Zeiss does not recommend nor recalibrates reference spheres. The brief reasoning being that any change to the initial recorded size of the reference sphere is actually detrimental to the accuracy of the CMM. If the reference sphere has been damaged in some way, Zeiss does recommend reaching out to the Service Technical Support team at cic.metrology.us@zeiss.com or call 1-800-327-9735. Depending on the situation, Zeiss may advise replacing the reference sphere and recalibrating the machine instead to ensure accuracy of the CMM.

There is also a formal letter on a Zeiss letterhead from the Quality Manager on the Z: drive you may want to attach to your correspondence with the customer that reads:

Re:  Calibration of CMM Reference Sphere

The reference sphere on a coordinate measuring machine (CMM) does not require recalibration to maintain accuracy or measurement traceability of the CMM. Traceability of the CMM's measurements is accomplished through the calibration standards utilized during the calibration process.

Changing of the recorded size of the reference sphere after calibration will have a negative effect on CMM accuracy. Any deviation between the recorded and actual reference sphere size and form will be evidenced during calibration and subsequent stylus size determinations.

It is the recommendation of Carl Zeiss IMT not to have the reference spheres sent out for recalibration. If the sphere has been damaged, or .is suspect, customers are encouraged to contact Carl Zeiss IMT Technical Support for assistance.  Although CMM recalibration is the best way to ensure accuracy after a reference sphere has been replaced, it is not required.  It is, however, the responsibility of the equipment user to ensure the continuing accuracy of the CMM, and document as necessary.

Sincerely,

Glenn Knight
Quality Systems & Calibration Manager
Carl Zeiss Industrial Metrology, LLC
6250 Sycamore Lane North
Maple Grove, MN  55369