Kavo plumbing; Y-axis limits, take III

5 Bears Home Homebrew CNC bench mill

With the functional Kavo split mounting block completed, and the spindle physically mounted, I had to "plumb" the Kavo for the necessary air. This wasn't as easy as it sounds... I needed two separate pneumatic air sources, clean and dry, at different pressures, and I had to control both. Eventually, this control aspect will be automated via software and solenoids, but for now, I am using manual pneumatic toggle switches from MSC, and a large assortment of pneumatic fittings.

An aluminum angle was cut and prepared to act as a fixture mounting for the air. The source would be compressed shop air. It is first fed through a filtering unit, far right. The connector is a PTC (Push To Connect) fitting for 6mm polyurethane tube. The plumbing itself overall is a weird mix of 6 and 4mm tubing and fittings, generally from materials that I already had on hand.

After the filter, the air proceeds to a tiny Festo regulator, where the pressure is dropped to 6 bar, or ~ 87 PSI. The straight 6 bar air is used to actuate the collet holder with a pneumatic switch.

A "T" fitting splits the 6 bar air and feeds it through another toggle switch, and thence into a needle valve for metering into the spindle body for overpressurization of the bearing housing. This keeps dust and swarf from entering the spindle body and wrecking the expensive ceramic bearings.

The operator side of the plumbing. The tiny Festo regulator and its adjustment are upper left. Below that is the switch for the collet. Right of that cluster is the switch for the body pressure, and the needle valve.

This bracket will be mounted to the back of the mill's column, and extend to the left for easy access.

Both pneumatic tubes (yellow = collet, blue = body) are routed, along with the power cable, in an "Igus" cable sheilding unit which reticulates like a snake as the spindle travels up and down.
With the pneumatics done, I did a bit more testing. I found that the Kavo spindle really tosses fine swarf around, and I spent some tme fashioning various swarf guards for the table. One in particular limits the Y-axis travel when in place, and I found out quickly that if I didn't set up some Y axis limit switches which were both accessible and adjustable, it would become pretty tedious, fast. So for the third time, I had to rework the Y-axis limit switch assembly.

The switch harness and bracket was removed from the inside of the mill, beneath the table. The plan was to mount them outside the base of the mill, on the right hand side.

An aluminum angle was cut and drilled as shown for the switch bracket. The brass buttons stand the bracket off the base enough to make use of the tiny T-nuts, which allow the switches to travel.

In place is the rearmost switch. A slot was milled in the top of the unit to allow a steel "finger", bolted to the Y-axis saddle, to reach down and trip the switches. This will be clear in the next photo.

On the mill, looking up from below. Note how the switches may be moved longitudinally on their bracket, and in addition, the finger may be tilted fore and aft from its normal, vertical position and so alter when the switches are tripped.

The slot, finger, and bracket make for a neat, and importantly, a swarf-free setup.