Types of interchangeability:
- complete (functional);
- incomplete (restricted).
Complete interchangeability is an interchangeability, at which all types of parameters are ensured with the accuracy that allows to perform fittingless assembling (or replacement at repair) of any independently produced parts to obtain finished items. That is, parts can be manufactured independently in several shops (factories, towns, countries), and be assembled into assembly units or items in other factories.
Basic advantages of products produced under conditions of complete interchangeability are:
1) Development works for creation of new items are easier, faster, and cheaper, because basic elements are standardised (threads, splines, toothed gearing, etc.);
2) Manufacture of items is easier and cheaper (accuracy of blanks is specified, improved inspection methods, easier assembling and others);
3) Exploitation is cheaper (shortening of repair period and its high quality).
Along with complete interchangeability the restricted (incomplete) interchangeability is permitted. Its types are:
1) Group interchangeability (selective assembling);
2) Assembling on the basis of probability calculations;
3) Assembling with adjusting of dimensions or positions of separate parts;
4) Assembling with fitting of one of several assembling parts.
There is also difference between external and internal interchangeability.
External interchangeability is interchangeability of finished items, mainly, deliverables (aggregates, instruments, frictionless bearings, etc.), from which interchangeability is required by service indexes and geometric parameters of joint surfaces. External interchangeability is always complete. For example, when replacing the failed electric motor, a new motor is mounted on the same place, on the same joint surfaces, with the same dimensions. This is interchangeability by joint dimensions or dimensional interchangeability. New motor should be interchangeable also by operation indexes – by power, rotational velocity and other indexes. This is parametric interchangeability.
Internal interchangeability is interchangeability of separate parts, assembly units and mechanism inside of each item. For example, complete interchangeability by joint diameters of bearing rings and restricted interchangeability by rolling elements. That is, internal interchangeability can be complete and incomplete. Interchangeability is inconceivable without accuracy.
