Silicon gripper

SM actuators may have very many different shapes and offer a variety of shape changes (i. e. actuator strokes). This property can be exploited so as to adapt the SM elements shape to the actuating task. As an application example, a miniature parallel gripper with electrically heated SM wires integrated into its mechanical structure was presented. Further on the performance of pseudo-elastic shape memory flexure hinges in parallel robots for micro-assembly tasks was shown. The future opportunity for thin-fllm SM actuators to drive micromechanical systems and devices was demonstrated by a miniature silicon gripper. 

Biitefisch, S. Pokar, G. Biittenbach, S. Hesselbach, J. A New SMA Actuated Miniature Silicon Gripper for Micro Assembley. Proc. 7th Int. Conf. on New Actuators, June 19-21, Bremen, Germany (2000), pp. 334-337... 

The performance of control rod drive mechanism (CRDM) has been satisfactory with friction force within limits and drop time less than 400 ms. An on-line system to monitor the drop time of control rod (CR) during scram was commissioned. Similarly a system was developed to measure friction force of CR during power operation. The 3 s interlock on CR raise movement, which was introduced before the first criticality was deleted as it was giving rise to large time in raising power and high start up duty demand on CRDM motors. The lower parts of two CRDM were replaced, one due to failure of translation bellows, and another due to failure of gripper bellows. Leaky silicone bellows of one CRDM was replaced in-situ. 

Electrical activation. The required heat energy may also be generated directly within the SM element by electrical current. Joule heating allows the construction of very small and compact electrically controlled SM actuators. Experimental applications for robotic devices and grippers (such as silicon wafer grippers) have proven the feasibility of such actuators [72]. The remaining part of this article will mostly cover electrically heated SM actuators because they can be utilized in automation devices. 

The micro gripper in Fig. 6.61 consists of a silicon structure with a dimension of approximately 7 x 4mm. In the open position the gripping jaws are 0.5 mm apart. The flexure hinges have a minimum thickness of 30 im. By machining a sputtered NiTi foil the SMA actuator has been realized with a minimum thickness of 30 pm. The gripping force averages by circa 11 mN. 

Recently, a miniaturized gripper that is propelled by an LCF film has been introduced [107]. Using lithographic methods, an LCF film and the silicon pincers... 

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