Design and automatic assembly sequence generation of a d.c. motor

Abstract

A design–for–assembly (DFA) method is used to analyse a family of d.c. motors and to design them with emphasis on meeting the criteria of the market demands while allowing for robotic assembly. Production cost, production facilities, development time and tooling were also taken into consideration. This article describes both old and new designs and highlights those design changes which have resulted in a 68 per cent reduction in parts and a 60 per cent reduction in assembly time, according to the DFA analysis. A market survey was performed to identify the applications in the automotive market for such motors. It identified the possible model variations such as shaft length, speed/torque specifications, double–ended shaft possibilities and mounting–bracket positions. The variation in motor models, low production batch sizes and fluctuating market demands make flexible and programmable assembly a very attractive option. The redesigned motor is currently being assembled manually in a production environment, and technical and economic proposals have been completed for automating the final motor assembly process. A knowledge–based approach has been used to generate the assembly sequence of the redesigned motor automatically. A new failure–based description language was used to express the motor design features and their functional relationships. Expert assembly rules were then used to generate the motor assembly sequence automatically.