Research On Additive Manufacturing Of Propellants Based On Extrusion Deposition

The propellant is an important part of the weapon,which determines the effectiveness of weapons to a certain extent.The traditional manufacturing of propellants requires molds,which is difficult to meet the needs of complex structure.3D printing technology is a digital rapid prototyping manufacturing technology based on digital files,which accumulates materials layer by layer into physical goods.It can meet the requirement that propellant can be formed without physical mold,and can quickly and precisely prepare required propellant.It has the characteristics of short research and development cycle,on-demand printing and high safety.Aiming at the problem that the propellant has high viscosity and cannot be heated,based on the extrusion principle and the characteristics of solvent preparation,considering the fact that propellant cannot be heated at high temperature,an extrusion system without heating and easy to charge was designed,and a 3D printer of propellant extrusion molding with flexible heating was built.On this basis,the forming process and key technological parameters were studied,and the propellant was prepared.The main achievements of this paper are as follows:Firstly,according to the characteristics of the propellant,the rheological properties of the propellant are studied,and the flow control equation under the propellant extrusion condition is established.On this basis,the analysis and calculation methods of the extrusion pressure,flow and material deposition under the plunger extrusion condition are derived.The overall design of the mechanical system and software control system of the propellant 3D printer is carried out.Based on the overall design of the whole machine,the main systems composing the propellant printer system include extrusion system,heating system,motion system and control software system.The design of the main structure of each system of the propellant 3D printing prototype is completed to develop,assemble and build the whole machine,which lays a foundation for the subsequent research on 3D printing of propellant.Secondly,select a ZY propellant as the raw material of 3D printing,and establish the polynomial function relationship between material concentration and nozzle inner diameter through nozzle extrusion theory and experimental research:the functional relationship between the maximum inner diameter(y)of the needle and the material concentration(x)is:y=4×10^-6x⁴-0.0006x³+0.035x²-0.8487x+7.8174;The functional relationship between the minimum inner diameter(y)of the needle and the material concentration(x)is:y=2×10^-6x⁴-0.0003x³+0.0177x²-0.4543x+4.434.Finally,the influences of the process parameters,such as the inside diameter of the needle,printing speed and floor temperature,on the size shrinkage and tensile mechanical properties of the propellant are studied by single-factor variable experiment.The results show that the three process parameters all affect the size shrinkage and tensile mechanical properties of the propellant.In terms of size shrinkage,the overall size shrinkage of the sample is the lowest when the needle diameter was 0.7mm,the printing speed was 3mm/s and the floor temperature was 35?.In terms of mechanical properties,when the inner diameter of the needle is 0.7mm,the printing speed is 4mm/s,and the floor temperature is 35?,the tensile strength of the sample is highest.