Following our introduction to cutting and cooling fluids, and the potential dangers and safety points, we thought we’d look more specifically at the application of these materials. This in an important factor in determining environmental effects of fluids as well as their effectiveness at performing their function.
Different Types of Pumps
There are essentially three distinct types of pump for applying fluids to different machining processes. Which approach to take will be dictated by need and of course, budget. Probably the most common type of application is the “pump based” system. A pneumatic pump drives fluid from a chamber through a nozzle and onto the targeted area of machining. The pump stroke and frequency, how deep it pumps and how many times a second, can typically be closely controlled. This means that the output of the pump can be controlled more precisely than is the case for simpler methods of application. These can often be more expensive over time, with the dynamic part within the system, a lot of movement is required by parts within the pump. This movement can cause wear and tear over time and inevitably parts need to be replaced in order to maintain the same performance from the pump system. The flow of fluid can be monitored by control panels such as these used in the automotive industry. These will then address any inconsistency in the rate at which the fluid is delivered to the machining apparatus by sending commands to the pump.
A simpler alternative is the “Venturi system” of application. A reservoir of the chosen fluid is stored. The Venturi effect (named after Italian physicist Giovanni Battista Venturi the fluid is driven from the reservoir and out of a nozzle. Whilst this method doesn’t have the same potential for wear over time as the pneumatic pump method, it isn’t as responsive or as controllable as a pump system.
The other alternative is a “pressure” based system. Pressure is applied to a tank or reservoir of cutting fluid or lubricant, which is driven as a result from the tank and out of a nozzle. Although the pressure is able to be regulated in most systems, there is still some uncertainty in the consistency of the output from the system. Again, controlling the delivery of fluids is more difficult than with a pump system. More than one output will likely result in a drop in pressure as well.
Whilst the pump based system will deliver the fluid in fluid form at the point of contact with the machining process (known as flood cooling), other options can be considered. Transforming the fluid into a mist is the major alternative mode of application. This approach has its draw backs, but in most cases, if performed correctly, can reduce the amount of fluid applied. Known as MQL, (minimum quantity lubrication), it also reduces the emission output of the process. Using only just the right amount of air is important in making sure that the mist leaves the nozzle in a focused channel of fluid, rather than as a broader spray, which won’t have the same effect on the area of application. Although a mist can reduce the amount of fluid used, this is a false economy if the fluid isn’t actually being applied to the machining process in sufficient volume to function.