Design tolerance has tremendous influence on both manufacturing cost and quality of a product. The purpose of the paper is to propose a new way of the product optimal tolerance design based on service quality, which is more realistic because the service quality loss model describes the present worth model of quality loss based on the service life distribution, and expresses an actual loss that a product imparts on society after the product is put into service by considering the parts processing equipment during product manufacturing process, operating environment, and lubrication condition during product service. However, many scholars consider manufacturing cost and quality loss for the optimal tolerance design of product at present, in which uses Taguchi quality loss model or Teran quality loss model. The former reflects the forecast of a loss that a product may bring to the society on the time node before it leaves the factory. Although the latter involves the changes of the product quality characteristics after the product is put into service, but its essence is to transform the product quality loss in a certain service life into the present worth on the time node before the product is put into service, and it is still the forecast of a loss for the society, and has many shortages that it takes quality loss cost as cash flow and service life as a certain value. So the proposed way can extend the product tolerance design from the manufacturing stage to the service stage, and enriches the theory of the product optimal tolerance design.

Their high-power-density design combined with their limited space make planetary gear trains often high power losses difficult to dissipate to the surround in time. The thermal network model for temperature prediction in planetary gear trains has been proposed. According to the principle of the conservation of energy, the thermal network model have been built and the model have been employed to analyze the transient temperature of the three stage 2K-H planetary gear trains used in Φ6.3m earth pressure balance(EPB) shield machine in series. The computed temperature results of the proposed TNM were in very good agreement with experimental measurements. It has been shown that this method is capable of performing temperature analysis. The results stemmed from the TNM have been shown that the temperature rise of the sun gears is quicker than the other parts and the PGT doesn’t reach thermal balance after the oil temperature reached 90 degrees, so the cooling system should be compelled.

A model for the transmission efficiency of the planetary gear train has been proposed based on the principle of energy. The network topology for the planetary gear train is established with the graph theory by substitution the net nodes for the parts. According to the principle of conservation of energy, the interaction model of the energy transfer of the gear train is built by the way of integration the energy transfer equations between the nodes. With the investigation on the power losses, the transmission efficiency of planetary gear train can be calculated.

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The product smaller-the-better (STB) quality characteristics are continually changing and out of specification limits because of the constant stress, wear and others after the product is put into use, which will cause loss because of the product rejected and scrapped. On the basis of the quality viewpoint that product quality loss is present worth of a loss caused as a result of its quality characteristics because its quality characteristic is out of specification and lead to product scrap after the product is put into service, the paper establishes the present worth model of quality loss of STB characteristic based on service life distribution, and proposes the calculation method on the probability density function (PDF) of the product service life based on the technical specifications of STB quality characteristic. It takes the concentricity between the inner cylindrical surface and the outer cylindrical surface of the link bushing as an example to analysis the various factors that impact on the present worth of concentricity quality loss in the new model, and contrast with Taguchi quality loss model. The results show that the new model describes an actual loss that a product imparts to society after the product is put into service, and can reflect the quality loss of STB characteristic in the product service process, and is more realistic than Taguchi quality loss model of STB. The new model extends tolerance design of STB characteristic from the manufacturing stage to the service stage.