Page 15 - MetalForming June 2010

required. While many conveyors of this type may seem less expensive at the outset, the additional costs of frequent changeovers can lead to unexpected, unpleasant surprises.
To build as much flexibility into a packaging or other manufacturing oper- ation as possible, many companies turn to conveyors with an extruded alu- minum frame, whose T-slotted design lets them reconfigure the system virtu- ally at will, adding to or repositioning the originally purchased equipment. These anodized aluminum frames don’t need welding or painting, so they install quickly. The available T-slots in the extruded aluminum frame also provide a convenient attachment point for other accessory equipment such as lights, vision systems and labeling devices.
If for hygienic reasons stainless steel is required, the better systems are designed to provide flexibility similar to that of aluminum systems, with slot- type openings along the conveyor rails, and similar bolt-together conveyor modules.
By investing in conveyors that can adapt to constantly changing require- ments, manufacturers can significantly reduce the total cost of ownership in their material-handling conveyors.
Curve Design to Fight Friction
Large-scale handling and packaging systems often require sophisticated product routing. Welded assemblies of stamped parts, for example, or boxes and cartons of smaller stampings being transferred by a conveyor may need to
be elevated or lowered, accumulated or repositioned, and transferred around tight or long, sweeping curves.
Most conveyors transfer packages or parts on a transport chain that slides along the conveyor frame on a slide rail of some type. For straight conveyor sections, the friction inherent to any given system will be a function of mate- rial choices and the use of the appro- priate chain types. Putting curves in the system significantly increases fric-
tion; for example, a typical 90-deg. hor- izontal curve can cause a 60 percent increase in friction. This in turn causes the drive motor and gearbox combi- nation to work harder to pull the chain through the system. Adding the multi- ple horizontal and vertical curves com- mon in many layouts increases friction, of course, and may require the use of additional drive motors—typically the most costly component in any convey- or system.
So, the trick is to find a system design that will achieve the transport objectives while using the smallest reliable number of drives. Choosing a conveyor whose chain features a high tensile strength can help, since it allows handling longer stretches of chain with fewer drives. But for the lowest total cost of owner- ship and maintenance—and if there’s a need to accumulate product over a good portion of the conveyor—manufactur- ers may need to look for ways to reduce friction in the conveyor’s curves.
Assisted Curves
Many suppliers of flexible chain con- veyors supply curve wheels, which essentially comprise a rotating disc that replaces the slide rail on the inside part of the curve where friction is greatest. This wheel allows the chain to move smoothly around the curve via the turn- ing disc, rather than sliding around a stationary rail. Using a curve wheel in a 90-deg. curve can reduce friction to virtually that of a straight conveyor sec- tion, significantly improving the safety factors of the drive and the chain.
In other words, curve wheels allow a manufacturer to reduce the number of drives in an overall system and have substantially greater confidence in the integrity of the chain during long-term operation.
Some conveyor manufacturers offer calculation tools to help identify weak- nesses in system design—overloaded drives or chain, for example—based on a given set of parameters. It’s important to perform these calculations, or to ask your conveyor supplier to do them for you, to develop the most cost-effective system over the long term that avoids
Most packaging conveyors are modular by design, available in preconfigured straight or curved sections that bolt together on the shop floor. They prove ideal for complex routing where assemblies and packages of small stamped parts must move up, down, and around equipment and other obstructions in the plant.
To build as much flexibility into a packaging operation as possible, many companies turn to conveyors with an extruded aluminum frame, whose T-slotted design lets them reconfigure the system virtually at will.
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