Molding Characteristic Research Of Polymer Melt Droplet Deposition

Polymer melt droplet deposition manufacture technology is a new rapid prototyping method, based on the idea of "calculus" of polymer materials, which make the polymer melt droplets moved according to the planned path and deposited a three-dimensional object. The technology has the advantages of short cycle, high precision and wide application of materials, and is becoming a promising rapid prototyping method.However, the droplet deposition process is influenced by many factors,which involves the thermodynamics behavior and the interaction in the successive deposition process. These factors have an important effect on the precision of the droplet deposition. At present, the above problems have not been systematically and in-depth studied.In this paper, a polymer melt droplet deposition equipment was developed based on the previous research results summarized on the droplet ejection and deposition mechanism and polymer characteristics.The temperature field of the polymer melt droplet deposition and the influence of different parameters on the precision of droplet deposition were studied deeply by the methods of simulation, theoretical analysis and experimental research. The main contents and results in this paper are as follows:(1) A polymer melt droplet deposition equipment was designed and developed based on the principle of polymer melt droplet deposition,which includes the mechanical structure parts and the control system parts.The mechanical structure parts comprise a plasticizing device, a droplet ejection device and a three-dimensional moving platform; the control system parts comprise a motion control system, a temperature control system and a pressure regulating system. The equipment provides an experimental platform for the subsequent research.(2) Through the finite element analysis of transient nonlinear temperature field, the temperature field of droplet deposition process was simulated by "element birth and death" technique and APDL command stream. It was studied that regular pattern of the temperature field of the forming products, the change of the node temperature, the variation of the characteristic points and the influence of the forming path on the forming precision of the products. The above analysis results provided guidance for the following droplet deposition experiments.(3) The experiment analysis the regular pattern of the four parameters such as injection frequency, screw speed, nozzle-to-substrate distance and moving speed of the substrate effect on the droplet diameter and droplet space, and confirm the effects of each parameter on droplet diameter and droplet space. The effects of droplet space Wx, Wy, Wz and forming path on the forming precision of droplet' deposition were also analyzed. The experimental results provided an important experimental basis for the polymer melt droplet stacking process.(4) The mathematical model of the warping deformation was established by analyzing the source of the warping deformation of the polymer melt droplet deposition. It analyzed the effect law of the layer thickness, the number of layers, the temperature of the forming chamber,the length of the cross-section of the product for the droplet diameter and the droplet space. The correctness of the theoretical model was proved by experiments. All of these were provide a theoretical basis for planning path and parameter control.