Statistical analysis of surface roughness and cutting forces using response surface methodology in hard turning of AISI 52100 bearing steel with CBN tool

The present work concerns an experimental study of hard turning with CBN tool of AISI 52100 bearing steel, hardened at 64 HRC. The main objectives are firstly focused on delimiting the hard turning domain and investigating tool wear and forces behaviour evolution versus variations of workpiece hardness and cutting speed. Secondly, the relationship between cutting parameters (cutting speed, feed rate and depth of cut) and machining output variables (surface roughness, cutting forces) through the response surface methodology (RSM) are analysed and modeled. The combined effects of the cutting parameters on machining output variables are investigated while employing the analysis of variance (ANOVA). The quadratic model of RSM associated with response optimization technique and composite desirability was used to find optimum values of machining parameters with respect to objectives (surface roughness and cutting force values). Results show how much surface roughness is mainly influenced by feed rate and cutting speed. Also, it is underlined that the thrust force is the highest of cutting force components, and it is highly sensitive to workpiece hardness, negative rake angle and tool wear evolution. Finally, the depth of cut exhibits maximum influence on cutting forces as compared to the feed rate and cutting speed.     

微沟槽织构对切削力和表面粗糙度的影响

为研究微织构对切削过程中产生的切削力和已加工表面粗糙度的影响,在聚晶立方氮化硼(PCBN)刀片前刀面制备与主切削刃平行的宽度为32.6μm的微沟槽织构。分别用微沟槽刀具和无织构刀具在主轴转速为450、500、600 r/min的条件下切削淬硬钢GCr15,分析切削力和已加工表面粗糙度。试验结果表明:微沟槽改善了刀具的切削性能,主切削力、进给力和切深力均小于无织构刀具;进给力、切深力随着主轴转速的增加均变大,主切削力表现为先减小再增大;用微沟槽织构刀具切削的已加工表面粗糙度大于无织构刀具,表明微沟槽不利于获得表面质量较好的工件;随着主轴转速增加,微沟槽刀具和无织构刀具切削的表面粗糙度均减小。     

小直径磨棒磨削加工TiC颗粒增强钢基复合材料GT35

为探究TiC颗粒增强钢基复合材料GT35合理的加工参数和冷却润滑条件,研究其对切削力、表面质量及刀具磨损的影响规律,采用小直径磨棒以侧面磨削方式开展试验。结果表明:干磨削会引起磨棒烧伤,极压磨削油的润滑效果优于水基合成磨削液的;磨棒在极压磨削油润滑下,磨削工件12 min后进入稳定磨损状态,其主要磨损形式为磨粒破碎、磨粒磨耗和磨粒脱落;主轴转速对切削力的影响大于进给速度的,且转速越高,切削力越小;工件表面粗糙度主要与磨棒磨粒出露高度的平整度有关,受加工参数的影响较小。用小直径磨棒磨削加工GT35材料时,应选择极压磨削油润滑,高主轴转速、中速进给的加工方式,以获得良好的刀具寿命、工件加工表面质量及适当的加工效率。      

切削参数对子午线轮胎模具侧板切削比能及表面粗糙度的影响研究

以子午线轮胎模具侧板为研究对象进行铣削试验,着重研究主轴转速、每齿进给量、切削深度对轮胎模具侧板切削比能、材料去除率和表面粗糙度的影响规律。分析试验结果可知:切削比能随着切削参数的增大而减小,说明适当增大切削参数可以提高切削效率并节约能量;表面粗糙度随主轴转速增大呈先增大后减小的趋势,随切削深度和每齿进给量的增加而增大。结果表明:提高主轴转速既有利于降低切削比能(节能)也有利于改善表面粗糙度,增大每齿进给量和切削深度会降低切削比能但会恶化表面质量。因此,为同时达到高效节能和良好表面质量的要求,应尽量提高主轴转速。     

微粉金刚石钎焊砂轮磨削氧化铝陶瓷的磨削力和表面粗糙度特征

在不同磨削深度、砂轮转速和进给速度组合下,研究微粉金刚石钎焊砂轮磨削氧化铝陶瓷过程的磨削力及工件的表面粗糙度的变化规律,并筛选出低磨削力和低工件表面粗糙度的加工工艺参数。试验结果表明:在微粉金刚石钎焊砂轮的磨削过程中,氧化铝陶瓷主要通过脆性断裂的方式去除;随着磨削深度、进给速度的增加,砂轮在进给方向和切深方向的力以及工件表面粗糙度都上升;随着砂轮转速的增加,进给方向和切深方向的力以及工件表面粗糙度都下降。试验获得的低磨削力和低工件表面粗糙度精密加工工艺参数分别为:磨削深度为1.0 μm,进给速度为12 mm/min,砂轮转速为24 000 r/min和磨削深度为1.0 μm,进给速度为1 mm/min,砂轮转速为20 000 r/min。低磨削力磨削时,微粉金刚石钎焊砂轮受到的X方向和Z方向的磨削力分别为0.15 N和0.72 N;精密加工后的氧化铝陶瓷的表面粗糙度值可达0.438 μm。      

高速铣削模具钢3Cr2NiMo表面粗糙度试验研究

采用单因素试验法和正交试验法,在高速加工中心上对模具钢3Cr2NiMo进行切削试验,通过改变影响加工过程的切削参数:主轴转速、进给速度、轴向切削深度和径向切削深度,研究了影响工件加工表面粗糙度值程度的因素。结果表明:增大机床的主轴转速,粗糙度值显著降低,而增大进给速度、轴向铣削深度,粗糙度值增大,但增大的幅度不同,径向铣削深度的影响不明显。     

PCD刀具加工氮化硅陶瓷孔的试验研究

使用PCD刀具对氮化硅陶瓷内孔进行切削试验,首先研究氮化硅陶瓷材料的去除机理,主要包括脆性去除和塑性去除,且以脆性去除为主。其次,研究刀具前角、切削速度、背吃刀量和进给量对切削力的影响。结果表明:刀具前角对切削力的影响不明显;随切削速度、背吃刀量和进给量的增加,切削力均增大,且背向力大于进给力和主切削力。最后,重点研究各参数对内孔侧壁表面粗糙度的影响。结果表明:进给量对表面粗糙度的影响最显著,其次是背吃刀量和切削速度,刀具前角几乎没有影响,且当刀具前角为-5°,切削速度为32.97m/min,背吃刀量为0.10mm,进给量为0.08mm/r时,可以得到较好的表面粗糙度和刀具寿命的综合效益。      

58SiMn高强度钢车削表面完整性的试验研究

目的研究58Si Mn高强度钢表面完整性评价指标受切削参数影响的变化规律。方法分别设计单因素和正交试验,采用涂层硬质合金刀具对58Si Mn高强度钢进行车削加工试验,通过采集相关数据,分别讨论了切削深度、进给速度和切削速度变化对表面粗糙度、残余应力、显微硬度和表层微观组织变化等方面的影响。结果进给速度对表面粗糙度的影响最显著,切削速度次之,切削深度的变化对表面粗糙度无直接影响。已加工表面的残余应力随切削速度和进给量的增大而增大。显微硬度随切削深度的增大而减小,随进给量的增大而增大,层深上的显微硬度则呈现先减小后增大的趋势。表层微观组织受切削速度影响不大,未出现明显的相变和晶粒歪曲。结论降低进给速度是减小工件表面粗糙度最直接有效的方法,提高切削速度并不能使表面粗糙度明显减小。工件表面的轴向和切向残余应力均为拉应力,为提高零件使用性能,应采取相应的措施使之转化为压应力。     

CuZn30微铣削表面完整性影响规律试验研究

采用直径φ1的硬质合金铣刀对CuZn30合金进行单因素槽铣试验,研究加工表面完整性、顶毛刺和切屑随铣削参数的变化规律。通过试验得到以下结论:切削参数对加工表面完整性影响比较显著,其中表面粗糙度随主轴转速的增大而减小,随每齿进给量增大而增大,切削深度对粗糙度影响不太显著。残余应力随着每齿进给量的增大有明显增大趋势,而主轴转速与切削深度对残余应力的影响不太显著。显微硬度随铣削参数变化没有显著的变化。顶毛刺主要受每齿进给量的影响,毛刺尺寸随着每齿进给量的增加先急速减小后趋于平稳,切屑形态主要受切削深度的影响,随着切削深度的增加,切屑由短小的碎屑逐渐变为平滑的连续卷曲切屑。     

Cutting performance of end mills with different helix angles

In this paper an investigation of the cutting performance of several end mills with right and left hand helix angles is reported. Cutting tests were performed on aluminum alloy L65 for three milling processes in which cutting force, surface roughness and concavity of a machined plane surface were measured. The cutting performance of the end mills was assessed using variance analysis. The investigation showed that end mills with left hand helix angles are generally less effective than those with right hand helix angles, except for the case where the helix angle is small. The effects of spindle speed, depth of cut and feed rate on the cutting force and the surface roughness are generally significant. There is no significant difference between down milling and up milling with regard to the cutting force, although the difference between them regarding the surface roughness was large.     

基于切削技术的金刚石刀具磨损特征分析

金刚石刀具的磨损情况决定其使用寿命。用金刚石PCD刀具切削6061-T6镁铝合金工件,通过不同切削速度、切削深度、振动频率、刀具后角时的切削力及切削温度变化,研究不同刀具前后角、进给量、切削转速时的工件表面粗糙度及刀具磨损面积。结果表明:金刚石刀具的切削力和切削温度随切削速度、切削深度的增加而增大,随振动频率的增加而减小;刀具后角增大,金刚石刀具的切削力呈先下降而后缓缓上升趋势,但对切削温度的影响很小。当刀具前角为10°,刀具后角为8°,切削速度为0.46?m/s,切削深度为28?μm,进给量为0.10?mm/r,切削转速为4100?r/min,振动频率为22?kHz,切削振幅为9?μm时,金刚石刀具的磨损面积最小,磨损程度最低,使用寿命最长,但工件的表面粗糙度稍高。      

二维超声加工淬硬钢的建模与参数优化

利用正交设计方法研究了硬质合金刀具二维超声加工(UEVC)淬硬钢Cr12Mo V时切削用量的三个因素对加工表面粗糙度和切削力的影响,并利用信噪比、方差及贡献率等方法对各因素间的相互作用进行了分析。以切削参数为独立变量,以切削力和表面粗糙度为响应,利用回归分析建立数学模型。实验结果表明:进给量是对表面粗糙度(Ra、Rz)影响最大的因数,贡献率分别为91.8%和88.8%;其次是切削深度,贡献率分别为3.72%和9.77%;对切削力(Fz)影响最大的二个因素是进给量和切削深度,贡献率分别为56.69%和38.46%;切削速度对表面粗糙度、切削力的贡献率均最小。此外,建立的回归方程对Ra、Rz和Fz均有很高的可决系数,分别为91.8%、94.3%和88.2%,说明所建线性回归模型的准确性。     

CVD金刚石厚膜刀具切削参数对切削力及粗糙度影响的研究

为了探究CVD金刚石厚膜刀具切削参数(包括刀具后角、刀尖圆弧半径、切削速度、进给量和切削深度)对切削力和被加工表面粗糙度影响的初步规律,采用单因素方法进行了一系列CVD金刚石厚膜刀具车削仿真和试验研究。结果表明:AdvantEdge有限元仿真软件模拟切削力过程有一定的准确性;在试验参数范围内,随着刀具后角的增大,切削力和表面粗糙度都是先减小后增大,当后角为11°时,切削力和表面粗糙度值最小;随着刀尖圆弧半径的增大,切削力逐渐增大,而表面粗糙度则逐渐减小;随着切削速度的增大,切削力和表面粗糙度都是先增大后减小,当切削速度为90m/min时,切削力和表面粗糙度值最大;随着进给量的增大,切削力和表面粗糙度都显著增大;随着切削深度的增大,切削力和表面粗糙度都逐渐增大,但切削深度对表面粗糙度的影响较小。     

Experimental investigation on hard milling of high strength steel using PVD-AlTiN coated cemented carbide tool

High strength steel 30Cr3SiNiMoVA (30Cr3) is usually used to manufacture the key parts in aviation industry owing to its outstanding mechanical properties. However, 30Cr3 has poor machinability due to its high strength and high hardness. Hard milling is an efficient way in machining high strength steels. This paper investigated hard milling of 30Cr3 using a PVD-AlTiN coated cemented carbide tool with regard to cutting forces, surface roughness, chip formation and tool wear, respectively. The experimental results indicated that the increase of cutting speed from 70 to 110 m/min leads to direct reduction of cutting forces and improvement of surface finish, while both feed rate and depth of cut have negative effect on surface finish. The occurrence of oxidation on chip surfaces under high cutting temperature makes the chips show different colors which are strongly influenced by cutting speed. Saw-toothed chips were observed with the occurrence of the thermo-plastic instability within the primary shear zone. Micro-chipping and coating peeling were confirmed to be the primary tool failure modes. Serious abrasion wear and adhesive wear with some oxidative wear were confimed to be the main wear mode in hard milling of 30Cr3.     

硬脆材料的环形电镀金刚石线锯加工试验研究

本文利用环形电镀金刚石线锯对硬脆材料单晶硅、LT55陶瓷进行了切割试验,研究了锯切力、材料加工表面质量及锯丝的磨损.研究发现,在相同加工参数下,切割LT55陶瓷时的法向力与切向力之比小于单晶硅,与磨削相比,线锯加工的法向力与切向力之比非常小;在本实验条件下,单晶硅和LT55陶瓷均为脆性去除方式;因为LT55陶瓷断裂韧性高,在同样加工条件下,陶瓷加工表面质量优于单晶硅;恒进给压力条件下,锯丝速度增加,粗糙度值略微减小,恒进给压力增加,粗糙度值明显增大;锯丝首先在焊口处断裂,由于锯丝不能自转,沿锯丝圆周方向磨损不均匀.     

Mechanisms involved in the improvement of Inconel 718 machinability by laser assisted machining (LAM)

The aim of the present research work has been to gain a broader understanding of how or why laser assisted machining (LAM) improves machinability of Inconel 718, a hard-to-machine material of interest in the aeronautic industry. This has been accomplished by, first, running short run tests to determine the laser parameters and configuration for which highest force reductions are obtained and also to determine the effect of cutting parameters (feed, cutting speed and depth of cut) on force reduction. Secondly, long run tests have been performed in order to analyze process variables such as cutting forces, tool wear and surface roughness. Temperatures and hardness have been also measured in order to gain a broader perspective of the process.Experimental results have demonstrated that LAM improves machinability of Inconel 718 since machining forces and final surface roughness are reduced. The novelty reached with the present research work is the identification of three mechanisms associated to the laser heating as the responsible of this machinability improvement: material yield strength reduction, material base hardness reduction (only in precipitation hardened Inconel 718) and elimination of the work hardening generated in previous machining passes. The reduction of the work hardening leads also to a lower notch wear that limits the risk of sudden failure of the cutting tool and thus the wear mode is changed to flank wear, which leads to a controllable tool life and better surface roughness.     

PCD和HTi10刀具铣削CFRP试验研究

针对碳纤维复合材料(CFRP)难加工的特性,文中采用PCD和HTi10刀具进行了CFRP铣削试验,对加工过程中的铣削力、刀具磨损和表面粗糙度进行了分析。结果表明:PCD和HTi10刀具的铣削力和表面粗糙度变化规律一致,均随转速的增大而减小,随进给速度的增大而增大,但PCD刀具的铣削力更小,加工质量更好;与HTi10相比,PCD刀具的铣削力对刀具磨损更加敏感,更适合应用在加工环境较好的条件下。在CFRP加工过程中,粗加工时优选HTi10刀具,精加工时优选PCD刀具,宜选用高转速、低进给的切削参数。     

纳米金刚石涂层刀具高速铣削7075铝合金的工艺参数优化

采用热丝CVD法制备纳米金刚石薄膜涂层刀具,利用场发射扫描电子显微镜表征薄膜的表面形貌,并用已制备的CVD金刚石涂层刀具,在无润滑干切条件下高速铣削7075铝合金工件,对其精铣工艺参数进行单因素及正交试验,探索精铣后工件的表面粗糙度变化规律并进行工艺参数优化。结果表明:随着主轴转速n从5000 r/min提高到8000 r/min, 工件平均表面粗糙度在逐级缓慢降低;当进给速度v_f在1000～7000 mm/min范围内,随着v_f提高工件平均表面粗糙度快速增大,在v_f为7000 mm/min时,其值达1.790 μm;当轴向切削深度a_p在0.1～0.4 mm范围内,随着a_p提高,工件平均表面粗糙度逐步增大,但a_p在0.2 mm之后其增大趋势变缓。对7075铝合金工件精铣表面粗糙度影响最大的是v_f,其次为n,a_p的影响最弱;其精铣的最优参数组合是a_p=0.2 mm、v_f=1 000 mm/min、n=8 000 r/min,精铣后的表面粗糙度平均值为0.516 μm。选用纳米金刚石薄膜涂层刀具精铣7075铝合金时,为得到较低的表面粗糙度,应选择高主轴转速、低进给速度、合适的轴向切削深度。      

基于微量润滑的微铣削单晶高温合金表面粗糙度研究

以单晶镍基高温合金DD98材料为研究对象,搭建微量润滑冷却系统微铣削平台。对比微量润滑和干切削冷却条件下,微铣削工艺参数对表面粗糙度的影响机制和规律。结果表明:在微量润滑冷却条件下,单晶高温合金的表面粗糙度获得较大提升;两种不同冷却方式条件下,微铣削表面粗糙度均随着主轴转速的升高而减小,随着进给速度的增加在克服尺度效应后缓慢增大,随着背吃刀量的增加而增大。     

Characteristics of cutting forces and chip formation in machining of titanium alloys

Chip formation during dry turning of Ti6Al4V alloy has been examined in association with dynamic cutting force measurements under different cutting speeds, feed rates and depths of cut. Both continuous and segmented chip formation processes were observed in one cut under conditions of low cutting speed and large feed rate. The slipping angle in the segmented chip was 55°, which was higher than that in the continuous chip (38°). A cyclic force was produced during the formation of segmented chips and the force frequency was the same as the chip segmentation frequency. The peak of the cyclic force when producing segmented chips was 1.18 times that producing the continuous chip.The undeformed surface length in the segmented chip was found to increase linearly with the feed rate but was independent of cutting speed and depth of cut. The cyclic force frequency increased linearly with cutting speed and decreased inversely with feed rate. The cutting force increased with the feed rate and depth of cut at constant cutting speed due to the large volume of material being removed. The increase in cutting force with increasing cutting speed from 10 to 16 and 57 to 75 m/min was attributed to the strain rate hardening at low and high strain rates, respectively. The decrease in cutting force with increasing cutting speed outside these speed ranges was due to the thermal softening of the material. The amplitude variation of the high-frequency cyclic force associated with the segmented chip formation increased with increasing depth of cut and feed rate, and decreased with increasing cutting speed from 57 m/min except at the cutting speeds where harmonic vibration of the machine occurs.