Weighing Your Options
The basics of a straightener-feeder
Not all coil handling equipment is created equal. At first glance, conventional coil lines and straighteners-feeders seem to perform the same task, but when they are examined throoughly, these units are very different.
Different but Similar
The main difference between a conventional coil line and a close-coupled straightener-feeder unit is the space they consume on the factory floor. Often referred to as space-saving units, straightener-feeders can be as small as one-half to two-thirds the length of a conventional line.
In a conventional coil line, the material is uncoiled, straightened, fed into a large floor pit, comes back out of the pit, and is fed into the press. The straightener-feeder unit eliminates the pit, shortening the process to two steps: uncoiling and straightening-feeding the material into the press (see Figure 1).
Despite their space-saving design, straightener-feeders are not completely flexible. A drawback to these units is that they generally don't have the production range of conventional units. Straightener-feeders are limited to a combination of feed lengths during continuous press speeds.
If production demand exceeds a unit's capacity, its control system will need to be designed to make the straightener-feeder a master controller of the press cycle rate. The combination of feed length and press cycle rate is directly related to its limited material loop storage.
A conventional line with a more generous material loop storage is generally sufficient to allow a wider range of this combination at a continuous press speed. Because it's used with a floor pit, an uncoiler in a conventional coil line can build up excess slack, called loop storage. Loop storage is designed to create a smooth transition and a flawless finished product.
Straightener-feeders do not have this excess loop storage because of the uncoiler's proximity to the straightener-feeder. Because no excess slack is produced, the press has to stop and wait for material to fill the loop storage area.
Certain parts made from coil that has gone through a straightener-feeder sometimes may have more imperfections than parts produced with a conventional unit. For example, if the fed material is surface-sensitive, such as painted or plated, the starting and stopping of the straightener-feeder's straightening rolls may bruise the material's surface. With a conventional line, the continuous running of the straightener can decrease starts and stops of the straightening rolls.
Metal imperfections can be costly if a stamper produces, for example, car doors, but they would not be a concern on brackets. Therefore, a conventional coil line generally is most appropriate for manufacturers that use Class A material for products such as appliance shells, which require a smooth, flawless outer surface.
If a stamper requires long feed lengths and a smooth surface on the finished product, a conventional line may be an option. However, if a stamper needs to conserve space and can sacrifice surface quality, a straightener-feeder may be the option.
Control and Other Issues.
Master-Slave. The press is the "slave" and the straightener-feeder is the "master" because it has advanced controls. On conventional coil lines, the slave and master roles are reversed. Older lines in particular usually do not control press functions as easily, because three separate machines —the uncoiler, straightener, and feeder—all have to be programmed separately.
Because a straightener-feeder generally has more advanced controls and can control the press, it can give a stamper more flexibility. For example, punch gauging allows a stamper to program the feed length, press stroke number, die codes, and press operation status for every procedure.
Other features available on straightener-feeders, including automatic roll lift, no-loop detector, and loop control, are designed to free the operator to perform other tasks and reduce part changeover downtime.
Maintenance. A conventional line has three separate units—an uncoiler, straightener, and a feeder—and so it runs on three separate motors. More units means more chances for malfunction. Because a straightener-feeder has essentially two units, it may not break down as often.
Safety. Because straightener-feeders eliminate floor pits, they can be considered safer than a conventional line. Also, if stampers place safety guards around the machine, a straightener-feeder has less area to guard. Computer controls available on many types of straightener-feeders are designed to help prevent operator mistakes and enhance safety.
Making the Choice
Attempting to fully understand all of the options available to today's metal stampers can be a daunting task. Metal formers are constantly faced with choices —choices that promise faster production, save space, provide high quality, and more safety.
Before purchasing any equipment, stampers should study their unique coil handling requirements of the specific industry they supply. Understanding the capabilities and differences of coil handling systems can help stampers decide which equipment is most appropriate.
Gabrielle Dion is sales and marketing administrator at Oriimec Corporation of America, 1840 Airport Exchange Blvd. #200, Erlanger, KY 41018, phone 859-746-3318, fax 859-746-3319, e-mail email@example.com, Web site www.oriimec.com. Oriimec manufactures and sells coil handling systems and pressroom robots. Jerry Hill, vice president of sales and marketing, and Jeff Taylor, sales manager, contributed to this article.
STAMPING Journal is the only industrial publication dedicated solely to serving the needs of the metal stamping market. In 1987 the American Metal Stamping Association broadened its horizons and renamed itself and its publication, known then as Metal Stamping.