Category Archives: CNC

Vacuum Pump System

Most of my projects last for months, so the other day was a bit different when I managed to start and finish a project all in one in one day.  I built a vacuum pump system based on the free plans for the EVS vacuum system found on

Vacuum Pump System

I’ll be using it for vacuum clamping on my milling machine as well as for the vacuum pickup nozzle on my pick and place machine.

It isn’t a complicated system, but still, everything went together very easy. The nice thing about the plans are that they are proven, and there are lots of examples of custom systems that Joe has put up on his website. I made a few changes to the plans to meet my needs. The first was to move the filter to the system input instead of putting it on the pump input as in the plans. I forgot to order the high flow filter from so I’m stuck using a cheap filter from Princess Auto for now. It probably has a higher resistance, but for now that should be ok since my application doesn’t need a high flow rate.  The filter will protect the vacuum switch and Mac valve better in this position. Second was to mount my pump up on the tank with some big hose clamps. My piping worked out a bit different than in the plans, but my system takes up about half the floor space.

One problem I have is that the hysteresis of the vacuum switch is not adjustable. There is only one adjustment screw to set the point at which the pump turns off. When the vacuum drops to about 4inHg below this point the pump turns back on. I would like to either find a pressure switch that has adjustable hysteresis, or come up with a simple way of doing it by adding another pressure switch.

GEC Gemini motor controller is working

I got a Boxford TCL 125 CNC lathe a few years ago that I have been working on getting up and running. I gutted all the electronics except for the spindle motor controller, and replaced the stepper drivers and built a PC right into the lathe enclosure. I’ll post more on those upgrades later. All the new stuff I added is working fine, it is the old GEC Gemini motor controller that was giving me a hard time. But, after reading this post I got it working, it looks like I was just missing the kill switch connection.

So here are the connections to the big orange header:

  1. NC
  2. 0-8 VDC – This sets the motor speed
  3. 10VDC – Supply voltage for the controller
  4. NC
  5. NC
  6. NC
  7. GND
  8. GND
  9. Kill switch input – This needs to be connected to pin 3 for the motor to run
  10. GND
  11. NC
  12. NC

It looks like there are traces on the PCB that go to the pins that I have labeled as NC, but I’m not sure what they are for and the motor is working without them. If you know what they are used for leave some feedback.