A Better No Fog Coolant System Design Improving On The Fogbuster Mist and Fog Free Coolant Sprayer
One major issue with the Fogbuster and other similar fogless coolant applicators that use air pressure is that they can have issues with the consistency of the coolant flow rate. If the coolant flow rate could be either measured or controlled, then the application would be much more reliable.
The coolant volume that's being applied to the tool/cut only needs to be about 1 drop per 2 seconds (30 drops per minute). 1 drop of water equals 0.05ml. 1ml = 20 drops. So the pump needs to have a flow rate as low as 1.5 ml per minute. This is a very small flow rate, and there are few pumps capable of delivering such low flow rates.
Peristaltic pumps are ideal flow rate metering pumps for relatively low flows. Using a stepper motor to drive the pump allows for fine-tuned control and very low flow rates. The solution being pumped never comes into contact with the mechanical systems of the pump, so it's a low-maintenance system. The downside to peristaltic pumps is that they have a pulsation on the output. This is caused by the stretching and contracting of the tubing. For applications were volume metering is the important factor, the pulsing is not an issue. But for constant, low-flow rate applications like this, the pulsing becomes an issue because it results in periods of time where there's no flow. The solution is to add more rollers to the pump head and decrease the diameter of the tubing such that the pump can be run at a higher rpm.
Micro Gear Pumps
Gear pumps are generally used in high-pressure, low-volumetric flow rate applications, such as hydraulic systems. They are therefore well suited for very low flow rate applications. They do not have pulsation issues. Microgear pumps are generally more expensive than peristaltic pumps, and the pump is exposed to the fluid (which in the case of metal cutting coolant is probably not an issue because it has lubricants and rust preventatives in it, so it's similar to running oil through the pumps).
This inexpensive micro gear pump as a flow rate of 0.8ml/revolution. To achieve a 1.5ml per minute flow rate, the pump would need to be turned at about 2 RPM, which is easy to achieve using a stepper motor.
WHERE TO BUY
Name: Hydraulic Pump-1A-0.8
Sputum volume: 0.8ml/r
Preset pressure: 21MPa (3045 psi)
Maximum speed: 4300 rpm
Minimum speed: 1000 rpm
Mechanical efficiency: 85%
Flange mounting method: SAE standard
Input shaft connection form: Flat key
Inlet and outlet connection type: Thread
Oil inlet: PT3/8”
Oil outlet: PT3/8”
Product Weight: 0.95KG
Product size: 10.1*8.12*6.75cm