VSD controller squeezes injection moulding costs
Typically, 30-50% of the power consumed by all but the latest hydraulic injection-moulding machines is wasted on pumping far more oil than the various stages of the moulding process really need. The fixed oil delivery from the hydraulic pumps passes through proportional hydraulic valves, which act as energy shunts, delivering some of the pressurised oil to the press and diverting the rest back into an oil reservoir.
Now, a research and development company based in Newcastle-upon-Tyne in the UK claims to have come up with a cost-effective technique for reducing this wasted energy using variable speed drives.
Several years ago, the company, Powermiser, pioneered the use of VSDs to cut the energy used by injection moulding machines by 30-70%, depending on the capacity of the machine, the shot size and the cycle time. This technique, which can be applied to all leading makes of moulding machine, requires a sophisticated control system to over-ride the proportional valves and to provide speed reference signals to the VSDs.
Until recently, the technique required considerable programming skills, and was therefore relatively costly and time-consuming. Now, however, Powermiser has developed a circuit board (shown above) pre-programmed with the necessary run-time software, and an accompanying Windows software tool that allows all of the configuration data to be entered via an intuitive user interface.
No programming skills or experience of injection-moulding machines are needed, because the system includes a comprehensive instruction manual. The PDI (Powermiser Drive Interface) supports ABB and Vacon drives via Mobus, but can be adapted for most other makes of drive.
Earlier this year, a pre-release version of the PDI package was trialled successfully by Powermiser`s Singaporean distributor, Westec Concepts. The installation, on a 200-tonne Toshiba press at the Singapore plant of a multi-national company, uses an ABB ACS-550 drive. It has cut the kWh consumption by a third, far exceeding the expectations of the client.
Powermiser is now establishing a network of distributors and installers in the UK and mainland Europe. The package is on the list of products approved by the UK Government for ECA (Enhanced Capital Allowances) tax relief under the Climate Change Levy.
