Numerical Simulation of Temperature Field for Laser Rapid Prototyping
The temperature field model for laser rapid prototyping is established by the mathematical treatment of laser power input. Temperature fields with different process conditions are numerical simulated, and the temperature is Gaussian distribution as the intensity distribution on laser beam cross-section. Temperature fields for laser rapid prototyping ware measured by thermal imager in real time. The simulation results agree with the experimental measurement. Experiments show that the temperature field model can be used for computer analysis and optimizing of laser rapid prototyping processing.
CAD/CAE/CAM integration for increasing the accuracy of mask rapid prototyping system
Stereolithography is a rapid prototyping (RP) process that uses photopolymers as the raw materials from which the prototypes are built. The photo-polymeric RP system uses lasers or other light sources to expose selectively the surface of the liquid resin. The absorption of energy causes photo-polymerization that changes the liquid resin into a solid, expanding the cured volume expanding but shrinking simultaneously. The volume shrinkage and curl distortion of the resin during photo-polymerization are the main reasons for the poor accuracy of the built prototype, especially when the part is hollow, in which case the bending is greater because of the bending stress and cannot be compensated for. Normally, a designer builds a support in this stage to limit the further bending and deformation of the prototype. However, after the support has been removed from the built prototype, the geometric profile is easily damaged and deformed, so time is wasted. This study initially uses dynamic finite element simulation code to simulate photo-polymerization, to determine the distortion of the outer profile of the part and thus reduce the deformation. Then, a reverse distortion correction is applied to the outer profile of the part. A new reverse compensation CAD model is produced and loaded into a RP machine for practical prototype processing, to increase the accuracy of the process. Finally, the ''H-4'' diagnostic part is used as an example to verify the experimental results. The results of the simulation and experiment on the final after compensation were accurate.
EFFECT OF SAMPLE PREPARATION ON WATER TREE RESISTANCE OF XLPE/SEBS BLENDS
The effects of an aromatic polymer, such as poly[styrene-b-(ethylene-co-butylene)b-styrene] (SEBS), and its preparation processes on water tree resistance, morphology, crystallinity, dielectric constant and dielectric loss tangent of crosslinked polyethylene (XLPE)/SEBS and XLPE/SEBS/ethylene vinyl acetate (EVA) blends were investigated. The XLPE/SEBS samples were characterized by means of differential scanning calorimetry, scanning electron microscopy, dielectric spectral analysis and the accelerated water treeing experiment. The results clearly showed that although SEBS was partially compatible with LDPE and it was dispersed evenly in XLPE matrix, the blends demonstrated excellent dielectric performances, such as dielectric constant and dissipation factor. The crystallinity of XLPE/SEBS blends was decreased with increase in SEBS content and it was further decreased with the addition of EVA. SEBS could effectively improve the water-tree resistance of XLPE and both SEBS and EVA were found to improve the water tree resistance of XLPE synergistically as expected. The differences in sample preparation processes could change the phase morphology and dielectric performance of the blends, and could also influence the dispersion of SEBS in XLPE matrix as well as the crystallinity of the blends. Different preparation processes led to different water tree resistance behaviours of the samples. The improvement of SEBS dispersion in XLPE matrix helped to improve the water tree resistance of XLPE.