The advancements in hydraulics and variable speed drives (VSD) were running in parallel for many years but on opposite sides of the fence from each other in solving paper converting industrial applications. Once the engineers on both sides met in the middle and shared their knowledge, a door opened to a new way of thinking and problem-solving. Combining VSD and hydraulics was difficult at first; the unforgiving nature of positive displacement pumps, the non-compressibility (incompressibility) of the fluids, demanded a different solution than what VSD engineers had experienced with more forgiving lower pressure centrifugal pumps. The combination of hydraulics and VSD has created a new type of system with lower noise, fewer components, and higher energy efficiencies.
Download our white paper and learn how Drive Controlled Pump (DCP) technology can make center winders the ideal winding technology for the paper converting industry.
Hydraulic systems are known for their ability to deliver significant power density in a small package. Electric motors and variable speed drives are known for their programmability and responsiveness. Dating back to the 1990s, hydraulic and drive system engineers could see the potential for combining the two technologies. Historically, the motion control industry has had limited success in combining the technologies. However, in today’s manufacturing environment, the higher cost of electrical power, the increasing global concern for the CO2 footprint and the need for quieter industrial solutions offer opportunities to reevaluate the combined technology. Today, the advancement in new Variable Frequency Drives (VFD) control algorithms, faster programmable VFDs and more efficient hydraulic pumps specifically designed for variable speed applications allows our engineers from both technologies to work together with greater opportunities for success by implementing an ideal technology known as Drive Controlled Pump technology (DCP).
Traditionally, electromechanical drive systems are used for the majority of converting line’s center winders or combined center surface winders. These drive systems use electric motors larger than the web horsepower by the factor of their buildup ratio. DCP can keep the electric motor size close to its web horsepower by eliminating the buildup factor in a winding application. This takes advantage of the continuously variable flow and pressure feature of an electronically controlled variable displacement hydraulic pump operating at variable radial speeds.
Taking advantage of electric drive and hydraulic technology yields a positive outcome in winding and unwinding techniques. DCP technology allows us to create a wide constant HP range and trade speed for torque during the buildup process while reducing the size requirements for the electric motor. Since this technology operates the hydraulic pump at a variable speed; it uses fewer and simpler hydraulic valves. DCP hydraulic systems are less complex and more efficient than traditional hydraulic systems; it operates at much lower noise and temperatures resulting in quieter and cooler surroundings.
This system is very flexible; a variable displacement motor and a fixed displacement pump can be used to achieve the same results. The following diagrams show the control schematic of a DCP winding system using a variable displacement hydraulic motor and a fixed displacement open loop pump.
The system can also be adapted to closed loopX hydraulics and unwinding applications quite easily as shown below.
Paper converting lines employ surface, center, and center/surface combination winders and each winding technique has inherent benefits and limitations. Download our white paper and learn more about how Drive Controlled Pump (DCP) technology can make center winders the ideal winding technology for the paper converting industry.
Article contributed by Rashid Aidun, application engineer, Parker Hannifin.
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