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Jun. 20th 2000
Mechanical Engineering Laboratory
Micro-Lathe Equipped with Numerical Control
Micro-lathe, a palm-top micro-machine tool, was developed in 1996 by Mechanical Engineering Laboratory and their collaborators. The micro-lathe was one of key components in "Micro-factories" claiming "small machine tools for small mechanical parts". However, since, the micro-lathe at that time had only simple axis control, its machining capability in form generation and accuracy was limited. Now the micro-lathe has been successfully equipped with numerical control, to have functionality similar to that of ordinary machine tools.
Modified inchworm type micro-sliders of a unique design are employed, in which slides are guided and held with friction. It has 25 nm of positioning resolution, itself. By optimizing the drive pattern, smooth feed up to 400μm/s has been achieved, despite of its stepwise feed action. The movement of the slide is detected by a micro-linear encoder developed by Olympus Optical Co. Ltd., so that 0.1μm resolution of motion control is achieved by closed-loop control. Integrated with a small custom NC, a very small desktop micro NC machine tool has been developed. The Servo system is realized using a single board computer.
Due to the slider's negligible inertia, remarkable characteristics have been achieved； small amplitude bandwidth of 50Hz, following error of less than 1μm for sinusoidal command of 40μm amplitude, 1Hz, and positioning error of 0.2μm, etc. Some machining quality, surface roughness of 0.5μmRy on a 2mmφ brass cylinder and circular error of 0.4μm, corresponds to that of full-sized precision lathes. Secured axis feed and simultaneous axis control based on closed loop control enables flexible form generation. Rear end machining and cutout are available using two tools.
The spindle drive is a coreless DC motor of 1.2W rated power. Even though, the power directed to machining is only s few percent of the input power. Why not once think over the optimal size and design of machine tools, to meet the workpiece size?
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| fig. 1 Revised Micro-Lathe | fig. 2 Numerical Control Micro-Lathe system | |
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| fig. 3 Machined "needle pin" out of brass | fig. 4 Machined "maicro-hat" out of brass |
Mr. OKAZAKI Yuichi,
Manufacturing Machinery Div.,
Mechanical Engineering Laboratory
Namiki 1-2, Tsukuba, 305-8564- Japan
TEL +81-298-61-7224
FAX +81-298-61-7201
E-mail ： oka@mel.go.jp
