Organizing Maintenance on Production Lines
Page 43
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PRINCIPLES governing the preparation of fleet maintenance programmes were outlined by Mr. E. C. Oaaway, M.I.Mech.E., in a paper entitled, "The Organization of Large-scale Vehicle Overhaul and Repair," which was read before the Institution of Mechanical Engineers, in London, on Tuesday last.
Mr. Ottaway said that the ideal vehicle for maintenance would be the " one-hoss shay," with a life of 100 years. Although not possible to emulate in practice, the conception of a vehicle assembly contained in a number of defined and self-contained units would enable the maximum economic life to be obtained from each unit individually.
Standardization and interchangeability should be observed in operating a fleet of vehicles, although modifications would doubtless be made as a result of service experience. Major developments could be made on existing vehicles before adopting a change of type. Mr. Ottaway advocated that from one to four types of chassis should be employed, according to the size of the fleet. If four types were operated, a change of one model could be introduced at five-yearly intervals, presupposing the expected life of the chassis to be 15 years.
The general principles of process planning for a repair works do not differ from those commonly employed for manufacturing, Mr. Ottaway continued. Working under this system, a repair programme could be broken down to repe. titive operations and would be susceptible to precise time rating. Thus, the complete overhaul programme could be planned and the cost of reconditioning could be compared with the price of a new cart.
A regular and uninterrupted flow of material, he said, was the metronome upon which the rhythm of production depended. Effective material control, always a complex problem, was doubly so when dealing with the requirements of a repair works, where the demand must be met by statistical methods and continually checked by reference to use.
When planning a programme of work, production periods of six months' duration should be defined and coded, and a separate programme should be issued for each period. In order to provide a headway for material ordering, provisional programmes should be planned for four periods in advance. Thus during the course of a current period, the programme for one beginning 18 months later should be in the course of preparation.
Requirements in new material would clearly depend on the flow of parts passing through the repair works and the proportion of these parts which were worn beyond use or repair. The number expected to pass through the factory in a given production period could be derived from an analysis of a forward programme.