Re: ATM Alternative grinding machine (Simplier?)

["Kenneth Hunter" <kb7h@onemain.com>]

Yes,

The abrasive size at grinding is a million times larger than the total correction of the parabola. The grit size deviation is usually +/- 25% of the nominal grit size or roughly 200,000 times the parabolic correction.

We already use very fine diamond tools to generate a spherical surface and are lucky if it's close enough to use #320 grit to get to a real sphere... so there is no way you could generate a parabola with rough grinding grit.

Not even close to a good idea. Why don't you go through the process once to make a mirror before coming up with a thousand ideas to modify something you do not understand?

Sorry to be so negative but you are wasting a lot of our time with all these hair brained ideas.

Ken Hunter

-----Original Message-----
From: "Jim Smyser" <jim@idexer.com>
Date: Wed, 27 Feb 2002 06:20:23 -0700
To: atm@shore.net
Subject: ATM Alternative grinding machine (Simplier?)


> 
> Before I turn in <yawn>, I have another idea for a grinding machine for you
> guys that might even be better and more precise, and simpler (no guarantee
> of course since this is still idea stage).
> 
> Picture a square plastic container with a rotating turn table 4' off the
> bottom being belt turned from a motor from the outside. Picture maybe highly
> concentrate level of water grit concentrate. We will have a simple water
> cooler like pump laying on the bottom to circulate the water grit
> concentrate thru a tub.
> 
> Now for grinding we have what I will call the grinding arm. It will have a
> very small grinding surface at the tip. Picture a record player arm and
> needle where the needle will be the grinding surface. The arm's grinding
> surface will start at top dead center of the mirror and retract towards the
> outer edge and then back to center for a cycle all while the mirror is
> spinning. Also, our pump will be empting in front of the grinding surface
> via a tube to provide water and grit. Also may want to apply  alittle weight
> over the tip for grinding force.
> 
> Now to develop a nice acceptable figure we will rely on timing of the
> grinding arm cycle. Obiviously for a parabolic figure we want the grinding
> surface move slower towards the center and move faster as it reaches the
> edge so we remove more glass from the center then towards the outer edges.
> So our figuration will be totally dependent on how the arm is adjusted in
> its cycle rate across the mirrors surface.
> 
> Seems to me this be much more simplier to construct, however not sure what
> the end result would be in practice since it would not use any W motions!
> Any grinding experts see any issues with this grinding approach?
> 
> Jim S.
> 
> 
> 
> 

-- 

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