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Polishing procedures for ultraprecise silicon spheres

PTB-News 3.2016
Especially interesting for

manufacturers of precision spheres

national metrology institutes

Production line of a 1 kg silicon sphere based on the example of the Avogadro project; representation of the different steps of the procedure: all the way from the ingot to the perfect sphere

Ultraprecise spheres exhibit form errors and roughness in the nanometer range. Their crystal surfaces are free of metallic contaminations and show no crystal structure damage. These properties place extremely high requirements on their manufacturing process. Through the use of a PTB invention, it is possible to produce spheres with small form errors (on the order of 20 nm) in a reproducible manner by an ultraprecise manufacturing procedure. The invention is based on a pivoting polishing tool equipped with a membrane bearing for optimized control of the polishing operation. (Technology Offer 0404)


small form errors on the order of 20 nm

average roughness values of less than 1 nm

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