Re: [CAD_CAM_EDM_DRO] ...but how much precision????

Thanks for sharing your experiences guys...what I was basically after, is,
how precise must my machine's backlash be, to attain a reasonable amount of
precision, all other things being equal, without having to resort to
ballscrew conversion. And additionally, how much precision is typically
merited in machining work As I understand it now, most professional cnc
machines are lucky to attain 0.0005 to .0015 accuracy. Sound correct?
I spent a part of last evening adjusting the acme screws on the old 1945 Van
Norman mill that I will be converting to cnc, and using a dial indicator,
was able to reduce the backlash on all 3 axes to within (1) thou. The
handwheels are a bit tighter than I would want for manual use now, but I
don't intend to do a LOT of hand turning :-) This machine is in great
shape, they don't make things like they used to.


Bill Kichman
103 Old Furnace Road
Cornwall, PA 17016-0643
tel/fax 717/270-0714

----- Original Message -----
From: "Les Watts" <leswatts@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Friday, May 09, 2003 12:16 PM
Subject: Re: [CAD_CAM_EDM_DRO] ...but how much precision????


> I have also measured and mapped my gantry machine.
>
> I used 12", 6", and 3" precision micrometer test bars in various
> combinations
> to measure over the entire 5'x5'x1.5' work envelope. I also have a huge
> class
> N precision square. After correction I was within 0.001 positioning
> everywhere
> at precisely 25 degrees c. Cutting error is of course poorer.
>
> And if the shop temperature rises just from 25c to 30c the whole thing
grows
> about
> 5 thousandths. Expansion from ballscrew heating in hard use results in
even
> more error.
>
> I think position error goes as to about the inverse square of cost. It is
a
> big
> deal and big $$$ to do this.
>
> Les
> Leslie Watts
> L M Watts Furniture
> Tiger, Georgia USA
> http://www.alltel.net/~leswatts/wattsfurniturewp.html
> engineering page:
> http://www.alltel.net/~leswatts/shop.html
> Surplus cnc for sale:
> http://www.alltel.net/~leswatts/forsale.html
> ----- Original Message -----
> From: "Bill Kichman" <billkichman@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Thursday, May 08, 2003 10:39 PM
> Subject: [CAD_CAM_EDM_DRO] ...but how much precision????
>
>
> > Has anybody truly measured the degree or precision you are getting from
> your installation? Is 1 thousandth attainable from home cnc?
> >
> > Bill K
> >
>
>
>
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