VFD for Hydraulics and injection moulding

Posted on 27th Dec 2022

Darwin Motion – VFD & Servo Drive manufacturer blog explain how plastics injection moulding machines that features a hydraulic system offers a reliable performance.  

Through continuous production cycling, there are many motion control sub-circuits to close the mould, for nozzle approach, extruder screw rotation and the screw injection plunge. Screw rotation & plunge need very steady motion to effortlessly move the granular plastic material via the heated, plasticized condition and then into the mould. These hydraulic movements can simply become as a quality concern for the moulded equipment if there are any irregularities in their control.

Nozzle approach, plunge screw injection, extruder screw rotation, and the mould closing needs various motion activated sub-circuits. Granular plastic material needs a highly steady movement to move effortlessly through the heated plasticized condition since it flows into the mould, during the rotation of screw and plunge phase. The moulded product quality could become questionable if there are any irregularities occur due to the hydraulic motions.

The cylinder which plunges the screw onward during injection and mould packing along with the rotating mechanism for the screw, which is turned by the hydraulic motor, become a difficult mechanism with challenging hydraulic seal necessities. Modern seal technology has advanced which allow leak-free hydraulic machines, suitable for moulding plastic products for usage in food and medical industry.

Injection moulding machine manufacturers also faces many design changes which are considerable.

The main hydraulic pump choice is important to offer smooth flow across the complete range of working pressures, while cutting down input energy waste and building up of heat. While the adjustable volume piston pump has been utilized on some moulders, moving to always higher efficiency can be very difficult—and similar piston pumps need the utilization of a system accumulator to minimalize flow pulsations.

To offer smooth flow across various working pressures while cutting down heat build-up and input energy waste, making the perfect choice for your main hydraulic pump is important.

A popular selection because of its level flow and high volumetric efficacy has been the vane pump. When paired with a Darwin Motion MATRIX 180 variable frequency drive motor some fixed displacement wide range of vane pumps execute high efficiency due to its ability at high system pressures. Older injection moulders which might look out-of-date and incompetent have been retrofitted with a servomotor-driven pump or Variable Frequency Drive controlled pump of any internal gear or vane design. By altering the prime mover speed you can control the VFD pump pumping rate.

During the last injection moulding cooling stages, virtually no motion is essential. The rotation of pump is slowed by the Variable Frequency Drive providing only the required flow. This will uphold the required pressure for such functionality as mould clamping and offer only the required flow to reimburse for internal system leakage.

As a least requirement for several years, a pressure-compensated, variable-volume pump has been a valued standard. While the shaft on such pump type continuously turns at full speed even when no flow is required, reducing the pumping chambers size or by shrinking piston stroke reduces the displacement. Till a valve is opened to move a cylinder, which restarts flow demand, extreme system pressure will be sustained.

The aim of lessening pump displacement in the earlier scenarios will help in saving considerably on input energy when negligible or no motion is required for the moulding machine. In injection moulding industry getting such profit margins is extremely valuable. Excess heat is even lessening. Cutting down the heat amount produced is highly important for the long life span of a machine, which already radiates and absorbs the heat made from plasticizing heaters.

For more details, to use hydraulics within injection moulding, you can contact Darwin Motion professionals 24/7.