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PIISMA: the variable-speed pump drives for hydraulic applications

The revolutionary innovation in the hydraulic systems market

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MAIN APPLICATIONS

  • Injection molding
  • Rubber injection molding processes
  • Metalforming
  • Punch presses
In many industrial processes involving a hydraulic pump, an unregulated motor running at maximum speed is probably wasting energy.

Reducing the motor speed during low flow demand or parts of the cycle requiring pressure to be held can achieve significant energy savings.

By automatically adapting the pump’s speed to match changes in demand, Interfluid’s servo pump systems are the perfect addition to many hydraulic systems

The PIISMA hydraulic servo pump system consists of a variable speedservomotor controlled by  inverter coupled with an internal gear pump, whose power may be constantly adapted to suit effective needs, in such a way as to eliminate idle machinery losses almost entirely. The basic PIISMA version of these pump systems also consists of three main components:

  1. Inverter
  2. Synchronous servo motor
  3. Internal gear pump

The traditional system: in a conventional hydraulic system, a fixed-speed motor drives the pump that circulates the hydraulic oil from the reservoir to the hydraulic cylinder. To keep the oil circulating, the pump needs to run constantly, consuming energy even when the actuator is stationary. Pumps in hydraulic systems are commonly driven by induction motors, which are inherently less efficient than the permanent-magnet motors used in servo designs. Induction motors have to draw current in order to generate the magnetic field required to get the rotor to turn. Their efficiency also decreases when they are run below their rated speed.

The new PIISMA system: PIISMA variable-speed pump drive consists of a system equipped with frequency converter and contro electronics, a syncronous electric motor and an internal gear hydraulic pump.

The flow rate of the system results from the drive speed of the electric motor and the pump adjustment. The machine control transfers the pressure/volume flow target values to the control during the running operation. The system pressure is measured by a pressure transducer and is also sent to the controller. Based on the control deviation, the built-in PID controller calculates the required motor speed and adapts it accordingly to the existing system requirement of flow rate and pressure.

Benefits:

  • Longer lifespan of the pump;
  • Machine efficiency gains;
  • Simplification of the hydraulic system thanks to the elimination of the proportional valves, for instance.
  • Reduction of tank volume by as much as 80%
  • Maximum repeatability of Pressure/Displacement parameters
  • Reduced overall weight of the motor-pump group
  • No electrical interference on the electricity supply line.
  • Less money spent on both purchase and disposal of the hydraulic oil.
  • The level of control provided by closed-loop feedback leads to more precise motion
  • The big benefits of the servo motor are the response time and the fact that you’re able to run those motors up to really, really high RPMs to get to where you need to be much quicker.”
Further benefits:

  • Reduced energy costs: the hydraulic servo pump can help you cut energy consumption by up to 80% (depending on the machine duty cycle) adjusting the pump pressure and flow to the hydraulic actuator without the need for additional control valves. Instead of operating constantly at 1500 RPM, PIISMA hydraulic servo pump system can be controlled to match the load requirements of the current duty cycle via intelligent control
  • Reduction of noise up to 20 dB during the machine duty cycle and by 100% during between-cycle intervals. One of the main sources of machine noise in a hydraulic press is the hydraulic pump. The sound pressure level depends on the pump’s rotational speed and operating pressure. Higher speeds will produce greater noise. The electric motor and pump speed is constantly varied by PIISMA to match the duty cycle requirement. This results in remarkable noise reduction in the overall system, which helps protect operators’ hearing and meets more stringent noise regulations.
  • More compact size: the PIISMA system has provided the possibility to reduce the size of your pumps and cut costs. Since the system can run higher than 1500 RPM, it is possible to reduce the pump displacement capacity proportionally for the same amount of flow, thus reducing the overall footprint of the machine.   Backed up by an engineering department with experience in applications, service, training and sales support, Eckerle-tested pump and variable speed actuators can provide a powerful combination for addressing today’s highly demanding market.
  • Reduced oil heating requirements: a variable speed pump drastically reduces the heat load on the system. In the case of a system run by a fixed-speed pump, the motor would be running the entire time, consuming power and generating heat, even though it is only maintaining pressure. With a servo pump, the holding torque of the motor is sufficient to generate the required pressure.
Main applications Applications like injection molding are perfectly positioned to benefit from the technology of PIISMA hydraulic servo pump. Rubber injection molding processes, for example, require the pressure to be applied and then maintained at a set level for an extended period of time while the rubber fills all nooks and crannies of the mold. In the case of a system run by a fixed-speed pump, the motor would be running the entire time, consuming power and generating heat, even though it is only maintaining pressure. With a servo pump, the holding torque of the motor is sufficient to generate the required pressure The biggest share of a hydraulic injection machine’s energy use is by the hydraulic drive. This is where servo-driven hydraulics can make a cost-effective difference. The instant response delivered by servo motors enables the actuator to operate much more quickly and deterministically, making it a good fit for applications like punch presses This level of fine control can benefit applications like metalforming. When metal is deformed into a shape, it has to be slightly over bent so that it will assume the correct form after recoil. For best results, full force should only be applied in the last millimeter or two of motion. Servo pumps enable much more accurate control of the motion of the hydraulic actuator, creating better quality parts.
Retrofitting The PIISMA servopump can be retrofit into existing machines that formerly used hydraulic servovalves. The result would be up to 70% lower energy consumption and noise reduction as much as 20 dBA. Consider modernizing and simplifying the hydraulic system. Because older stamping presses use fixed-displacement pumps with relief valves, or variable-displacement pumps with proportional valves, or older load-sensing directional control valve technologies, the value of a retrofit can be determined by asking several age-related questions:

  • What are the ages of these components? Are they still available or re-buildable to like-new condition?
  • What are the maintenance requirements of the system? Is there fluid leakage from these components?
  • Do you need to operate at higher pressure/flow rates to maintain current production requirements, or are you operating frequently at less than full tonnage and wasting energy?

The solution: Retrofitting to a variable-speed system that can simplify the hydraulic system and will head off future component replacements and greatly reduce maintenance costs. Reduction of operating costs, so your investment can quickly pay for itself, The end-user gets energy savings very similar to that of an all-electric driven machine.

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