Hydraulic versus Electric

by R Tomlinson - Plastic Moulding Solutions

Introduction

The debate within the injection moulding industry continues to be discussed about the merits of both types of machines and which will come out on top, my view is the electric version having seen the first electric machine some years ago my first reaction was as it is now this is the way forward for injection moulding.

I clearly remember the reactions of all the European manufacturer's saying at the time that they would never take off yet nearly all of them now produce an electric version or a hybrid version of the machine. At the last Interplas several machines from different manufacturer's where on display proving that they now believe that the electric machine is not only here to stay but is the future of injection moulding with one company quoting that electric machine sales now accounted for 40% of their sales world wide.

Why has it taken Europe so long to catch on I believe that initial cost differential was probably the major factor in holding back sales but this differential is closing all the time and is now about 20% compared to the original 50% this difference will continue to reduce through competition. However, if you compare the relative merits of the electric machine against the hydraulic version the differential I believe is already gone in fact if you compare the lifetime costs of each type of machine over a 10 year period the saving in reduced energy cost alone justifies the extra investment, the overall maintenance cost is lower by 50% and the overall downtime attributed to breakdowns is 50% lower in fact no matter how you look at each attribute of the two types of machine the electric machine it comes out top and the cost down savings do not stop.

The only area at present that the electric machine falls down on is performance in the fast cycling thin wall packaging applications this is due to the technology not being able to match that of hydraulic machines in the injection pressure/speed area but a solution will be found, in every other area of the injection control system the electric machine out performs and is superior to the hydraulic machine. The injection moulding process relies on several factors to produce quality parts and this is an area that in my view not been marketed or sold by the manufacturers to produce good parts you need accuracy, repeatability, consistency and reliability by removing the hydraulics you remove a variable that affects all of these factors and therefore reducing the probability of rejects which in turn takes you closer to the goal of zero defect and that is why I would choose the electric machine.

Benefits of the Electric Moulding Machine. 

These benefits may apply to new manufacturing or existing operations using both hydraulic and electric machines and have not been listed in any priority.

Advancements in on board computers will allow manufacturer's to build in more monitoring of the machine and process it will allow an increase in the planned preventative maintenance control that is actioned by the machine, data acquisition and monitoring will prevent breakdowns before they occur. These advancements along with production data and quality monitoring will reduce the labour involvement and requirements still further. Interfacing with other equipment and operations will become commonplace rather than the exception.

I have already given an estimate that 50% of all maintenance costs are hydraulic related in some way or other this figure may actually be 75% based on my experience couple this with my estimated figure that power consumption and other related overhead and variable cost savings could amount to a further 40% in savings.

From a manufacturing point of view a 40% reduction in the machine hour rate alone would increase the competitiveness of any moulding operation and in these difficult times should at least be considered before making a capital investment.

This article is my own viewpoint regarding the hydraulic versus the electric machine debate if you would like discuss to it in anyway or require further information then please contact myself. 

Copyright R Tomlinson - Plastic Moulding Solutions 2003