Tolerance-based structural design of tubular–structure loading equipments

Mechanical loading equipments are wildly used in transportation system. Positioning precision is one of the basic functions of machine tools, and structure design is the key to ensuring accuracy. According to the assembly process of tubular–structure, the paper analyzes motion modes to achieve tubular–structure loading. In terms of assembly tolerance of tubular–structure, a tolerance model to guide structure design of loading equipment is formulated. Based on tolerance analysis of each motion mode, the maximum available size of the tubular–structure is calculated under different linear rolling guide, and the minimum available size of the interior rail in the cover box is worked out under different ball screws, trapezoidal screw threads, worm and worm gears. To meet the requirement of tolerance in tubular–structure assembly, mechanisms for all motions are defined. The design of loading equipment is tested and assessed by experiments, and the result shows the design is highly qualified for its assembly.