When changing tooling in the spindle, the Sieg SX3.5 DZP manual instructs you to loosen the drawbar and gently tap the top of the drawbar, to eject the tooling from the taper.
I used this method for a few months. It only took one or two very gentle taps on the top of the drawbar with the allen wrench to eject the tooling.
I kept reading about self ejection toolbars on the internet. I found that the SX3.5DZP already has a screwed cap that covers the drawbar, and so, I was nearly there with a self ejecting mechanism.
Your dimensions may have to vary from those above; because your drawbar and cap dimensions may be different to mine.
Screw the cap down into position in the pulley cover.
Release the quill lock.
Release the fine feed mechanism, and carefully let the quill raise up. Disengaging the fine feed gears seems to be the sensible thing to do. You do not want to damage those gears.
Lock the quill. The quill must be locked, else it will move downwards when the drawbar presses against the cap later on.
Hold the quill steady and undo the drawbar using the allen wrench. The drawbar is loosened from the tooling that is in the R8 taper.
Undo the drawbar still further. Eventually the drawbar will press against the top surface on the inside of the stationary cap.
The drawbar cannot move vertically any more. The cap is now preventing the drawbar from moving vertically.
Because the drawbar is screwed into the tooling, further turning (loosening) of the drawbar causes the tooling to be pushed down, and ejected from the taper.
The sound that is heard as the tooling is ejected from the taper is quite frightening when you first hear it. It sounds like something is breaking!.
On my machine I hear a 'pop'. I think the 'pop' sound is caused when the tooling is ejected and the force on the cap is suddenly released, causing a sound in the hollow pulley cover box.
Let me know if you think this is a bad way to eject the tooling. I must admit, a gentle tap on the top of the drawbar appears to require less force to release the tooling from the taper.
I am thinking that a short sharp gentle shock maybe a better way to release the tooling from the taper, as opposed to pressing the tooling out of the taper.