Ultrasonic Vibration Assisted Machining Of Germanium

Ultrasonic elliptical vibration cutting' technology,which has been deveoped by the Norikazu SUZUKI',Zhenmin YAN,Rei HINO and others,is applied to ultraprecision machining of single crystal germanium in the present research.The germanium is an excellent material for infrared optical devices,whereas ultraprecision micro-machining of the germanium is difficult due to its brittleness.Micro grooving experiments are carried out on the(101),(110)and(011)surfaces of single crystal germanium substrates,and basic effects of the elliptical vibration on the ductile micro-machining are clarified as follows.Critical depth of cut to generate a completely fracturefree surface on the single crystal germanium is increased significantly in all crystal orientations on the(110),(011)and(110)surfaces,and ultraprecision micro grooving is realized successfully at a large depth of cut of 1 gm by applying the elliptical vibration cutting.This improvement by the elliptical vibration cutting is considered to be caused by reduction of instantaneous uncut chip thickness and cutting force in each cycle of the elliptical vibration.When the rake angle becomes negative,influence of the crystal orientation on the critical depth of cut becomes negligible,while it is considerable at 0 degree.On the other hand,the rake angle does not have considerable influence on average values of the critical depth of cut between-20 to 0 degree The critical depth of cut is increased in all crystal orientations as the cutting speed is reduced in the elliptical vibration cutting.First,were determined the slip planes of a single crystal of germanium,since parallelism of the slip plane and the direction of the cutting force leads to the formation of cracks.The crack develops in the slip plane with the speed of sound and leads to chips.It was required to find such regimes for which there are no stresses in the directions of the slip planes above permissible.Next,were determined the optimum cutting parameters,both conventional and with a vibrating installation.It was necessary to understand how the indicators,when using the new technology,exceed the previous ones(using standard technology).After this,a study was carried out to study the elastic depressions of the tool,in the process of vibrational cutting,and comparison of the indicators with standard cutting.This was necessary for subsequent experiments with the treatment of surfaces of Fresnel lenses.At the same time,work will be done to find the optimal tool geometry(the radius at the tip of the tool is chosen).Was compared two instruments,with a radius of 1 mm and 60 mm.If the roughness' s coincide and the critical wear is not received,it can be considered promising to work with tools with a large radius at the apex.After this part there is a series of wholesale to obtain surfaces of Fresnel lenses in compliance with all norms.Fresnel lenses are widely used in all branches of life,and are also an excellent indicator of the technology's ability to carry out trace elements on the surface of brittle optical materials with a predetermined accuracy.Further,it was made study methods of processing Fresnel lenses in order to identify the optimal treatment strategy.The final part was concluded in relation to the most productive scheme for processing these lens data.