Drive Utilized in Filament Respooler
- Friday, 01 December 2006
Optical fiber, now the mainstay of telecommunications as well as sensor, illumination, and imaging systems, is made by first pulling a large-diameter preform into a long, filimentous fiber. Then divided into bunches, a resin cladding is applied to keep the transmital of light uncontamintated. The finished product is then wound onto large spools to await shipment to customers. Showmark (Downingtown, PA) developed the automatic UniSpooler to customize the amount of cable a customer gets based on need, and uses the Kinemax KI3-15-5 linear drive from Amacoil/Uhling (Aston, PA) to help guide filaments from the supply spool to smaller takeup spool with the desired amount of fiber or wire.
Particularly with fiber optics, certain design/component issues must be considered in matters of storage, transportation, and distribution, such as the fiber’s minimum bend radius. Additionally, certain kinds of fiber optics must be wound at a constant take-up rate, and a spooling device must be able to measure filament without damaging it. If too much line tension is applied during the winding process, the filament can “stress,” developing kinks or becoming distended, rendering the fiber damaged and its ability to conduct energy hampered. Using the “roller ring” principle, the KI3-15-5 drive is designed for a simple back-and-forth motion. While the drive unit (the box) is off the shelf, Amacoil customizes the drive assembly to a user’s requirements — with regard to respooling mechanisms, customization involves what kind of cording is to be wound, from fine copper wiring to magnet wire to suspension bridge cable, and the traverse distance as dictated by the flanges of the spool. Amacoil’s drive is mechanically controlled; the drive shaft upon which the unit rides is linked via a pulley to the spool shaft. By way of the mechanical link, the drive automatically stays in sync with the spool as it fills, thereby removing the need for a reversal of the motor, a controller, or other electronics to synchronize the various components of the spooling process. This simplicity, plus the lack of threads along the shaft (which can grind metal scrapings into the moving components) particularly attracted Showmark’s designers.
Fiber optic manufactures usually do not customize the amount of cable they spool; the cable is wound onto a single-size general supply spool. Some optics, such as erbium optical fibers, used to make erbium-doped fiber amplifiers (EDFAs) found in high-bandwidth communcation systems, come in supply spools containing 10,000 meters of cabling — and at $10 a meter, most customers will not pay extra for left-over cable they will never use. The Show-mark’s tabletop UniSpooler, used by manufacturers and distributors alike, takes a supply spool of optic fiber, wire, or other fine filament and transfers it to a smaller, more economic spool or mandrel that holds an exact length of fiber/wire that the user specifies, in lengths up to 100 kilometers. The Uni-Spooler holds spools with a maximum diameter of 300 mm and a maximum width of 225 mm. An adapter system is provided to fit any spool with a bore size from 11–56 mm; spool diameters up to 400 mm can be accommodated, and a chuck can be provided for particularly small spools (called “bobbins”).
The UniSpooler operates on a screw-based design. The supply and takeup spools are mounted on universal hubs located at either end of the device. Between the two spool hubs, there are two guide wheels (called “sheaves”) mounted to a vertical post. The top wheel, called the length tracking roller (LTR), is used to measure the length of material being spooled, and contains a length-measuring sensor that keeps track of its rotations. The bottom sheave is a guide to get a good wrap around the LTR. Both sheaves have extremely smooth bearings and a smooth surface so that they do not put any extra “load” on the filament, or nick or dent the surface of the fiber and lessen its ability to transmit light. A third sheave is mounted at the end of a “steering arm” that is carried by the traversing unit (the Amacoil/Uhling drive); the drive, designed for light duty, provides seven pounds of thrust while operating at 13 ft. per second over travel distances of 16 ft. The arm moves back and forth to layer fiber on the take-up spool, receiving a tight and even wind across its spool shaft without crossovers in a process where proper tension and length is constantly maintained. The rate of the traversing motion is adjusted by turning a dial on the drive unit. This accounts for different diameter wires to be spooled. The take-up spool automatically slows its rotation as it fills to maintain a constant speed as the supply spool empties.
The UniSpooler can also be utilized in the construction of mechanisms where a coil of fiber is a component: EDFAs, fiber optic gyroscopes (used in the sensory guidance systems of ships, aircraft, and in robots, and coming in fiber lengths as much as five kilometers), and fiber optic time delays have all been constructed using the respooler’s winding process.
Although designed for optic fiber or wire, the respooler is also used for other types of cording; while able to wind metal strands for wiring, or silica or plastic (from which most optic fibers are spun) the UniSpooler is gentle (and cool) enough to wind even very delicate filaments such as food-grade paraffin wax. The wax thread, the size of fishing line, is used to trace food products: a food producer’s logo or a pattern unique to that company is incorporated into the waxen thread. The filament is then sliced into small disks and mixed in with the food product; in the event of a emergency situation, the wax disks act as tags to identify the food’s point of origin.