Manufacturing of products in sizes from a millimeter down to a nanometer is playing an increasing role in the Danish industry. It can be components like screws to be used in hearing aids or in metal devices used for repairing veins. Handling of 3D micro objects like these poses special challenges due to the small absolute scale. In a recent PhD project, a fully automatic screwdriver was designed and manufactured to solve several problems of the assembly process.
Most of the micro objects in industrial production are handled with manual labour or in semiautomatic stations. Manual labour usually makes handling and assembly operations highly flexible, but slow, relatively imprecise and expensive. The goal of the project has been to find solutions for handling and assembly in an automated way.
On November 6 Asta Gegeckaite successfully defended the thesis entitled “'Handling and assembly of microproducts”. As an example of a 3D assembly of micromechanical parts Asta Gegeckait in her project had selected a small push button used for hearing aids. She studied profoundly the individual parts with respect to materials, weight, geometry, dimensions etc. and the specifications of the assembly processes in terms of batch sizes, speed, flexibility etc.. Handling and assembly at a microscale is challenging because these processes are dominated by surface forces and not the gravity force, which gives problems such as stiction to the gripping tool, centering, alignment, precision, tolerance, etc.
In the project a fully automatic screwdriver based on torque and displacement control was developed. “The screwdriver fulfills both the role as handling device for e.g. picking up, transporting and releasing the screw and as an assembly tool for the screwing operation”, says Asta Gegeckaite.
In order to screw a microscrew into a plastic material counterpart, measurements of the torque were required. For this purpose Asta Gegeckaite as well designed and manufactured a dedicated torque measurement. Asta Gegeckaite also implemented and tested a design method based on biomimetics. The principle is based on the introduction of an intermediate plastic part between robot and screw.
Further she investigated the handling and assembly of the different microparts of the push button by means of a specially developed mechanical gripper. The results show that reduced surface area reduces stiction effects, and thereby make the gripping process more efficient.
Asta Gegeckaite expects Danish dental and medico industries working with micro mechanical products to benefit from the projects outcome, especially the discovered new principles applied in e.g. new automation solutions like gluing processes.
The research was supported by The Danish Ministry of Science, Technology and Innovation in the project The Danish Microfactory
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