The economics of selecting a coil feed line

Metal stamping in today's market has never been more challenging. With dynamic forces causing financial stress from all sides, metal stamping companies need the most cost-effective methods to produce parts. Naturally, economics should be considered in the selection of a coil feed line as well.

Some space-saving lines may be surprisingly affordable. In terms of capital investment, some are less costly than conventional feed lines with similar specifications. Factoring in the economics inherent in a small footprint—if a building expansion is required for a larger line, for example—a space-saving line may be the most economical option.

Categories of space-saving coil feed lines, from the least expensive to the most expensive, are the paddle loop, underslung, and synchronous.

Paddle Loop Line

The paddle loop line (see Figure 1) includes a powered feeder/straightener or a servo feed with a pull-through straightener and a powered reel. A load car is optional. To conserve space, the loop is developed below the reel's spindle and controlled with a laser or loop light system.

If the feeder is equipped with a pilot release-capable pull-through straightener or a powered feeder/straightener with a piloting straightener is used, all upper rolls can be released for piloting, making this line suitable for progressive-die applications. The addition of a stand-alone hold-down arm/peeler/threader/debender with exit flip table provides a hands-free threading process.

Capabilities and limitations are:

•The line is compact, ranging in length from 16 to 26 feet, depending on the passline.

•It can be sized for any coil weight and width.

•It is simple to operate and learn.

•Optional equipment allows hands-free threading and pilot release.

•Maximum material thickness is limited to approximately 0.25 inch.

•The material travels over itself at the top of the coil, possibly causing marks in some high-polish materials.

•Long progressions must be reviewed carefully to determine if the desired speed is attainable.

Because the process stops and starts, it is not suitable for cosmetic parts. It is designed for limited-space applications in which progressions are not excessively long.

Underslung Compact Line

This system includes a powered feeder/straightener or a servo feed with pull-through straightener with a powered reel and load car (see lead image). To conserve space, the loop is developed below the reel's spindle and controlled with a laser or loop light system.

Again, if the system is equipped with a pilot release-capable pull-through straightener or a high-powered feeder/straightener, all upper rolls can release for piloting, thus allowing for proper pilot registration. This feature is especially helpful in progressive-die applications. Powered rollers included on the load car (or under-coil tongue) and the optional rocker arm assembly with debender provide a means for hands-free threading.

•It is very compact, often measuring in the 15-ft. range.

•Line length is not as dependent on passline height as with the paddle loop.

•The line can be sized for any coil weight and width.

•Material can thread hands-free.

•Maximum material thickness is limited to about 0.156 in.

•Long progressions must be carefully reviewed to determine if the desired speed is possible.

The system is suitable for general progressive-die and transfer applications in which space is the highest priority and progressions are not excessively long. The process stops and starts, making it unsuitable for cosmetic applications.

Underslung Compact Line With Pulloff Rolls

This system is similar to the under-slung compact line with one major exception—it uses massive, powered pinch rolls to pull the material off of the pulloff reel and drive the material into a loop behind and below the reel (see Figure 2). The system typically is used with a powered, heavy-duty feeder/straightener. Powered rollers on the load car and the rocker arm assembly with debender provide hands-free threading.

Several capabilities and limitations should be noted:

•The system is very compact, typically about 20 ft. long, even with wide, thick material.

•Line length is not as dependent on passline height as with the paddle loop.

•It can be sized for any coil weight and width.

•It has hands-free threading.

•The line can run thicker material and longer feed lengths than the standard underslung compact line.

•Maximum material thickness is about 0.250 in.

This line is most suitable for progressive-die and transfer applications in which space is a priority. The process stops and starts, making it less than ideal for cosmetic applications.

Two-axis Synchronous Line

The two-axis synchronous line includes a powered feeder/straightener with a powered reel, and the reel and feeder speeds are synchronized. Because the drives for the reel and feeder straightener are synchronized, this system needs no loop. Just a small wrap of material below the spindle allows a little slack for pilot release.

A coil outside diameter (OD) sensor is used to adjust the reel's speed based on the coil OD, which is a must when there is no slack loop in the line (see Figure 3). All upper rolls release for piloting. The pilot release can be pneumatic or hydraulic, depending on the material thickness and yield strength.

The system has several notable capabilities and limitations:

•It is very compact—sometimes shorter than 20 ft. long.

•It can run very thick material—even 1/2-in.-thick material and high-strength steel (HSS).

•The line can be sized for any coil weight, width, and thickness.

•It can be equipped with an auxiliary pull-through straightener to accommodate light-gauge materials.

•The line requires 30 to 60 percent of the space of a conventional feed line.

•Potential complications from advanced controls, PLCs, and sensors can occur.

•The learning curve for operators is typically longer than for less sophisticated systems.

•Long progressions must be reviewed carefully to determine if the required speed is possible. Because there is no loop, long progressions must be reviewed on a case-by-case basis to determine if the drives can handle the progression, strokes per minute (SPM), and available feed window for the application.

The line is suitable for tight-space applications in which heavy-gauge (0.25 in. or thicker) high-strength steel is being run and there is no space for a cradle or conventional feed line. The process stops and starts, so it is not the most ideal for cosmetic applications.

Three-axis Synchronous Line

The three-axis synchronous line is like a conventional feed line—with a servo feed, powered straightener, and reel with load car—but it has no slack loop. Instead, a small "belly" of material between the feeder and straightener allows a little slack for pilot release. The drives on the feeder and straightener are synchronized, as is the reel speed.

A coil OD sensor is used to "trim" the reel's speed based on coil OD. The motor size is significantly larger than that on a conventional line because of the lower gear ratios required to maintain line speed.

•It is compact (about 32 ft. long) when compared to a conventional line running the same thickness of material.

•No looping pit is required, which reduces the preparation expense and makes the system more modular.

•It can run thick material and high-strength steel in a short distance.

•The line can be sized for any coil weight, width, and thickness.

•It can be equipped with an auxiliary pull-through straightener to accommodate light-guage materials on the same line.

•Setup is similar to conventional feed lines, shortening the operator learning curve.

•Material capabilities are versatile.

•Long progressions must be reviewed carefully to determine if the required speed is possible.

This system generally is more expensive than conventional looping lines, so the cost would need to be reviewed relative to its space savings to determine if the higher investment is justified. This line is suitable for tight-space applications in which versatility and operator familiarity are important and there is no need for a cradle or space for a conventional feed line. The process stops and starts, making it less than ideal for cosmetic applications.