不同冷却条件下切削仿真的研究

为了改善切削加工过程中切削温度高,刀具与工件发生粘连现象等不良影响,在切削中加入冷却因素,以达到较好的切削效果。针对较为常见的几种冷却方式(低温冷风、高压水射流、冷温冷风雾化射流、切削液),通过仿真做了一系列对比分析,分析了切屑形态、切屑形成速度、切削力、温度以及工件表面应力在不同冷却切削条件下的变化。通过比较发现,冷温冷风雾化射流的冷却效果最好。     

绿色加工中刀具磨损对表面粗糙度影响的研究

在切削镍基高温合金材料过程中,由于不稳定因素造成已加工表面粗糙度很难控制,尤其是刀具磨损直接影响着表面粗糙度。通过对冷风油雾、冷风和常温油雾等不同冷却切削条件下刀具磨损和工件表面粗糙度微观形貌的实验,研究了高速切削镍基高温合金材料时,在不同冷却切削条件下刀具磨损对工件表面粗糙度的影响,揭示了用冷风高速切削提高表面加工质量的规律。     

刀具冷却液油槽的改进

<正>众所周知,刀具在切削过程中将产生切削热,它可以传入刀具、切屑和工件中,并使它们温度升高,引起工件热变形,加速刀具的磨损.因此,在刀具设计时,对带有起定位作用的引导部分均设计有冷却液油槽,以便使切削部位散热降温.我厂设计的刀具,冷却液油槽形状如图1所示,但在使用中发现冷却效果不理想.据分析和实验,建议将冷却液槽改进为图2所示的形状.它与图1所示形状相比较,具有以下优点:(1)冷却液通道面积大,在同样的油压下,冷却液流入多,在切削面上冷却效果好.(2)油槽设计为与切削刃旋向相反的螺旋形状,使刀具在旋转的过程中,冷却润滑液有向切削表面压人的趋势.(3)加工不同的材料时,由于产生的切削热不同,可以选用不同角度的螺旋角,以改变冷却液的压力.螺旋角越大,油向下流出的压力越     

弧网式过滤机在集中过滤中的应用

在金属切削过程中，为提高切削效率，提高工件的精度和降低工件表面粗糙度，延长刀具使用寿命，达到最佳的经济效果，就必须减少刀具与工件、刀具与切屑之间的摩擦，及时带走切削区内因材料变形而产生的热量。要达到这些目的，采用性能优良的切（磨）削液往往可以明显提高切削效率，降低工件表面粗糙度，延长刀具使用寿命，取得良好的经济效益。切削液作用有如下四个方面：冷却、润滑、清洗和防锈。     

钛合金的高质高效超声振动切削加工

作为一种广泛应用于航空航天领域内的难加工材料,钛合金的高质高效切削一直是机械加工领域中的热点问题.针对其加工过程中的力热聚集问题,一种将高压冷却方式辅助于垂直于切削速度方向振动分离的超声振动切削加工方法被应用于其高质高效加工.首先,刀具和工件周期性的分离条件通过数学方法导出.随后基于此开展了钛合金的车削试验,通过设定不同的切削参数(切削速度、进给量和切深)和冷却参数(冷却液压力),研究了切削力、切削温度、刀具磨损过程、工件表面质量和刀具寿命与相关参数之间的关系.试验结果表明,在满足分离条件的情况下,高压冷却状态下的超声振动切削加工能有效降低切削力和切削温度、延缓刀具磨损速度、改善表面质量和提高刀具寿命.在冷却液压力20 MPa的条件下,钛合金的切削速度能提至400 m/min并保证工件表面质量Ra不超过0.4 μm,实现了刀具长寿命和工件高质高效的切削精加工.     

气体风冷高速铣削的刀具磨损研究

立铣刀高速铣削方式加工可显著提高淬硬钢模具的加工效率,但同时也存在切削温度高、刀具磨损快的问题。对刀具与工件的切削接触区域进行充分冷却及润滑是解决此问题的有效方法。对气体风冷高速切削展开刀具磨损研究,涉及两种气体冷却方法—压缩气体冷却法以及涡流管冷却法。实验结果表明,涡流管冷却法相比压缩气体冷却法可降低切削区域温度,有效减轻切屑粘结及粘结磨损现象,最终有效降低立铣刀刀刃的剥落宽度以及刀具磨损程度。     

干式镗削静电冷却系统的设计

静电冷却技术是用于干式切削中的一种新型冷却工艺。在金属切削加工过程中,电晕放电装置产生的活性气体,可以对刀具及工件进行冷却、润滑,以提高刀具的寿命和已加工工件的表面质量。以镗削加工为例,设计了具有外接气路的干式切削静电冷却系统,搭建了活性气体浓度测量平台,在不同气路中进行活性气体浓度衰减规律实验。该干式静电冷却系统应用于镗床切削加工,结果表明,此系统具有良好的可靠性和安全性,能够作为干式镗削的冷却装置在实际镗削加工中使用。     

润滑方式对高速铣削淬硬钢的影响

使用TiSiN和TiAlN涂层刀具在3种不同冷却润滑方式下,在高速加工中心上采用固定的切削工艺参数,对淬硬钢SKD11(HRC 62)进行切削试验,研究加工工件的表面粗糙度、切削力、刀具磨损及切屑形态的不同.结果 表明:TiSiN涂层铣刀相对于TiAlN涂层能更好地降低已加工面的表面粗糙度,减小切削力,降低刀具的磨损;在微量润滑(MQL)方式下,已加工面的表面粗糙度值低于干切削和冷风切削条件;在减小切削力、降低刀具磨损、改善切屑形态方面,冷风切削的效果优于干切削,MQL润滑方式增大了刀具切削力.     

硬质合金刀具高速切削Ti6Al4V合金时扩散磨损的数值模拟

应用通用商业有限元软件Deform-2D,对航空用钛合金Ti6Al4V进行了不同冷却润滑条件下的正交切削有限元模拟。在参考已有刀具扩散磨损率模型的基础上,利用有限元模拟出的刀具/工件接触区的切削温度与相对滑动速度等基本变量,对高速切削钛合金Ti6Al4V时的WC-Co类硬质合金刀具前刀面的扩散磨损率进行了预测,进而分析了切削介质的冷却与润滑作用对刀具扩散磨损率的影响。研究结果表明:切削介质的润滑作用对刀具前刀面的扩散磨损率具有较大影响,而切削介质的冷却作用则对刀具前刀面扩散磨损率无显著影响。     

钛合金车削中的低温油膜水滴冷却润滑技术

简述了低温油膜水滴(cryogenic Oils on Water,低温OoW)切削液的冷却润滑原理。通过测量常规浇注、低温冷风和低温OoW切削液三种冷却润滑方式下切削钛合金的切削温度、刀具寿命和工件表面质量的对比试验,研究低温OoW切削液的冷却润滑性能。试验结果表明,低温OoW切削液具有良好的冷却润滑效果,能有效降低切削温度、提高刀具寿命和降低表面粗糙度值,且在切削速度提高时,对比效果更为明显。     

Wear behavior of natural diamond tool in cutting tungsten-based alloy

Natural diamond tool is quickly worn out while cutting a workpiece made of a tungsten-based alloy. This paper presents a new approach to reduce tool wear: ultrasonic vibration cutting of a workpiece made of a tungsten-based alloy based on gas–liquid atomization cooling. An atomizer is a device which mixes carbon dioxide gas with vegetable oil and changes the liquid into minute droplets, which are carried by a stream of gas. Atomizer is also a device that incorporates a venture device to translate liquid into a gas stream. The atomized minute droplets act as the cooling and lubricating medium to protect the tools. The system is designed to ensure that droplets can spread all over the surface of a work piece. At a constant spindle speed, feed rate, and cutting depth, the experiments were carried out for investigating the effects of the tool vibration parameters, carbon tetrachloride liquid flow rate, carbon dioxide gas flow, and gas–liquid mass ratio on the tool wear. The experiments showed that the technology of ultrasonic vibration with gas–liquid atomization cooling effectively prolongs the tool life in cutting tungsten-based alloy.     

陶瓷刀具在大型薄壁件加工中的应用

从分析优质合金钢的薄壁件质量不合格的原因入手，结合难加工材料的高速切削机理，改进工艺流程。提出利用陶瓷刀具实现大型薄壁件高速切削的可行性，澄清了利用陶瓷刀具加工的几个误区，并对切削过程中的注意事项及切削参数的选择提出一些建议。实际使用表明在中型机床上利用陶瓷刀具可以实现大型薄壁件的高速切削，实现以车代磨，从而降低了生产成本，提高了生产效率，满足了产品的质量要求。     

Cutting tool damage in interrupted cutting

The shaping and turning of a workpiece with key ways, milling and the high speed turning of small workpieces, in which the risk of tool chipping and breakage decreases in the order given, exhibit three danger areas: tool entry, tool exit and cyclic heating and cooling. The relative importance of these depends on the dimensions of the cut, the cutting speed, the heating time/cooling time, the workpiece and tool materials, the shape of the tool and the geometry of the entry and exit. A better understanding of the phenomena occurring during tool entry is required, and therefore the cutting forces during entry and exit have been studied. The chipping caused by the exit phenomena has been explained using the results of a finite element study of the workpiece and the tool. The effect of rounding or chamfering the edges of carbide cutting tools for interrupted cutting, e.g. milling, is discussed and the work required before this can be optimized is outlined.     

切削液的供给净化与回收

切削液的正确供给、净化和回收,既可提高切削液的使用效果,保证工件加工质量,又可延长刀具寿命,降低加工成本.该文介绍了它们的新进展.     

EFFECTS OF COOLANT SUPPLY METHODS AND CUTTING CONDITIONS ON TOOL LIFE IN END MILLING TITANIUM ALLOY

Titanium machining poses a great challenge to cutting tools due to its severe negative influence on tool life primarily due to high temperature generated and strong adhesion in the cutting area. Thus, various coolant supply methods are widely used to improve the machining process. On account of this, tool life and cutting force are investigated based on dry cutting, flood cooling, and minimum quantity lubrication (MQL) techniques. The experimental results show that MQL machining can remarkably and reliably improve tool life, and reduce cutting force due to the better lubrication and cooling effect.     

EFFECTS OF COOLANT SUPPLY METHODS AND CUTTING CONDITIONS ON TOOL LIFE IN END MILLING TITANIUM ALLOY

Titanium machining poses a great challenge to cutting tools due to its severe negative influence on tool life primarily due to high temperature generated and strong adhesion in the cutting area. Thus, various coolant supply methods are widely used to improve the machining process. On account of this, tool life and cutting force are investigated based on dry cutting, flood cooling, and minimum quantity lubrication (MQL) techniques. The experimental results show that MQL machining can remarkably and reliably improve tool life, and reduce cutting force due to the better lubrication and cooling effect.     

INDUCTION-HEATED TOOL MACHINING OF ELASTOMERS—PART 2: CHIP MORPHOLOGY, CUTTING FORCES, AND MACHINED SURFACES

The induction-heated tool and cryogenically cooled workpiece are investigated for end milling of elastomers to generate desirable shape and surface roughness. Elastomer end milling experiments are conducted to study effects of the cutting speed, tool heating, and workpiece cooling on the chip formation, cutting forces, groove width, and surface roughness. At high cutting speed, smoke is generated and becomes an environmental hazard. At low cutting speeds, induction heated tool, if properly utilized, has demonstrated to be beneficial for the precision machining of elastomer with better surface roughness and dimensional control. Frequency analysis of cutting forces shows that the soft elastomer workpiece has low frequency vibration, which can be correlated to the surface machining marks. The width of end-milled grooves is only 68 to 78% of the tool diameter. The correlation between the machined groove width and cutting force reveals the importance of the workpiece compliance to precision machining of elastomer. This study also explores the use of both contact profilometer and non-contact confocal microscope to measure the roughness of machined elastomer surfaces. The comparison of measurement results shows the advantages and limitations of both measurement methods.     

Investigation of the feasibility and effectiveness in using heat pipe-embedded drills by finite element analysis

Drilling is a sufficiently severe machining process coupled with thermomechanical effect, in which mechanical work is converted to heat through the plastic deformation involved in chip formation and friction between tool and workpiece. The elevated temperature at the tool–chip interface has deleterious effects on the dimensional accuracy of the workpiece and shortens the service life of the tool. In this paper, the feasibility and effectiveness of heat pipe cooling in drilling operations are investigated numerically. A new embedded heat pipe technology was utilized to remove the heat generated at the tool interface in the foregoing cutting process. Numerical studies involved four different cooling conditions, i.e., dry drilling, fluid cooling, heat pipe cooling, and heat pipe cooling with cutting fluid supplied. The thermal, structural static, and dynamic characteristics of the drill were investigated using a numerical calculation with fast finite element plus solvers based on explicit finite element analysis software COSMOS\works. The results demonstrate that the heat pipe drill is most feasible and effective in the actual drilling processes.     

INDUCTION-HEATED TOOL MACHINING OF ELASTOMERS—PART 2: CHIP MORPHOLOGY,CUTTING FORCES,AND MACHINED SURFACES

ABSTRACT

The induction-heated tool and cryogenically cooled workpiece are investigated for end milling of elastomers to generate desirable shape and surface roughness. Elastomer end milling experiments are conducted to study effects of the cutting speed, tool heating, and workpiece cooling on the chip formation, cutting forces, groove width, and surface roughness. At high cutting speed, smoke is generated and becomes an environmental hazard. At low cutting speeds, induction heated tool, if properly utilized, has demonstrated to be beneficial for the precision machining of elastomer with better surface roughness and dimensional control. Frequency analysis of cutting forces shows that the soft elastomer workpiece has low frequency vibration, which can be correlated to the surface machining marks. The width of end-milled grooves is only 68 to 78% of the tool diameter. The correlation between the machined groove width and cutting force reveals the importance of the workpiece compliance to precision machining of elastomer. This study also explores the use of both contact profilometer and non-contact confocal microscope to measure the roughness of machined elastomer surfaces. The comparison of measurement results shows the advantages and limitations of both measurement methods.     

切削润滑液对车削噪声及表面质量的影响

在切削加工中， 使用切削液润滑，可减小刀具与工件面之间的摩擦，从而减小振动，减小切削噪声。配制适当的切削液，可使切削过程中的噪声降到机床本底噪声以下，工件表面质量也有明显提高。