While extrusion molding with single-screw extruder, extrusion pressure comes into being from feeding section; it is one of the basic conditions to ensure that extrusion process can be carried on normally, in order to ensure molding process goes smoothly, it must meet the following requirement: extrusion pressure generated during the process must be sufficient. Therefore it has certain engineering significance to design structure of a single screw correctly that a mathematical model for formation of extrusion pressure during single-screw extrusion molding will have to be established. This paper conducted a research on theory of extrusion pressure when powder of pure UHMWPE resin is still in feeding section by molding in barrel of the single screw extruder specially designed for pure UHMWPE, and established a n-lamina model of powder materials or grain materials which is in feeding section and at the state of non-plug flow solid conveying, and it provided a method to calculate extrusion pressure of the n-lamina model, thus it enriched and perfected theory of single-screw extrusion molding.

This paper analyzed several important issues in theory of non-plug flow solid conveying, which is about the extrusion molding process of the single screw extruder, they are mainly: compressive stress on the front and rear ends of the surface, and ; an increase trend of compressive stress , ; pressure in feeding compression section of the screw, .

To make single-screw extruder with extrusion pressure enough, through theory of friction-induced extrusion pressure，which has been generally accepted in the industry. The barrel designed modular structure, in the before barrel carved groove, to add the friction coefficient between barrel and solid material. It form extrusion pressure In this section by exponential increase. This papers analyze that use of spiral groove instead of linear grooves can effectively reduce the frictional heat generation.

According to the theory of extrusion pressure by molding in barrel of the single screw extruder specially designed for pure UHMWPE, extrusion pressure generated during the process must be sufficient while extrusion molding with single-screw extruder. The mathematical model for formation of extrusion pressure in feeding section during single-screw extrusion molding has been established. This paper conducted a research on theory of extrusion pressure which is part of n-lamina model of non-plug flow solid conveying in feeding section by single-screw extrusion molding.

Screw rotor is a vital factor affecting the working efficiency of twin screw air compressor. Therefore, a type of twin screw air compressor in coal mine production process is taken as the research object. Firstly, the working principle and process of female and male rotor was introduced and analyzed. Then, according to the principle of parameter selection of the female and male rotor, the relevant design parameters of the female and male rotor are given. Finally, the vector equation and the tooth surface equation of the segmented line are deduced and established respectively for the end face profile and end face tooth surface of the rotor, the area and volume of the tooth are also calculated. The equation of the tooth surface is set up by rotation of rotor’s tooth direction, the inter-tooth area is composed of multi-section smooth curve and the top arc connected to form a circle, which can be obtained by means of analytical method. In order to better meet the requirements of the machining process, it is necessary to coordinate the female and male rotor profile on the coordinate axis when the end face of the rotor is non-symmetrical. This paper provides an important reference for selecting parameters of the rotor of the female and male and calculation of rotor profile.