Seeking the energy-saving benefits of electrics and the power of hydraulics, molders are increasingly turning to hydraulic-electric hybrid injection molding machines.

Seeking the energy-saving benefits of electrics and the power of hydraulics, molders are increasingly turning to hydraulic-electric hybrid injection molding machines. However, these machines often fall somewhat short of energy-efficiency goals.

The reason is that, while the typical hybrid machine has an electric screw drive, three of the four axes are hydraulic – meaning that nearly all of those hoses, valves and pumps associated with a hydraulic system are still part of the machine. Along the way, energy is lost as it is in all hydraulic systems.

A simple comparison of comparable tonnage machines, a typical hybrid and an all-electric, shows the major differences:

 

Typical Hybrid 550

 

All-Electric 550

 

Hydraulic clamp

4 Pulleys

 

Hydraulic injection

 

Hydraulic eject

 

2 Rollerscrews

1 rack/pinion

 

1-2 Motors

 

5 motors

 

85 Power Factor

 

95 power factor

 

Motor/Drive creates harmonics

 

Low harmonics

 

Hydraulic HP does not decrease to keep same injection rate and clamp speed

HP decreases when not needed

 

 

A New Kind of Hydraulic-Electric Hybrid

Unlike the typical hybrid, a new electric-based hybrid injection molding machine for the first time delivers electric efficiency along with hydraulic force.

The new system uses a hydraulic accumulator to provide the force that would otherwise require an all-hydraulic machine. The rest of the machine is electric-driven, maximizing the energy savings.

In other words, molders using the new hybrid configuration, available on Milacron POWERPAK娪 machines, get all the benefits of an electric machine, but with injection rates up to 300+ cubic inches per second (compared to all-electric machines, which top out around 100).

These rates are necessary especially for applications with thin-walled parts with high length over thickness (L/T) ratios, in which the material must fill the entire part before setting in the thinnest areas.