It is made with the fixed mold pull at different points in the second was pulling a rolling friction between the pipe and the roller, and the fixed die and be rubbed between the sliding extubation; fixed die hole is a fully enclosed hole, and roll die There exists a non-grooved roll gap completely closed hole. Roll mode is more suitable for pulling system with angular shaped tubes. Pipes used to pull the roller die system has two roll and four roll. Pipes is the use of conventional fixed die empty pull pull pull mandrel or lining system. Fatal drawback of this method, i.e., between the second metal mold with great friction, which causes energy consumption and poor quality of the steel surface, the second lower die life, and pull the pull system and the pipe is limited by the speed of dimensional precision and straightness Tool cabinet manufacturers affected. In order to reduce friction on the surface to be coated with the lubricant pipe, thereby complicating the production of work, and pipes stented high processing costs. Also lining mandrel pull system often does not bite and easy to throw short mandrel, causing the yield decreases. And lining have inserted mandrel rod force operating time, resulting in reduced productivity and so on. Roll die to extubation is rolling friction and sliding friction lining mandrel does not take a shape. Two-roll molding system is higher than the fixed mold pull pull system output, long mold life, outside of the tube does not produce galling. Two-roll molding system for drawing positive curvature pipes, such as elliptical tube with a two-roll system with molded pull angle pipes is not ideal. This is because the two-roll mode is by three rollers to form the car pass deformation zone, leading to various points on the section is inconsistent speed, speed large, slip large, and the symmetry of the deformation zone is not good, so easy to pull out of the product round - cause, after pulling the pipe is not straight, easy to produce distortion, and it will produce a roller and roller wear faster moving and other shortcomings. Therefore, the development direction of the production of multi-shaped tube is molded pull-roll system. Four-roll mode with four rollers to form the deformation zone. Four die-roll system applicable to pull varieties and specifications of different dumped tube. Its advantage is the speed difference is small, the deformation zone is good symmetry is possible to use a roller to adjust the diameter of the deformation zone size. With a four-roll steel mold pull pull out of the two-roll steel mold high quality, straightness, long tool life, low energy consumption, and most pipes can not pull into a liner mandrel. Four roll roller die structure to determine how to choose and the forming method of free wall Yixingguan pull method with expanding mandrel pull system and pull system III. Optimization method of choice to pull the empty roller die drawing system. Mandrel pull system with increased wall supporting role to improve the pull system stability, but also improve the adaptability of deformation specifications. This method is used to pull the system complex shaped steel sections. According to the complex shape of the degree of optimization methods, the choice of a fixed mold roller die or pull system. Method for expanding Stubbs Stubbs made simple large wall thickness less than 5mm diameter pipe section, because instability or other methods easy to pull off. Wide diameter pull system of law is relatively simple, the drawing process is, first deformation specifications on rod, then put on a mandrel diameter of the tube end after a period of extended length, cold hammer be pulled. This method is suitable for high-precision thin-walled tube drawing system. Outer mold using simple fixed mold section tube or roll mode.