Vacuum Linear Stage

Abstract

The invention concerns a vacuum compatible motorized long stroke (up to meters) positioning stage for accurate positioning in one direction. Special focus has been attended to realize highest 10 repeatability over long periods, minimized dissipation and minimized wear with respect to state-of-the-art motorized positioners. Due to introduction of constant spring preloading of the roller guides, occurring play within these guides over 15 lifetime will be avoided as well as stresses due to temperature variations in the positioning stage.

Description

1 Vacuum Linear Stage The invention concerns a vacuum compatible motorized long stroke (up to meters) positioning stage for 5 accurate positioning in one direction. Special focus has been attended to realize highest repeatability over long periods, minimized dissipation and minimized wear with respect to state-of-the-art 10 motorized positioners. Motorized stages are a combination of a few essential building blocks like: guides, enabling only 1 degree of freedom, an actuator to introduce displacement between 15 a base frame and a moving platform and a sensor to determine the displacement between the base frame an the moving platform. Actuators for vacuum compatible motorized positioning stages can be roughly divided in most commonly spindle 20 based (position) actuators, linear motor (force) actuators or piezo based (position) actuators. To achieve reasonable speeds to overcome long strokes, piezo based actuators are no option. So, for this case only electromagnetic actuators like rotational motors 25 for spindle drives or linear motors would be a viable option. Position repeatability of the moving platform with respect to the base frame in all 6 degrees of freedom is apart from the actuator / sensor control also defined by 30 careful adjustment of the roller guides at initial assembly of the system. During operation, preload will change due to thermal effects or wear, which can lead to play or extensive preload in the roller guides and 2 repeatability in the fixed 5 degrees of freedom will be compromised or friction in drive direction will be enhanced. Drive friction which compromises resolution and dissipation will not be constant during operation. 5 By using motorized spindle drives, the stiffness in drive direction is lirnited and depending on the position of the moving stage with respect to the base frame and therefore compromises the positioning resolution. 10 The above-mentioned disadvantages have been overcome in the presented concept vv here we propose a combination of force preloaded roller guides with a linear motor drive. The exact nature of this invention, as well as its 15 objectives become clear in the accompanying drawings wherein: Fig.l Is the 3D view of the system indicating the various components to realize the required performance. Is a detailed 3D view of the system. Fig.2 Fig.3 Is a cross section of the system The base frame 1, is equipped with two straight roller 25 guides 2, aligned in a parallel way to ensure precise translation of the moving platform 3. The moving platform 3, is foreseen with three interface points 4, for stress-free mounting of additional equipment. 30 The moving platform 3, is foreseen with a fixed guide 5, and an auto-alignment guide 6 which is mounted in such a way that it is connected to the moving platform 3, enabling only two degrees of freedom; Rz and Y, due to 3 a compliant connection realized by the flexible hinges 7. The tension springs 8, take care of a well defined and constant preload of the rollers 9, between the guide 2 5 and 5 and the guide 2 and auto-alignment guide 6. A linear motor comprising of static magnets 10 and a coil 11, takes care of the drive force in X direction. The position feedback is taken care off by an encoder readout head 12 and a fixed scale 13. 10 The stroke of the moving platform is limited by two elastic end-stops 14, to limit shock forces under unforeseen circumstances. For secure cable routing a C-shaped elastic leaf spring 15, is connected between the moving platform 3 and the 15 base frame 1. To enhance thermal conductivity between the moving platform 3 and the base frame 1, a C-shaped thermal link 16, is mounted between both parts.

Claims

1 The invention concerns a device with the characteristic that: An electromagnetically driven vacuum-compatible translation table for long stroke (tens of centimeters) is realized; A base frame is equipped with two straight roller guides, in such a way that they are parallel walking whereby the moving platform that also is equipped with two straight roller guides an accurate translation of idler rollers can execute in a defined direction; The moving platform is designed in such a way that a monolithic whole is created with permanent flexible elements that ensure that a of the roller guides a certain degree of has flexibility so that it splits into two can align degrees of freedom with respect to the static, mounted to the base frame guides, and in such a way that all rollers have experience equal preload; The preload of the idler rollers, defined and kept constant throughout its lifespan is realized by one or more in metal executed elastic springs and has the aim to to avoid play in the guide and to the rolling friction during its lifetime to be constant to keep and minimize; The chosen materials all be vacuum compatible and where the rolling elements 5 is made of ceramic material, whereby there an unlubricated roller guide can be realized; The drive of the moving platform is realized by a linear motor whereby the electrical coil section on the moving part platform is connected and the magnets to the base frame; The position of the moving platform is measured by means of an encoder where the encoder head is connected to the moving platform and the ruler with the base frame; The total stroke of the moving platform in the two extreme positions is limited by an in elastic element made of metal whereby the forces resulting from collisions during an emergency stop be minimized; 2. An establishment in accordance with the preceding conclusion, with the characteristic that: The electrical wiring via an elastic leaf spring in a C shape of the movable platform be guided to the base frame so that displacement of the platform relative to the base frame consumes virtually no energy; 3. An arrangement according to one of the foregoing conclusions, characterized by the fact that: There is a connection of the movable platform is led to the base frame by means of one or more leaf springs with a good thermal conduction in a C shape such that displacement of the platform relative to the basic frame consumes virtually no energy and the by 6 the heat produced by the engine can via conduction be disposed of; 4. An establishment within the meaning of claim 1 with the characteristic that: The rolls are not made of a ceramic material manufactured, but from a metal and whereby a Vacuum-compatible lubricating grease is used to the to achieve required service life ; 5. An establishment within the meaning of claim 1 with the characteristic that: The drive is not by a linear motor, but is provided by another type of drive such as: a rotary spindle drive, friction wheel drive, belt drive or piezo- actuator-based drives; 6. An establishment within the meaning of claim 1 with the characteristic that Position measurement using an interferometer is provided whereby the moving platform is equipped with a light-reflecting element and the is located on the base frame; 10z R7 R 1 2 1 / 3 Fig1

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