Mating Type Surface Digital Manufacturing Technology

The large-scale honeycomb structure, an important component of the last stage fuel tank of launch vehicles, is composed of the honeycomb sandwich and thin aluminum alloy sheets with ellipsoid shape. As the inner shape of the thin aluminum alloy sheets will deform and differ from the theoretical ellipsoid to some extent after welding processing, it is very difficult to meet the requirements of the tolerance between the honeycomb sandwich and thin aluminum sheets when only conventional CNC and traditional manual manufacturing techniques are used.To solve this difficult problem, this paper presents an innovated digital matching machining method, which integrates many techniques such as curved surface automatic tracking, data acquisition, mathematical analysis, CNC and digitizing. A new algorithm is introduced to track and sample a large-scale rotary surface with the use of three-dimensional scanning probes. To machine the honeycomb sandwich, an interpolation method based on a rotary axis is also studied.With the round vector function and rotary movement group, a model of the error curved surface of the theoretical ellipsoid is set up to describe the actually measured surface. To eliminate or lessen the system errors caused by the offset and slope of the thin aluminum sheet when measuring its surface, and to avoid over-cutting while machining the honeycomb surface, the saddle-point programming is applied to the position optimization of the theoretical surface. To generate the CNC program of the honeycomb sandwich, the equidistant calculation of the actual surface is produced and the data processing software is developed.An open architecture CNC system based on PC, which has not only the general characters of CNC but the specific digitizing function as well, is developed and successfully employed to machine plural pieces of large-scale honeycomb components. This unique system bridges the gap of China's space flight industry.