Re: [ATM] HCF ripple

[Jarvis Krumbein <jkoptic@juno.com>]

A couple of other factors to consider-  1) HCF, because of its honeycomb
structure, polishes very fast, far faster than a pitch lap and as a
result, there is probably local heating of the glass surface.  2) HCF
doesn't flow and as a result doesnt maintain good conformity and surface
contact unless mounted to the tool with a flowable medium such as pitch.

I've used HCF over the years and found that great care is required.

Jarvis Krumbein


On Sat, 12 Feb 2005 10:38:11 -0500 Gilbert Gagne <gil5941@earthlink.net>
writes:
> Vladimir wrote:
> 
> <The trouble with HCF is the ripple.
> 
> <HCF lap has 5mm hexagons and they should be averaged out very 
> efficiently
> <but this is according to literature not the case.
> <How come?
> <I could not find any plausible explanation.
> 
> The reason the ripple develops is obviously related to the periodic 
> structure
> of the HCF lap. Ever drive on a "washboard" gravel road or notice 
> the "thump-
> thump" associated with expansion gaps on old concrete roadways? 
> Smooth surfaces
> are by nature unstable and once irregularities develop, motion tends 
> to amplify 
> them. The forces generated by polishing motions are being modulated 
> by the periodic 
> structure of the HCF lap setting up vibrations that result in the 
> observed ripple.
> Once this ripple develops it is very difficult to eliminate even if 
> polishing 
> resumes on a pitch lap as the ripple will now generate similar 
> vibrations.
> 
> Gil Gagne
> Port Orange, FL
> 
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