Abstract: To improve assembly precision and assembly quality stability for complex mechanical products, an online tolerance optimization approach based on shortest path is put forward. The tolerance zone of the key process is divided into several zones with fine granularity; the assembly cost-tolerance function is structured from the prospect of the assembly precision; considering the time adjustment cost of the two different operations (basic operations and auxiliary operations) in the assembly process, the assembly time cost-function is established; based on the two functions, the assembly cost-tolerance function model is put forward by the means of the weighted clustering to describe the relationship between the assembly tolerance and the cost. The online tolerance optimization model based on shortest path is established, and the assembly cost-tolerance function is defined as the weight function to realize the online tolerance optimization by searching the online tolerance optimization model for gaining the minimum assembly cost. An example of online tolerance optimization model in the assembly process of the engine cylinder head is given to demonstrate the feasibility and effectiveness of this method.

Key words: Assembly cost-tolerance function, Assembly quality, Online tolerance optimization, Shortest path