Automation of Gluing Processes in the Optical Manufacturing Industry

The purpose of this thesis is to investigate the possibilities of automating a gluing process in the optical manufacturing industry. Aimpoint, a Swedish company that manufactures red-dot sights was the industrial partner in this thesis. Since the optical quality of their products is of the highest importance and the lenses and protective glass are for the most part glued using traditional, manual methods, the company aims to find improvements and methods to ensure the qualityof their products by automating this process. A number of requests were submitted, including the ability of such an improved process to be able to glue lenses of more complex geometries than the mostly round lenses currently used. To allow precise adhesive dispensing around the lens of a sight with a complex geometry, Aimpoint has two Cartesian tabletop dispensing robots. This kind of robot servesas a baseline for the comparisons in this thesis. A Franka Emika articulating robot arm was used to test the possibilities of au-tomating the process using such a robot system. Firstly, a motion was generatedbased on the CAD model of the product. The motion generation and manipulation was performed in MATLAB where the Peter Corke robotics toolbox was used for initial simulations. Unfortunately, the robot model in the toolbox was not able to take joint limitations into account and a migration to ROS was in order. Since there was no implementation for Cartesian control in the simulation software for Franka Emika, a decision was made to start physical tests using the robot pre-maturely. As for the adhesive dispensing, tests were conducted to investigate the parameters that affect the termination of a glue joint such as the retract setup and timings. A repeatability test was also conducted to test the performance of dis-pensing using a direct pressure fed adhesives syringe versus using a dispensingvalve. With the knowledge and data from these tests, the experimental setup was built at the robot lab in Lund where a computer ran the controller implementation, controlling the robot and an Arduino was utilized to actuate the dispenser. Several details were glued on this setup, both with vertical and angled nozzle. Asa reference for gluing, a detail was glued using the Cartesian dispensing robotat Aimpoint with the same limited path as previously described. To analyse the performance of the glued joint, a push-out test was conducted at Aimpoint usinga tensile strength machine. The results from this test showed that a glue joint glued with an angled nozzle was stronger and a higher force was required to deform the joint compared to one glued with a vertical nozzle. On average, the joint glued with an angled nozzle required 721 N and the vertical required 395 N. It is concluded that keeping the nozzle angled during the dispensing operation yield a stronger glue joint and makes the system less sensitive to positionand orientation errors. As for the impedance controller used in this thesis, it is concluded to not be suitable for the considered application and its requirements. Regarding the robotic solution investigated in this thesis, it was observed to bebeneficial to utilize a high number of axes when generating the motion for the gluing operation. However, case-consistent inverse kinematics is a requirementto further investigate this claim