Re: Re: Engraving and engine turning

Hello Peter,

I understand that backlash is not good and pre-load will in many cases fix it.

What I do not understand is why pre-load "up" versus removing the return spring in the quill handle and let the weight of the
quill pre-load it self "down" or even adding weights if needed. Also being pre-loaded "down", the cutter can never catch and
dig deeper.

I have a related question but I will start a separate thread from the engraving on that one.

Best Regards,
Bertho

Peter Smith wrote:

> From: "Peter Smith" <peter@...>
>
> -----Original Message-----
> From: Bertho Boman <boman@...>
> To: CAD_CAM_EDM_DRO@onelist.com <CAD_CAM_EDM_DRO@onelist.com>
> Date: Saturday, July 31, 1999 7:25 PM
> Subject: Re: [CAD_CAM_EDM_DRO] Re: Engraving and engine turning
>
> >From: Bertho Boman <boman@...>
>
> Bertho
> If you have backlash on the quill, and it is not preloaded, when taking a
> deep or heavy cut, the action of the cutter will take over and pull the
> cutter into the job by the amount of backlash that you have, not very good
> if you want a nice flat surface, hence the preload to keep the cutter up,
> and the quill pulled against the pinion and worm drive.
>
> Peter Smith
> >
> >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
> >========================================
> >
> >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)
> >
> >
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