Tool Wear and Its Effect on Surface Roughness in Diamond Cutting of Glass Soda-lime

For the technology of diamond cutting of optical glass, the high tool wear rate is a main reason for hindering the practical application of this technology. Many researches on diamond tool wear in glass cutting rest on wear phenomenon describing simply without analyzing the genesis of wear phenomenon and interpreting the formation process of tool wear in mechanics. For in depth understanding of the tool wear and its effect on surface roughness in diamond cutting of glass, experiments of diamond turning with cutting distance increasing gradually are carried out on soda-lime glass. The wear morphology of rake face and flank face, the corresponding surface features of workpiece and the surface roughness, and the material compositions of flank wear area are detected. Experimental results indicate that the flank wear is predominant in diamond cutting glass and the flank wear land is characterized by micro-grooves, some smooth crater on the rake face is also seen. The surface roughness begins to increase rapidly, when the cutting mode changes from ductile to brittle for the aggravation of tool wear with the cutting distance over 150 m. The main mechanisms of inducing tool wear in diamond cutting of glass are diffusion, mechanical friction, thermo-chemical action and abrasive wear. The proposed research makes analysis and research from wear mechanism on the tool wear and its effect on surface roughness in diamond cutting of glass, and provides theoretical basis for minimizing the tool wear in diamond cutting brittle materials, such as optical glass.

SURFACE ROUGHNESS PREDICTION MODEL FOR ULTRAPRECISION TURNING ALUMINIUM ALLOY WITH A SINGLE CRYSTAL DIAMOND TOOL

A surface roughness model utilizing regression analysis method is developedfor predicting roughness of ultra-precision machined surface with a single crystal diamond tool. Theeffects of the main variables, such as cutting speed, feed, and depth of cut on surface roughnessare also analyzed in diamond turning aluminum alloy. In order to predict the optimum cuttingconditions during process planning. A lot of experimental results show that the model can predictthe surface roughness effectively under a certain cutting conditions.

Influence of Minimum Quantity Lubrication Parameters on Tool Wear and Surface Roughness in Milling of Forged Steel

The minimum quantity of lubrication（MQL） technique is becoming increasingly more popular due to the safety of environment.Moreover,MQL technique not only leads to economical benefits by way of saving lubricant costs but also presents better machinability.However,the effect of MQL parameters on machining is still not clear,which needs to be overcome.In this paper,the effect of different modes of lubrication,i.e.,conventional way using flushing,dry cutting and using the minimum quantity lubrication（MQL） technique on the machinability in end milling of a forged steel（50CrMnMo）,is investigated.The influence of MQL parameters on tool wear and surface roughness is also discussed.MQL parameters include nozzle direction in relation to feed direction,nozzle elevation angle,distance from the nozzle tip to the cutting zone,lubricant flow rate and air pressure.The investigation results show that MQL technique lowers the tool wear and surface roughness values compared with that of conventional flood cutting fluid supply and dry cutting conditions.Based on the investigations of chip morphology and color,MQL technique reduces the cutting temperature to some extent.The relative nozzle-feed position at 120°,the angle elevation of 60° and distance from nozzle tip to cutting zone at 20 mm provide the prolonged tool life and reduced surface roughness values.This fact is due to the oil mists can penetrate in the inner zones of the tool edges in a very efficient way.Improvement in tool life and surface finish could be achieved utilizing higher oil flow rate and higher compressed air pressure.Moreover,oil flow rate increased from 43.8 mL？h to 58.4 mL？h leads to a small decrease of flank wear,but it is not very significant.The results obtained in this paper can be used to determine optimal conditions for milling of forged steel under MQL conditions.

Experimentation on Tool Wear and Surface Roughness in AISI D2 Steel Turning with WC Insert

The Taguchi method, based on an orthogonal arrangement (L9, 33), the vari-ance analysis, the signal-to-noise ratios and the response surface methodol-ogy have been used to optimize maximum flank wear (VBmax) and surface roughness (Ra) of the cutting tool when turning a hardened steel AISI D2 (65 HRC) with PVD—TiAlN coated WC insert upon dry environment. By em-ploying regression models;cutting speed, cutting depth and feed rate, which optimize maximum flank wear and surface roughness were validated. Results of relation signal-to-noise ratios, showed that with cutting speed of 200 m/min, cutting depth of 0.2 mm and feed rate of 0.20 mm/rev, Ra is opti-mized. With cutting speed of 150 m/min, cutting depth of 0.4 mm and feed rate of 0.3 mm/rev, VBmax is optimized. Through the variance analysis it was concluded that the depth of cut was the main parameter that affected on the surface roughness;whereas, the feed rate was the most influential parameter on the flank wear. Confirmation test results showed that the Taguchi method was very successful in the optimization of machining parameters for mini-mum surface roughness and flank wear in the turning of the D2 steel.

Performance evaluation of minimum quantity lubrication by vege-table oil in terms of cutting force,cutting zone temperature,tool wear,job dimension and surface finish in turning AISI-1060 steel

In all machining processes, tool wear is a natural phenomenon and it leads to tool failure. The growing demands for high productivity of machining need use of high cutting velocity and feed rate. Such machining inherently produces high cutting temperature, which not only reduces tool life but also impairs the product quality. Metal cutting fluid changes the performance of machining operations because of their lubrication, cooling and chip flushing functions, but the use of cutting fluid has become more problematic in terms of both employee health and environmental pollution. The minimization of cutting fluid also leads to economical benefits by way of saving lubricant costs and workpiece/tool/machine cleaning cycle time. The concept of minimum quantity lubrication (MQL) has been suggested since a decade ago as a means of addressing the issues of environmental intru- siveness and occupational hazards associated with the airborne cutting fluid particles on factory shop floors. This paper deals with experimental investigation on the role of MQL by vegetable oil on cutting temperature, tool wear, surface roughness and dimen- sional deviation in turning AISI-1060 steel at industrial speed-feed combinations by uncoated carbide insert. The encouraging results include significant reduction in tool wear rate, dimensional inaccuracy and surface roughness by MQL mainly through reduction in the cutting zone temperature and favorable change in the chip-tool and work-tool interaction.

Investigation on tool wear and tool life prediction in micro-milling of Ti-6Al-4V

Short tool life and rapid tool wear in micromachining of hard-to-machine materials remain a barrier to the process being economically viable. In this study, standard procedures and conditions set by the ISO for tool life testing in milling were used to analyze the wear of tungsten carbide micro-end-milling tools through slot milling conducted on titanium alloy Ti-6 Al-4 V. Tool wear was characterized by flank wear rate,cutting-edge radius change, and tool volumetric change. The effect of machining parameters, such as cutting speed and feedrate, on tool wear was investigated with reference to surface roughness and geometric accuracy of the finished workpiece. Experimental data indicate different modes of tool wear throughout machining, where nonuniform flank wear and abrasive wear are the dominant wear modes. High cutting speed and low feedrate can reduce the tool wear rate and improve the tool life during micromachining.However, the low feedrate enhances the plowing effect on the cutting zone, resulting in reduced surface quality and leading to burr formation and premature tool failure. This study concludes with a proposal of tool rejection criteria for micro-milling of Ti-6 Al-4 V.

Approach for Polishing Diamond Coated Complicated Cutting Tool: Abrasive Flow Machining(AFM)

Lower surface roughness and sharper cutting edge are beneficial for improving the machining quality of the cut?ting tool, while coatings often deteriorate them. Focusing on the diamond coated WC?Co milling cutter, the abrasive flow machining(AFM) is selected for reducing the surface roughness and sharpening the cutting edge. Comparative cutting tests are conducted on di erent types of coated cutters before and after AFM, as well as uncoated WC?Co one, demonstrating that the boron?doped microcrystalline and undoped fine?grained composite diamond coated cutter after the AFM(AFM?BDM?UFGCD) is a good choice for the finish milling of the 6063 Al alloy in the present case, because it shows favorable machining quality close to the uncoated one, but much prolonged tool lifetime. Besides, compared with the micro?sized diamond films, it is much more convenient and e cient to finish the BDM?UFGCD coated cutter covered by nano?sized diamond grains, and resharpen its cutting edge by the AFM, owing to the lower initial surface roughness and hardness. Moreover, the boron incorporation and micro?sized grains in the underly?ing layer can enhance the film?substrate adhesion, avoid the rapid film removal in the machining process, and thus maximize the tool life(1040 m, four times more than the uncoated one). In general, the AFM is firstly proposed and discussed for post?processing the diamond coated complicated cutting tools, which is proved to be feasible for improving the cutting performance

Tool wear criterion,tool life,and surface roughness during high-speed end milling Ti-6Al-4V alloy

The objective of the present research is to investigate the relationship among tool wear, surface topography, and surface roughness when high-speed end milling Ti-6Al-4V alloy, and also to define an optimal flank wear criterion for the cutting tool to integrate tool life and the surface roughness requirements of the finish milling process. An annealed Ti-6Al-4V alloy was selected as the workpiece material, undergoing end milling with uncoated carbide inserts. The flank wear of the insert was observed and measured with the toolmaker's microscope. To examine machined surfaces, 3D surface topography was provided by the white light interferometer, and the arithmetical mean roughness (Ra) was calculated with the WYKO Vision32 software. The flank wear increases with cutting time, and the maximal flank wear is set as the flank wear criterion. As the cutting process progresses, tool wear is the predominant factor affecting the variation of surface roughness. According to the plots for the tool wear propagation and surface roughness variation, an optimal flank wear criterion can be defined which integrates the tool life and the surface roughness requirements for the finish milling process.

Influence of tool deflection on micro channel pattern of 6:4 brass with rectangular tool

Machining experiment of micro channel structure with 6:4 brass was carried out by shaping process using a single crystal diamond tool. FEM simulation using solid cantilever beam model was analyzed. In result of experiment, tool deflection is observed as machining characteristics through result of experiments such as surface roughness, cutting force and burr formations. And the influence of tool deflection is experimentally proved.

Status of research on non-conventional technology assisted single-point diamond turning

With the increasing use of difficult-to-machine materials in aerospace applications,machining requirements are becoming ever more rigorous.However,traditional single-point diamond turning(SPDT)can cause surface damage and tool wear.Thus,it is difficult for SPDT to meet the processing requirements,and it has significant limitations.Research indicates that supplementing SPDT with unconventional techniques can,importantly,solve problems due to the high cutting forces and poor surface quality for difficult-to-machine materials.This paper first introduces SPDT and reviews research into unconventional techniques for use with SPDT.The machining mechanism is discussed,and the main advantages and disadvantages of various methods are investigated.Second,hybrid SPDT is briefly described,which encompasses ultrasonic-vibration magnetic-field SPDT,ultrasonic-vibration laser SPDT,and ultrasonic-vibration cold-plasma SPDT.Compared with the traditional SPDT method,hybrid SPDT produces a better optical surface quality.The current status of research into unconventional techniques to supplement SPDT is then summarized.Finally,future development trends and the application prospects of unconventional assisted SPDT are discussed.

干式高速高效车削D6AC高强钢的试验研究

研究了TiCN+Al_(2)O_(3)涂层硬质合金刀具在高速高效车削未淬火处理的D6AC高强钢时,刀具磨损的特点及加工过程中切削力、切削温度和工件表面粗糙度的变化规律。结果表明:刀具磨损形态主要为后刀面磨损,在切削后期刀具前刀面发生局部破损,后刀面发生剧烈磨损;刀具正常磨损阶段,各切削分力增长缓慢,主切削力>轴向力>径向力,当刀具破损发生剧烈磨损时,轴向力和径向力均波动较大,其平均值下降;刀具切出位置最高温度远高于工件已加工表面最高温度,在刀具正常磨损阶段,温度增长较平缓;加工表面粗糙度变化,刀具破损后工件表面沟痕明显加深。

纳米粒子微量润滑磨削加工氧化锆研究

氧化锆陶瓷拥有高的强度、硬度、断裂韧度以及耐高温、耐腐蚀等性能,在3C电子、生物医疗、化工、机械、新能源等领域有着广泛的应用。但氧化锆陶瓷器件磨削加工效率低、工具磨损严重,难以获得高的表面质量。磨削加工过程中冷却润滑方式对氧化锆陶瓷加工效率和表面质量有着重要影响。文章研究了不同纳米粒子微量润滑条件下电镀金刚石工具磨削加工对氧化锆陶瓷的磨削力和表面质量。结果表明添加纳米金刚石、石墨烯、MoS2纳米冷却液的微量润滑条件下可以降低氧化锆陶瓷的磨削力,其中MoS2纳米冷却液的磨削力最小;而使用浇注式冷却条件下的法向磨削力最大,干式磨削条件下的切向磨削力最大;不同冷却方式加工的氧化锆陶瓷的表面粗糙度差异不大。

基于金刚石涂层的石墨铣刀磨损特性研究

为深入分析金刚石涂层铣刀加工石墨的磨损机理以及对表面粗糙度的影响,采用单因素实验对石墨进行铣削加工,通过超景深显微镜对刀具的端齿进行测量,同时采用三维测量仪对刀具的周刃进行轮廓检测,并采用手持式粗糙度检测仪对加工表面进行粗糙度检测。结果表明:石墨铣削加工中,刀具的磨损形式以磨粒磨损为主,随着切削距离的增加,刀具端齿磨损不断加剧,出现从涂层脱落到刃口崩缺的变化,而周刃刃口轮廓出现较大的磨损;工件表面粗糙度在垂直进给方向上随着刀具磨损和切削距离的增加而增大。

金刚石飞切加工微结构表面的工艺参数优化

为了获得具有纳米级表面质量的微结构表面,利用‘Nanosys-300’超精密复合加工系统实现了微结构表面的三维金刚石飞切加工,研究了主轴转速、进给量以及背吃刀量对微结构表面粗糙度的影响。理论分析表明,金刚石飞切加工微结构时理论表面粗糙度沿法线方向并没有变化,而沿进给方向存在着周期变化。减小进给量和金刚石飞刀前端角或增大切削半径可以降低理论粗糙度值。实验分析表明,表面粗糙度值Ra随进给量的增加而增加,主轴转速对Ra影响不大。切削聚碳酸酯（PC）时,在5~40μmRa随背吃刀量的增加而增加;而切削铝合金（LY12）时,在2~10μmRa随背吃刀量的增加而减小。实验中Ra最好可达38 nm（LY12）和43 nm（PC）。最后,利用优化工艺参数加工出了微沟槽阵列和微金字塔矩阵微结构。

刀具后刀面磨损量对切削力及加工表面粗糙度的影响

通过切削试验探索了在相同的工件材料、刀具材料、切削参数(切削深度、进给量)和不同的刀具磨损状态(后刀面磨损量)下,刀具后刀面磨损量(VB)对切削过程中的切削力及工件表面粗糙度的影响,并对这些影响的产生机理进行了讨论。

金刚石车削表面微观形貌形成机理的研究

为了在超精密加工前预测并控制表面粗糙度 ,提出一种建立圆弧刃车刀金刚石车削表面微观形貌的几何模型的新方法 ,开发并编写了表面微观形貌的仿真程序 ,在程序中考虑了刀具几何参数、振动和最小切削厚度对已加工表面特性的影响 .通过理论分析和试验研究确定了最小切削厚度与切削刃钝圆半径之间的关系 ,分析了影响已加工表面粗糙度的若干因素 ,并在仿真生成的表面微观形貌中成功地加入了随机振动信号 .大量切削试验是在自行研制的亚微米CNC超精密机床上进行的 .结果表明 :利用所建立的表面微观形貌几何模型 。

纤维状聚晶金刚石复合片刀具的切削性能及刀具磨损机理

设计并制备一种纤维状聚晶金刚石复合片(Polycrystalline diamond compacts,PDC)刀具,制备的PDC刀具具有同时参与切削的刀刃多、刀刃间隔距离和切削角度可人为控制、刃口锋利平直等特点。开展了新型PDC刀具与金刚石砂轮在相同条件下加工WC/12Co涂层的对比试验。结果表明,制备的PDC刀具能获得与金刚石砂轮磨削相媲美的加工质量,实现WC/12Co涂层硬脆材料的精密加工;同时其具有良好的容屑空间,断续切削的结构特点使其更容易散热,因此,切削加工过程中又可以适当地提高切削参数实现材料的高效加工。PDC刀具在长时间的加工过程中,由于受到频繁的冲击作用,在PDC刀具的后刀面出现了小凹坑和轻微的磨粒磨损,随着切削的进行,在切刃处出现局部崩刃现象,须对其刃磨。

SiC_p/Al复合材料的超精密车削试验

试验研究了碳化硅颗粒增强铝基复合材料(SiCp/Al)的超精密车削加工性能。使用扫描电镜(SEM)对已加工表面、切屑及其根部、刀具前/后刀面磨损带进行观察,使用表面粗糙度轮廓仪对各种切削条件下的加工表面粗糙度轮廓进行测试分析。结果表明,该材料的加工表面常残留微孔洞、微裂纹、坑洞、划痕、残留物突起及基体材料撕裂等微观缺陷,刀具几何参数、切削速度、进给量、增强颗粒尺寸和材料体积分数是影响表面粗糙度的主要因素。由于切削变形区微裂纹动态形成的作用,超精密切削该材料时一般形成锯齿型切屑。刀具-工件的相对振动、基体撕裂增强颗粒拔出、破碎、压入等是该材料超精密车削表面形成的主要机制。单晶金刚石(SCD)刀具主要发生微磨损、崩刃、剥落和磨粒磨损,聚晶金刚石(PCD)刀具主要发生磨粒磨损和粘结磨损。结论表明SiCp/Al的超精密切削加工性较差,但通过选择合适的工艺参数,体积分数为15%的SiCp/2024Al加工表面粗糙度Ra可达24.7nm。

MACHINING OF METAL MATRIX COMPOSITES

Two types of aluminium-based composites reinforced respectively with 20 vol short fibre alumina and with a hybrid of 15 vol SiC particle and 5 vol short alumina fibre are machined with different tool materials:cemented carbide,ceramic,cubic boron nitride(CBN)and polycrystalline diamond(PCD).The analysis on tool wear shows that the various tool materials exhibite different tool wear behaviours,and the tool wear mechanisma are discussed.Apparently,PCD tools do not necessarily guarantee dimensional stability but they can provide the most economic means for machining all sorts of composites.Consequently,a suitable tool material is suggested for machining each metal matrix composite(MMC) from the standpoints of tool wear and machined surface finish.

钛合金铣削刀具磨损对表面完整性影响研究

为了掌握钛合金TC4铣削过程中刀具磨损对表面完整性的影响规律,通过对不同刀具后刀面磨损量下铣削钛合金工件的表面完整性测试,得出了刀具磨损对表面完整性的影响规律,并对其影响机理进行了分析。结果表明,在刀具处于初期磨损和正常磨损阶段,刀具的挤光效应引起的压应力占主导地位,而在刀具剧烈磨损阶段,加工过程中的热塑性变形引起的拉应力占主导地位;随着刀具后刀面磨损量的增加,刀具正常磨损阶段粗糙度值缓慢增加,剧烈磨损阶段粗糙度值迅速增加;随着刀具后刀面磨损量的增加,已加工表面的显微硬度值和表面层的硬化深度都随之增大。