Cutting out bacterial issues

How do you stop a user-friendly, bactericide-free cutting fluid from becoming contaminated with bacteria, resulting in the emulsion splitting and producing bad odours? One solution is with patented emulsifier technology, the main feature of a new cutting fluid from Henkel. Peter Homfray- Cooper, a technology specialist at the company, explains

The bacterial contamination of commonly available metal cutting emulsions is a natural biological process. However, once bacteria have multiplied to a certain level, the emulsion can split and become unusable. Traditionally there have been two ways of avoiding such problems. The first option is to use conventional bactericide-free metalworking fluids where bacterial growth is initially tolerated to a certain level of concentration, then combated by adding bactericides. The disadvantage here is that the dead microorganisms act as excellent nutrients for the generation of bacteria, so the remedial process has to be repeated at ever-shorter intervals. The second option is to use fluids that contain bactericides, which permanently suppress bacterial growth.

In both cases, use of bactericides has to be viewed critically. Exposure to bacteria or bactericides represents a potential health hazard for employees who may develop skin irritations or increased sensitisation after contact with the fluids. Frequent changing of slip emulsions is also costly, putting an additional burden on the environment.

Henkel has developed a water-miscible, bactericide free cutting fluid technology. The company believes that what makes it different is its patented formulation that actively prevents bacteria from absorbing nutrients from the degradation of emulsifiers once a certain minimum bacteria concentration has been reached. In effect bacterial growth is impeded because these micro-organisms have nothing to sustain them.

In this way, this new generation of Multan fluids fully comply with the revised EU Biocide Regulations. They save manufacturers the cost of regular fluid replacement and enable them to demonstrate good environmental responsibility.

Two of these fluids are now available in the UK: Multan 71-2, described as the generalist; and Multan 77-4, the specialist.

Multan 71-2 is multifunctional due to its high lubricity which makes it suitable for a broad variety of metalworking processes, including grinding. Multan 77-4 is for high alloy steel and aluminium machining.

Henkel believes it takes lubricity to a higher order, even at low concentration. It is especially suitable for centreless grinding.

Although a relative newcomer to the UK, Multan 71-2 has a proven track record on mainland Europe. For example, the tooling manufacturer Walter AG, uses it in its training and demonstration centre as its former coolant was responsible for a strong build-up of odour when machines were left idle.

The company manufactures high quality, high precision metal cutting tools and offers some 48,000 items for turning, milling, drilling and threading. The selection of metalworking fluids is of vital importance, not just in the efficient manufacture of carbide tools but also a recommendation to customers to get the best return on tool life.

Not only did Multan 71-2 immediately resolve the bad odour problem in the training centre, it demonstrated a high degree of process stability. This led to the product being adopted on the production line for the manufacturing of turning tool holders for indexable inserts. In addition to providing important health and safety benefits, it delivered quality performance in volume production and cost efficiency.

Another important point for Walter AG is that Multan 71-2 performs well in de-ionised water without foaming and without the need for additives. In the past fluids had to be diluted with tap water to avoid heavy foaming. While solving this problem, the hard water also led to heavy deposits of lime scale and mineral salts accumulating in the manufacturing system.

In the UK, Multan 71-2 is now being used successfully by a number of manufacturers.

Indeed several of these companies plan to extend its use to more machines and different processes on the strength of the early results. These users are tier suppliers to the aerospace, automotive and offshore industries as well as a number of high precision, specialist machine shops.