Extrusion International 2-2021

37 Extrusion International 2/2021 In 2004, the first German KfW energy efficiency prize was awarded to a twisted cabling machine that made use of a CVT process for production of wire cable (winding and strand- ing process). The jury included two luminaries of international energy research: Dr. Ernst Ulrich von Weiz- säcker and Dr. Eberhard Jochem. By directing braking energy back into an on-site power network, the sys- tem reduced net power consumption by approximately 20%. During sub- sequent years, energy regeneration units (or the intermediate voltage circuit) have become standard equip- ment. With newer machines, where the unwinder (generator operated) and rewinder (motor operated) are energetically-linked via an interme- diate voltage circuit, energy savings are known to be in the area of 40%. In 2014, Kabel.Consult.Ing filed for patent protection of its Electronic Continuously Variable Transmission. It brings together the achievements of the first three industrial revolu- tions and sets the stage for the era of Industry 4.0. In formula form: In- dustry 1.0 + 2.0 -> fundamentals, pio- neer achievements; Industry 3.0 -> semiconductor technology, PLC pro- gramming, CIM; and Industry 4.0 -> automation of intelligent behavior, programming of algorithms using statistics and mathematics. Research conducted at University of Technology Sydney and Hunan University Changsha (2018) likewise concluded that mechanical CVT drive technology is the most efficient and economical way to power large and small electric vehicles. Summary. Use of networked CVT technology can boost average ef- ficiency of motors from well below 60% currently to 80% or even 100%, resulting in greatly increased total efficiency of motor- and generator- powered applications. This results in minimized energy costs, maximized energy outputs, and ultimately to standardization throughout a pro- duction plant. From a macro-eco- nomic perspective, (networked) CVT technology makes a valuable con- tribution to “decarbonization” and lower CO2 emissions. CVT processes have become common in high-speed applications in the cable, wire, and stranding industry To remain competitive, manufactur- ers have for decades sought to ac- celerate production by continually increasing the speeds of their cable and stranding machines. Higher speeds result in tremendous centrif- ugal and Coriolis forces that impart tension into the rotating elements. For these reasons, engineers have until now focused on optimizing the drives. Little by little, purely mechani- cal drives have been replaced by elec- tric and then mechatronic solutions. In the cable industry, twist stranding and central winding spinners are im- portant components in this effort. Stranding machines, where twist- ing is accomplished with individual or group components or the cable itself, have been in vogue since at least the era of data cables (and no later than the hybrid cable era) due to their universality and variable abil- ity to reverse direction. With twist stranding, the stranded elements are threaded through a stationary guide disc and fed to a (rotating) strand- ing nipple. As soon as the bound strands leave the nipple, a stranding rotor twists them together into a he- lix shape and guides them through a system of deflection rollers to the traversing spooling device. Theoretically, the prod- uct has reached its final condition long before the stranding rotor. This can be exploited by adding steps to the stranding process, such as filling with petroleum jelly, swelling powder, or talcum powder; insertion of insulation; longitudinal water sealing with film or tape; labeling; spinning with thread; and shielding with film, tape, or wire. Central winding spinners are an important com- Hybrid product with added value (Source: 123RF) ponent of fiber optic cable strand- ing machines, on which the speed of an entire production line largely depends. A central winding spinner is used to twist a thread in a screw shape around the fiber optic cable. The spun material, e.g. aramid or cotton yarn, lies in the rotational axis and the cable is fed through the ma- chine’s central opening. Next, during binding, the thread passes through a series of rollers, deflection rods, or thread guides, applying it to the ca- ble in a helix shape. As the rotational speed of the central winding spinner increases, the cable machine’s line speed increases automatically. Until recently, having a refined CVT process with drive and control com- ponents optimized for the machines and parameters was decisive for boosting productivity and effective- ness of mechanical processes in cable production. Intrinsic advantages of networked CVT drive technology Conventional systems are character- ized by “one motor, one transmis- sion, one inverter” and follow Euro- pean standard EN 50598. By contrast, a networked CVT drive consists of: at least one servo amplifier/inverter; two rotary current servo motors, ro- tary current asynchronous motors, or synchronous reluctance motors; and a planetary linkage via a heavy-