Re: [CAD_CAM_EDM_DRO] Backlash Fixes

IMO if your only doing one job the best way is to do the job manually. If
you know how to do precision machining you can get the job done much faster
and at no cost whatever. All you need to set up and test the job is a
couple of dial indicators and a calculator.

If your doing several that need to be identical, invest in a taper
attachment. Once it's set up accurately, you can machine them all at one
go.

Smoke

----- Original Message -----
From: <ccs@...>
To: <cad_cam_edm_dro@yahoogroups.com>; <southbendlathe@yahoogroups.com>
Sent: Tuesday, October 09, 2001 8:36 AM
Subject: [CAD_CAM_EDM_DRO] Backlash Fixes


>
> I'm trying to find a way to get zero backlash on a 9" south bend
> lathe, over a crosslide travel of about half an inch, in order to do
> some high precision taper work with a sort of single motor cnc taper
> attachment setup. Zero backlash is necessary because the stepper
> motor will be retracting the tool in the direction of cutting force.
> I should also mention that this is not a production setting - ie, it
> only needs to work for about an hour at a time, and some rebuilding
> between uses is acceptable.
>
> There is no way a ballnut will fit, and I don't want to mill out the
> channel in the crosslide like I did on my bigger lathe. So far I have
> two ideas.
>
> 1) Install a spring that will push the tool away from the work. Using
> a fairly long one, the variation in force over half an inch of travel
> won't be large. The total force can be quite large, as the stepper
> actually only has to retract the tool, never advance it. This seems
> like a simple fix (which could be suited to longer travel with some
> sort of constant force device) but I never hear of it being used.
>
> OR
>
> 2) Buy some new screw stock, obtain a loose fitting nut, and inject
> moglice (the teflon-matrix-epoxy bearing rebuilding material). I'd
> use new screw material to get consistent unworn threads, sacrificial
> material for any needed lapping, to be able to simply throw it away if
> I don't get the release agent right, and to maybe choose an ideal
> threadform. Anyone done this successfully? What would the ideal
> threadform for moglice be?
>
> Thanks for any ideas,
>
> Chris Stratton
> ccs@...
>
>
>
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