Re: Re: Engraving and engine turning

Ian, Pete and ....

I think we are mixing two different subjects that relates to each other:

1. QUILL BACK LASH.
Pre-loading the quill in either direction will help to reduce back lash. That brings back a previous question. Why not let
the quill just "hang" or if that is insufficient down force, pre-load it down. More weights or springs could be used. That
would basically be true regardless if the quill is controlled via a ball screw or through a rack and pinion.

2. UNEVEN SERVO LOAD:
The load on the Z-axis servo motor will be different in up versus down direction and the servo gain constants can only be
optimized for one direction. By proper spring or weight and pulley arrangement, the quill can be equalized to require the same
force up and down. By using springs, no significant mass is added and therefore faster acceleration can be achieved.

Bertho Boman
===================================

> From: "Pete Jarman" <pete.jarman@...>
>
> Ian,
> The way Turner used a "Tensator" spring was to fix the outer end of the
> spring to the quill and the spindle fixed to the centre of the coil to the
> underside of the quill housing with a suitable bracket which allowed the
> spindle to be rotated and locked to set the preload. As the quill is lowered
> the spring is wound up. If you used this with a feedscrew it would give you
> the necessary preload of the nut against the thread to eliminate the
> backlash. I'm considering using this idea to eliminate the backlash in a
> Stent cutter grinder I'm finishing off at the moment.
>
> Pete Jarman
> North of Bedford, England