Machine Monitoring

At some point in the energy-management process, you’ll want to measure the real energy use of individual machines. It’s not difficult to measure current using a simple clamp meter and to convert this into the power drawn and the energy used (by knowing the voltage and the power factor).

The problem in plastics processing (and particularly in injection molding) is that the current and power vary rapidly with time, and it will be almost impossible to get an accurate value for the current because it changes so rapidly. Fortunately plastics processors are not alone here, and there are many instruments available to measure current at specific intervals and then to use software to convert these readings into power drawn and energy used.

I use the Elcomponent “SPC Mini” for quick jobs and “SPC Pro” for full 3-phase monitoring, with factor calculation and reference voltage recording, to give more accuracy (www.elcomponent.co.uk). There are other manufacturers, but I like the Elcomponent software for data handling.Whichever meter you choose, it’s also important to check that the data-handling software is also user-friendly. Try it before you buy it!

Actions:

Buy a logging clamp meter. This will record the current at intervals, and these units generally will have software supplied to convert this into the power and energy used during the process cycle.
Use machine monitoring to “look inside the cycle” in injection molding.•Use machine monitoring to look at energy use in compressors and see that an idling compressor is still using energy even if it’s producing no compressed air.
Machine monitoring can be fun, but electricity is dangerous (especially 3-phase). Follow good health and safety practices and stay safe.

Note: Dr. Robin Kent is the author of Energy Management in Plastics Processing, published by Plastics Information Direct, and managing director of Tangram Technology Ltd., consulting engineers specializing in energy management in plastics processing. rkent@tangram.co.uk.