Research And Improvement On Control Methods Of FDM Three-dimensional Printer

Under the background of the rising of intelligent manufacturing concept and the popularization of three-dimensional printing technology,the users are paying more attention on the qualities of the products of three-dimensional printers.The fused deposition modeling(FDM)technology is chosen as the researching object of this paper.Taking into account the defects lying in the existing FDM technology,such as lack of forming accuracy and efficiency,this paper studies and then optimizes some crucial control algorithms applied in the control system of FDM three-dimensional printers.Firstly,based on the printing work flow of a typical FDM three-dimensional printer,this paper discusses and expounds functional requirements for the control system of the printer.Furthermore,according to the interaction process between the control system and other hardware peripherals of the printer,the core control methods of the control system are extracted and analyzed.Then,the significance and feasibility of the improvement for each method is underlined.Secondly,in view of the shortcomings of the path speed planning model of the FDM three-dimensional printer's,such as,acceleration jump and impact vibration,a five-phase S-curve model of velocity to plan the change of speed in stepper motors is introduced.While it avoids acceleration jump,this model could also maintain the simplicity of calculation process.According to the mathematical principle of S-curve model,a speed planning strategy of G-code path based on optimal location principle is proposed.Furthermore,a multi-path prospective method of speed planning with look-ahead algorithm is proposed,which combines the speed planning of multiple paths and improves the efficiency of path execution on the premise of ensuring smooth transition speed of paths.A simulation test is carried out and the results indicate that the speed of the nozzle in the start-up phase of the stepper motors changes more smoothly,which reduces the defects caused by flexible impacts.The application of the speed prediction algorithm is also proved to improve the efficiency of path generation process.Thirdly,in order to solve the problem of low efficiency in the algorithm of linear path interpolation of FDM three-dimensional printer,a modified Bresenham algorithm which could predict the number of interpolation points on a single row is applied as the interpolation method when the nozzle is running at a constant speed.Aiming at the difference of the working planes where the nozzle path is located,a combined Bresenham algorithm which consists of the three-dimensional Bresenham algorithm and the modified Bresenham algorithm for two-dimensional plane is proposed.On this basis,the work flow of the path planner which could execute the path generation precisely in the three-dimensional printer control system is analyzed.After that,simulation test and online monitoring are combined to detect the efficiency advantages of the improved algorithm,and the results are compared and discussed.Fourthly,considering some defects of FDM three-dimensional printer's temperature control algorithm,such as large overshoot and long period to enter steady state,this paper focuses on precise PID tuning of parameters based on Astrom-Hagglund relay feedback experiment.Ziegler-Nichols tuning method is applied to calculate the initial value of PID parameters,and the fuzzy control theory is introduced to adjust the parameters of PID method adaptively.The modified PID controller has a good response curve and the overshoot of temperature is reduced.Finally,through the printing test of actual models on the experimental printing platform,the effects of several modified algorithms are verified.The experiment result shows that the surface quality of the complete test model is improved,and the PID temperature control algorithm based on fuzzy theory is proved to have good outcomes which is reducing the overshoot of the signal and avoiding the deformation of the printing material caused by high temperature.