I'm building a 4' x 8' gantry-style CNC router table. The spindle motor uses pneumatics to power its draw bar (for automatic tool changes). There are three separate pneumatic supply lines that go to the spindle motor.

One is a constant air supply of low pressure that serves to blow debris out of the tool mount during tool changes. The other two are the "open" and "close" lines.

I can choose to place the electrically-actuated pneumatic valves and various pneumatic components on the base of the machine, on the gantry, or on the spindle mount itself.

In the first case, three pneumatic lines must run several meters to reach the spindle, but the bulk of the pneumatic hardware is kept off the moving parts of the machine (reducing vibration and moving mass).

In the last case, the electrical control lines have to be run, but the pneumatic control lines are shortened (except for the main supply line), and a number of valves and regulators have to be placed on the gantry carriage. The second case is similar, but the equipment is mounted to the gantry itself.

I'm leaning toward just running the three pneumatic lines the full distance and keeping as much equipment as possible off the moving parts of the machine. But I don't know if the long pneumatic lines will cause other problems, perhaps sluggishness due to the elasticity of the tubing (they're typical poly or PVC pneumatic tubing). Is this even a concern?


I would keep all the control hardware/components off of the moving members as much as possible and in the same general area for ease of wiring and trouble shooting. Use nylon tubing, its more "rigid" such that the tubing diameter will not flex or change.

In electro-pneumatic machines, I usually build a pneumatic "panel/enclosure" with all my air prep/sensors/valves/etc, just as you would your electrical control, and keep it close to the electrical panel/enclosure.

In this application, I wouldn't consider any time delays due to the tubing lengths to be significant.

  • $\begingroup$ Any reason not to combine pneumatic and electronic stuff into one enclosure? $\endgroup$
    – Rick
    Oct 24 '18 at 22:16
  • 1
    $\begingroup$ I personally don't see it as good practice. Your air supply can be dirty/wet/oily, if a line ruptures/leaks/exausts inside an enclosure with electrical components you can have a bunch of troubles. I also vent my pneumatic enclosures in case of rupture, there is no pressure build up, not always allowed to vent electrical enclosures. So as a professional machine builder for a client, I wouldn't. But in your case, you can go for it if you want. Just make sure to plumb the exhaust ports on your solenoid valves to outside the enclosure. $\endgroup$
    – Corey
    Oct 25 '18 at 12:37

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