51994

Polishing for circular finishes in ultra high vacuum chambers  

April 23, 2009

I am having trouble achieving the ultra high vacuum requirements due to leakage in the circular finishing. The vendor that is producing the chambers for me claim that it requires manual polishing from an experienced hand and they are sometimes prone to error. Othes have told me electropolishing will solve the problem. Please help as it has taken over a year and the quality is still not stable.

Paul

Paul Foot
Customer - Concord, Canada

If you have a gasket or rubber seal, hand work is still a preferable method of insuring a good seal. The abrasive hand work must be done in a pattern or the direction of the seal with no perpendicular pattern lines.

AF Kenton Nova Finishing Systems Inc. Huntingdon Valley, PA

Paul

In a past life working with UHV components, the circular finish was obtained by machining a circular pattern with approximately a 32 microinch finish. The pattern would allow multiple 'ridges' of the finish to contact and seal agains the o-ring. As mentioned, lines, grooves, and scratches perpendicular to the pattern allow leakage.

Willie Alexander
- Colorado Springs, CO

I have no much knowledge of the special requirements to the polishing you want to achieve. However if the material you want to polish is stainless steel of 300 or 400-series or higher carbon steel, we have a good method of electropolishing and sharpening (simultaneously) for such steels. Maybe it will solve your problems.

Anna Berkovich Russamer Lab Pittsburgh, Pennsylvania

Dear Paul,

I agree with Anna. If your vacuumchamber is in Stainless Steel, electropolishing is, by far, the best finish. After electropolish , the threedimensional surface is up to 80% smaller, much less porosities, thus quicker vacuum.
For vacuum parts (semiconductorindusty, wafer production, PVD and CVD chambers, pharmaceutical,....) electropolish is a standard spec in Europe.

Kind regards,

Marc Quaghebeur
- Diksmuide, Belgium, Europe