Michael Mischkot

Application of Functional Nano-Patterning to Polymer Medical Micro Implants

(07/10/2019) Application of Functional Nano-Patterning to Polymer Medical Micro Implants Improvement of cells adhesion to medical implants can be achieved through specific surface nano-patterns. The application of nano-patterns to planar surfaces can be obtained in a number of ways. However, the application of functional nano-patterns to complex 3D surfaces is a challenging task. In this paper the application of a nano-pattern deriving from aluminium anodizing to 3D micro mould inserts for replication of polymer medical micro implants is described. A process chain earlier developed at DTU was applied, where the main steps include the fabrication of an aluminium master, anodizing, etching of aluminium oxide, nickel and copper electroplating and selective etching of the aluminium master. The resulting nanostructure consists of tightly packed hemispherical features with average diameter of approximately 400 nm. Characterization of the obtained nanostructure on the micro mould inserts was carried out by means of atomic force microscopy and scanning electron microscopy. Results show that the specific nano-pattern was successfully generated on the 3D mould inserts exploiting the proposed process chain.

A Soft Tooling Process Chain for Injection Molding of a 3D Component with Micro Pillars

The purpose of this paper is to present the method of a soft tooling process chain employing Additive Manufacturing (AM) for fabrication of injection molding inserts with micro surface features. The Soft Tooling inserts are manufactured by Digital Light Processing (vat photo polymerization) using a photopolymer that can withstand relatively high temperaturea. The part manufactured here has four tines with an angle of 60°. Micro pillars (Ø200 µm, aspect ratio of 1) are arranged on the surfaces by two rows. Polyethylene (PE) injection molding with the soft tooling inserts is used to fabricate the final parts. This method demonstrates that it is feasible to obtain injection-molded parts with microstructures on complex geometry by additive manufactured inserts. The machining time and cost is reduced significantly compared to conventional tooling processes based on computer numerical control (CNC) machining. The dimensions of the micro features are influenced by the applied additive manufacturing process. The lifetime of the inserts determines that this process is more suitable for pilot production. The precision of the inserts production is limited by the additive manufacturing process as well.

Performance Simulation and Verification of Vat Photopolymerization Based, Additively Manufactured Injection Molding Inserts with Micro-Features

Injection molding soft tooling inserts manufactured additively with vat photopolymerization represent a valid technology for prototyping and pilot production of polymer parts. However, a significant drawback is the low heat conductivity of photopolymers influencing cycle time and part quality. In this research, the thermal performance of a \(20 \times 20 \times 2.7\,\mathrm{mm}^{3}\) injection molding insert was simulated. A thermal camera was used to assess the quality and accuracy of the simulation. Both, simulation and measurements showed that the temperature cycle during injection molding becomes stationary within 3 to 5 cycles. After 2800 injection molding cycles, the experiment was stopped and the insert was still intact.

Integration of Fiber-Reinforced Polymers in a Life Cycle Assessment of Injection Molding Process Chains with Additive Manufacturing

Additive manufacturing technologies applied to injection molding process chain have acquired an increasingly important role in the context of tool inserts production, especially by vat polymerization. Despite the decreased lifetime during their use in the injection molding process, the inserts come with improvements in terms of production time, costs, flexibility, as well as potentially improved environmental performance as compared to conventional materials in a life cycle perspective.

Calibration of a numerical model for heat transfer and fluid flow in an extruder

This paper discusses experiments performed in order to validate simulations on a fused deposition modelling (FDM) extruder. The nozzle has been simulated in terms of heat transfer and fluid flow. In order to calibrate and validate these simulations, experiments were performed giving a significant look into the physical behaviour of the nozzle, heating and cooling systems. Experiments on the model were performed at different sub-mm diameters of the extruder. Physical parameters of the model - especially temperature-dependent parameters - were set into analytical relationships in order to receive dynamical parameters. This research sets the foundation for further research within melted extrusion based additive manufacturing. The heating process of the extruder will be described and a note on the material feeding will be given.