Looking for information about lapping

[arobustus]

As part of my Master's thesis, I need to get some good technical information about lapping. How it works, what is going on at the micro level, how does the lapping action proceed over time, etc. Does anyone know of any good information sources?
Thanx,
-plh

[Pressfit]

Lapping is a precision abrading process used to achieve, parallelism, flatness size and surface finishes to extremely tight and demanding tolerances. It's a manufacturing method that employs particles of an abrasive material to remove material from a surface. It is comparable to sanding or grinding, except that sanding and grinding use abrasives which are fixed (bonded abrasives) whereas lapping uses abrasives(often diamond)which are suspended in a liquid carrier and are free to move.

Lapping and fine grinding are processes used where the surface finish, flatness, or parallelism of the work piece must be held to very close tolerances. Lapping can achieve a flatness rating of one millionth of an inch (0.000001"), parallelism tolerances of ten millionths of an inch (.00001") and surface finishes to 0.6Ra. using special handling and tooling techniques.

At this level of smoothness and flatness, two items may be "wrung" together(known as wringability) with such closeness that atmospheric pressure is keeping them in contact. There is also been suggestions that a small percentage of the holding force is at the sub-atomic level where the short-range nuclear attraction of individual atoms prevail, such as in the areas of Optical Lapping.

Sorry I don't have any info other than this link and it's probably not considered a primary source for research.

http://en.wikipedia.org/wiki/Lapping

[Andre' B]

Google books will get you some historical info.
http://books.google.com/books?lr=&as...G=Search+Books

I find today that a lot of people will tape a sheet of abrasive(sand) paper to a flat plate and then rub the part on it and call the process lapping. What they are doing is more accurately called flat sanding.

In all the stuff I have seen on lapping two things seem to be common to all.
First the abrasive is carried in some type of fluid.
Second the part being lapped is always harder then the lapping tool. That abrasive grains can then become imbedded in the tool and so make little scratches on the part.
The end result is a process much the same as flat sanding but the effective grit size is very much smaller. And the surface accuracy depends only on that of the tool and not the paper or cloth backing between the tool and the part.

[ebigfoot2]

Visit the Peter Wolter's web page:
http://www.peter-wolters.com/us/solprocess/laeppen.aspx
If you can get it translated, there is a good lapping manual in German under Know-How Download.

[arobustus]

Originally Posted by ebigfoot2 Visit the Peter Wolter's web page: http://www.peter-wolters.com/us/solprocess/laeppen.aspx If you can get it translated, there is a good lapping manual in German under Know-How Download.

Thanks. Between my 3 semesters of German and a copy of Langenscheidts, maybe I can tough it out!
-plh

[ImanCarrot]

Oh dear... lapping. How accurate do you want to go?

I've spent over half my life lapping and polishing to optical tolerances where you're talking flatness tolerances over (say) a 12" diameter surface of a twentieth of a wavelength of light. For you sheddies out there using micrometers, this roughly equates to 32 nanometres (at 633nm wavelength) over 12" diameter... that's peak to valley form error by the way, or departure from perfection.

You can't really measure better than this cos light diffracts after this and no longer behaves properly lol, you use test plates (look up Newton's Rings) or Interferometry (Phase Shifting Interferomery is better), but the old techniques used since Newton's time are still just as relevant.

Read F. Twyman's "Prism and Lens Making"- all the other books just copy him really.

(even he don't say really how to do it, but it's as close as you'll get, us optical folk keep the techniques jelously guarded hehe).

Bear in mind at this level of operation glass can be considered as a supercooled liquid