March 2011 > UNCC APP
QED Technologies welcomes the UNCC to the Academic Partner Program
The University of North Carolina Charlotte is one of the first participants of QED’s Academic Partner Program
QED established the Academic Partner Program (APP) to support academic institutions worldwide, in their optics manufacturing research, development and educational programs. As a part of its mission to support world class research, QED has offered state-of-the-art polishing and metrology systems to academic institutions that are engaged in or planning specific optics-based research programs.
As an APP participant, Dr. Chris Evans, Professor at UNCC's Department of Mechanical Engineering and Engineering Sciences, will explore the potential of a 2-step process combining diamond turning (using polycrystalline diamond tools) with MRF® on the Q22-XE, thereby eliminating the need for an intermediate conventional polishing process. Read more> (links to QED web page with the following)
QED established the Academic Partner (APP) Program to support academic institutions worldwide, in their optics manufacturing research, development and educational programs. As a part of its mission to support world class research, QED has offered state-of-the-art polishing and metrology systems to academic institutions that are engaged in or planning specific optics-based research programs.
As an APP participant, Dr. Chris Evans, Professor at UNCC's Department of Mechanical Engineering and Engineering Sciences, will explore the potential of a 2-step process combining diamond turning (using polycrystalline diamond tools) with MRF® on the Q22-XE, thereby eliminating the need for an intermediate conventional polishing process.
Technical summary of project:
Silicon is a very attractive material for near infra-red imaging systems; aspheric designs also offer significant advantages. Single point diamond turning is – at first sight – an ideal manufacturing process for such optics. Unfortunately, tool wear when diamond turning silicon is relatively high, making it difficult to achieve the required finish and figure and costly in terms of the wear of single crystal diamond tools. Conventional wisdom suggests that an intermediate polishing process is required before using Magnetorheological Finishing (MRF®) to correct the optical surface figure.
It is well known that, in diamond turning of silicon, there is a critical combination of tool (radius, rake) and process (feed, depth of cut) parameters that allows essentially fracture free machining – for "sharp" tools. Outside that range, fractures (or pits in the surface) are observed, depending on the crystallographic orientation of the silicon. The morphology of the pits also depends on crystallographic orientation. UNCC will investigate the evolution of such pits during MRF based in their initial morphology. This information may allow optimization of MRF material removal strategies to minimize the propagation of initial damage (fracture) sites.
In summary, the UNCC project will explore the multi-variate process parameter space for a 2 step silicon optics manufacturing process. The underlying idea is that, since the diamond turning process is not required to produce the final finish, large nose radius tools and high feed rates can be used. This combination will give longer spatial wavelength tool marks, which will be attenuated more effectively than for a more conventional process. MRF is expected to be more effective on this domain. UNCC will evaluate the key parameters in a trade-off between diamond turning and MRF process controls to achieve simultaneously good figure and good finish.
About Dr. Chris Evans and the University of North Carolina Charlotte Department of Engineering and Engineering Sciences
Dr. Chris Evans has over 25 years experience in precision metrology and optics fabrication in government research and private industry. He has authored or co-authored over 100 papers and is an inventor on more than 10 US patents in ultra-precision machining, polishing, and optics metrology.
The UNCC Department of Mechanical Engineering and Engineering Sciences is home to the world renowned Center of Precision Metrology and has a concentration of expertise in the areas of precision engineering, metrology, bio engineering, computational methods, mechanics, materials and motorsports engineering. The department works closely with the UNCC Center of Optoelectronics and Optical Communications, and the Department of Physics and Optical Sciences which has areas of focus in optics metrology and silicon characterization.
