Abstract:
For the use of Computer Numerical Control CNC machine tools is more and more extensive, its fault diagnosis research is becoming more essential. Failure forms are diversified, and fault reasons are very complicated. It should not be left unattended to, because this could lead to further deterioration. Whenever any machine tool breaks down in workshop, there is need for the technical personnel to locate the fault(s) and subsequently diagnose the faulty components for repair. The diagnostic exercise may be difficult especially in a complex machine tool like Computer Numerical Control CNC milling machines where parts are interrelated together in a complex manner. Since one of the parameters used in determining the efficiency of a technician (who repairs machine tools) is the time saved in locating faults, so there is a need to develop a diagnostic schedule which shows the sequential means of troubleshooting within a possible shortest time. In this project two approaches were used; Forward Pass (FP) which involves the diagnosis from electrical parts through Computer (CNC) to mechanical component and Backward Pass (BP) which involves the diagnosis from computer component through electrical parts to mechanical parts. Three different trials were conducted for each of the mode of diagnosis and the time to diagnose each component part was recorded. Based on the interrelationship of the component parts, two separate PERT (Project Evaluation & Review Techniques) network diagrams were drawn and their Critical Paths were determined. The Diagnostic schedule developed was evaluated and was transformed to a flow chart which was later used to write a simple Microsoft- Excel programme using VBA codes. The Forward Pass method saved three thousand four hundred and seventy seconds (3470s) and was chosen over the Backward Pass method to develop a Diagnostic schedule. Findings indicated superiority in terms of time savings to be achieved through deployment of a good scheduling discipline.
