During the past decade,
Three, four, and five-axis machining centers are used for grinding, polishing and shaping the lenses with diamond tooling. Even though there is five times more equipment operating over three shifts (a nearly lOx increase in spindle hours), the manpower required to write programs for and operate this advanced CNC equipment has barely doubled. Being able to output ten times the work with only double the manpower translates into roughly a five-fold increase in manufacturing productivity. Of course, the actual productivity increase is significantly greater than that because fourand fiveaxis equipment allows many of the more complex operations to be performed at high speeds with a single setup.
AI Gould, mechanical engineer for
Many of the R&D initiatives that have taken place at
Recent R&D programs have focused on asymmetric lenses, which are even more geometrically complex optics. These completely free form optics are in development for both commercial and defense applications. Asymmetric lenses can be used as windows that correct distortions present in other optical devices that are focused through them. The shape of an asymmetric lens for a particular application is defined by a unique equation that is translated into a Mastercam program governing the precise grinding of the shape into a glass substrate using a five-axis machining center.
A goal of recent asymmetric lens projects has been to meet form tolerances of approximately one micron over an area of approximately 250 mm2. Manufacturing them involves a meticulous process that begins by fine grinding lenses on the machining center. Intense polishing then imparts additional dimensional properties and surface finish. After measuring the lens, a final polishing step corrects any deviation from spec found during measurement. Gould explained that there is no room for error in this process, since a blank of the material that you can hold in the palms of two hands can cost up to
Gould said that Mastercam has provided a number of advancements that have significantly improved the throughput of both its conventional and R&D optics manufacturing. For example, integration with solid models is easily accomplished. Some projects come in as marked up drawings via PDF. Most typical geometries for objects can be defined with four terms: thickness, diameter, and radius. "We just drop them into Mastercam and away we go," Gould said.
Machine configurations for all of CNC equipment, regardless of type, are available from within the Mastercam programming environment. So there are times where operations for milling, lathe and wire EDM are generated from within a single program.
"Creating a program to make a new lens is really quick. You pick the machine, you pick the toolpath, and you set a few parameters using menus. The longest part is waiting for the CAM program to generate the toolpath, if there's a lot of complex geometry or for it to generate the posts. One of the nice features of Mastercam is that it is multi-threaded, so while those things are going on in the background, you can be working on another part," said Gould.
Toolpath selection is critical in using diamond tools to grind super precise shapes that require minimal polishing. One of the most frequently used is Mastercam's multi-axis
Programmers continually use Mastercam's Backplot and Simulation modes to assure that toolpaths have no interferences and that material removal is correct. This prevents damage to expensive materials that may be irreplaceable.
The five-axis machine is one of the most heavily scheduled pieces of equipment in the building because of it exceptional productivity.
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