Plant & Works Engineering
Cutting fluid problem solved
Published:  08 July, 2011


A new generation of bactericide-free cutting fluids has removed the problem of emulsions splitting in use and the related bad odour nuisance. PWE reports.


In demanding metalworking applications, coolant fluids are vital. Indeed, they are essential when it comes to exploiting the full potential of modern high-performance machine tools. At the same time, users everywhere are increasingly clamouring for advanced coolant fluid concepts with enhanced manufacturing shop performance.

Bacterial contamination with its well-known, unpleasant side-effects leading to emulsion splitting, is one factor that has been singled out repeatedly as a major cost driver. In Germany, Walter AG had precisely this problem at its plant at Tübingen.

This long-established company ranks among the world’s leading manufacturers of high-quality precision metal-cutting tools. Its catalogue comprises some 48,000 items for turning, milling, drilling and threading. It goes without saying that metalworking fluids are indispensable here, both throughout manufacture of these carbide tools and during their later use by customers.

For Manfred Hähnle, Walter AG’s maintenance department head, one especially important criterion when selecting the products is the assurance of high process stability. Not too long ago, therefore, the company decided to switch to a new cutting fluid - Multan 71-2.  This Henkel product contains no bactericides, yet has proved itself to be significantly more durable for many operations.


Unwanted micro-organisms

“We urgently needed to find a solution for our advanced technology centre, because we had repeatedly experienced a strong build-up of odour when the machines had been idle for a long time,” reported Hähnle. “The centre is regularly used for training sessions and demonstrations on all aspects of metal cutting.”

The reason for these unpleasant odours was bacterial contamination of the metal cutting emulsion. Although this is a natural biological process, once the bacteria have multiplied to a certain level, the emulsion can split and become unusable.

Basically, there are two ways of avoiding such problems. The first option is to use conventional, bactericide-free metalworking fluids where bacterial growth is initially tolerated up to a certain concentration. The effect is then combated by adding bactericides. The disadvantage here is that the dead microorganisms act as excellent nutrients for the next generation of bacteria, so the process has to be repeated at ever-shorter intervals.

The second option is to use fluids that contain bactericides, which permanently suppress bacterial growth.


Focus on safety, health and environment

In both cases, the 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 following contact. Frequent changing of emulsions that have split is not only very costly, but also puts an additional burden on the environment.

Henkel offers a sustainable solution to this cutting fluid problem with the patented emulsifier technology of its Multan 71-2 products. After intensive development work, a microbiologically robust cutting fluid was formulated that contains no bactericides (such as formaldehyde splitters).  What’s more, it does not need any later addition of bactericides to keep it stable. The new product is suitable for many different kinds of machining from roughing to grinding and has impressed Walter AG with its performance in practice.

“Environmental protection and health and safety are top priorities in our company, having the same status as product quality and optimal cost-effectiveness”, said Hähnle. His verdict on the novel, skin-friendly, bactericide-free cutting fluid technology is entirely positive: “The product not only significantly improves workplace conditions, it also shows outstanding process stability. Even after pauses of up to four weeks, we’ve had no problems at all – bad odour nuisance is not an issue anymore.”


High stability, low consumption

After its successful introduction in the advanced technology machining centre, Multan 71-2 has now also been in use for eighteen months on the production line for manufacturing turning tool holders for indexable inserts. Hähnle regularly carries out extensive checks on the metalworking fluids used in the manufacturing shop. The Tübingen plant uses some 10,000 kilograms of concentrate every year. Measurements show that Multan 71-2 satisfies Walter AG’s high standards regarding quality, process stability and usage in a continuous production environment as well.

Compared with conventional products, the initial concentration needed in water to make up the emulsion is only 5 percent. And when it comes to top-ups, a concentration of just 0.5 per cent is needed.

 “Another point is that Multan 71-2 performs excellently in deionised water right from the beginning, without foaming and without needing any additives”, emphasised Hähnle. In the past, the fluids had to be made up with water from the city network to avoid heavy foaming. The disadvantage with this source is that, after a certain bath life, continuous evaporation losses tended to result in heavy deposits of lime scale and mineral salts, which have a negative effect on the entire manufacturing process.

Walter AG gains further benefits through the significantly longer bath lifetime – an important factor in terms of economy and ecology when choosing the most suitable metalworking coolant. “In the past, we had to replace the entire coolant bath once a year on this line because the emulsions had split due to the high bacterial contamination,” said Hähnle. With the bactericide-free cutting fluid Multan 71-2 from Henkel, the process has now been running perfectly stable for eighteen months with a constant pH of around 9.1. This reduces the consumption of water and chemicals as well as cutting costs for initial bath preparation, topping up, and disposal.

“Our experience with using Henkel’s bactericide-free cutting fluid shows what a difference the right choice of fluid can make in improving efficiency in manufacturing”, affirmed Hähnle.


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