| As the most promising 3D printing technology,selective laser sintering printing(SLS)technology has the advantages of high precision and easy to print complex parts.Especially in metal casting,the sand core produced by SLS printer can be used as the casting mold to greatly reduce the production cost.This paper,on the basis of the principle of selective laser sintering powder bed in coated sand for sintering material,give priority to with domestic electrical components,design to produce a foundry sand core can achieve rapid prototyping of industrial-grade SLS printer,printing devices for SLS in powder feeding mode,laser scanning system,temperature control system and control system software of four key technologies for detailed research.In addition to supporting localization,it lays a foundation for further research on SLS technology.The main research contents of this paper are as follows:Aiming at the design of feeding mode,this paper selects worm screw elevator as z-axis transmission mechanism,and selects high precision servo motor equipped with 23 bit resolution encoder to improve the accuracy of Z-axis,after the actual measurement of the elevator accuracy can reach within 0.001 mm.Using the inverted triangle structure design of the powder car,and complete the synchronous belt and linear guide rail combined with the transmission system,can realize the function of bi-directional powder.In order to realize high-speed laser scanning,a post-focusing scanning system is built according to the printing format of 300×300mm.A 40 W CO2 rf laser,an 8x beam expanding mirror,a scanning galvanometer with an entry aperture of 20 mm and an F-Theta field mirror were selected to form the entire optical system.The CO2 laser was used as the energy source,and the scanning path was controlled by the galvanometer and F-Theta field mirror.In order to achieve high precision preheating control,this paper adopts PID control algorithm for temperature control,and completes A/D and D/A conversion by data acquisition card to realize temperature acquisition and variable power temperature regulation.Through the analysis of the experimental data,when the values of,and are 7,0.015 and 35 respectively,the temperature change curve is stable,the control accuracy is within ±0.5℃,when the installation height of the heating cover is 265 mm,the maximum temperature difference at each position on the surface of the powder bed does not exceed 2.5℃.Is adopted in this paper in view of the control system software design,because of "PC +card" as main controller device,according to the demand of programming to VS2013 as control software development platform,design the friendly human-computer interaction interface,and complete the back-end C++ code implementation,by calling the complete motion control card function library,laser scanning control and temperature control program design,And use regular expression to complete the analysis of G code,and finally design a friendly interface,open source parameters of the control software SLS-DJTU.In order to verify the feasibility of the device,the following parameters are set in this paper after studying the printing parameters: The laser power is 35 W,the scanning speed is1000mm/s,the preheating temperature is 50℃,the preset time is 30 minutes,and the height is0.3mm.The SLS-DJTU control software designed is used to complete the 3D model rapid prototyping,and the sand core model is finally obtained,which proves that the SLS printer designed in this paper has reliable function. |
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