Screw Geometry Design And Its Computer Aided Design In Differential Twin Screw Kneader

Differential twin screw kneader is a new kind of kneading and delivery equipment with discreteness, mixing, kneading and delivery functions together and it can well deal with problems appearing in mixing and kneading high viscosity materials. The key parts of twin screw kneader are a couple of intermeshing screws, just like the heart of the screw kneader. How to design this couple of screws is the key way to enhance the performance of the machine. Surrounding how to design the end section curves of screws, basing on the principle of screw and milling cutter design, a series of investigation have been done in this paper. Main content and conclusion of the paper are listed below:(1) Basing on theories of relative motion and gear conjugate, derivation of screw end section curves formation has been finished, and parameter expressions and engagement equations were obtained from the derivation;(2) Different kind of end section curves have been computed with different ratio of screw teeth, and influence to screw end section curves was analyzed because of different teeth ratios.(3) Mathematic models of helical surface have been built, at the same time, equations of line of engagement and contact have also been deduced. With these models and equations, some main geometric characters were calculated and analyzed. By the way, variation curves were drawn after analyzing the influence of different screw parameters to these geometric characters.(4) Blades of disc milling cutter and figure milling cutter have been computed. And the blades were corrected according to clearance between the helical surfaces of screws. After this, practical end section curves were calculated with the corrected blades.At the same time, comparison of screw theoretical and practical end section curves was executed in order to verify the method using to correct the cutter blades.(5) Three dimensional models have been built for simulation by using the famous CAD software, Pro/Engineer, produced by America PTC Company. Intermeshing simulation of the couple of screws and interfere check when cutter machining the workpiece have been run. Simulation results illuminated the designs of screws and cutters were correct.(6) Influence of two mechaning parameters was analyzed.