Study On Molding And Sintering Process Of Copper Slurry Extrusion 3D Printing Technology

This paper studies the copper powder sintering by 3D printing of extrusion forming technology, with the copper paste forming by improved chocolate 3D printer. Then the sintering process is researched in this paper. In the beginning the chocolate 3D printer is improved, making it better prints copper paste. Then test printing and optimize the printing parameters and confect the copper paste which is suitable for printing. It is followed by the dewaxing and sintering process were studies.The copper paste is studied by changing the ratio of paraffin wax and copper powder. The formula is tested by TGA, DSC and so on. The result shows that the ratio of 100 to 9 between copper powder and paraffin wax forms the best formula. It is very suitable for printing.The heating system is added on printer head to ensure the proper temperature of copper paste. The E-axis step motor has been changed to another bigger torque. The motive is drived by gears, and the gears can increase the squeeze pressure and thus improve printing precision. In addition, the printing parameters are changed to the optimal. The optimized printing parameters include object infill, layer height, feedrate, travel feedrate, retraction distance, drive gear diameter and so on, and we can acquire perfect surface simples without gap. The printing simple indicates that the printer can print 45° dip angle without supporting structure and the bore diameter of 2mm.In the debinding part, the method of thermal debinding is used. Thermogravimetric analysis and SEM are tested in different temperatures, and the ratio of shrinking, the ratio of weight lose are figured out. Experiment data indicates that the best debinding process is: heat from room temperature to 200℃ by 2℃/min, dwell time for 120min; heat from 200℃ to 300℃ by 0.5℃/min, dwell time 90min; then cool with sintering furnace. The simple have no defect and the degreasing rate is 98% with this debinding process.Sintering is the final step of 3D printing of extrusion forming technology, it has a great influence on the densification, microstructure and dimensional accuracy, and it determines the final performance of sintered materials as well. Parameter optimization is achieved by using SEM and TGA investigation, which focus upon relationship between sintering effect and heating temperature, heating rate, holding time. The result indicates that heating of 5℃/min to 1000℃, dwelling for 90 min achieve a positive influence. The sintered density is 90% and hardness was 77.98 Hv.A blend of 0.5μm and 2μm 0f copper powder is studied in the paper. When the copper paste is mixed with copper powder of 9:1:20.5WW?, the shrinkage ratio and weight loss ratio are the minimum, only 5.11%. As a result, the forming size is easier to control.