The crucial role of the flow switch in the cutting fluid and grinding fluid systems

2026-03-27

In the field of metal processing, cutting fluid and grinding fluid are known as the "blood of the machine tool". They not only undertake the tasks of cooling, lubrication and chip removal, but also directly determine the surface quality of the workpiece, the lifespan of the cutting tool, and the safety of the equipment operation. However, in actual production, problems such as pipeline blockage, pump failure, liquid leakage or insufficient flow occur frequently. Once the flow is abnormal, it can lead to minor issues like tool burnout and workpiece scrapping, or even serious consequences such as equipment damage or production safety accidents.

I. Why is a flow switch needed?

Cutting and grinding operations are usually carried out under high pressure and high flow conditions. During deep hole drilling, high-pressure center water supply (CTS), or precision grinding processes, the nozzles or cooling pipelines are prone to blockage due to debris accumulation, water scale formation, or aging seals.

The traditional approach relies on operators' visual inspection of the liquid outlet, which is not only inefficient but also has a lag. Once the flow stops, the instantaneous high temperature generated can rapidly change the metal hardness of the cutting tool, causing it to chip or wear out within a few seconds, and even causing expensive precision spindles to seize due to thermal expansion.

II. Solution

The core value of the flow switch lies in real-time sensing of the fluid state and achieving electrical linkage. Depending on different processing techniques, the current mainstream solutions on the market can be classified into the following categories:

Piston-type/Blade-type Flow Switch (Low cost, large flow monitoring)

For ordinary turning and milling operations, these mechanical flow switches exhibit extremely high stability. When the liquid flow reaches the set value, the internal magnetic reed switch is triggered. If the flow decreases or stops, the switch immediately disconnects and sends a "stop" or "alarm" signal to the CNC system, forcing the machine to stop feed or retract.

Thermal Conductivity Flow Switch (No pressure loss, suitable for low flow)

In precision grinding or micro-lubrication (MQL) applications, the flow is often small and the pipelines are thin. The thermal conductivity flow switch does not require mechanical moving parts. It determines the flow rate by sensing the temperature difference caused by the heat dissipation of the liquid. Its advantage is that it remains sensitive to extremely low flow rates and does not get stuck due to tiny particles in the fluid, making it ideal for environments where the grinding fluid contains fine sand-like debris.

Electronic Digital Flow Switch (Intelligent, data-driven)

With the advancement of Industry 4.0, more and more intelligent factories require equipment to have self-diagnostic capabilities. Electronic flow switches not only output digital signals but can also upload real-time flow values via 4-20mA analog signals to PLC or MES systems. Managers can set "upper and lower limit warnings" to arrange for cleaning filters or pump maintenance in advance when the flow shows a trend of decline, transforming "passive shutdown" into "predictive maintenance".

III. Application Cases

In the engine cylinder block production line of a well-known automotive parts manufacturer, the filter of the high-pressure cooling pump was clogged multiple times, resulting in tool breakage. After introducing high-precision electronic flow switches, the system triggered an early warning when the flow dropped to 80% of the rated value, "Please clean the filter", completely eliminating batch waste accidents caused by flow interruption.

On the precision grinding machine used for grinding the bearing raceways, since the grinding fluid needs to cool the grinding wheel and rinse the workpiece simultaneously, fluctuations in flow rate directly affect the surface finish. By installing a thermal flow switch, the equipment operator discovered that when the flow rate fell below the safety threshold, the equipment would automatically trigger an alarm and pause the processing, ensuring the consistency of the product size and the yield rate for each batch.