Metalworking fluid foam problems
Bothered by an emulsion that foams?
There are two types of foam: stable foam and unstable foam.
Both types of foam can be eliminated, regardless of their causes. Usually, this is time-consuming work, but it can also be handled for you quickly and automatically.
Will-Fill to the rescue!
Recognizing the two different types of foam
Foam formation in metalworking fluids is often considered to have a negative impact on your processes.
In fact, foam drastically reduces the cooling capacity and the lubrication of the processes that utilize the metalworking fluid. Therefore, it is important to discover the cause and to remove it or make the necessary adjustments.
What is crucial in this story, of course, is the ability to recognize the two different types of foam. Unstable foam is characterized by large air bubbles that appear on the surface of the emulsion; these bubbles are comparable to bath soap foam. Stable foam is more difficult to recognize, because the air bubbles are much smaller and therefore not immediately visible. You can compare stable foam to whipped egg white that forms a thick mousse-like layer, several centimetres thick, before transitioning to the metalworking fluid. The two different types of foam rarely form simultaneously, since they each arise due to different causes.
The first cause of unstable foam is insufficient surface tension of the metalworking fluid. Experience in the field shows us that this type of foam usually appears in new or in extremely clean installations where the mixing water has an extremely low microsiemens level. This indicates that the fluid contains very few salts and minerals, which are needed to increase the surface tension. A second cause of the generation of unstable foam is the improper preparation of the emulsion.
There are several ways to prevent unstable foam. Additives can be used to increase the surface tension of your metalworking fluid. The use of additives is highly recommended when your process must comply with certain purity classes. This way you are aware of the substances that go into your process. When the purity level is not an issue, you can choose an alternative working method, for example by using water with a higher microsiemens value as part of the first filling charge. Some caution is advised when choosing this method.
Regardless of the cause of your unstable foam, using Will-Fill will guarantee the proper preparation of your metalworking fluid.
This device features a patented mechanical mixer that automatically mixes the mixing water and the emulsion oil at the ideal composition using the extracted metalworking fluid that is already present in your installation.
The causes of stable foam formation can be subdivided into three categories: the mechanical construction of the installation, the production process and the composition of the metalworking fluid.
All three can contribute to the formation of stable foam. Where unstable foam is easy to attribute to a specific cause, the same cannot be said of stable foam.
A commonly occurring problem in the mechanical construction is that, for economic reasons, the correct ratio between the flow rates of the process pumps and the maximum volume of the metalworking fluid reservoirs is not maintained. This results in an emulsion that has not had a long enough retention time. Another issue is the control of the temperature of the metalworking fluid. What is of prime importance here is the avoidance of significant fluctuations.
Will-Fill directly handles both of these problems. In fact, with Will-Fill, two smaller filling charges are used, which prevents large temperature fluctuations. This is beneficial to all processes, whether they are temperature-conditioned or not, and will consistently ensure that the process does not undergo contraction when new, cold metalworking fluids are introduced.
Furthermore, since Will-Fill carries out these filling charges fully automatically, the presence of the maximum volume of metalworking fluid in the reservoir is always guaranteed. This, in turn, maintains the optimal ratio between the flow rates of the process pumps and the volume required, while also ensuring that the process pumps do not generate foam due to excessive volume reductions.
By production process, we mean operations that initiate the formation of stable foam. Practical experience shows us that deep hole drilling, grinding nozzles and deep pocket milling can cause the formation of stable foams.
Deep pocket milling and deep hole drilling bring about the same phenomena. Here, the fluid stream of the metalworking fluid is drastically interrupted because the emulsion must make an about-face, as it were, in order to flow back out of the bore hole or chamber. High pump-outlet pressures in combination with nozzles may also result in an emulsion forming stable foams.
What is important in the production process is that the correct outlet pressures are used and that bypass systems are implemented where needed so that the fluid stream is interrupted less drastically. Certainly an interesting Will-Fill functionality.
Composition of the metalworking fluid.
One of the most important, if not the most important, cause of stable foam is the chemical composition of the metalworking fluid. Certain products are not as resistant as others to the formation of stable foam. But a poor mixing ratio and contamination by foreign substances can also have an effect on whether or not stable foams are formed.
Some products simply foam faster than others. But Will-Fill completely eliminates poor mixing ratios. Before each filling charge, Will-Fill analyses the measurements it takes to determine how many units of water and oil are necessary to maintain the mixing ratio at the values you set. In addition, Will-Fill can monitor pH and EC values, making it possible to detect contamination by foreign substances before it’s too late. This prevents even greater problems down the line.