天然金刚石刀具前刀面的表面粗糙度控制技术

介绍了金刚石刀具的发展和技术特点,设计了一种天然金刚石刀具前刀面表面粗糙度修磨控制方法,并通过工艺实验完成了对金刚石刀具的修磨。结果表明:验证了(100)面的金刚石的难磨方向,沿此方向加工后金刚石的表面粗糙度值较低、磨削热较多;易磨方向表面粗糙度较差、磨削热较少。优化修磨角度修磨后,金刚石刀具前刀面表面粗糙度R_a值可达0.3 nm,将其应用在超精密切削中效果良好。      

超精密切削加工的刀具温升和加工误差

本文叙述了铝和无氧铜超精密金刚石车削中刀具的温度分布以及切削条件对温升的影响,讨论了由于刀具热膨胀引起的加工误差.利用红外线摄象机测量了温度分布,根据图象,借助图象处理装置分析了刀具任意点的温升变化.利用电容式位移计测量了加工误差-加工表面和进给工作台之间的相对位移.在本实验条件下,烧结金刚石刀尖的温升达15℃;而单晶金刚石刀尖的温升约为5℃.加工误差的产生对应于刀具温升模式,幅度约为1μm.     

单点金刚石车削的工艺参数对表面粗糙度影响的实验研究

超精密车削中单点金刚石刀具切削参数的设置非常重要,这不仅关系到金刚石刀具的使用寿命,而且对于提高车削效率以及得到更好的工件表面车削质量都有着深远的意义.文章着眼于实验,首先对超精密车削中切削量、刀尖圆弧半径、进给量和主轴转速对表面微观形貌的影响进行了实验研究.然后对实验的数据结果进行了系统的归纳整理,最后分析了这些影响所产生的原因.根据实验的研究及分析的结果,可得到超精密加工切削参数的优化组合,为提高实际车削后工件的表面粗糙度提供了依据.     

Research Progress of Diamond Tool Machining Technology for Ferrous MetalsEI北大核心CSCD

金刚石刀具是超精密加工最理想的刀具之一,但在黑色金属超精密加工领域“石墨化”导致刀具快速磨损,其应用极大地受到了限制。首先,针对金刚石刀具的磨损机理进行介绍。然后,综述金刚石刀具切削黑色金属的几种常见方法,如刀具表面改性、工件表面改性、低温辅助切削、超声振动辅助切削等,通过研究实例来分析各方法的应用效果和存在问题,并从技术层面分析影响金刚石刀具在黑色金属加工领域发展的关键因素。最后,对金刚石刀具切削黑色金属未来的发展趋势进行探讨。总结金刚石刀具在黑色金属领域的加工方法,分析加工黑色金属时抑制金刚石刀具磨损的核心技术,对黑色金属的精密超精密加工具有重要的引领和推动作用。     

超精密车削中精确对刀方法

在超精密车削球面和非球面零件过程中,对刀的精度是影响加工件面形精度的最主要因素之一。介绍一种试切小直径球面对刀件的方法,可实现圆弧刃金刚石刀具的精确对刀,并加工完成直径75 mm、顶部球径为250 mm的凸球面纯铝工件,其面形精度优于0.2μm。     

数控车削加工中刀尖圆弧半径补偿的应用

刀尖圆弧半径补偿功能在数控车削加工中应用非常广泛，它是数控车削加工的重点和难点。正确、灵活的运用刀尖圆弧半径补偿功能对锥面、圆弧面、曲面等的加工精度控制及提高刀具使用寿命有着十分重要的意义。     

金刚石砂轮V形尖端的数控对磨微细修整技术

针对金刚石砂轮V形尖端的微细修整困难的问题,开发出一种对磨成型的V形尖端修整技术。在数控修整中,砂轮作V形的直线插补运动与修整工具对磨,逐渐被修整成V形尖端。本实验中修整工具分别是#600和#180绿碳化硅(GC)油石,砂轮分别为SD 400和SD 600金刚石砂轮。实验结果表明,较细粒度的修整工具不仅可以将砂轮V形尖端修整出更小的圆弧半径,而且也能够将微小磨粒修锐得更锋利,从而使加工的单晶硅微沟槽形状更加整齐。此外,采用修整后的圆弧半径小于20μm的SD 600金刚石砂轮V形尖端可以实现光纤石英微阵列沟槽的微细加工,也可以在SiC陶瓷和WC合金基板上加工出微锥塔阵列空间的功能表面。因此,数控对磨在位修整的工艺可以用于金刚石砂轮V形尖端的微细修整,实现硬脆性基板的微细磨削加工。     

机械加工刀具的表面涂层和摩擦磨损性能研究

采用圆形电弧技术和线性离子源技术在高速钢和硬质合金刀具表面制备了类金刚石涂层,对涂层表面形貌和物相组成进行了观察,对比分析了膜层成分和耐磨性能。结果表明,在高速钢和硬质合金表面分别制备了0.84μm和1.23μm厚涂层;对磨过程中Al的粘附量由少至多为:N1涂层N2涂层硬质合金基材高速钢基材,涂层对机械加工刀具基材耐磨性能提高具有明显改善作用。     

CN1751848高效低廉的高精度金刚石刀具机械刃磨加工方法

高效低廉的高精度金刚石刀具机械刃磨加工方法，它属于超精密切削加工技术领域。为解决金刚石刀具的制备比较困难的问题，本发明按照下述步骤进行：调节金刚石刀具机械刃磨机床平衡；研磨盘工作表面经过精车成形后进行精细抛光，然后涂覆金刚石磨粒；对研磨机床主轴系统进行精细动平衡；装卡金刚石刀具，刀体卡具调水平；打开气源，开启金刚石刀具刃磨机床电源，调节机床主轴转速；调整前刀面刃磨方向为易磨方向，并调节刀具前角；在主轴工作转速为1800—2500r／min、研磨压力为金刚石刀具装卡系统自重的条件下刃磨刀具。本发明具有刃磨工艺简单、     

微棱镜反光阵列超声振动刨削试验研究

通过超声振动刨削加工微棱镜阵列的正交试验,分析了刀具材料、刀具工作前角、切削速度、第三次切削深度对微棱镜阵列表面质量和刀具寿命的影响。结果表明：刀具材料是试验指标粗糙度Ra、V形槽夹角β、加工后刀尖圆弧半径R的第一影响因素;第三次切削深度ap是磨损量NB的第一影响因素;切削速度v是四个试验指标的第二影响因素;当刀具材料选用PCD,刀具前角为-3.8°,切削速度为900mm/min,第三次切深为2μm时,微棱镜阵列表面加工质量好,刀具寿命高。     

在线电解修整(ELID)超精密磨削中的金刚石磨具特性研究

ELID(Electrolytic In-process Dressing)磨削技术是在电化学加工、电解磨削原理基础上发展起来的一项磨削新技术,主要用于硬脆材料超精密磨削过程中金属基结合剂超硬微细磨粒砂轮的在线修整.本文以金刚石微粉砂轮在线电解修整(ELID)磨削氮化硅陶瓷为例,着重研究了磨具特性对硬脆材料超精密磨削过程的影响.研究表明,磨具组织沿砂轮圆周的不均匀性将会导致砂轮表面钝化膜状态的不一致,这将直接影响砂轮局部参与切削的磨粒数量,影响单个磨料的实际磨削厚度.这首先将对工件表面的磨削质量,特别是对表面粗糙度产生直接影响,同时也非常不利于实现材料的高效去除.     

三轴超精密单点金刚石车床SGDT350研制

文章介绍了基于静压支承技术自主研制的三轴超精密单点金刚石车床SGDT350。机床采用模块化设计,构建了开放式控制体系,成功实现了机床的高精度运动。经实测机床主轴回转跳动≤50nm,导轨直线度允差≤0.3μm/250mm,加工φ75mm口径SR250mm铝合金凸球面面形PV值达0.24μm,表面粗糙度Sa值达3.5nm,表明了机床具有较好的运动精度和加工性能。     

Brittle–ductile transition during diamond turning of single crystal silicon carbide

In this experimental study, diamond turning of single crystal 6H-SiC was performed at a cutting speed of 1 m/s on an ultra-precision diamond turning machine (Moore Nanotech 350 UPL) to elucidate the microscopic origin of ductile-regime machining. Distilled water (pH value 7) was used as a preferred coolant during the course of machining in order to improve the tribological performance. A high magnification scanning electron microscope (SEM FIB- FEI Quanta 3D FEG) was used to examine the cutting tool before and after the machining. A surface finish of Ra=9.2 nm, better than any previously reported value on SiC was obtained. Also, tremendously high cutting resistance was offered by SiC resulting in the observation of significant wear marks on the cutting tool just after 1 km of cutting length. It was found out through a DXR Raman microscope that similar to other classical brittle materials (silicon, germanium, etc.) an occurrence of brittle-ductile transition is responsible for the ductile-regime machining of 6H-SiC. It has also been demonstrated that the structural phase transformations associated with the diamond turning of brittle materials which are normally considered as a prerequisite to ductile-regime machining, may not be observed during ductile-regime machining of polycrystalline materials.     

Ultra-precision machining of Fresnel microstructure on die steel using single crystal diamond tool

With the increasing demand for the replication of structured optical elements such as Fresnel lenses and prism arrays, more attention is being paid to the development of ultra-precision diamond machining technology for the fabrication of die steel molds. However, the machining process would be a catastrophic failure because of rapid and excessive tool wear if a diamond tool is used to machine die steel. In the present paper, a micromachining method for fabricating microstructures on die steel using single crystal diamond tool is presented. The presented technology is based on a thermochemical technique that uses plasma nitriding treatment to suppress the rapid and excessive tool wear in the diamond machining of steel. Experimental findings revealed that severe chemical tool wear, which is the main wear mechanism in the diamond machining of steel, was reduced significantly after plasma nitriding treatment, and a mirror-quality surface with an average surface roughness of 20 nm root-mean-square (RMS) was achieved over a cutting distance of approximately 5.4 km. Furthermore, a Fresnel microstructure with surface roughness RMS better than 40 nm was precisely fabricated on AISI 4140 die steel using single crystal diamond tool.     

Development of monitoring system on the diamond tool wear

Recently, ultra-precision machining using a single crystal diamond tool has been developing very rapidly, especially in the fields of production processes for optical or magnetic parts such as magnetic discs, laser mirrors, polygon mirrors and copier drums. As a result, it has been successfully extended to machine various soft materials, generating mirror-like surfaces to sub-micron geometric accuracy with the ultra-precision CNC machine and the single crystal diamond tool. With the real cutting operation, the geometric accuracy and the surface finish attainable in machined surfaces are mainly determined by both of the sharpness of a cutting tool and stability of the machine vibration. In this study, for monitoring the progress of machining state for assuring the machining accuracy and the surface quality, a new monitoring method of machining states in face-cutting with diamond tool is proposed, using the frequency response of multi-sensors signal, which includes wear state of tool in terms of the energy within the specific frequency band. A magnetic disc is machined on the ultra-precision lathe.     

Application potential of coarse-grained diamond grinding wheels for precision grinding of optical materials

Fine-grained resin bonded diamond tools are often used for ultra-precision machining of brittle materials to achieve optical surfaces. A well-known drawback is the high tool wear. Therefore, grinding processes need to be developed exhibiting less wear and higher profitability. Consequently, the presented work focuses on conditioning a mono-layered, coarse-grained diamond grinding wheel with a spherical profile and an average grain size of 301 µm by combining a thermo-chemical and a mechanical-abrasive dressing technique. This processing leads to a run-out error of the grinding wheel in a low-micrometer range. Additionally, the thermo-chemical dressing leads to flattened grains, which supports the generation of hydrostatic pressure in the cutting zone and enables ductile-mode grinding of hard and brittle materials. After dressing, the application characteristics of coarse-grained diamond grinding wheels were examined by grinding optical glasses, fused silica and glass–ceramics in two different kinematics, plunge-cut surface grinding and cross grinding. For plunge-cut surface grinding, a critical depth of cut and surface roughness were determined and for cross-grinding experiments the subsurface damage was analyzed additionally. Finally, the identified parameters for ductile-machining with coarse-grained diamond grinding wheels were used for grinding a surface of 2000 mm² in glass–ceramics.     

Precision and micro CVD diamond-coated grinding tools

Both for ultra-precision and for micro-machining diamond is used very often as tool material. The reason is the very high dimensional stability of diamond due to its extreme hardness. Diamond is used for two kinds of machining processes: for cutting, like turning, drilling or milling, as well as for abrasive processes, like grinding. Diamond cutting tools can be made with massive diamond (monocrystal, CVD diamond, PCD) or with diamond coatings. Standard diamond abrasive tools are made by bonding diamond monocrystals onto a base body. A new grinding layer technology is presented: chemical vapour-deposited microcrystalline diamond layers have crystallite tips with very sharp edges that can act for grinding processes. Base body materials and coating technology is presented. Application results of grinding experiments show that very high workpiece quality can be reached, e.g. a roughness Ra of 5 nm with glass workpieces. Truing and recoating techniques are discussed for reuse of worn CVD diamond grinding wheels. Micro grinding tools (abrasive pencils, burrs) can be manufactured with the same coating technology. Very small tools with diameters of 50 μm have been made and successfully tested.     

金属基金刚石圆弧砂轮电火花修整的廓形仿真与实验研究

根据金属基金刚石圆弧砂轮修整的需要,研制了杯型修整电极式电火花修整装置,并介绍了装置的结构特点。分析了修整电极与砂轮尺寸对砂轮修整圆弧廓形的影响,根据修整电极与砂轮的尺寸推导出圆弧廓形的表达式,并利用Matlab进行了仿真计算。结果表明:修整宽度为10mm的砂轮时,圆弧半径理论误差在0.02mm以内。通过研制的杯型修整电极式电火花修整装置进行了电火花修整实验,修整后的砂轮实际廓形与仿真廓形误差小于3μm。     

Development of a micro diamond grinding tool by compound process

This study presents a novel micro-diamond tool which is 100 μm in diameter and that allows precise and micro-grinding during miniature die machining. A novel integrated process technology is proposed that combines “micro-EDM” with “precision composite electroforming” for fabricating micro-diamond tools. First, the metal substrate is cut down to 50 μm in diameter using WEDG, then, the micro-diamonds with 0–2 μm grain is “plated” on the surface of the substrate by composite electroforming, thereby becoming a multilayer micro-grinding tool. The thickness of the electroformed layer is controlled to within 25 μm. The nickel and diamond form the bonder and cutter, respectively. To generate good convection for the electroforming solution, a partition designed with an array of drilled holes is recommended and verified. Besides effectively decreasing the impact energy of the circulatory electroforming solution, the dispersion of the diamond grains and displacement of the nickel ions are noticeably improved. Experimental results indicate that good circularity of the diamond tool can be obtained by arranging the nickel spherules array on the anode. To allow the diamond grains to converge toward the cathode, so as to increase the opportunity of reposing on the substrate, a miniature funnel mold is designed. Then the distribution of the diamond grains on the substrate surface is improved. A micro-ZrO₂ ceramic ferrule is grinded to verify the proposed approach. The surface roughness of R_a = 0.085 μm is obtained. It is demonstrated that the micro-diamond grinding tool with various outer diameters is successfully developed in this study. The suggested approach, which depends on machining applications, can be applied during the final machining. Applications include dental drilling tools, precision optic dies, molds and tools, and biomedical instruments.