精切活塞环槽侧向微进给系统设计

提出了一种精切活塞环槽时刀具侧向微进给方案:在切槽刀具切到槽底后,再作一个微量的侧向进给运动,对环槽的一侧进行微量切削,使加工后的环槽宽度恢复到理想尺寸,达到延长刀具寿命的目的。文中对该方案进行了研究、设计,给出了侧向微位移刀架总体结构设计以及配套的刀具设计方案,并对弹性铰链,刀具结构等关键问题给了出设计公式或设计参数。     

淬硬钢密封槽高效加工工艺研究

分析了动力转向器齿条活塞密封槽磨削工艺易出现的质量问题和采用硬车淬硬钢密封槽工艺的技术难点,提出了一种高效的淬硬钢密封槽加工工艺方案。采用正交试验法设计实验,得到不同工艺参数对刀具寿命的影响规律,并根据分析结果对车削工艺参数进行了优化。实践表明,车削淬硬钢密封槽时切槽刀径向和两侧面切削余量的选择最为关键。采用粗车密封槽,热处理后再精车密封槽的工艺方案不仅能保证加工质量、提高生产效率、降低成本,还绿色环保。该研究为齿条活塞密封槽的车削加工提供了依据,也为其他类似零件的加工提供了可资借鉴的经验。     

涂层硬质合金刀片微槽微织构复合设计

文章在涂层硬质合金刀片前刀面切屑刃近域微槽设计基础上,为了更好的降低刀片的切削温度,设计了(条纹型、波纹型、梳齿形)三种微织构形式,并将之与微槽复合形成刀具前刀面微结构造型,通过DEFORM3D仿真实验,研究了三种微织构参数对降温效果的影响,分别优选出三种微槽微织构复合刀具,并对比分析所优选出的三种微槽微织构复合刀具与原刀具及微槽刀具切削力及已加工表面残余应力。研究表明:新的微槽微织构复合设计均具有一定的降温效果,梳齿形微槽微织构降温效果最好;波纹型微织构的置入能够有效减低刀具的切削力,减少切削热的产生,而条纹型微织构的置入可以有效减少切削热向刀具的传递,从而降低刀具切削温度;与原刀相比,优选出的三种微槽微织构刀具能够有效增大工件表层的残余压应力。     

加工静态O型环槽的车刀片

Kaiser刀具公司的Thinbit车刀片为其加工静态O型环槽的Groove‘N Turn系列刀具增加了新品种。这种用于外径车削和表面切槽的刀片采用7°夹角,有两种亚微晶粒硬质合金牌号,还可以选择与之配套的刀柄和各种类型的涂层。     

转子叶片槽零偏角检具

叶片泵的转子在铣削零偏角叶片槽工序中,由于机床调整不当和更换刀具的疏忽,常出现角度误差a及a’,如图1所示。这一误差给后续磨槽工序增加了难度,因两侧磨削量不均,易造成薄片砂轮前角单边磨损,影响了槽的磨削质量和产品性能。这里介绍一种简便的检测     

橡胶压模余胶槽小议

<正> 橡胶压模的余胶槽(排料槽)系模具的非成型部分,故模具工作者对此往往不够重视。图一是一模两巢的胶套压模,下模中间部位沿型糟边缘已开制出余胶槽,两侧部位,因考虑距离模体边缘(起模槽)较近而省去     

微槽刀具切削GH4169的工件表面完整性研究

针对如何改善零件的已加工表面完整性,提高零件的服役能力,文章基于温度场形状开展切削GH4169的刀具前刀面微槽设计研究,设计并制备了新型微槽刀具,并将原刀具和微槽刀具加工后的工件表面完整性进行对比试验研究,结果表明:微槽结构改变了刀具的平衡力系,使其切削力和切削温度降低,进而使得在推荐切削参数下,使用微槽刀具切削的表面质量优于原刀具,粗糙度降低了22.96%,残余拉应力降低了30.7%,工件表面显微硬度随切削速度的增加而加剧,且微槽刀具切削后的工件硬化程度和深度均有所降低。     

切槽刀具

本文介绍一种用于加工环形槽的刀具。该刀具结构简单,使用方便。图1幅。     

连续变焦系统凸轮槽建模及加工方法优化

在机械补偿连续变焦光学系统中,核心零件曲线套筒变倍凸轮槽和补偿凸轮槽两侧面的加工精度和表面质量直接影响变焦系统在连续变焦过程中能否成像清晰、稳定。采用直纹面加厚的方式完成了凸轮槽建模,且在曲线点阵拟合的过程进行了公差控制。用四轴联动全顺铣的走刀方式,对进、退刀点进行特别处理完成凸轮槽的加工。经过实际加工验证,采用该方法大幅地提高了凸轮槽的加工精度和表面质量。     

人造金刚石新型槽刀的研制

本文针对硬质合金刀具切削中硅铝合金活塞槽存在的问题，研制出一种新型人造金刚石切槽刀，使用该刀，加工效率可提高二倍，加工成本降低６２％，并且还提高了加工精度。从本文研究结果可以看出，人造金刚石刀具加工硅铝合金与硬质合金刀具相比，具有许多优点，是值得进一步开发和推广的刀具，本文不仅探讨了人造金刚石切槽刀的制造，还探讨了对刀具各参数的检测。     

Effects of the friction coefficient on the minimum cutting thickness in micro cutting

In the ultra precision diamond cutting process, the rake angle of the tool is likely to become negative because the edge radius of tool is considerably large compared to the sub-micrometer depth of cut. The round edge of the tool might sometimes cause plowing results in a poor surface, or burnishing which results in a shiny surface depending on the depth of cut. This study deals with the relationship between the friction of a tool-workpiece and the minimum cutting thickness in micro cutting. Proposed is an ultra precision cutting model in which the tool edge radius and the friction coefficient are the principal factors determining the minimum cutting thickness with a continuous chip. According to the model, a smaller edge radius and a higher friction coefficient make the cutting depth thinner. The experimental results verify the proposed model and provide various supporting evidence.     

采煤机截齿刀体温挤压精密成形力学模型定量解析

采煤机截齿是一种用量极大的消耗性采煤工具。其刀体的传统生产工艺是铸造,或粗锻后切削加工,或直接用棒料切削加工,前者产品性能差,后两者材料利用率低,生产成本高。本文所述采煤机截齿刀体温挤压精密成形技术完全克服了上述缺点。从分析采煤机截齿刀体温挤压成形特点入手,采用功平衡原理求解变形力的近似解,推导出采煤机截齿刀体温挤压力的近似计算公式。从理论上确定了挤压力的主要影响因素及其变化规律,为该项新工艺的模具设计和设备选择提供了理论依据。     

PCBN刀具高速切削淬硬钢材料的研究

以PCBN复合片为刀具材料进行相关力学性能分析,并将其制成SNGN120408型刀具后在刀具机床上进行淬硬钢切削试验。分析结果表明:PCBN复合片的结合剂主要为TiN和TiB₂,其内部结构均匀,且有良好的致密性。切削试验表明:在干式切削淬硬钢的试验中,切削进给量以及切削速度对PCBN刀具的磨损有较为明显的影响。相比于切削速度,进给量对淬硬钢工件表面的粗糙度影响更大。PCBN刀具高速干式切削淬硬钢的磨损为黏结磨损、局部剥落和扩散磨损等多重磨损共同作用的结果。      

Impact of the cooling system on the cutting of medical cobalt chromium with ceramic cutting inserts

This paper presents a study of tool life, process forces and surface integrity. The focus is on the continuous turning of biocompatible cobalt chromium using ceramic cutting inserts and different cooling systems. The goal when using cooling lubricants with tungsten carbide tools is on the one hand to extend tool life time and on the other hand to achieve a better surface quality on the workpiece. When using ceramic cutting tool materials usually cooling lubricants are dispensable. The heating of the component and thus the reduction in strength is desired, since the ceramic cutting materials withstand higher temperatures. Tool life of ceramic cutting materials without cooling lubricants is often rather low. Therefore, cooling lubricants should help to extend the tool life. It will also be investigated how the different cooling systems affect the surface integrity of the workpiece. The investigations were performed under constant cutting parameters.     

Identification of the specific cutting force for geometrically defined cutting edges and varying cutting conditions

Cutting force modeling is a major discipline in the research of cutting processes. The exact prediction of cutting forces is crucial for process characterization and optimization. Semi-empirical and mechanistic force models have been established, but the identification of the specific cutting force for a pair of tool and workpiece material is still challenging. Existing approaches are depending on geometrical idealizations and on an extensive calibration process, which make practical and industrial application difficult. For nonstandard tools and five axis kinematics there does not exist a reasonable solution for the identification problem.In this paper a co-operative force model for the identification of the specific cutting forces and prediction of integral forces is presented. The model is coupled bidirectionally with a multi-dexel based material removal model that provides geometrical contact zone information. The nonlinear specific forces are modeled as polynomials of uncut chip thickness. The presented force model is not subjected to principal restrictions on tool shape or kinematics, the specific force and phase shift are identified with help of least square minimization. The benefit of this technique is that no special calibration experiments are needed anymore, which qualifies the method to determine the specific forces simultaneously during the machining process. In this paper, experiments with different cutting conditions are analyzed and systematically rated. Finally, the method is validated by experiments using different cutting conditions.     

Tool wear control in single-crystal diamond cutting of steel by using the ultra-intermittent cutting method

Excessive tool wear is a major drawback to the ultraprecision cutting of steel with geometrically defined single-crystal diamond tools. This paper presents a new approach to reduce this wear. In general, the wear of the diamond tool is due to chemical reactions such as diffusion into the steel, oxidation, graphitization, and carbide formation under cutting conditions of high temperature and high pressure. To suppress these types of chemical reactions, the contact time between the diamond tool and the steel in the cutting process was controlled by intermittent cutting method such as fly-cutting or milling. A series of intermittent cutting experiments were carried out to control the tool–workpiece contact time in one cutting cycle by changing the cutting speed and cutting length in each cutting cycle. The experimental results showed that the diamond tool wear was highly dependent on the tool–workpiece contact time, regardless of the cutting speed, and that the wear was greatly reduced by decreasing the contact time to less than 0.3 ms under these cutting conditions. It is expected that steel can be successfully cut with a single-crystal diamond tool by controlling the tool–workpiece contact time.     

Multi-grooved cutting tool to reduce cutting force and temperature during bone machining

The cutting temperature of a cutting tool are required to be low during bone machining for preventing damage to bone cells. However, conventional tools are practically the same as those used for metal cutting, and many operational limitations have been reported. In this study, a dedicated cutting tool was designed for reducing cutting force and temperature. A short contact between the workpiece and the cutting edge leads to a reduction in the cutting force. Furthermore, a straight-line edge improves surface roughness. The effectiveness was evaluated using bovine bone, and the cutting force was found to be decreased by about 40%.     

A new methodology for designing a curve-edged twist drill with an arbitrarily given distribution of the cutting angles along the tool cutting edge

The present study aims at the development of a new methodology for designing a curve-edged twist drill with an arbitrarily given distribution of the cutting angles along the tool cutting edge. The new methodology consists of 81 major mathematical equations and is developed using a method of mapping relevant planes and straight lines of a cutting tool (such as the cutting plane and the cutting edge) as corresponding image points and image lines on a projection plane. The developed methodology is used to intuitively and graphically analyze and determine the relationship between the orientation of the cutting edge and the cutting angles at each point on the cutting edge. A set of image points and image lines is established to calculate the cutting angles on the cutting edge of a twist drill, including the working tool rake angle, the working tool inclination angle, the working cutting edge angle, and the working normal rake angle. Three computer case studies are provided to show curved cutting edges that correspond, respectively, to a linear distribution of the working tool rake angle, a combined linear and uniform distribution of the working tool rake angle, and a linear distribution of the working tool inclination angle along the tool cutting edge. Finally, a set of metal drilling experiments is performed to compare the drilling torque and the thrust force between a conventional straight-edged twist drill and a new curve-edged twist drill that has a combined linear and uniform distribution of the working tool rake angle along the tool cutting edge. The experimental results show that the new curve-edged drill reduces the drilling torque by 28.5% and the thrust force by 24.6% on average.     

A chaotic cutting process and determining optimal cutting parameter values using neural networks

A model of an orthogonal cutting system is described as an elastic structure deformable in two directions. In the system, a cutting force is generated by material flow against the tool. Nonlinear dependency of the cutting force on the cutting velocity can cause chaotic vibrations of the cutting tool which influence the quality of a manufactured surface. The intensity and the characteristics of vibrations are determined by the values of the cutting parameters. The influence of cutting depth on system dynamics is described by bifurcation diagrams. The properties of oscillations are illustrated by the time dependence of tool displacement, the corresponding frequency spectra and phase portraits. The corresponding strange attractors are characterized by correlation dimension. The vibrations are characterized by the maximum Lyapunov exponent. The manufactured surface at the first cut is taken as the incoming surface in the second cut, thus incorporating the influence of the rough surface in the model. Again, bifurcation diagrams, the correlation dimension and the maximum Lyapunov exponent are employed to describe the effects of parametrical excitation on the cutting dynamics. A cost function is defined which describes the dependence of the cutting performance on cutting depth. The cost function is empirically modeled using a self-organizing neural network. A conditional average estimator is applied to determine the optimal value of the cutting depth applicable as a control variable of the cutting process.     

Prediction of the cutting forces for chamfered main cutting edge tools

A new cutting model of various tool geometries for tools with a chamfered main cutting edge has been built. Theoretical values of cutting forces were calculated and compared with the experimental results; the forces predicted by this model were consistent with the experimental values. Special tool holders were designed and manufactured to obtain various tool geometries. Cutting experiments were conducted on a carbon steel to examine the mechanism of secondary chip formation; the relationship between the shapes of secondary chips and tool geometries was observed.