Energy in Injection Moulding

Nowadays identifying the environmental footprint of products and processes is of great importance to determine if they are viable in the long term, or whether they will have negative impacts to human health, non-renewable resources, animals, etc. One way to assess a process is to identify the energy sources and energy amounts that are required to fulfil this. As a very basic definition, energy can be defined as the property that must be transferred to an object to perform work. This means that for an injection machine to function adequately, electrical energy must be transformed into heat and mechanical energies. In the past few years a lot of attention has been given to determine the energy associated with all the various steps in injection moulding. The usual trend observed is that melting of the polymer and clamping of the mould are the steps with the higher energetic contribution.

Table 1. Energy breakdown in percentages for injection moulding of different products (Thiriez, 2006).

Product Melting Injection Clamping Ejector Idle Heaters Cycle time [s]
Dairy container 53% 8% 27% 0% 0% 15% 6.45
Medical Syring 46% 5% 8% 2% 29% 15% 23.1
Pail 50% 10% 13% 0% 15% 11% 18.25
Closure 66% 7% 12% 3% 0% 12% 16.75

 

The energy can be calculated directly from the monitoring of the equipment’s electrical signal, or alternatively from the cavity’s pressure and temperature information. One of PREVIEW’s main advantages is the fact that real-time data can be obtained directly from the mould, and hence can provide essential information for the calculation of energy consumption estimates.

Bibliography

Thiriez, A. (2006, May). An Environmental Analysis of Injection Moulding. Thesis submitted for the degree of Master of Science in Mechanical Engineering. Massachusetts, Cambridge, United States of America: Massachusetts Institute of Technology.