definition of spark out

[sliceitdiceit]

Hello:

Just wanted to know if anyone could give me a definition of the term 'spark out' as it relates to the grinding/lapping process. I have been doing ID slicing, dicing, and lapping for years, but I have never heard this term until recently and I only have an idea of what it actually means.

Thanks in advance,
Pete

 

[unclesyd]

The term is used during the approach to a finish dimension as one lowers the infeed on the grinder. On the last adjustment of the infeed you make a few additional passes until you see no sparks.
A case in point is grinding a part on a Blanchard Grinder going from rough to flat and parallel. When the surface clears you make a very small adjustment on the infeed and let it "spark out". This is to average out any imperfections caused by the grinding wheel or machine. This is more of a concern with solid wheels than on segment wheels.

 

[grinderguy]

this is the stage that has zero additional feeding of the wheel head. Generally you use a timer and set it to a time large enough for the part to stop sparking. I have seen many high volume applications where the sparks did not stop, the part did get rounder.

Robert Setree

http://www.advanced-grinding.com

 

[unclesyd]

Wouldn't you think in high volume production grinding that the last infeed would tend to be a little high? I have seen a few thick pieces that had a little problem when the coolant stopped too quick after having a heavy cut.

We had (4) 48" Blanchards with one having an in house designed infeed system that would slow the approach down and change it from stepped to linear. This machine along with diamond lapping could produce flat to less than a quarter light band.

 

[Biffi]

the sparkout is a dweel in the grinding cycle to get a round part. It is need due system machine-grinding wheel-part elastic deformation when the gw and part are in contact.