ULTRASONIC ASSISTED TURNING OF HARDENED STEEL WITH MONOCRYSTALLINE DIAMOND
INTRODUCTION The demand for ultra-precise steel parts with optical surface qualities and complex shaped geometries is increasing and could be applied for plastic injection molding or precision glass molding processes. Nowadays optical molds for injection molding are coated with a nickel layer, in order to be able to machine the surface with diamond tools. Directly machined steel parts would decrease manufacturing time, making the coating process step unnecessary. Additionally, the life time of the mold is increased dramatically. Uncoated steel tools have a higher scratch resistance and no risk of delamination. Therefore the potential of directly machining steel with monocrystalline diamond is exceptionally high.
Ultraprecision machining of nitrocarburized steels
Ultra precision machining processes generate surfaces in optical quality and with sub-micron form accuracies. These specifications can be realised by applying single crystal diamond tools with nanometric edge sharpness. Typical workpiece materials are non-ferrous metals which can be machined without significant tool wear. But for optical mould making these materials have disadvantages regarding tool life in injection moulding of plastics. Alternatively diamond cutting of thermo-chemically treated steel is a new way to machine hardened steel moulds. This paper presents results from the machining of two thermo-chemically treated steel alloys. Analyzing and evaluating the machining results regarding surface integrity will lead to recommendations for the ultra precision machining of nitrocarburized steels. The influence of the thermo-chemically generated compound layer composition on surface quality and tool wear has been investigated. Therefore, diamond turning experiments have been carried out on a five axes ultra precision lathe in different depth beneath the surface. Here, both steels can be machined in optical surface quality with a surface roughness Sa < 10 nm, but the achievable surface quality strongly depends on the depth beneath the surface in which the machining takes place. The results show that with increasing depth beneath the surface the roughness values increase as well. Therefore, diamond machining at the edge between compound layer and diffusion layer has to be avoided to gain the best possible surface quality.
The Analysis on Fire Smoke Exhausting Robot Vibration Based on Wavelet Transform
Belt relaxation, which affects a lot on operation reliability of the fire smoke exhausting robot, is hard to detect. In this paper, a new method for belt relaxation feature recognition based on continuous wavelet transform (CWT) is proposed, and a vibration model which simplified the robot as a 2-dof forced vibration system under harmonic excitation is established. The vibration acceleration signal has been collected using the IEPE sensor and data acquisition card, experimental results verified the accuracy of the vibration model, and weak impact signal caused by the belt relaxation was distinguished, that testify the practicability of the CWT method in belt relaxation feature recognition.