Giovanni Legnani

Handling and Manipulation of Microcomponents: Work-Cell Design and Preliminary Experiments

The paper introduces an experimental setup for the automatic manipulation of microcomponents, based on a 4 dof robot with Shoenflies motion and a two-camera vision system. The general architecture of the work-cell is presented. The work-cell functionality was tested via repeatability experiments using a set of vacuum grippers. Due to their intrinsic simplicity, vacuum grippers are very cheap and appear a promising solution for micromanipulation. An innovative nozzle for a vacuum gripper was designed, fabricated and tested, comparing its performance with traditional needles. The design was conceived to reduce the frequency of occlusions of the gripper and handle a wide range of particles. The performed tests evaluate the success and precision of the part release. Indeed, this is a crucial aspect of micromanipulation because microparts tend to stick to the gripper preventing the successful performance of manipulation tasks. The results confirm that adhesive effects prevent the release of components. For this reason different strategies were adopted in order to improve the efficiency in the release of stuck components. This solution increases the percentage of release and, setting appropriately the intensity of the pressure, it does not affect negatively the accuracy nor the repeatability of the positioning.

A mini work-cell for handling and assembling microcomponents

Purpose – The purpose of this paper was the design, development, and test of a flexible and reconfigurable experimental setup for the automatic manipulation of microcomponents, enhanced by an accurately developed vision-based control. Design/methodology/approach – To achieve a flexible and reconfigurable system, an experimental setup based on 4 degrees of freedom robot and a two-camera vision system was designed. Vision-based strategies were adopted to suitably support the motion system in easily performing precise manipulation operations. A portable and flexible program, incorporating the machine vision module and the control module of the task operation, was developed. Non-conventional calibration strategies were also conceived for the complete calibration of the work-cell. The developed setup was tested and exploited in the execution of repetitive tests of the grasping and releasing of microcomponents, testing also different grasping and releasing strategies. Findings – The system showed its ability in...

Flexible Vision Based Control for Micro-Factories

In the micro-manipulation field, the adoption of vision-based strategies can suitably support the motion system in easily performing precise manipulation operations. In this context, the cooperation between the robot and the vision system is fundamental to achieve high performance. The paper introduces and critically discusses the main issues related to the design and implementation of vision-based control for a micro-manipulation work-cell. The core issues of the developed software architecture, such as the work-cell calibration and the task execution module, are described and its main characteristics highlighted. The application of this program within a micro-assembly work-cell set-up allowed the execution of various manipulation operations, thus representing a test bench for its capabilities evaluation. The actual execution of a pick&place task is finally discussed.Copyright

Precision Handling of Electronic Components for PCB Rework

The paper focuses on the study of strategies and tools to handle miniaturized components in the electronic industry. In particular, the paper presents an innovative device and method to manipulate microcomponents by vacuum. The device includes an original releasing system, that does not require any external actuation, to assist their release. Indeed, at the microscale, adhesion forces predominate over the gravitational force due to the small masses of the microcomponents, often leading to the failure of the release phase if a release strategy is not implemented. The device, able to eliminate the adhesion problem, is compared with a traditional vacuum microgripper in terms of grasping and releasing error and percentage. The results of preliminary experimental tests are discussed, demonstrating that the innovative microgripper represents an interesting solution for handling electronic components as well as different microparts.

A Novel Method and Mechanism for Micro-Sphere Singularization

The paper presents an innovative mechanism for the singularization of micro-spheres, which can be effectively employed in a diverse range of robotized applications in micro-electronics and micro-mechanics. Many miniaturized devices are currently being developed and consist of different micro-components to be precisely assembled. The demanding product and process requirements can be met by automating the assembly phases, which include sorting and feeding the micro-components. Therefore, accurate, high-throughput, and modular mechanisms and tools able to supply a number of micro-components, or even a single element for the subsequent operations, play a significant role. In this context, this work focused on the development of a novel strategy for separating a single component from an unstructured stock of identical parts, in particular of micro-spheres with diameters of 0.2–1 mm. Suitable expedients were considered to overcome the adhesive effects that can become significant at the micro-scale due to the very small size and low mass of the micro-spheres. The paper describes the operating principle and the actuation strategies of the mechanism. The design and the development of a prototype for singularizing micro-spheres with a diameter of 0.6 mm are thoroughly discussed. Finally, the results of experimental singularization tests demonstrate the method effectiveness and the mechanism performance.

A Laser Calibration Device for Mini Robots

The paper describes a new laser device conceived for surface scanning and more specifically for mini robot calibrations. The system is based on a laser triangulation sensor which is moved by an extremely accurate device to collect a set of 3D points lying on surfaces. If the surfaces belong to the gripper of a robot that must be calibrated and a sufficient number of points of this gripper are collected, the pose of the robot can be measured. If the robot is moved to several different configurations and the gripper poses are measured for each of them, it is possible to reconstruct the kinematics of the robot and calibrate it. The paper presents the theory and describes the design, tests and calibration of the laser instrumentation with a focus on the first experimental results. These results are obtained in a working cell including a vision system, a 4-dof (xyz,θ) mini robot and a 2-dof rotating platform.Copyright

Performance Evaluation Methods for Microgrippers

In precise manipulation and assembly of components with sub-millimetric dimensions, the role of the gripping tools is fundamental. In the literature, many different types of the so-called microgrippers have been presented, based on different working principles, to cope with the issues related to the gripping, the handling and the release of different micro-components. Depending on the component properties, the task requirements and the system constraints, a microgripper could be more suitable than another and allow the achievement of higher performance. However, the performance assessment of the microgrippers lacks of a standardized and quantitative methodology. Many authors declare the good capabilities of their tools in a qualitative way or according to the results obtained executing specific and different tasks. For this reason, it is often difficult to compare different microgrippers and estimate the actual results that can be obtained e.g. in the gripping or the release of a component. In this context, after a preliminary survey of the adopted approaches in literature and of their meaning, this paper investigates the conception and formalization of methods and procedures to evaluate the performance of a generic microgripper and the definition of standard performance indices to support the presentation of the microgripper characteristics.© 2014 ASME