Assembly's Automated Workhorses
Short product life cycles complicate the situation. As products change or volume increases, traditional material handling methods may prove inadequate or counterproductive. The right conveyor technology can help increase productivity and reduce assembly costs. But how do assemblers choose the right conveyor type?
"The basic principle of a conveyor is that it is simpler to drag something than it is to lift it. If you can break down your process and put it on a conveyor, you can build a product very fast and very efficiently. But the dilemma is that the processes keep changing too quickly," says Gregory Ferguson, principal engineer for Smart Move Conveyor Group (Fall River, MA).
Avoiding the PitfallsTo avoid costly mistakes when choosing conveyors, assemblers should consider conveyance methods early in the product design process, advises Kevin Gingerich, marketing services manager for Bosch Rexroth Corp. (Buchanan, MI). What operations will be required to assemble the product? Will those operations be performed manually or automatically? How many stations will be needed? How will the product move from station to station? Will the assembly need to be fixtured?
"It’s very important for companies to have a design-for-manufacture approach," says Gingerich. "The part is going to dictate the type of operation."
Conveyors enable parts to move from station to station on an as-needed basis. Work can be independently routed along a path. This allows for product customization, and there are virtually no limitations on the number or complexity of assembly steps. Manual tasks can be integrated with automated operations, because conveyance Arial can be adjusted to accommodate varying cycle Arial.
Assemblers should provide conveyor suppliers with as much information about the project as possible, says Aaron Williams, project manager for Krups Conveyor Systems (Fort Worth, TX). For example, by knowing how many parts per minute or parts per hour will be assembled, manufacturers will be able to gauge how fast the conveyor will need to operate. How much room is available at the facility is another factor to consider. If space is at a premium, an over-under conveyor configuration might be necessary.
Manufacturers should also specify the width, length, height and weight of the parts; how far and how fast the parts must be moved; environmental considerations; and whether the product is bulk or individual parts, says Gary Wemmert, director of marketing at Dorner Manufacturing Corp. (Hartland, WI).
Keeping the conveyor supplier "in the loop" will ensure that assemblers will get the best conveyor for the job. "Nowadays, time-to-market windows are so short that if [companies] make a mistake in implementing manufacturing technology, they lose their competitive advantage," says Gingerich.
Conveyor TechnologiesThere are three basic conveyor technologies for assembly line applications: belts, chains and rollers. All three styles can be built in straight or curved sections, and all three are usually supplied in modular sections that can be rearranged and reused as line needs change.
The simple belt conveyor is probably the most widely used conveyor technology. It can be used to transport loose, packaged or palletized products. It is ideal for conveying items with irregular bottom surfaces, small items that would fall between rollers, or bags that would sag between rollers.
Belt conveyors are available in a wide range of sizes. Short, narrow belts are often used in parts feeding and machine tending applications. Wider belts are often placed between two parallel assembly lines to transport finished products to a central location for inspection, testing and packaging.
A popular variant of the belt conveyor is the edge-belt conveyor. Instead a single, wide belt, this conveyor has two narrow belts. The assembly travels on a pallet that rides between the two belts.
Chain conveyors are similar to belt conveyors, except that they have a flexible, flat plastic chain instead of a belt. The product can travel directly on the chain or in a puck or pallet.
Roller conveyors move products on a bed of steel or rubber rollers. These conveyors are most often used to transport boxes in warehousing and packaging applications, but they can be used to move pallets in assembly line applications, too. They are easily adapted to side-loading applications, and they’re ideal for applications requiring transfers and merges. Like belt conveyors, roller conveyors are also available in edge-style versions.
The rollers can be powered or unpowered. Powered rollers can be programmed to automatically accumulate pallets, rotate pallets or to divert them to splinter lines. One benefit unique to roller conveyors is that they can take advantage of gravity. If the conveyor is built on a slight angle, the product will roll downhill to its destination without any help from a motor. (By the same token, it’s difficult for a roller conveyor to move products up an incline.)