Procedure and Schedule of Preventive Maintenance For Machine Tools

Procedure and Schedule of Preventive Maintenance For Machine Tools

Procedure and Schedule of Preventive Maintenance For Machine Tools - The object of preventive maintenance, as explained above, is to reduce wear and tear and to prevent disruption to production by the planned withdrawal of machines for corrective repairs before failure occurs; this necessitates routine lubrication and inspection of machine elements.

Corrective maintenance is concerned with the replacement of worn parts brought to light by preventive maintenance and the carrying out of repairs.

Reconditioning can be defined as the stripping down .and rebuilding of a machine, to bring it back to a condition which is at least as good as the maker's original specification. The need to recondition can be determined by the frequency of corrective maintenance.

Bearing in mind the objectives of preventive maintenance, then it becomes apparent that two aspects are of vital importance to a successful system: cleanliness and strict adherence to the routine lay down. If wear is to be reduced to a minimum, then the need for cleanliness is obvious; the necessity for cleanliness, however, cannot be over emphasized and this aspect is becoming increasingly important with the introduction of more sophisticated machines.

Oiling Diagram

The success of preventive maintenance is entirely dependent on the system laid down and the quality of the people who operate it and therefore it must be strictly controlled by supervision.

Machine tool makers provide excellent manuals, containing well illustrated servicing instructions, and these provide the basis for a preventive maintenance schedule. Fig. shows a typical oiling diagram included in the manual supplied by the manufacturer of a capstan lathe.

From a control point of view, a record card of the type shown in Fig. should be maintained to show that servicing has been carried out, this should preferably be kept at the machine, so that both the operator and supervisor can refer to it. It is regularity of servicing rather than spring cleaning which will ensure that the machine operates efficiently, with the minimum of disruption to production.

That aspect of preventive maintenance concerned with inspection involves two distinct but related activities: inspection of specified elements of the machine itself and inspection of the piece parts being produced.

The former necessitates the preparation of a schedule for the maintenance engineer to examine specific elements of the machine, in order to determine whether wear has reached the stage when corrective maintenance should be carried out before a failure occurs.

In addition to inspecting the obvious elements where wear takes place, such as bearings and slideways, examination of the corrective maintenance record will highlight other aspects which need regular inspection.

For a particular class of machine, the need for such inspection could vary quite considerably from company to company, according to the nature of its products and the preventive maintenance policy which is operated.

With machines engaged on high quantity production, inspection of the piece parts produced, using statistical sampling techniques, can not only be used to show that the cutting tools need to be replaced but also that certain machine elements, bearings in particular, need attention.