Running-in was considered on the basis of reliability and wear concepts. Ways to reduce the wear of gears, accelerate the running-in of gearings and improve their quality were described. Surfaces formed during finishing and machine operation differ significantly in their quality. The differences concern the surface geometry, structure, properties and stress state of surface layers. During the initial period of friction unit operation the surface layers shift from their original state to the working one. The first period of running-in evolves during the breaking-in stage. It is characterized by the initial wear stage. One of the important tasks in wear resistance improvement is to make the transition to the working state of surfaces as quickly as possible. Three ways can be used to solve the problem, namely design, processing, and maintenance methods. The first group of methods comprises the selection of materials and coatings of friction pairs, provision of liquid lubrication conditions, selection of part shape and treatment techniques favoring the required contact state, keeping of optimal temperature regimes, etc. The following methods make up the second group: the improvement of the fabrication and assembling accuracy of a friction unit and the use of modern surface engineering techniques such as surface modification and coating deposition. The third group of methods involves the selection of optimal and reasonable velocity, load, and temperature regimes in order to accelerate running-in, then providing optimal service conditions. The running-in of surfaces is a long technological process. According to the data published elsewhere [1], the running-in of most of car friction units lasts no less than 30-40 hours and it lasts 60-100 hours for heavy-duty friction units such as power transmission parts. Spinners, twisters, and roving frames consist of many sections being about 15m long. For this reason their complete running-in evolves during operation under specific and often mild dynamic regimes. The failure flow parameter is the most reasonable when determining the duration of running-in for such machines. When the manufacturer assembles the machines only the short breaking-in of their mechanisms (reducers, gear boxes) is performed to check some output machine characteristics after assembling. This assessment is subjective, as a rule. Therefore, the duration of the running-in of single mechanisms is assessed together with the duration of the running-in of the machine as a whole. Original reducers are run-in during the breaking-in regime on benches involving open power flow. The regimes (time, load, etc.) differ essentially even for similar members produced by different manufacturers. As a rule, the duration and regimes of running-in are not substantiated from a scientific viewpoint and they are selected experimentally by manufacturers or proceeding from the market state. For example, the duration of the running-in of ring spinners is 1500 hours [2, 3].
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