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Freeform machining of molds for replication of plastic optics

: Brecher, C.


Brinksmeier, E.:
Fabrication of complex optical components : From mold design to product
Berlin: Springer, 2013 (Lecture Notes in Production Engineering)
ISBN: 3-642-33000-2
ISBN: 978-3-642-33000-1 (Print)
ISBN: 978-3-642-33001-8 (Online)
Aufsatz in Buch
Fraunhofer IPT ()

The success of plastic optics relies on the availability of molds needed for mass production. This chapter deals with the machining of molds with continuous surfaces exhibiting aspheric and free-form shapes, while the machining of molds with discontinuous surfaces (prisms, facets, Fresnel structures, etc.) will be discussed in Chapter 6. Molds may be classified according to size, shape, and tolerance requirements. As a mold material for replication of plastic optics, a nickel-phosphorous plated steel alloy is frequently chosen, which meets temperature and wear resistance requirements and can be machined with monocrystalline diamond tools. Basically, there are three methods for machining asymmetric shapes: raster milling, ball-end milling, and tool- or slide-servo turning. The discussion of this chapter includes material response to diamond machining, selection of machining parameters, programming and data handling, machining strategy, and achievable surface roughness and figure accuracy. Since the machining of molds is still the most cost-effective factor of the production chain, a reduction of set-up and machining times remains the biggest challenge for future research.