A High Speed Assembly Force Monitoring System for Quality Control

Abstract

A major SERC sponsored research project is in progress at Bristol Polytechnic in collaboration with Du Pont Electronics, to investigate and develop improved systems of quality control.

Du Pont Electronics manufacture connectors for the electronics and computer industries. These connectors are assembled using a high speed special purpose machine which inserts the connector pins into the injection moulded plastic body of the connector. The automatic quality monitoring of the production of these connectors is under investigation as part of a scheme to integrate and automate the entire quality control operation at Du Pont, using standard general purpose microcomputers as the main elements, linked to a quality database held on a minicomputer.

It is anticipated that individual production processes, including the assembly process, will each have a supervisory microcomputer to monitor the state of the production process and take appropriate action should an error condition develop. Because of the speed of the assembly process and the need to perform various other on-line tasks, such as batch quality reporting and job scheduling, it was considered inappropriate for the monitoring microcomputer to operate in realtime, and a distributed processing approach using a front end processor has been adopted.

In this system, the force of insertion for each pin is sampled and digitised a number of times for each insertion, and a force signature developed, which is compared with a ”master” force signature representing a perfect insertion.

Error states are communicated to the microcomputer on the IEEE-488 interface, by which the micro is also linked to the assembly machine controller units.