Advanced gripper development and tests for automated photovoltaic wafer handling

Abstract

Purpose - The purpose of this paper is to provide a technical review of a new Bernoulli gripper development using computed fluid dynamics (CFD) modeling, and also to outline an appropriate independent testing method for validating and evaluating process capability in terms of automated thin wafer handling. The investigation has been carried out by a collaborative way of Festo and Fraunhofer IPA as a connecting link between applied research and industrial needs. Design/methodology/approach - Following an introduction, the paper first describes the basic development and fundamental principles of a gripper based on Bernoulli's law. The gripper was dimensioned and designed with the aid of CFD methods. The performance of the hardware was tested using extreme parameter settings while gripping thin, fragile workpieces. The performance of the gripper was tested from the aspects of shortest cycle times, positioning accuracy and air consumption and followed a manufacturer-independent design of experiments. A characterization of the gripping force generated during horizontal and vertical tension tests provides conclusive closed loop validation with regard to the gripper's air flow in the initial CFD model. Findings - Photovoltaic (PV) grippers are challenging components since the handling objects, 200-120 µmm thin crystalline silicon wafers with an area of 156 × 156 mm, are one of the most fragile parts as far as required handling speeds and cycle times are concerned. Originality/value - The paper provides a detailed technical review of a CFD application used in the development of a Bernoulli gripper and also describes a method for testing and evaluating PV grippers for industrial scale applications. The article presents the results of a close cooperation regarding an industrial development (Festo AG & Co. KG) and independent applied research (Fraunhofer IPA) for advanced product benchmarking and validation in a relatively young but dynamic and increasingly-automated PV industry

PetriJet Platform Technology: An Automated Platform for Culture Dish Handling and Monitoring of the Contents

“…Vacuum suction grippers are often used for handling operations, 24 and for the PetriJet platform, a customary 20-mm diameter vacuum suction gripper was found to be sufficient ( Fig. 3 , number 8).…”

Optimization of outer diameter of Bernoulli gripper

“…Meanwhile, the value of P is at least several kPa (absolute pressure), so 1 P dP dr is very small in comparison with 1 r . Therefore, 1 r þ 1 P dP dr À Á can be approximated to 1 r . Such a simplification makes the analytical solution of the pressure distribution possible.…”

“…As a result, Bernoulli grippers are widely used as a suction tool. Giesen et al and Brun and Melkote used Bernoulli grippers to suck and carry flat workpieces [1][2][3], e.g., solar panels. Furthermore, Li and Kagawa built a device based on a Bernoulli gripper that could suck a silicon wafer without actually touching it [4].…”

“…Meanwhile, the friction force caused by the contact between the rubber pads and the workpiece prevents the workpiece from slipping or falling while being moved horizontally [2,3]. To eliminate the repulsive force resulting from the impact of the supply air flow on the workpiece in the central region, many researchers have introduced a deflector (also called the ''core" or ''cone mill" in articles by Giesen et al and Brun and Melkote, respectively) [1,3,5] in the center of the gripper. Another function of such a deflector is to increase the velocity of the air flow when it enters the gap, so that the deceleration of the air flow is enhanced and, therefore, the suction force is increased.…”

Challenges and key technologies in robotic cell layout design and optimization

“…Some previous studies have taken a step forward in gripper design optimization, for example see literatures. [86][87][88][89][90][91][92][93] The system published in Schmalz and Reinhart 94 aims to automatically generate the best gripper capable of handling the parts to be assembled, by identifying their geometric structures and dimensions and then grouping them in families by considering the object-related factors listed above. The similar approaches can also be found in the CAD modelbased gripper selection.…”