This paper combines nonabrasive polishing with cryogenic polishing and proposes a new method to get super-smooth surface with angstrom dimension -- cryogenic polishing without abrasive. We describe its process and give some experiments to show how to keep stabilization in polishing and how to reduce effects of water quality of ice disk on surface roughness. Experiment results show that modifying ice disk before polishing for eliminating vibration and water quality of ice disk have a vital effect on surface roughness. Experiments of polishing K9(Chinese type) glass with ice disk of tape water, pure water and de-ionized water show that workpiece surface roughness polished by ice disk of de-ionized water is the lowest, up to about Ra 0.5 nanometer (nm). This is a new process to gain super-smooth surface with angstrom level on optical material.
Lapping is an important method in optical element machining. In lapping a workpiece is pressed on the lapping to by a press head through a press disc, which produces a friction force between the lapping tool and the workpiece and forms lapping. The friction moment between the press head and press disc resists workpiece rotating and affects machining accuracy. This paper in theory discusses this moment in detail. According to the press head and press disc elastic deformation produced under action of pressure, the contact stress distribution between them can be got. By means of this stress distribution function, the infinitesimal moment can be got. Through integrating an analytic result of resultant moment can be got too. From this result we can easily find that the factors affecting the moment and affecting role, which provides a theoretical base for increasing lapping accuracy, reducing the moment and a base for researching relative motion in floating lapping deeply.
This paper discusses the improvement of high speed flat lapping machine with grating measuring length system and an MCS-51 single chip computer, which makes the machine possesses the ability of measuring and controlling for lapping quantity and improves the machine property and machining accuracy. The original size and need size of workpiece are known. The difference between of them is lapping quantity (before lapping) is input into the computer. In lapping the grating measuring length system on- line measures the lapping quantity, the computer compares the measured lapping quantity with l, makes a decision according to the comparing result and decides whether to stop the machine. When the measured lapping quantity equals l, it is expressed that the workpiece is lapped to required size, the computer makes the machine stop, which assures the workpiece size accuracy automatically, improves machine automaticity and makes up the disadvantages that an ordinary flat lapping machine can not control the lapping size effectively. Through experiments it is found that measuring and controlling accuracy of improved lapping machine is +/- 2 micrometers .
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