Research On 3D Printing And Milling Combined Machining Technology And Process Of Polyetheretherketone

Polyetheretherketone(PEEK)is a semi-crystalline polymer material with good mechanical properties and biocompatibility for a wide range of applications in the biomedical,aerospace,and electronics industries.3D printing technology has received a great deal of attention in the field of PEEK parts manufacturing due to its advantages of high design freedom,fast molding speed,and short product development cycle.However,due to the limitations of the layered stacking manufacturing principle,the surface of 3D-printed parts is subject to unavoidable stepped layer patterns,which seriously affect the surface quality of manufactured PEEK parts.The additive and subtractive combined machining offers significant advantages in the field of rapid customization of high-quality PEEK parts due to its ability to remove the staircase effect of printing while rapid prototyping is taking place.Combined machining technology research on PEEK materials is currently in its infancy and there is a lack of research on its related technologies and processes.To this end,in this subject,experimental research is carried out to investigate the technology and processes involved in the combined machining of fused deposition molding(FDM)printing and dry milling of PEEK materials.The main research elements are as follows:The design of the temperature-controlled part and nozzle structure of the FDM printing module is combined with a milling machine to develop a 3D printing and milling combined machining system based on PEEK material.By improving the hardware of the machining system and coordinating the cooperation between the various data processing processes,key issues such as first-layer bonding,workpiece clamping,and synergy between additive and subtractive coordinates in the combined machining process are solved.A specific solution for 3D printing and milling combined machining of PEEK materials is proposed and its feasibility is verified by typically combined machining experiments.In response to the problem of surface morphology defects in combined machining PEEK parts,milling experiments are carried out on 3D-printed PEEK parts from the structural characteristics of the printed parts themselves.The effects of the milling method,print directions,and annealing treatment on the milled surface quality of 3D-printed PEEK are investigated.The analysis of surface morphology,surface roughness values,chip morphology,and burr morphology reveals the influence of the structural characteristics of the part on the state of the milling process.The results show that the milled surface quality of 3D-printed PEEK parts is mainly influenced by the internal material bonding characteristics,with poor Z-direction interlayer bonding strength being the main cause of defects such as delamination burrs on the milled surface.In order to enhance the Z-direction interlayer bonding strength directionally,the force state between the Z-direction bonding layers during the formation of surface defects in the combined machining is analyzed,and a mechanical test protocol is designed accordingly.Shear strength and storage modulus are selected as characterization indicators of Z-direction interlayer bonding strength.The influence of FDM printing parameters(nozzle temperature,layer thickness,and hotbed temperature)on the two indicators are analyzed by means of an orthogonal experimental design,and a regression model and optimal combination of printing parameters are obtained.On this basis,the optimal combination of printing parameters corresponding to the two indicators is compared and analyzed in a combined machining process.The suitability of the three printing infill patterns(grid,rectilinear,and gyroid)for combined machining is then compared.The results show that the storage modulus is a more accurate predictor of milling delamination in printed PEEK parts than the shear strength.PEEK parts printed at a process parameter combination of nozzle temperature of 450°C,layer thickness of 0.1mm,hotbed temperature of 260°C and rectilinear infilling has a milling surface free of delamination burrs and a combined machining quality comparable to that of the injection molding process.This work is a guide to the research of combined machining of PEEK and such polymer materials in additive and subtractive.