Hydraulics for Electric Plastic Injection Molding Machines

Posted 7th March 2018

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If you’ve ever been to a doctor or have sat in an automobile, chances are that you’ve been in contact with a plastic assembly part produced from an injection molding machine. Over the years, injection molding machines have changed from primarily hydraulic press type machines to electric press types.

Although the switch to electrical brought benefits like reduced energy consumption costs, many of the molds that went into the machines still have cores, ejectors or valve gates that require hydraulic auxiliary power around 1500 -2500 PSI combined with a high flow rate to pop the core out quickly without deforming the molded part. A reliable servo option that could do the same job is often rare and very expensive.

The traditional hydraulic power pack is technology from the 1960’s which usually requires plumbing a chilled water heat exchanger, adds to the noise level of a molding facility and is an energy hog. Few actually realize the amount of energy consumed by a standard industrial electric motor while driving a hydraulic pump at idle or standby.  The majority of the wasted energy is converted into heat which is typically absorbed by the hydraulic system or your HVAC system.

A typical mold running a core may have a 10 -15 second cycle time.  An auxiliary function takes about 1 second to “set” and 1 second to “pull”.  The remainder of the cycle is spent holding pressure in a static condition.  During this time the hydraulic system is maintaining pressure using a variable displacement pump or driving a fixed displacement pump which is unloaded.  Either way, little “work” is being accomplished and a high amount of energy is being consumed resulting in wasted energy and excessive heat.

Many plastic injection machine manufacturers (and customers alike) don’t want to pair a loud, inefficient, hot and huge hydraulic system next to a clean, efficient machine. That’s why All World Machinery Supply offers plastic injection molding machine specific hybrid hydraulic system, aptly named the “Corepull,” with an inverter controlled variable speed electric motor which spins only as fast as needed to produce the required flow and pressure (speed of cylinder or hydraulic motor).

Once the desired pressure is met, the Corepull unit slows to approximately 300 RPM while maintaining pressure. After a hydraulic valve is shifted it will automatically sense the required power and respond by accelerating to 4,000 RPM within 1/10 of a second.  This is accomplished using an on-board closed loop control system. Another benefit of this technology is that a “heat exchangers” is not required unless your total cycle time is less than 5 seconds. An unlimited amount of cores or multiple auxiliary functions can be run using a manifold with a variety of circuit configurations.


For better functionality, the keypad on the front of the Corepull units allows for a fast and easy way to change pressure and flow. The wheel kits under the unit allows for it to be easily moved machine to machine.

The Corepull is essentially the perfect hydraulic pairing to all-electric injection molding machines that want to match the efficiency of their machine to the power of a hydraulic system. Common or custom, contact All World to inquire about a Corepull solution for your plastic injection molding machine or click here for more details.