Steve Meister

Influence of Mold Temperature on Mold Filling Behavior and Part Properties in Micro Injection Molding

Abstract A variety of polymer parts used in microsystems technology is manufactured by injection molding processes. Particularly the high cooling velocity negatively affects the process and the resulting part properties. The scope of this paper is to investigate the influence of the mold temperature during the injection phase on the melt flow and the mold filling as well as on the resulting part properties. The results indicate that an increasing mold temperature supports the filling behavior, although the injection pressure has more impact. An increasing mold temperature also influences the part properties. It was found that a higher mold temperature leads to a more homogeneous and spherulitic structure as well as to an increasing degree of crystallinity. As a consequence the mechanical part properties are affected, too.

Correlation of Processing, Inner Structure, and Part Properties of Injection Moulded Thin-Wall Parts on Example of Polyamide 66

In micro- and thin-wall injection moulding the process conditions affect the developed internal structures and thus the resulting part properties. This paper investigates exemplarily on polyamide 66 the interactions of different cooling conditions on the morphological and crystalline structures. The investigations reveal that a slow cooling rate of the melt results in a homogeneous morphology and a higher degree of crystallinity and also a favoured crystalline structure. Consequently, the dielectric behaviour and light transmitting part properties are affected.

Affecting the Ageing Behaviour of Injection-Moulded Microparts Using Variothermal Mould Tempering

The fast cooling of the melt in an injection moulding process for manufacturing polymer microparts can lead to a modified inner structure, resulting in minor mechanical properties. Furthermore, the ageing can be also dependent on the process-induced properties. The results indicate that especially physical ageing processes occur in parts with unpropitious inner properties. Chemical ageing processes seem to occur independently of the process conditions in microparts. Tensile tests indicate that a process-induced favoured morphology can reduce the ageing-based change of mechanical properties.

Characterization of Material Stiffness on Injection Moulded Microspecimens Using Different Test Methods

Injection moulding of polymer microparts can result in modified material behaviour due to process-induced changes in the internal properties. Thus, a transfer of the mechanical material properties in microparts, determined and valid on standardized test specimens, is only partially possible and should be verified on microtest specimens. This paper investigates both tensile and bending test methods for a suitable characterization of material stiffness in polymer microparts. For this purpose a down-scaled standard specimen is used and tested with different testing methods. The investigations reveal that the different testing methods result in comparable mechanical values. The effects of process-induced modified mechanical behaviour are observable in the investigated testing methods. Consequently, a microbending test is potentially a suitable method for characterizing material stiffness using microspecimens.

Investigation on the Achievable Flow Length in Injection Moulding of Polymeric Materials with Dynamic Mould Tempering

A variety of parts in microsystems technology are manufactured by injection moulding of polymeric materials. In Particular the high cooling velocity affects negatively the process and the resulting part properties. The scope of this paper is to investigate the influence on the reachable flow length in injection moulding of different polymeric materials. The results indicate that the mould temperature has less impact on the achievable flow length of the polymer melt as the injection pressure. A higher mould temperature leads only to a slight increase in flow length. In addition, a transcending of the glass or the crystallization temperature of polymeric materials with the mould temperature shows no effect on the achievable flow length of the material.

Effect of fillers on the metallization of laser-structured polymer parts

Abstract Molded interconnect devices offer great potential as a substitute for circuit boards, especially regarding three-dimensional shaping and functional integration. Applying circuits to polymer substrates can be performed by means of LPKF laser direct structuring® (LDS). There, the matrix polymer is filled with a special metal additive, enabling laser activation and subsequent metallization. Important effects emerge from additional inorganic fillers inside the matrix polymer, e.g. the (thermo)mechanical behavior and the processing properties. In this work, the degree to which inorganic fillers affect the quality of metallization is investigated. An increase in the plating thickness was successfully achieved by adding varying amounts of talc platelets (diameter 7 μm) to a PA10T-based copolyamide filled with 4 and 8 wt% LDS additive, in contrast to poor metal deposition adding only LDS additive. Additionally, talc and glass spheres with a diameter of 50 μm were used, leading to unsatisfactory metallization results. To explain this behavior, adhering LDS particles were found on the talc platelets with a diameter of 7 μm on the surface of the laser-structured specimen. The talc platelets and glass spheres of 50 μm were not available in sufficient dimensions on the surface and thus led to worse plating results.