|摘要：||Present paper adoped improved local smoke-flow visualization and 2D CFD similation method to control atomosphere in the printing chamber. This is first time to study the atomosphere control of 3D printing experimentally. The atomosphere control inside the chamber of 3D printer is mainly to make the temperature drop properly and take away unwanted impurities. Therefore the flow field pass through the substrate must be laminar flow to avoid complex condition when vortex begain to develop. The purpose of wind tunnel test is to well know the flow development of the nozzle which size is similar to that in the printing chamber. Results indicated that the flow field maintains laminar because the secondary flow does not develop at position of 2.5-3 times nozzle height under proper exit speed (see Figure 1). At this condition, the atmosphere control is the best.
Limited to too few information about printing chamber, the CFD simulation is applied to investigate the flow condition inside the chamber. Simulation results indicate if the velocity of inlet and outlet are similar, the flow pattern inside the chamber just likes a circle. When the velocity of inlet is slightly higher than that of outlet, the circle is disappear and this might be the best situation of atmosphere control (see Figure 2). But inlet velocity increases to more than twice the velocity of lutlet, the obvious circle will appear again. That will enhance internal turbidity of the cavity, which will be very unfavorable for printing results.
Results of present work provide useful information about the atmosphere control to improve printing product. Including dimension of nozzle and velocity setting of inlet and outlet, they are two of control factors of atmosphere control. For the current printing machine, this part of the information has not been fully understood and the flow field inside the chamber can be further explored in the future by quantitative measurement. Those results will be revealed in our next work.