z-axis lock

After reading Robin Hewitt's post about his Warco mill drill conversion I started wondering if there is an easy way to incorporate a z-axis lock into my mill / drill conversion, I've got a Rong Fu that looks identical to the Warco.

Rather than using an electrovalve and pneumatic set up, as Robin has done, is it possible to use a shot bolt solenoid fitted to press directly against the spindle sleeve?

Ideally I would like to control the solenoid via a diycnc.com system 4 board, which has two spare outputs, one of which I currently intend to use for a motor on/off relay signal. As an alternative to tying up the other board output I'm thinking that it might be possible to trigger the solenoid to only activate when the z-axis is inactive (probably best to ask Roy at diycnc about that one)?

The mills quill lock mechanism is rather spongy, there's quite a movement between free and locked. Move the quill up and down while tightening the lock and you'll see what I mean.

If you changed the lock mechanism to a straight push and lost the sponginess then the short power throw on the solenoid would not limit your lever length.

Presume you are aware that solenoids come with a duty cycle? If you turn a 20% duty cycle solenoid on for 10 seconds you have to leave it off for 50. You can get latching solenoids but they require pulses in both directions and the electronics becomes awkward.

I second Robin's concern about the solenoid idea.

You might get away with a motor and a cam, or perhaps just motorise the locking bolt. It'll be slower than Robin's cylinder, but would be all electric in operation.

Thanks for the responses, I didn't know about the duty cycle, the last machine I worked on that didn't use pneumatics came out of the ark and the solenoid on that machine was on most of the time. I guess you don't know unless you ask.

The problem I think I've got is that the quill seems to move quite a lot, not necessarily in the z plane, but locking the axis stops all movement.

I think I'll finish my conversion and see how much of a problem the movement is.