OptiPro Systems (United States)

The subsurface mechanical damage (SSD) depth after grinding fused silica glass with a comprehensive set of sub-aperture fixed abrasive grinding tools [cup, wheel, belt, pad, and rotary face mill (with and without ultrasonics)] and process parameters has been statistically measured using the taper wedge technique and evaluated. Consistent with a previously reported grinding model [J. Non-Cryst. Solids352, 5601-5617 (2006)10.1016/j.jnoncrysol.2006.09.012, Materials Science and Technology of Optical Fabrication (Wiley & Sons, 2018)], based on the sliding indentation fracture by sliding particles or asperities where the normal load per particle determines the depth of the fracture (and ultimately the overall SSD depth), the dominant factor controlling SSD depth was found to be the abrasive size regardless of the tool type and process conditions. Compared to full aperture grinding methods, the overall SSD depth was higher using the sub-aperture tools, likely due to the higher effective pressure and higher load per particle distribution. In addition to abrasive size, a significant reduction in SSD depth was achieved by: (1) reducing the load distribution on the abrasive particles via increase in contact area and/or decrease in mechanical loading; (2) using a more compliant host tool medium; and (3) in what we believe is a more novel way, using ultrasonics. Combining low abrasive size, larger contact area, and a compliant host, the 6µm diamond in a resin matrix (Trizact) on a foam pad led to very low SSD depth (∼4.6µm), relatively fast grinding rate (186mm3/h), and little or no figure degradation. This grinding tool/process is an attractive choice for final grind, resulting in significantly reduced polish out (i.e.,"grey out") times. With the rotary face mill tool, the use of ultrasonics consistently led to a SSD depth reduction (ranging from 17%-34%). A new fracture mechanics-based model, to the best of our knowledge, where the relevant normal load is parallel to the feed direction, has been developed to explain how ultrasonics leads to lower SSD depth. The key factors, supported by finite element stress analysis and load measurements, are (1) the initiation of fractures at higher z heights during the tool's ultrasonic vertical oscillations, thus propagating less deep into workpiece; (2) reduction in load (and therefore reduction in fracture propagation distance) due to smaller tool-workpiece feed direction contact area (again caused by higher z heights relative to depth of cut); (3) upward movement of the tool during oscillation leads to fracturing toward the surface instead into the depth; and finally (4) at tool's lowest point of oscillation cycle, there may not be enough time for the fracture to propagate to its full length.

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High-quality aspherical and freeform surfaces are in high demand, and the high-accuracy form measurement of such surfaces is a challenging task. To explore the current status of form measurement systems for complex surfaces such as aspheres and freeforms, interlaboratory comparison measurements are performed. This study presents the pseudonymized results obtained using three different surfaces (metal asphere, glass asphere, toroidal surface) in a total of six different round robins. These results were taken from a total of 13 different measurement instruments based on 9 different measurement principles and operated at 12 different laboratories. They were analyzed using a sophisticated procedure that was first developed in 2018 and then refined and tested on simulated data in 2022 to address the challenges of such a comparison at this level of accuracy. In the current study, we applied these refined methods to data acquired from tactile and optical point measurements as well as from optical areal measurements. As there are no absolutely measured and very well characterized reference standard aspherical and freeform surfaces available at the accuracy level of a few tens of nanometers root-mean-square, the approximated true forms of the surfaces were derived from the measurements and indicate the manufacturing accuracy of the surface forms. Then, the measurement’s differences to the approximated true forms were analyzed, which directly indicate the systematic measurement errors of the instruments. By also comparing the approximated true forms from the two different round robins for each surface, additional insights into the reliability and stability of these so-called virtual reference topographies were gained.

Hard ceramic and optical materials can present substantial challenges in manufacturing due to their tough mechanical properties. The properties that make these materials ideal for a variety of applications also makes them incredibly difficult to machine. Some of the biggest challenges in machining parts are minimizing the amount of sub surface damage (SSD) imparted into the material, slow processing speeds, and increased tool wear. The amount of SSD directly impacts processing time of these parts as additional finer tooling is required for the process or additional polishing time is necessary. Using finer tooling will produce more tool wear and slow down the overall process. To overcome these challenges, OptiPro Systems has developed an ultrasonic assisted grinding technology, OpitSonic, which has been designed for the precision optics and ceramics industry. OptiSonic utilizes a custom tool holder designed to produce oscillations, in the micron amplitude range, in line with the rotating spindle. A software package, IntelliSonic, is integral to the function of the platform. IntelliSonic can automatically characterize tooling during setup to identify and select the ideal resonant peak to operate at. While grinding, IntelliSonic continuously adjusts the output frequency for optimal grinding efficiency while in contact with the part. Using a variety of instruments, tests have proven to show a reduction in SSD while using OptiSonic, leading to decreased processing times and minimized tool wear. This paper will present the challenges associated with these materials and the solutions created to overcome them.

One of the main motivations behind modeling has always been to use a higher level of abstraction than usual programming languages. Metamodeling added the ability to create models of models, and thus the creation of efficient, domain-specific workbenches became simple and fast. However, the rising popularity of model-driven development revealed an important limitation: in the case of classical metamodeling, the definition and the usage of the domain are separated in time and are not to be mixed. Moreover, in the age of Industry 4.0, there is a real need for solutions that support the fine-graded, stepwise refinement of concepts instead of having a rigid, two (or four) level modeling structure. In our research group, we are working on a new metamodeling approach that supports stepwise refinement and gradual constraining of concepts. Although we originally aimed to create a multi-level solution, we realized that the result is worth discussing from the flexibility's point of view as well. In this paper, we elaborate features related to flexible modeling that we have identified, and show how these features were realized in our approach.

Freeform optical systems are becoming increasingly common due to new design and manufacturing methods. We present an example compact freeform optical system and describe considerations for transfer of the prescription of freeform surfaces for fabrication.

Optimax uses a variety of different 3D printers in our manufacturing process that streamline many aspects of the process. Measurement fixtures, machine repair and slurry containment are areas where 3D printing helps streamline manufacturing.