Research On The Whirling Of Screws With Complex Helical Surfaces

Screws with complex helical surfaces are the most common and typical screws among special shaped screws, the design and manufacturing need much higher standard due to their widely increased use. There existing drawbacks in the traditional form milling and machining with disc milling cutters from the cost, preparing time as well as machining quality, they are not suitable in manufacturing screws with the demand of high speed and high precision machining.This study investigates the CNC manufacturing of screws with complex helical surfaces based on whirling process. Whirling proves to be an efficient method of producing screws with complex helical surfaces. During this whirling, the contact line between cutters and work piece is quite long, which keeps the machining steadily. In addition, it has advantages in high cutting rate and quality. Thus, whirling is a CNC machining technology which combines the high efficiency with flexibility of enveloping process.In this thesis, the enveloping theory and machining mechanism are presented, the complex helical surface of screws is mathematically modeled based on axial section profile. With regard to the axial and cross section profile given by sampled points, the cubic spline fitting and calculation between cross section and axial section are also investigated. Tool path calculation plays a very important role in whirling complex helical surfaces, a new tool path planning approach as well as the corresponding tool path calculation algorithm is presented, it is an algorithm that is used to calculate tool path based on axial section. In this algorithm, after adjusting the installation angle, standard cutters produce one axial section profile of a spiral groove one time, and then work piece rotates a step angle, another axial section profile can be manufactured. Repeat this process until the whole work piece is produced. The machining error is also analyzed with focuses on the axial and cross section scallop height and the machining error can be controlled by controlling model and process parameters. Finally, the simple CAM software is developed based on Matlab/GUI platform. It can generate cutter location points and C, X, Z data after those parameters are input in the interface. A case study is presented, which demonstrates the validity of the proposed theory and algorithm.