# Integrated Design of Process-Tolerance for Remanufacturing Based on Failure Feature
## 1 Introduction  
With the development of the scale of global industrialization and the shortening of the technological iteration cycle, the elimination quantity and speed of mechanical products increases. This causes countries to pay more attention to the circular economy. Remanufacturing as a technology to restore the performance, and finally reach the \"as new\" state of used products, can fully release the residual value of waste products [1]. It has become an important part of the circular economy [2, 3]. Compared to new product manufacturing, remanufacturing can reduce 60% of energy, 70% of materials, 50% of cost and 80% of air pollution while achieving the same product quality [4]. It is considered to be a technology with both environmental and commercial value [5, 6]. For the great advantage to be gained from remanufacturing, to a large degree this depends on the remanufacturing process and tolerance scheme. The process and tolerance scheme formulated for used parts was a critical step in remanufacturing of the remanufactured products, which established a key connection between used parts and remanufactured products. As a kind of mechanical processing, an optimal process and tolerance scheme of remanufacturing created more benefits inreducing production cost and quality loss [7; 8]. In process, ref. [9] used the ontology method to organize the remanufacturing information of the used part to formulate the optimal remanufacturing process scheme. Reference [10] presented an RS-CBR system matching method for selecting the optimal process planning from case databases to increase the efficiency of remanufacturing process formulation. In tolerance, ref. [11] studied the classified control method of remanufacturing dimension chains under different costs of tolerance levels, to realize the hierarchical assembly of remanufacturing dimension chains. The authors of [12] ensured the assembly precision of a remanufactured car engine by state space model. Undoubtedly, these above researchers gave a valuable establishment for remanufacturing process and tolerance scheme e.g., matching system and hierarchical method, whereas few studies have been done on remanufacturing process and tolerance scheme formulation based on uncertainty return status of the used parts. Compared to manufacturing, the process design of remanufacturing presents a high degree of uncertainty due to the different return status of the used parts [13]. As reflected by the different failure types and failure degrees of the surface of used parts, these series of failures have led to the diversity of feasible remanufacturing process plans of used parts, and process combinations of used products, which causes the tolerance design to be more difficult and complex. In order to reduce the effect of uncertainty failure on the remanufacturing process and tolerance formulation, many scholars have carried out research. Reference [14] proposed the remanufacturing process of the used machine tools based on the analysis of failure characteristics; Ref. [15], oriented to remanufacturing process design, proposed a hierarchical failure mode information transfer chain for remanufacturing products based on polychromatic model. Meanwhile, ref. [16], through the analysis of the failure characteristics of remanufacturing, optimized the remanufacturing process plan of used parts. Reference [17] established the mathematical sub-model with different dimensional precision remanufactured parts, and reassembled the remanufacturing dimension chain under the constraint. The authors of [18] redistributed the tolerance of the remanufactured assembly dimensional chain based on the uncertainty of used parts. These studies analyzed the influence of process and tolerance by uncertainty failure of the returned products from different aspects respectively, but ignored the connection between the process and tolerance under the uncertainty failure. At the present stage, the formulation of process and tolerance schemes of remanufacturing was in serial.