Water Mix Cutting Fluids - How Do You Keep Them Clean?

Water Mix Metalworking Fluids have to put up with a lot. Their life and performance will depend not only on how the product is mixed and used but what steps are taken to ensure they remain clean throughout their operating life cycle.

These are complex emulsions offering cooling from the water phase and cutting performance from the concentrate, be it oil based or synthetic. Inevitably contaminates from the metalworking process begin to have an effect on sump life and tool life and if not contained will eventually cause coolant failure.

That can mean shortened sump life, poor cutting performance and a deteriorating environment for operators exposed to the coolant. That means escalating costs for the end user.

A major issue with modern CNC machine tools are their total loss slideway lubrication systems which, while protecting the integrity of the machine, do nothing to enhance the metalworking fluid once the slideway oil is lost to the sump. A thick layer of tramp oil floating on the coolant surface cuts off oxygen from the cutting fluid allowing bacteria to grow underneath. Modern metalworking fluids are somewhat protected in their design parameters but they are not bullet proof and sooner or later will be overcome.

There are ways to remove tramp oil, as unwanted oil contamination is referred to, either manually or automatically. Manual methods are tedious, either it has to vacuumed off or soaked off with specially formulated blankets, not so popular with operators as one can imagine. Automatic methods include tramp oil skimmers attached to every machine tool sump.

However for these methods to work effectively there must be a relatively motionless surface where tramp oil can separate slowly to the surface. In agitated coolant flows, particularly in high pressure pumping systems, often tramp oil droplets remain suspended in the metalworking fluid making them difficult to remove.

The answer is to provide a process where coolants are able to quickly reject entrained droplets of oil, collect them together and remove them from the carrier fluid. If that can be done without any type of consumable filter media all the better.

Contaminated fluid is separated in a three phase lamella package in which both tramp oil and solid particulates are separated in a continuous operation. A lamella package consists of a series of steel plates mounted closely together so that tramp oil droplets and solid particulate have only a short distance to move before settling upon the plate surfaces. The coolant flow through the lamella's is slow enough to allow rapid separation of both oil droplets and small solid particles. 

Tramp oil quickly floats to the surface while solid particle stick to the lamella plates preventing further movement through the fluid system. Clean coolant is delivered continuously to a clean tank where it is pumped back to the machine tools connected. Tramp oil is collected for disposal while solid particulate in the form of sludge is removed usually by a scraper unit but dependent on application.

This simple separation principle uses no consumable media and can be scaled upwards or downwards to suit the flow rates required.

Central Coolant Management System

These systems operate automatically around the clock to provide connected machine tools with a stable and clean coolant. Sump levels are maintained at a constant level and dilution while tramp oil and floating particulate are removed to be sent back to the central separator for processing. The central unit is equipped with a topping up unit for fresh make up coolant. An automatic clean in place system (CIP) operates at timed intervals to ensure that the lamella packages remain free from contamination.

Supply and return pipework carry coolant to and from the central separator the method of connection at each machine depends on the application.

By-Pass Purification is used mainly on machine centres and lathes where the original sump and pumps provide for the flow rates at the machine tool. A smaller by-pass flow delivering clean coolant is replicated by a return flow from the installed return pump modules to remove tramp oil and small floating particulate. 

Full Flow Purification is usually used on grinding applications where the coolant is used to convey chips from machining operations with the entire coolant volume returned to the central separator. This allows for further processing of chips or grinding waste, for example centrifuging or sending through a briquette process.

Fluid Solutions offer the following options dependant on application: