3D Printing with a 5-Axis FDM Printer Using Bézier Techniques

In the last decade,3D printing,especially fused deposition modeling(FDM),has revolutionized manufacturing with intricate designs.Traditional 3-axis FDM printers face challenges with complex geometries,but 5-axis versions offer more design freedom.However,it requires specialized strategies.This research presents a model for 5-axis FDM printers using Bézier curves with an algorithm to enhance print quality.The result shows significant accuracy improvements,especially for curve-based tasks.In addition,this study deepens the understanding of 5-axis FDM technology,setting a solid basis for further research and potentially refining manufacturing methods.

葡萄嫁接苗木的切削特性研究

为给葡萄苗木嫁接机的切削装置提供设计依据和相关参数,研制苗木切削参数测量装置。该装置由切削模块、测控模块和支架模块三部分组成,可控制嫁接刀按设定速度切削,并可实时记录切削阻力、位移及速度等参数。选取SO4型葡萄砧木作为研究对象,对砧木切削阻力、切面质量随切削参数的变化规律进行试验研究。试验结果表明:增大切削速度可减少切面组织损伤,一般来说,当切削速度≥4 mm/s时,即可获得较理想的切面质量;粗度7.5~10.5 mm的砧木,当切削速度控制在4~10 mm/s之间,最大切削阻力最小,可称其为合理切削速度;在合理切削速度范围中的最大切削功在5.05 J左右;在合理切削速度范围内切削阻力随砧木粗度的增加而增大,最大切削力为728 N;该研究可为嫁接机切削装置的设计提供参考依据。

Feasibility Study on Cryogenic Milling of Carbon Fiber Reinforced Silicon Carbide Composites

Carbon fiber reinforced silicon carbide matrix(Cf/SiC)composites have the most potential application for high-temperature components of aerospace high-end equipment.However,high cutting temperature,rapid tool wear and severe surface damages are the main problems in dry cutting Cf/SiC composites process.The feasibility study on cryogenic milling of Cf/SiC composites using liquid nitrogen as coolant is investigated.Influences of milling parameters and coolant on temperature,cutting force,surface quality and tool wear are investigated,which is compared with dry cutting.Experimental results reveal that the cutting temperature in cryogenic milling of Cf/SiC composites is reduced by about 40%—60%compared with dry cutting.The milling force increases gradually with the increase of spindle speed,feed rate,depth and width of milling in cryogenic milling process.In addition,the machined surface quality in cryogenic milling is superior to that in dry cutting process.Fiber fracture,matrix damage and fiber matrix debonding are main material removal mechanisms.Flank face wear is the main wear form of the polycrystalline diamond(PCD)end mills.The tool life is prolonged in the cryogenic milling process because the reduced temperature inhibits the softening of Co binder and phase transition of diamond in the PCD end mills.

Investigation of Nanofluids as Potential Cutting Fluids in Gear Hobbing Processes of AISI 4118 Steel

The present work focuses on the performance of nanofluids called CN46-NanoAl2O3.80 formulated by using dispersions of nano aluminum oxide （Al2O3） in the ISO VG46 industrial oil on machining performance during gear hobbing of AISI 4118 steel. In machining gears, hobbing is one of the most important processes, especially to produce various gear shapes for adapting to diverse applications. However, the demand for high quality brings attention to product quality, particularly the roughness of the machined gear surface because of its effect on product appearance, function, and reliability. For additional improvement, applying nanofluids may produce superior product quality, as the rolling action of billions of nanoparticle units in the tool chip interface can significantly decrease the friction led to reduce the cutting forces. In addition, the characteristics of heat transfer of nanoparticles can contribute to reduce tool wear. In this experimental study, the performance of nanolubricant compared with the case of using ordinary cutting-fluid systems in the existing production line is investigated. The experimental results reveal that the tool life of the hob is significantly enhanced of 55.2%, gear surface roughness is smaller （27.3%）, and gear accuracy is significantly increased by using the nanofluid. This result, therefore, shows a promising solution to achieve the engineering-economy effectiveness in gear machining.

A synthetic criterion for early recognition of cutting chatter

Cutting chatter is a violent self-excited vibration between a tool and a workpiece.Its negative effects mainly include poor surface quality,inferior dimensional accuracy,disproportionate tool wear or tool breakage,and excessive noise.Therefore,early recognition and online suppression of chatter vibration are necessary.This paper proposes a novel synthetic criterion(SC)for early chatter recognition.The proposed SC integrates standard deviation(STD)and one-step autocorrelation function(OSAF).Moreover,this paper revised the fast algorithm of OSAF.We can quantitatively divide a chatter vibration signal into three stages,which are stable stage,transition stage and chatter stage according to the SC.Compared with STD,the SC can improve the reliability of chatter recognition and the threshold of SC is not sensitive to variable cutting conditions.This paper presents an original algorithm of SC and its fast algorithm in detail.The fast algorithm of SC in this paper improves the computation efficiency compared with the original algorithm of SC.To validate the effectiveness of the proposed SC,a series of milling experiments were conducted under different cutting conditions.In these experiments,the vibration signals were acquired by two accelerometers mounted on the spindle house.The experimental results showed that the proposed SC could effectively recognize chatter vibration at an early stage of chatter vibration,which saved valuable time for online chatter suppression.