Technologically advanced industrial machinery is requiring hydraulics to provide more efficient and quieter solutions with a smaller footprint, while maintaining the benefits traditionally associated with hydraulic systems, including high power density, precise control and enduring performance. Historically, these benefits have usually come hand-in-hand with inefficient energy allocation, heat generation and noise. 

Conventional hydraulic power units require very large capacity pumps and motors to ensure steady performance during the highest duty-cycle of the system. When energy costs were significantly lower and environmental regulations less stringent, the wasted energy and resulting carbon emissions were seen as inconsequential. However, in today’s eco-conscious and globally competitive economy, changing to systems where power is tightly modulated to the requirements of specific tasks within highly complex hydraulic systems is essential.

In light of this, REP International, a specialist in the construction of injection moulding machines for the rubber, thermoplastic and other polymer industries, was looking for a solution that would make energy efficiency one of the defining features of its machines.

The Lyon-based manufacturer turned to the research and development expertise of Parker Hannifin to develop an innovative immersed servo pump system to significantly reduce the energy consumption of their machines. With more than 12,000 REP presses installed worldwide, the machines are well known for their robustness, ease of use and longevity, with some presses operating for over forty years.

In addition to its large range of compression presses and economical injection moulding machines, the company also offers rubber devulcanising machines for customers wishing to recycle their production waste and laser mould cleaning machines. 

A complete, single-source system solution

Hydraulic power has long been utilised in industrial processes such as injection moulding. This is due to the inherent advantage of being able to transmit a large amount of power via a relatively compact system of pipes and hoses. In many of these systems, the source of pressurised hydraulic fluid is the hydraulic power unit (HPU). 

The most energy efficient alternative, which took three years of development and collaboration with REP International, proved to be an immersed servo motor pump system consisting of three separate elements: a pump, a servo motor and a drive for control. The original idea was to replace the self-regulating pumps with a solution that could very accurately match a flow rate to a real need.

“The principle is this: if I adapt the flow, I also adapt the speed,” explained Vincent Sinot, the Parker Hannifin sales manager for the Rhône-Alpes region. “The general principle is to use the rotational speed of the motor to control the flow rate at the pump outlet.”

With plastics machinery, there are many auxiliary movements in addition to opening and closing the moulds, plasticising and injecting. These movements take place partly sequentially but also occur in parallel. They must therefore be supplied centrally with the required flow and pressure. The often brief cycle times also demand supply with the highest dynamics. With the maximum speed of a small pump, a very high volume flow can be achieved. This significantly reduces investment costs.

The flow and pressure regulation – controlled by the speed and torque of the servomotor – offers undeniable advantages; not only in regard to the reduction of energy consumption, but also on the simplicity of the installation of the hydraulic components.

“In terms of space, the size of the motor pump has been reduced, quite a task because it was necessary to take into account the control system,” explained Laurent Terrier, product development manager at REP International. “After making this choice, we continued to work together on the development of the system. Today, the solution is stabilised and it has been installed as an option on all our machines since 2012. Parker is currently studying optimisation tracks. When the new evolutions for the system arrive, we will continue to carry out more tests and go even further in our environmentally-friendly approach.”

Developing drive controlled pump technology

Based on this fundamental modification of hydraulic constant pressure systems, Parker has developed an entire new generation of efficient hydraulic drives. The hydraulic electromechanical drive can be connected to a speed-controlled, electrohydraulic full-system solution called the Drive Controlled Pump (DCP).

By utilising an alternating current drive controller, the speed range can be regulated and tailored in advance to a predefined cycle. The precise amount of hydraulic energy required can therefore be generated for any particular point in time during the machine’s duty cycle, leading to cost savings for cycles with high part load amounts.

When selecting pumps, the most important considerations should not only be output but also minimum and maximum speeds. A smaller size generally enables higher speeds and causes lower noise emissions. In contrast, the minimum speed depends more on the design than on the size. When considering the various requirements,Parker believes two pump technologies are preferable: the vane pump (best for fixed displacement pumps) and the axial piston pump (recommended for high peak or long-term pressures).

In order to put together an energy efficient motor pump combination, the individual components must be selected in such a way that the sum of all losses in the specified operating points is at a minimum. Parker’s DriveCreator software tool  http://www.parker.com/drivecontrolledpump can help with this process. Furthermore, a start-up tool simplifies the task of putting the DCP into operation within the application.

A valuable collaboration

Parker’s ongoing collaboration in the development of an energy efficient hydraulic solution has already delivered the selling point REP International desired for their products – being able to offer an energy efficient option to every customer. With a strong customer base in manufacturing powerhouses such as India, China, Russia and Brazil, the potential exists for REP International’s products to make a palpable difference to climate change by reducing carbon emissions.

“We have worked with Parker for more than 20 years for the supply of various components, but in this case the solution we were looking for did not exist at the manufacturer,” said Terrier. “That’s when we started working closely with Parker’s R&D team to define our needs, perform numerous tests and develop a system that is innovative, powerful and not too expensive. The aim was to offer this as an option for our entire range of presses.”

“Parker Hannifin is more than just a manufacturer – they have proven to be our true partners in innovation,” added Terrier. “We have developed very good relations with the technical teams and the commercial manager, who has been fully available and has made every effort to respond to our requests.”