act as suppliers, but often must serve as consultants and system integrators. Increasingly, manufacturing end users are looking for turnkey operations, as many have eliminated in-house materials handling personnel.
"It used to be that a customer would receive bids from 25 different companies," says Jim Krempa, president of the Conveyor Equipment Manufacturers Association. "Now, they only bid out to three or four suppliers who can do full , broad-based systems." This is especially true for heavy manufacturing companies, adds Krempa.
Noise, quality, safety
Factories by nature are noisy places. The cacophony may be a symphony of production, but the noise can be harmful to workers and violate OSHA regulations.
"Noise continues to be an issue manufacturers are trying to contend with, especially where speed is a factor," notes Carbott of MHI.
More plastic is being used to reduce chatter and vibrations. Bearings and chains are quieter too with increased use of polymers and various composite materials. In addition, shrouds are being added to capture noise.
Electronic controls also reduce noise, as they are quieter to operate than mechanical controls. Rollers are being isolated and driver pads are being added to dampen sound.
All of these changes reflect an increasing trend toward quieter, improved designs.
Quality also continues to be a major issue . Krempa says that many end users are seeking units that have ISO-9000 or similar certification of quality. Better quality means longer service life and less maintenance. This is important because many companies have decreased their on-site maintenance personnel and have correspondingly raised their expectations for high uptime rates.
In the end, conveyors for manufacturing have more than kept up with the changes in manufacturing. And by all indications, that isn't going to change anytime soon.
Factors to consider when selecting a conveyor for manufacturing
- Speed
- Throughput
- Initial cost vs. cost of ownership
- Noise suppression
- Safety
- Durability
- Need for modularity
Eight common types of conveyors used in manufacturing
Gravity conveyors consist of a series of non-powered wheels or rollers packed tightly together. The materials ride on the surface, as the wheels or rollers spin under the weight of the materials and the force of gravity. These units normally convey materials a short distance.
Belt conveyors handle light or medium products. Some belt designs travel over rollers while others transport loads over a steel slider bed. These conveyors are especially suitable for tough to handle and irregularly shaped parts as well as small items that would normally be hard to convey by other means. Belt conveyors can also be used in incline and decline applications.
Slat conveyors consist of a series of steel, wood, or plastic slats joined to a drive chain. Light to medium weight finished goods and boxes are best conveyed with these units. Small parts should not be transported, as they have a tendency to drop between the slats.
Power-and-free conveyors are usually chain driven and can suspend materials overhead from a trolley or can be mounted into a factory floor. This type of conveyor is designed so that the trolleys can be engaged with the chain to move work along the assembly line, or can detach from the chain when materials need to stop at predetermined work stations.
Tow conveyors are most often found in heavy manufacturing of wheeled vehicles or facilities that place their products on wheeled carts during manufacturing. In-floor pushers convey trolleys along the assembly line. Some tow conveyors can also be supported from overhead.
Assembly conveyors are designed to transport slip sheets or small trays of work to various work stations, normally in a light manufacturing environment. They can be chain or pulley driven, and many are designed to be modular.
Modular conveyors are the most versatile conveyors to be introduced to manufacturing. Ideally suited to light manufacturing, these units are designed as plug-and-play units that can be shaped and adapted to meet changes in the manufacturing environment. They can be comprised of various designs from roller to belt, depending on the application.
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