Influence of the process parameters on the replication of microstructured freeform surfaces

Abstract

-Surfaces of technical parts are getting more and more attention in terms of functionalization. By modification, additional functionality is given to the part, e.g. self-cleaning effect or antireflection behavior. Nowadays mainly flat surfaces are structured which is a consequence of the available production methods. However, the demand of micro structured free form surfaces is increasing, enabling novel products. A major problem in the mass production (e.g. injection molding) of structured freeform surfaces is to demold these structures without ripping or deforming them due to occurring undercuts. Recently a novel concept was developed which overcomes this limitation. A nickel substrate containing a structure composed of lines orientated in two different directions, one orientated in melt flow direction, the other one perpendicular to that, but both with a cross-section of approximately 45 μm x 55 μm (w x h) was used as a premaster to cast a flexible master. This master made of poly(dimethylsiloxane) (PDMS) was mounted on a bending edge in an injection mold cavity. Within this paper the influence of process parameters on the replication grade of the structure lines depending on the structure orientation was evaluated, varying the holding pressure, melt and mold temperature using statistical design of experiment methods. The replication grade was evaluated by characterizing the shape of the structure lines along the entire process chain, using an infinite focus system. The results show, that the melt temperature has the biggest influence on the dimensions of the structures, the mold temperature only a slight one.

Surface characterization and analysis of textured injection moulded PC-ABS automotive interior components

“…The surface topography of study samples is measured using Zygo's Nexview 9000 4 coherence scanning interferometer (CSI) with 10X objective and 0.95 μm lateral resolution. The mould tool surfaces are replicated using Technovit ® Provil Black polyvinyl siloxanes 5 material.…”

“…The surface texture on the components is a replication of the grain pattern in the mold cavity, and to avoid variations in color and gloss it is important to have good replication of the grain pattern. Unfortunately, a large number of material and processing parameters affects the replication and a substantial number of investigations have therefore been carried out to improve the knowledge about robust injection moulding of textured components with high-aspect ratio [1][2][3][4][5][6][7][8]. In this study, the effect of texture, tool temperature, holding pressure and injection speed on surface texture replication of injection moulded PC-ABS (Polycarbonate-Acrylonitrile butadiene Styrene) samples and its relationship with measured gloss are investigated.…”

“…Zehntner 1120, https://media.screeningeagle.com/asset/ Downloads/ZGM%201120%20Instructions_English.pdf 4. Zygo newview 9000, https://zygo.com/products/metrologysystems/3d-optical-profilers/newview-9000 5.…”

Mastering of NIL Stamps with Undercut T-Shaped Features from Single Layer to Multilayer Stamps

“…The replication of nanostructures in the nanoimprint process is commonly limited to draft angles equal or smaller than 90°, but recently it was also shown that undercut structures as well as nano-cavities could be replicated when the right materials for the stamp and imprint material are chosen [ 11 , 29 ]. The process parameters of the replication—especially of the demolding step—are critical for freeform microstructures [ 30 ]. Also, innovative alternatives such as shape memory polymers have been reported [ 31 , 32 ].…”