Energy Saving Strategies for Plastics Injection Molding Operators – Part II

This is the second tip in a three-part series sharing U.S. Mobil field engineer Adam McMurtrey’s technical paper on energy savings strategies, which he delivered at ANTEC, the largest plastics technical conference in the U.S.

Last week’s portion of the paper highlighted why hydraulic oils are relevant to energy efficiency. This week, we dig deeper into the science of hydraulic oils to explore this relationship in more detail.

Switch to advanced hydraulic oil

It is important to use a hydraulic oil with excellent shear stability and a high viscosity index. High performance hydraulic oils maintain their optimum viscosity across a wide range of operating conditions, helping to protect equipment, improve energy efficiency and extend oil drain intervals. That, in turn, can help to reduce maintenance, cut costs and enhance operational safety by reducing employee interaction with machinery. Extending oil drain intervals can also cut waste lubricant disposal, improving a company’s overall environmental credentials.

The science behind advanced hydraulic oils

In hydraulic systems, a pump cannot be 100% efficient in its energy conversion, typically losing energy in two main areas: mechanical losses, where energy is lost to friction; and, volumetric losses, where energy is lost as a result of internal fluid leakage. Both types of energy loss are primarily a function of the hydraulic fluid’s viscosity and lubricity properties. Specially formulated high performance hydraulic fluids can reduce the magnitude of both mechanical and volumetric losses by utilizing a high viscosity index.

Viscosity index (VI) is an empirical and unit-less number used to specify the fluctuation in viscosity with respect to temperature. The viscosity of a fluid with a high VI does not change as rapidly with temperature when compare to a fluid with a lower index. The technology advantages of a higher VI include increased energy efficiency and a reduction in power consumption, as well as a longer operating life and cleaner oil. Together, these benefits help the equipment suffer less “energy loss” during the normal course of operation.

As shown in the graph below, which maps the energy consumption of an injection molding machine when using a conventional hydraulic oil (red line) compared to a more advanced oil (blue line), the more advanced oil delivers significant energy savings at key moments during operation.

If you’re in the plastics industry, or if you operate hydraulic equipment of any kind, this two-part tip series is for you. We hope you enjoy these tips, and please let us know if you have any questions via the comments section below!

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