Recommendations for diamond turning machine maintenance and quality assurance at Cleveland Crystal.

摘要

Laser damage patterns have been observed on NOVA debris shields that resemble the diamond turning patterns on KDP crystals. These patterns are circular arcs whose radius corresponds to the flycutting operation on the Pneumo diamond turning machine; the spacing between the arcs of damage is of the order of 1 mm. A trip was made to Cleveland Crystal (CC) for the purpose of identifying and possibly correcting machine tool problems associated with the damage pattern. Tests were run where the relative motion between the spindle and the chuck was monitored along with environmental variables such as shower oil and room air temperature. A 2 (mu)inch p-v spindle-to-chuck motion correlated with an 18 second cycle in the shower oil temperature; this cycle time corresponds to about a 1.1 mm spatial wavelength during machining. The replacement of a temperature sensor in the oil temperature control system dramatically reduced the spindle-to-chuck motion at this period. Beam modulation tests performed on KDP crystals prepared after the trip indicate that the waviness problem continues to persist. The ultimate cause of the problem may be associated with variables not measured during the trip, e.g. spindle or carriage motion errors. During the course of testing at Cleveland Crystal, several deficiencies in the machine tool set-up were observed (some identified by CC). One of the principal deficiencies is the lack of monitoring equipment and background information on the machine tool and the support systems. For example, minimal information (outside of our past experiences on similar machines) was available on the temperature control system for the shower oil.