The pump requirements for successfully applying high-pressure coolant concern pressure and flow.
The pressure requirement for breaking chips varies depending on the material and the cutting parameters. 80 bars (1160 psi) is adequate for most applications. Higher pressures, up to 150 bar (2176 psi), are used for hard-to-break chips in materials such as Inconel and Super Duplex
The flow required is driven by the number and diameter of coolant outlets.
- Use a 20 micron filter
- Turning: If using tool holders with three 1 mm (0.039 inch) coolant nozzles, the flow requirement is 20 liters/min per tool position. However, it is important to consider the number of tools being run with coolant at the same time (number of tools x 20 liters/min). Because of the size of the machine, a large tank is needed to provide time for circulation
- Drilling: The coolant hole diameters in the drill increase with the drill diameter, meaning that a higher flow rate is needed for larger diameter drills. The goal is volume of flow, not pressure. A variable pressure pump is recommended, as well as using lower pressures with larger diameter drills
|Drill diameter||20 l/min||40 l/min|
|12||70 bar||70 bar|
|20||30 bar||70 bar|
|25||12 bar||50 bar|
|30||6 bar||23 bar|
|40||1 bar||3 bar|
One of the main benefits of using high-pressure coolant systems is the reduction of coolant pipe setting. With external pipes, it normally takes two to three attempts to get the coolant position right. Poor chip control often knocks the pipe and resetting is quite a regular occurrence, meaning that the process is inconsistent and the red light is on.
When using tool holders with precision nozzles, the coolant delivery from the tool to the cutting edge is fixed, but the coolant still needs to be connected to the tool holder. Pipe connections to a shank holder can be used; however, this will increase the set-up time every time the tool is changed, as well as interference, in addition to creating a chip trap.
The best solution is to use quick change, a plug-and-play solution. The coolant is permanently plumbed into the tool holder clamping unit. With these solutions, the adoption of machining with high-pressure coolant has the additional benefit of reduced set-up times, on top of chip control and increased metal-cutting efficiency.
Coolant connection in turning centers and lathes
With Coromant Capto® clamping units, the coolant is plumbed through the turret, allowing for quick change and pre-measuring outside the machine. Clamping units are available for all lathe styles (turning centers, vertical lathes and flatbed lathes) and new clamping sets allow for a pressure of 200 bars (2900 psi).
Coolant connection in sliding head machines
Coolant delivery on a sliding head machine varies considerably compared to a turning center. Synthetic oil is used, rather than emulsion, to support the sliding guide way construction and the oil is delivered to all tools simultaneously regardless of which tool is in cut.
Although most machines are delivered with high-pressure pumps, without optimized tooling, the coolant delivery area (diameter of coolant outlet x number of outlets) will probably be too large for the flow capability of the pump, so maximum pressure will not be achieved.
It is important to reduce the delivery area by:
- Using tools with internal coolant supply and blocking off external supply to these tools
- Optimizing the coolant delivery area to minimize the flow required
The QS™ holding system includes tool holders that have the coolant plumbed into the stop, which is permanently mounted in the machine. A coolant tube in the back of the QS™ tool holder ensures that the coolant is channeled straight out to the nozzles at the same time that the tool is mounted.
The nozzles are 1 mm (0.039 inch) in diameter, ensuring an accurate jet to assist chip control while at the same time keeping the flow requirement to a minimum.
Sleeves for quick set-up of boring bars
High-pressure metallic sealed sleeves such as EasyFix provide quick set-up of cylindrical shank boring bars. The spring-loaded ball locates the groove in the boring bar to find the center position in seconds.