SECTOR FOCUS: METALWORKING FLUIDS
The development and characteristics of ultra-low foaming metalworking products
Simone Pota & Marco Bellini, Bellini SPa
Any development of new emulsifiable metalworking fluid (MWF) is not trivial and formulators’ choices are crucial in the finished performance of the product.
During the development process of a new product, one must take into account and also balance, three key considerations that pull in different ways. Firstly regulatory concerns narrow the variety of raw materials and substances that can be used to formulate a new product compelling the developer to find green, sustainable and safe alternatives. A second consideration is the machine tools design: with the trend to use high-pressure nozzles and small emulsion tanks being more frequently found in industry. The third and most important consideration is customer’s needs. Among these needs are the price of the finished formulation, maintenance costs of the fluid, water compatibility, detergency, machining performance, bio-stability and foaming tendency.
Over the past few decades technical developments in fluid formulation have led to higher performance MWFs with longer life expectancy. This, combined with a trend for companies to migrate towards semi-synthetic products providing a higher surfactant to oil ratio, and ester-based emulsifiable fluids requiring a higher oil to water emulsion and hence HLB numerical rating, can have a tendency to foam. Although emulsion filtration systems could gradually remove defoamer particles lowering its concentration. As generally known, foaming in MWFs can produce several problems which ranges from a change in appearance or aesthetics, to loss of lubrication and cooling performance, emulsion loss through leaking and chip and dirt retention in the fluid.
To counteract foaming in emulsions we developed 18 LUBE MAGAZINE NO.169 JUNE 2022
two different concepts: assuming that defoamer concentration will tend to zero over time. We developed the idea that an emulsifiable MWF must be low foaming even when defoamer-free. The most important part of the work involved a formulation study starting from raw materials screening, which has been combined with the selection of the best defoamer for each formulation.
Method
By collecting and analysing random samples from the field, we divided emulsifiable MWFs in three main categories according to their foaming behaviour. The root cause of foam is not always down to the customer, for example the water used to prepare the emulsion could be too soft, system design might be poor, and concentration levels could also be too high.
The aim of the formulation study is to replicate a closed and controlled metalworking fluid system to observe the same behaviour as that experienced in the field, and then use the outcome of this study to create new ultra-low foaming MWFs.
This is quite challenging because a huge number of tests must be performed in a short period, thus the instrument and the method used are key factors for research and development efficiency.
A tailored method of analysis has been developed according to iterative Deming Cycle (Plan Do Check Act or PDCA) which meant varying many test conditions such as water hardness, time and type
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