Research On Atypical Form Milling Theory And Application Technology Of Smooth Inner Helicoid

The screw drilling tool and the screw pump are widely used in the petroleum industry which is a kind of screw machinery. The stator and rotor compose one tooth difference meshing pair whose design and manufacturing quality will influence on many performances of the spiral machinery directly. The curve type of the stator is cycloid or other second-order continuous curve. So the work surface of the stator is smooth inner helical surface. The metal casing of traditional single screw’s motor stator is an equal thickness cylinder, and an unequal thickness rubber bushing is vulcanized in the cylinder. The metal casing of the new-style stator is an unequal thickness cylinder with premade inner helicoid, and equal thickness rubber bushing is vulcanized in it. The new-style stator which has an equal thickness rubble bushing can substantially improve the performance and service life of the machine. The metal stator’s cross section is equidistance curve of the working curve. In this paper, the forming theory and application technology of helical surfaces in the metal sleeve of the stator will be studied intensively. The major research works and contributions of the thesis are summarized as follows:The mathematical model of the metal casing’s cross section curves and of the helical surface for the stator have been deduced according to the principle of the equidistance curve when the rubber bushing curve style is known. Three-dimensional-entity modeling technology for the steel casing of the stator which is got by the measurement data of the stator using direct reconstruction of NURBS method when the rubber bushing curve style is unknown or is substituted by simple curve.A fire-new cutting method is proposed which is different from existing cutting method for the inner helical surface, it is named with Axial-Fixed size-Atypical Form Milling. Based on the analysis of the typical form milling theory of the helical surface, the new atypical method is proposed and the principles and characteristics of the processing method are expounded. The space meshing trace of the tool and the workpiece and disc cutter profile algorithm are studied according to the atypical cutting format. Firstly, geometric resolution algorithm for solving theory of the profile shape of the tool is researched by the motion of the tool relative to the workpiece. Then, a new method based on equidistance section and discrete values is advanced. This method has a fast calculation speed and high precision, and the algorithm does not need a lot of predictable geometric conditions. Milling force prediction method is studied and the cutting process simulation is carried out on the software platform based on FEM according to the chip formation mechanism and material plasticity theory.According to the Profile Design of complex cutter in the Axial-Fixed size-Atypical Form Milling, a approximate method based on piecewise least squares arc approximation theory of the tool profile shape approximating is brought forward. And the approximately error is also studied. Dynamic envelope algorithm is advanced to the calculate cross section curve of the workpiece according to different parameters of the tool edge shape in the event that its shape is arc. By the atypical forming principle and the shaping trajectory, the applicable conditions and the interference judgment method are given and the composition of the machining error is analyzed.The research results of the theory are applied to the manufacturing of helical surfaces within the PDM stator in technical applications. Some of the key technical problems are studied such as the guide and support of the slender milling rod, chip removal in the complex and deep hole, limited space transmission of the milling head and so on. A number of cutting tests are conducted and test results are analyzed to verify the theoretical studies mentioned above. Test result has proved, the theoretical research is feasible and correct.The studies enrich and expand the theory and analytic tools to the helical surfaces, especially to the inner helicoid surfaces. It bings forward a new atypical cutting method using a certain size disc-milling cutter which provides new ideas and new approaches to improve the helical surface parts cutting efficiency in the field of innovating approaches. It has major significance for the development of the cutting machine tools which can manufacture parts with inner helicoid surface widely used in spiral mechanical parts manufacturing industry.