Re: [CAD_CAM_EDM_DRO] Relation of a DRO to a CNC modification of a machine?

Hi Andy,
Do you use the Scales for your CNC feedback as well as the DRO350? Or
are you running two feedbacks on each axis?
I know there are dual output mods you can do but how did you do it? Now
that I think about it the Scale output would have to be amplified to Encoder
level output voltage.

Vince

----- Original Message -----
From: "Alan Rothenbush" <alan@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Monday, September 27, 2004 11:57 AM
Subject: Re: [CAD_CAM_EDM_DRO] Relation of a DRO to a CNC modification of a
machine?


> Gary;
>
> As the fellow owner of a CNC'd 3in1 machine, I feel it my duty to pipe
> up. <G>
>
> If your DRO is the type that uses the standard Chinese "legless
> caliper" type of scale, no, your DRO cannot be connected to the CNC
> system.
>
> As such, it is only useful when manually machining. Having said this,
> I do a lot of manual machining, so don't feel that you may have
> purchased something you won't be using. As cool as watching a CNC
> operation is, it's still kinda neat to do it by hand.
>
> Also, there are a number of operations where I use CNC to get it close
> to the right size, particularly when there is a lot of material to
> remove, then manually (using the DRO) to get it closer still, then
> manually using traditional measuring tools for the last few cuts.
>
> The issue is that there is enough play in my (and I suspect most) 3in1
> machine that .010" is about as close as I'm willing to believe the
> CNC can get something to (and I've upgraded mine with good-quality
> ballscrews and double-nuts).
>
> And there's enough stiction and flex in my "caliper" style DRO that I
> don't believe it to be repeatable to within .002", so anything closer
> than that gets mic'd.
>
> However, if your DRO is a more standard type, where the output of the
> encoders is conventional quadrature, then there IS a way use the
> feedback from the DRO to the CNC system to "compensate". You'll need
> (beside the DRO)
>
> a. a "Kulaga/Mauch" DRO input board
> b. a PC with an ISA connector to accept the above board, and
> c. either EMC or DeskNcRT software (there may be others I'm unaware
> of)
>
> (I'm building exactly such a thing right now for my little Taig mill,
> as I hope to make simple PCBs and .010" just isn't close enough.)
>
> Hope this helps.
>
> Alan
>
> P.S. Oh yeah, you'll need switches to establish a HOME position ..
> and you might want a few more just outside the HOME switches to act
> as LIMIT switches, for those occasions where
>
> a. you weren't careful enough during setup to consider where the table
> was going to move to, or
> b. you weren't careful enough during GCode generation, or
> c. you're milling pseudo-manually (finger on the jog button) and are
> paying more attention to the cutter and the work than the position of
> the table
>
> P.P.S.
>
> What did you buy ?
>
>
> --
> Alan Rothenbush
> Academic Computing Services
> Simon Fraser University
> Burnaby, B.C., Canada
>
>
> Before me things create were none, save things
> Eternal, and eternal I endure.
> All hope abandon ye who enter here.
>
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>
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