How a producer of winding equipment simplified machine design to conserve space and cut costs

Introduction

Fibre optic manufacturers typically incorporate some type of winding assembly into their extrusion lines to “spool” the fibre for distribution. Although spooling system options abound, Showmark Machines (Berwyn, Pennsylvania, USA) found a niche from which the company has been able to launch what has become a successful OEM business specialising in winding equipment.

Wanted in a fibre optic winder: compactness

Initially, Showmark focused solely on developing fibre optic winders. Whereas most fibre optic winding systems require dedicated floor space in the production facility, the Showmark system was designed as a benchtop model. The compact design grew out of a combination of hunch and solid market research conducted by Showmark founder Scott Markovitz. While attending an Optical Fibre Conference (OFC) show, Mr Markovitz talked with many users of fibre optic winders. Most of them expressed a wish for a winder that was simpler to operate, more compact, and less expensive than those available at the time. “We estimated that about four times as many of our prospects preferred a compact, less sophisticated winder, as opposed to the large, floor-mounted machines”, said Mr Markovitz.

Showmark Machines’ debut product (Figure 1) weighed about 32kg. The winder utilises a three-axis servo-controller to coordinate the precision movement of the linear traverse as well as to control tension in the fibre. A tension sensor is attached to one of the bottom rollers. The signal from the sensor is continuously monitored by the servo-system. Corrections to line tension are performed in real time by advancing or retarding the motion of the pay-off reel.

Figure 1: Showmark FS-230 fibre optic winder. Designed for fast winding of fibre onto application-specific take-up spools. The machine includes a tension controller and an electronically controlled clamp-and-cut system

The benchtop Showmark unit was released at roughly half the selling price of its larger counterparts. The lower cost is due partly to the company’s controlled manufacturing processes. Savings also were derived from Showmark’s targeting of applications for which no pricing precedents had been established. “Our main market”, said Mr Markovitz, “is for very simple general-purpose respoolers which can be used for breaking down bulk spools into smaller spools for distribution”.

Previously, the only choice was to use the same spooling equipment that was being used for such high-end applications as fibre test proofing, coating, and fibre colouring. Showmark Machines provided a more practical machine, offering basic features for everyday use.

Looking at all fibre optic winding requirements

“When we first opened the doors at Showmark”, said Mr Markovitz, “fibre optic was a hot topic. And it was technology we found interesting”. Showmark’s first customer was a company in the telecom industry whose fibre optics were doped with erbium, a soft, malleable metal which is fairly stable in air and not prone to oxidise as rapidly as other rare-earth metals. Special spools are used for winding erbium doped fibres (EDFAs) and fibre optic gyros (FOGs). There can be no crossover on the take-up spool, which typically has a very narrow core width. Also essential is proper line tension.

Precision winding of any material, including fibre, requires the designer to be aware of general winding application requirements and available equipment. The basics of a winding system include a take-up spool, usually driven by a DC motor. A pay-off system feeds the fibre or other material onto the rotating take-up spool. The pay-off may feed directly from the production line. Also needed is a linear traverse or traversing nut, which is a linear drive assembly that guides the fibre back and forth as it is wound onto the spool. Figure 2 shows the components in a traditional winding system.

Figure 2: The typical screw-based winding system requires synchronisation of the motor driving the take-up reel with the motor driving the traverse. This is usually accomplished with electronic controls and programming

Depending on the diameter or thickness of the material being wound, the traverse must move back and forth at a set linear pitch. This is the linear distance the traverse travels per one shaft revolution. The pitch differs for each diameter of material to be spooled. Proper pitch setting assures even placement of lines on the reel, thus the requirement to synchronise the rotational speed of the take-up reel with the linear speed of the traverse. In addition, the linear drive system moving the traverse must possess enough axial thrust to overcome feed line tension. Thrust increases as angle M increases (Figure 3). When the traverse reaches the flange of the spool, the thrust requirement is at a maximum.

Figure 3: In the design of a winding system, care must be taken to select a linear traverse with enough axial thrust capability to overcome moments created when the traverse is at the extreme end of its stroke on the widest reel. If distance B remains constant, as angle M increases, so does the thrust requirement

For optical fibres, other design issues must also be considered such as the minimum bend radius of the fibre. The material is easy to stress if too much line tension is applied during the winding process. If bending occurs, the fibre’s light transmission properties can be affected.

Some fibre optic materials must be wound at extremely slow take-up rates. As the take-up spool fills up, its rotational rate must be reduced to compensate for the increasing circumferential length the material is being wound around. In addition, the linear traverse must slow down to keep the material even and smooth. Special motion control is required over the traverse guide moving the fibre back and forth as it is wound onto the spool. Precise constant tension control while winding the fibre is often needed, usually in the 10 to 30g range (0.35 to 1.1 ozf). If the pay-off system is feeding out product at a slower rate than the rotation of the take-up reel, too much line tension can result. Conversely, if the take-up drive is running faster than the pay-off, it will pull the line increasing the tension. A linear traverse with too much thrust can also create line tension levels that can damage the fibre optic.

The coating on doped fibres is easily damaged. This can have adverse effects on performance characteristics. To prevent this, the surface area of the fibre needs to be friction-free during the winding process. To assure smooth, frictionless take-up, the bearings in the winding assembly must be highly efficient. Also, winding fibre optic material typically requires precision placement of the fibre on the take-up spool in perfectly even rows and smooth layers. Precise synchronisation of the take-up spool rotation with the movement of the traversing material guide (Figure 4) must be assured. If the system slows down or speeds up, this synchronisation must remain constant.

Figure 4: Two ways to synchronise linear movement of the traverse guide with the rotational movement of the take-up reel: with the use of electronics and programming (Figure 4a,) and a mechanical method (Figure 4b) using a pulley system

Locating the technology to make it all happen

“We found that the traditional controls and components required for controlling the motion of the traverse guide made the machines larger and more complicated to operate”, said Mr Markovitz.

Showmark engineers had considered ball screws and belt drive assemblies for their winder. These methods required stepper or servo-motors to control the movement of the traverse. Also needed was a separate motor for the spool drive. Examining other types of linear drive systems, Showmark found that the requirements for multi-speed, direct-braked reversible motors, valves and solenoids, gear head assemblies, and so forth added significantly to the size and complexity of the machine design, and significantly increased operating and maintenance expenses.

Showmark’s strategy was to simplify machine design to cut costs, conserve space, and facilitate operation and maintenance. The company’s engineers consulted Uhing’s US agent, Amacoil, and found that the company’s reciprocating linear drive provided automatically reversible linear motion control without complicated controls, components, and programming. Additionally, a Uhing system is not screw-based. The shaft is smooth so it will not trap the dirt and debris that can lead to clogging and jamming. Showmark chose the Uhing system because it was able to eliminate extra motors, controllers, electronics, and programming from the machine design. Figures 5 and 6 show a typical Uhing/Amacoil winding assembly set-up in a custom Showmark winder. “We were able to use a single DC motor to drive both the take-up spool and the linear traverse, which made the controls much simpler”, Mr Markovitz told EuroWire. The Uhing drive also enabled Showmark to design a more compact unit which was even lighter weight than the original benchtop winder.

Figure 5: Large, heavy spools of optical fibres are clamped to the steel framework of this Showmark custom designed winder. The fibre is then re-spooled for distribution

Figure 6: The inset shows the traverse winding system. A single DC motor behind the faceplate drives both the take-up reel and the Uhing drive, which remains synchronised with the reel rotation without electronics or programming

Additional features attractive to Showmark designers were adjustable pitch and variable stroke length. “The variable pitch makes the system flexible,” said Mr Markovitz. “It means the customer can fine-tune the winding procedure to enhance a level, smooth wind. It also lets the customer wind fibre of different diameters on the same machine without having to change gear heads or invest in electronic controls”.

A next-generation winding machine

Incorporating the Uhing/Amacoil system led to the release of Showmark's second-generation machine (Figure 7). This model permitted linear pitch adjustment without utilising controls or changing gear assemblies. “The new unit was more general-purpose,” observed Mr Markovitz. “Many different types of fibre could be spooled using a single unit because the pitch and travel direction of the traverse guide could be mechanically controlled”.

Figure 7: The Showmark FS-10 fibre optic winder is an easy-to-operate tabletop winder featuring built-in line counter and tension control. The linear motion of the fibre guide is automatically synchronised with the take-up drive motor without electronics or programming

Showmark also found that, with simple modifications, it could configure the general-purpose unit to meet many precision winding requirements. “Our design is flexible and modular so we can rapidly modify machine design to meet specific winding requirements”, said Mr Markovitz. Showmark has already sold a modified version of the general winder to a manufacturer who uses it to spool FOGs. Mr Markovitz sees few obstacles to adapting the winder to meet virtually any fibre optic spooling demand imposed on it.

Additional wire winding applications

Recently, Showmark Machines has been applying its technology to the development of equipment for such markets as winding magnet wire. Magnet wire is often fragile, and the Showmark winder provides the steady movement and smooth reversal needed to make sure the wire does not twist or snap. “We are planning to introduce even simpler models of our winder,” Mr Markovitz said. “We will also be designing units to meet high-precision applications in the aerospace market”.

Showmark Machines
156 Daylesford Boulevard
Berwyn, PA 19312 - USA
Fax: Int’l +1 610 644 8073
E-mail: [email protected]
Website: www.showmarkcorp.com