Application of Threadless Screw to Precise Linear Positioning

• Published in: International journal of precision engineering and manufacturing Vol. 22; no. 2; pp. 355 - 364
• Main Authors: Hojjat, Yousef, Shirkosh, Mohammad
• Format: Journal Article
• Language: English
• Published: Seoul Korean Society for Precision Engineering 01-02-2021; Springer Nature B.V
• Subjects: Engineering; Industrial and Production Engineering; Materials Science; Regular Paper; Rotating shafts; Thrust loads; Friction-based mechanism; Linear positioning; Precise positioning; Threadless screw
• ISSN: 2234-7593; 2005-4602
• DOI: 10.1007/s12541-020-00407-8

This paper presents a mechanism for linear movement which could be called threadless screw, in which a roller is pushed toward a rotating plain shaft and rotates with it. The roller moves on a helical path when its axis is not parallel to the axis of the shaft. Therefore, the roller moves in direction of the shaft axis, just as linear movement of a nut on a screw. The lead of this mechanism is not only a function of diameter of the shaft, but also the angle between axes of the roller and the shaft which gives the possibility to change the lead continuously from very fine to very rough leads. On the other hand the accuracy of this mechanism depends on the accuracy of a plain cylindrical surface which can be fabricated very accurately compared with the threads of a screw. Two configurations of this mechanism were designed and fabricated to verify the idea. Coarse and fine positioning speeds are 10 and 0.1 mm/sec over an effective range of 200 mm, respectively. The experimental results show that the fast positioning over wide range of movement with resolution of 10 nm is possible by this mechanism. Further investigation shows that applying thrust loads have considerable effect on the lead of the mechanism.