CNC Coolant Variable Speed Pump - Improvements for Mill and Lathe
Variable Speed Pump
The original coolant system that the Tormach PCNC1100 milling machine came with was far too small and weak. I replaced it with a Rubbermaid tub and a 1/5HP utility pump. This worked well for many years until the pump blew it's seal, and then the Rubbermaid tub leaked. The 1/5 HP utility pump was surprisingly strong, maybe too strong, but it was good to have surplus coolant pressure and flow vs the weak pump it came with. However, when we only needed a little bit of coolant flow, there was a lot of back pressure that eventually led to the gasket blowing out, which created a huge pressure loss. We reverse engineered the gasket (found out later that the manufacture does have a parts list, but I don't know if they actually have replacement parts available.), tried to improve the design to prevent breakage and blowout, 3D printed it out of ninjaflex TPU, and installled it. It worked for maybe a year before blowing out again.
I have a few ideas for solutions.
First, there should definitely be a pressure relief valve that dumps excess coolant back into the tank to prevent over working the pump motor.
Second, a variable speed pump would allow coolant flow adjustment without having to put excessive pressure on the pump and coolant line.
The coolant drops through the mesh at the base of the machine into a pan. I placed a HVAC filter cloth in the pan to filter out chips that get past the mesh basket, of which there are many. If the filter cloth gets clogged, coolant will simply overflow into the pan and flow into the tank.
I would like to add an additional filter after the pump for finer particulates, but I don't want a cloth filter that has to be cleaned. A centrifugal filter would be ideal, like a hydrocyclone or spin down filter.
Pressure Relief Valve
In order to get the right size pressure relief valve, I really need to install a pressure gauge on the coolant line so that I know how much pressure the pump is creating when stalled, and can pick the correct pressure range for the pressure relief valve.
AC Asynchronous Pump
Asynchronous pumps allow for variable speed control using a standard rheostat style speed control.
This is an example Anjon MS-550 Monsoon 550 gph Pump
This is the Variable Speed Controller that is sold for the Anjon pump, but it looks like a generic controller.
This pump looks like it could work well, because it can be placed vertical on end such that the intake is at the bottom.