Ingo G. Reichenbach

Micromachining of CP-Titanium on a Desktop Machine - Study on Bottom Surface Quality in Micro End Milling

With the ever-growing demand for micro products, the influence of micro-features and the functional performance of component surfaces represent a high economical potential. A competitive process for the manufacture of micro products is using micro end mills and a desktop milling machine. Since the topography of machined surfaces affects e.g. the wetting interaction or the bacterial cell adhesion, all relevant finishing steps such as the generation of a plane surface parallel to the machining table and the structuring with micro end mills have to be concerned in order to create functional surfaces. In this paper the generation of plane surfaces and chosen tool paths is described first and then the use of ultra-small micro end mills for slot milling in cp-titanium and the influence of process parameters on bottom surface quality is discussed.

Analyzing the influence of microstructured surfaces on the lactic acid production of Lactobacillus delbrueckii lactis in a flow-through cell system

Microorganisms growing in biofilms might be possible biocatalysts for future biotechnological production processes. Attached to a surface and embedded in an extracellular polymeric matrix, they create their preferred environment and form robust cultures for continuous systems. With the objective of implementing highly efficient processes, productive biofilms need to be understood comprehensively. In this study, the influence of microstructured metallic surfaces on biofilm productivity was researched. To conduct this study, titanium and stainless steel sheets were polished, micromilled, as well as coated with particles. Subsequently, the metal sheets were exposed to the lactic acid producing Lactobacillus delbrueckii subsp. lactis under laminar and homogeneous flow conditions in a custom‐built flow cell. A proof‐of‐concept showed that biofilm formation in the system only occurred on the designated substratum. Following a 24‐h batch cultivation for primary biofilm development, the culture was continuously provided with glucose containing medium. As different experimental series have indicated, the process resulted to be stable for up to eleven days. Primary metabolite productivity averaged around 6–7 g/(L h). Interestingly, the productivity was shown to be affected neither by the type of metal, nor by the applied microstructures. Nevertheless, a higher dry biomass weight determined on micro‐milled substratum indicates a complementary differentiation of biofilm components in future experiments.

Application of CAD/CAM and Micro End Mills with 20 to 120 μm Diameter for the Direct Machining of Microstructures in PMMA

The use of microfluidic devices brings some benefits such as low reagent consumption, shorter analysis time, portability and cost reduction. The potential of this technology has constantly grown over time and lead to the development of competitive manufacture processes. The production of such microfluidic devices is usually done by molding processes which allow mass production of polymer disposables with a low cost per unit. In a prototype phase these methods are, however, expensive. To overcome the multi-step fabrication the direct milling in polymer is an alternative. In this paper micro structures are directly milled in polymethyl methacrylate (PMMA) with self-developed micro end mills and the proper CAD/CAM integration offering a fast response in manufacturing of complex structures even in the micrometer range The direct milling of structures in PMMA with micro tools-diameter 120 μm is a feasible method to produce a physical prototype. The chosen micro end mills and strategies represent a competitive process in a prototyping level by reducing time to market.

Analytical Modeling and Experimental Investigation of Burr Formation in Grinding

Increasing industrial requirements on the precision of edge geometry lead to the investigation of burr formation, particularly in finishing operations such as grinding. In the presented paper the burr formation process at the workpiece edges during surface grinding is analyzed. Based upon a geometrical examination of the macroscopic contact situation between grinding wheel and workpiece, a qualitative analytical process model of burr formation is developed. Following experimental investigations verify this qualitative model and enable quantitative results. Several so called “grinding stops” are realized by specifically interrupting the grinding process. Thereby, the burrs at the edges of the temporary contact area are detected. To analyze the burr formation, metallographic sections of the workpiece edges are prepared and characteristic burr parameters are measured. Based on experimental results, a thermal impact on burr formation in grinding can be detected.