Re: [CAD_CAM_EDM_DRO] Timing Belts vs. Rack and Pinion drive

If you'll send me a sketch of what you have in mind, I could probably work something ouot for you...I was a machine tool design engineer for over thirty years before "retiring"....got more to do now they when I used to work for a living! Email it to Smoke@...

Smoke

-----Original Message-----
From: Terry Toddy <tltoddy@...>
To: CAD_CAM_EDM_DRO@egroups.com <CAD_CAM_EDM_DRO@egroups.com>
Date: Tuesday, October 24, 2000 6:29 AM
Subject: Re: [CAD_CAM_EDM_DRO] Timing Belts vs. Rack and Pinion drive


How do you support the leadscrew on a large machine? A 3/4" dia. x 10'
long leadscrew will have considerable sag when the gantry is at one end
of the machine.

As for the timing belt drive I think that as long as the length between
pitches is consistent any cumulative errors or stretch can be
compensated for with software. When driving the gantry from both sides
the trick is to get the belt tension equal on both sides.

I only need .060" accuracy over 10', but it is a challenge to try to do
better.

Terry

JanRwl@... wrote:

>
> In a message dated 23-Oct-00 10:38:47 Central Daylight Time,
> tltoddy@... writes:
>
> << this is my first cnc project. >>
>
> Hope it isn't your last! I have no clue what kind of accuracy, backlash, and
> repeatability you need, expect to get, will experience with the proposed
> lashup, but for the "X-Y Tables" I have built, with working-areas from
> 11"x17" to 5'x12', I used precision-rolled lead-screws; SS ACME on the
> smaller ones, with Turcite preloaded nuts, and 1/2" pitch preloaded
> ball-screws on the huge one. (Too expensive!). Timing chain, even Berg
> stuff such as their Min-e-Pitch, is accurate enough, unless you will be only
> cutting weldment parts.
>
>
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