Re: Re: Engraving and engine turning

There are fancy "constant force" springs available but the simple/ crude solution is to use rather long springs. That way the
percent elongation is not large and the force is rather constant. With the spring system there will not be any significant mass
added to accelerate and deaccelerate. I realize that this might not be important in some systems but it is always interesting
to compare options.

It also surprised me a little that you are using it as a method of pre-load. I thought the idea of weights and pulleys or
springs is to reduce the load on the motor and make the load similar in both directions. Thereafter the system's PID constants
can be optimized and will be optimum moving both up and down.

Bertho Boman
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Peter Smith wrote: <peter@...>

> Ian/Peter
> I have been using the wire rope, pulleys, and weights ploy, for a couple of
> years on my mill, it started as a quick fix to the backlash problem, but I
> must admit it works very well, maintaining a constant load on the quill,
> instead of as with a spring the further the quill goes down the tighter the
> spring gets the greater the load on the motor, but my god it does look ugly.
> The countrbalance is about 3lbs heavier than the quill, but as the Z stepper
> is at a ratio of 20 / 1 it does'nt seem to mind the preload.
> I might get around to doing one of Dans permanent fixes, but I suspect
> that the quality of the rack and pinion on my far eastern mill might not
> allow such a proper cure. ( why upset something thats working ok)