Papers by Keyword: Diamond Machining

Abstract: In recent years microfluidic devices became of great interest, as they offer a wide range of bio-analytical and fluid processing applications through the utilization of size effects. Especially a mass manufacturing of disposable polymeric microfluidic devices by hot embossing or injection molding is expected to have high economic potential. It is known, that channels and areas showing a localized change in wettability can considerably improve fluid processing tasks like mixing or droplet generation. Chemical approaches, like the polymerization of lauryl acrylate, were successfully shown to achieve hydrophobic coatings for micro channels but are not suitable for a mass manufacturing. Since microstructures are known to provide water repellent properties of surfaces, this paper focuses on the applicability of diamond grooving and Diamond Micro Chiseling (DMC) processes for the manufacture of microstructured areas in brass molds inserts, in order to achieve hydrophobic properties of their replica. Major design features of structures, like a height range of 6 to 16μm or aspect ratios in between 0.5 and 3.2 are derived from the natural example of the lotus leaf. Molding is carried out by using a two component silicone filler. The performance of the replicated hydrophobic surfaces is evaluated by droplet contact angle measurements. After presenting methodology and results, the paper will conclude on how to transfer the investigated microstructuring methods to the manufacture of mold inserts for the replication of polymeric microfluidic chips with localized hydrophobic areas and channels.

Abstract: For the replication of optical glass or plastic components moulding inserts with surface roughness in the nanometre range and form accuracy in the micron or sub-micron range are needed. Despite these requirements the applied moulding insert material has to suit further needs like high temperature stability and resistivity against abrasive and chemical wear. To satisfy the specific requirements of replication processes steel alloys can be heat treated in a way to meet these demands. Unfortunately, these steel alloys cannot be machined with single crystal diamond tools because catastrophic diamond tool wear occurs. In recent years good progress in the field of ultra precision machining of steel has been made by nitrocarburizing the steel alloy. This leads to a sub-surface compound layer which is diamond machinable with surface roughness Sa < 10 nm and reduced diamond tool wear. But the ultra precision machining of these nitrocarburized steels introduces new challenges caused by the high hardness of the compound layer. Typical values are about 1200HV0.025. Therefore, this paper presents results from ultra precision machining processes focusing on the material behaviour during the cutting process. Influences of depth of cut and material composition on the surface generation can be found by evaluating chip formation and the resulting chips. Furthermore, the sub-surface of ultra precision machined steels is characterized by metallographic analysis to evaluate the influence of the nitrocarburizing process on ultra precision machining. In conclusion this paper presents the results for a deeper understanding of the material removal mechanisms in ultra precision machining of nitrocarburized steels.

Abstract: The manufacturing of optics is an important field of technology and will serve keymarkets today and in the future. Nevertheless, the application of complex optical elements is much restricted today despite of their outstanding functional advantages. Furthermore, the replication of structured optical components requires high precision molds. Diamond machining processes like diamond milling and cutting as well as abrasive polishing are appropriate micro-structuring techniques for optical molds. The combination of these key machining technologies with replication techniques within closed process chains will open the possibility to produce high precision complex optical elements as mass-product articles for many optical applications. Important machining techniques for optical mold manufacture are presented and discussed.