Methods for highly accurate gripping of flexible micro parts

Abstract

Today, handling and assembly of flexible micro-components such as thin wires or glass fibres with diameters down to a few micrometers and lateral dimensions up to a few meters is an important challenge in hybrid micro-assembly (Brecher and Peschke 2004). Production of flow sensors for respirators in medical engineering or coupling a fibre to an active visual component in optical data communication are examples of such applications. Such products have one thing in common: The assembly of their most sensitive functional components is often carried out manually since the handling and positioning technology either has to be specially developed and is costly or is non-existent (Weck and Peschke 2003). However, in most cases the manual assembly is very time consuming and its repeatability and positioning accuracy is not adequate (Carrozza et al. 2000); Petersen (2003). This disadvantage is obvious especially in the assembly of hybrid micro-optical telecommunication systems such as switches or power splitters, because the required mounting tolerances are less than a micron. A deviation of 100 nm in the alignment between the optical components and the glass fibres leads to noticeable and non-tolerable losses when coupling light into the fibres. With this background, fundamental studies are carried out at Fraunhofer IPT for the optimization of gripper geometry, gripper materials and gripping parameters for handling flexible micro-components such as glass fibres. The aim of these studies, shown in chapter 2 of this paper, is primarily to investigate the effects on the reproducibility of the positioning when gripping these highly sensitive micro-components and to derive gripper optimization strategies. A further aim is to develop a large scale integrated, adaptive, rugged and economical gripper system particularly for handling and alignment of flexible micro-components accurate to the sub-micron level. This gripper system can be used on conventional robot systems for carrying out micro-assembly operations. The robot system carries out the pre-positioning, the positioning tolerances necessary for the micro-assembly are subsequently realised directly at the tip of the gripper with a multi-axes system integrated into the gripper. Positioning systems that achieve the required positioning increments in the sub-micron range are existent (Scheller 2001). The problem of such systems is that they are normally highly sensitive against mechanical impact. Also their gripper integration is problematical due to a high weight and size dimensions in the decimetre range for each axis. In this paper the development of a highly robust gripper-integrable multi-axes system is presented

Anisotropically etched silicon fibre-grippers

“…As outlined by Brecher and Peschke (Brecher and Peschke 2006), mechanical grippers can achieve the accuracy of vacuum grippers. However, an inaccuracy of the guidance in the fibre-magazine and the imprecise fibre coating (which should be gripped by the jaws in order to prevent the fibre from being damaged) can lead to alignment errors.…”