The production of medium to large lenses (200 - 500 mm) is becoming increasingly important against the background of the semiconductor crisis. The value of a lens increases enormously through the entire value chain. The grinding, polishing and correction processes must be precisely coordinated in order to achieve highest levels of shape accuracy and surface finish. This leads to increasing demands with respect to the manufacturing equipment and processes. Not only a single step but the whole process chain needs to be addressed during optimization. It starts with the reduction of MSF errors during grinding and ends with well converging correction cycles during polishing. The very consequent design of ultra-precision grinding machines comprises hydrostatic bearings and a gantry-type machine base made from granite. The efficient pre-polishing of aspheres and freeforms demands for tools with high removal rates even at relatively small polishing spot sizes. The reliability and convergence of the correction cycles during polishing strongly depends on stable and predictable removal functions. For each step we identify the key challenges and introduce ways to meet them.
More than ever, companies are pursuing the goal of displaying their production in a digital twin. This allows problems in production to be clarified and process difficulties to be made visible. The goal is usually achieved via machine or process data. The machine data describes data that is collected around the machine, whereas the process data strongly refers to the quality of the process and the resulting outcome. In order to generate added value for the user, it is necessary to draw correlations between data and criteria that are important for the customer, such as the quality and accuracy of the components to be manufactured.
In this context, it is shown to what extent the process data are interrelated with the component data.
The growing interest in providing additional degrees of freedom to the design of high-end optical systems has led to an increased demand for freeform optical elements. The efficient fabrication of such elements requires a polishing process that provides high removal rates and a stable removal function while working with a relatively small spot size. Taking these constraints into consideration this paper focuses on the successful implementation of polishing processes applying the A-WPT (Advanced Wheel Polishing Tool) technology. In order to maintain perpendicularity towards the freeform surface to be polished, the A-WPT is run on a 6-axis machining system with an optimized kinematics set-up. Herein the use of a tip-tilt unit successfully suppresses the formation of singularities, e.g. close to the surface vortex when polishing along a raster tool path. First results for the pre-polishing of an off-axis parabolic surface made of Zerodur are analyzed and discussed.
The automation of production steps is increasingly in focus due to the shortage of skilled workers. In addition to the handling of lenses and the automatic processing of lenses, the automated adjustment of process parameters is particularly necessary. Conventionally, this is done by means of feedback through the metrological recording of the manufactured component. Based on an evaluation by a specialist, the necessary parameters are then adjusted. Thus, in addition to fully automated production, fully automated evaluation and feedback is also an important topic on the way to controlled production. However, the problem here is the automated feedback of measured values to individual process parameters, which are usually only known in the minds of the operators.
In the following a concept is presented, which shows the coupling of the individual machine types as well as measuring instruments, in order to make a linkage possible on the hardware side. In addition, the feedback or correlation between machine parameters and measured values is shown in order to finally achieve the possibility of automated compensation.
The lack of trained machine operators is a significant challenge in modern optical fabrication facilities. The request for machine automation is growing through the entire range of production. This starts in the range of micro optical components for the use in life science applications, such as endoscopes and microscopes, as well as in larger applications such as sports optics (binoculars, scopes etc.) and even larger optics.
While large optics is a challenge by itself, the drive for automation currently can be seen more on the smaller end of the optical fabrication range.
This paper introduces a solution for fully automated production of optical components, especially for diamond pellet lapping and for polishing. The concept includes the innovative HydroSpeed Polishing Technology. Also aspects of process supervision and process control are considered. As a loading solution, the concept is based on a 6 axis robot, feeding pallets according to the DIN standard, as well as customised pallet solutions.
The presentation includes videos and photographs of the fully automated solution, but it is important to note, that the concept can be scaled down for more simplified solutions, using less complex loading technology and still produces optics autonomous.
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