圆弧车刀在工具磨床上的刃磨工艺

通常圆弧车刀的前刀面是平面型,其后刀面形面的正确磨削是刃磨的关键。为此就要求砂轮的工作曲面形状与车刀后刀面法剖面的椭圆曲线相吻合,而对砂轮进行正确的修形。对于圆弧刃半径R≤20毫米的车刀可采用投影法将砂轮修整成轴向截形为椭圆曲线的成形砂轮前进磨削,当车刀圆弧刃半径R>20毫米时,由于受盘型砂轮厚度的限制,采用上述方法较为困难。本文介绍利用万能工具磨床的可调性,根据车刀和砂轮磨削状态的相对位置关系,对圆弧车刀后刀面进行刃磨的方法。     

梯形螺纹精车刀的改进与应用

通过分析梯形螺纹精车刀纵向工作前角 (γ0 )对牙形精度的影响 ,提出对梯形螺纹精车刀的前刀面进行改进的措施 ,保证了梯形螺纹牙形的精度 ,使刀具刃磨、研磨更方便 ,提高了刀具的使用寿命。     

变曲率曲面构型前刀面车刀的减阻性能研究

为了降低切削过程中的阻力,通过对河狸牙齿前刀面的构型分析,设计出了具有变曲率准线曲面构型前刀面的车刀。在0.15～0.5 mm背吃刀量下,选取4种前刀面构型进行仿真切削对比分析。仿真结果表明,余弦函数准线构型前刀面刀具的切削力相对于其他构型前刀面刀具的降低了3.5%～11.96%,并通过直角切削实验对仿真结果进行了验证。随后通过仿真实验对余弦准线函数进行参数优化,得出了切削力随周期和幅值改变的变化规律。优化结果表明：当背吃刀量与前刀面余弦函数准线一个周期的比值为40%左右时,减阻效果最为显著。所设计的变曲率构型前刀面车刀不仅有效降低了切削力,还为金属切削刀具的构型设计提供了新思路,具有较强的应用价值。     

车刀智能化刃磨的理论研究与仿真分析

针对现有车刀刃磨方法的局限性,建立车刀各刀面刃磨数学模型,设计出刃磨装置,并进行仿真分析,通过车刀位姿调整,实现任意一个被刃磨刀面与砂轮的磨削平面重合,以获得最佳刃磨成形表面质量,最终为开发机床刀具刃磨中心奠定理论基础.     

车刀刃磨的调整计算

车刀的标注角度为γ_0、λ、(γ_(?),γ_p)等,只是把车刀看作一个几何体,并没有涉及车刀在夹具中(三向转台)绕坐标轴旋转的概念。而车刀在此类夹具中刃磨时角度的调整,却必须由坐标轴转动一定的角度来达到。本文介绍用三向转动夹具刀磨前刀面时角度的调整计算。     

麻花钻后刀面螺旋锥面刃磨法的研究

在分析和研究锥面刃磨法和变导程螺旋面刃磨法的基础上,提出了麻花钻后刀面螺旋锥面刃磨法并构建了相关的数学模型。采用螺旋锥面刃磨法不仅能得到麻花钻直线主刀刃和更理想的后角值分布,而且解决了采用变导程螺旋面刃磨法钻芯强度较弱以及采用锥面刃磨法存在的后刀面"翘尾"现象。     

基于智能化刃磨的车刀位姿调整

本文建立了外圆车刀各刀面的方程式，给出了各刀面从安装初始位姿到刃磨位姿的坐标变换过程．给出了车刀位姿调整机构的传动原理，为智能车刀刃磨机的研制提供了必要的技术保证。     

车刀前刀面温度的计算及参数调整

分析了车刀前刀面温度分布的计算方法及影响因素 ,认为车刀前刀面温度分布与切削力关系密切 ,而切削力不仅与切削速度而且与车刀位置有关。提出并通过计算实例证明合理调整车刀温度计算经验公式中的参数可显著提高计算精度     

球头立铣刀端刃前刀面的刃磨仿真

以Solidworks为开发平台,对球头立铣刀端刃前刀面的刃磨过程进行仿真.建立了一套铣刀端刃前刀面的虚拟加工系统,通过刃磨参数优化,可实现端刃前刀面与周刃前刀面的光滑连接和良好的"S"刃形.模拟仿真发现端刃前刀面有一个很窄的刃带,分析了砂轮姿态对刃带宽度的影响.     

麻花钻后刀面建模方法的优化

在分析和研究麻花钻锥面刃磨法、变导程螺旋面刃磨法及螺旋锥面刃磨法的基础上,提出了横刃及圆柱螺旋线扫掠法,并构建了其数学模型。该方法预先设计横刃,以横刃及螺旋线复合扫掠的方法构建主后刀面。采用该方法得到了麻花钻直线主刀刃和理想的横刃及后角值分布;解决了采用变导程螺旋面刃磨法钻芯强度较弱以及采用锥面刃磨法存在的主后刀面"翘尾"现象;解决了两主后刀面磨削自然形成横刃形状的可控性。     

Wear mechanism of the loose layer on the rake face of a new cemented carbide micro groove turning tool

The loose layer can appear on the rake face of a turning tool under certain cutting conditions and have an important influence on the rake face wear. In this paper, wear morphology and wear mechanism of loose layer on the rake face of the original turning tool and the new cemented carbide micro groove turning tool developed independently during the cutting process are studied, by the combination of theoretical analysis and cutting test. And the relationships between the diffusion wear and the adhesive wear of the loose layer on the rake face of the new micro groove turning tool are further analyzed and revealed. The research results show that the loose layer on the rake face of two turning tools is caused by the diffusion wear, which is formed by the brittleness-weakening of tool material in the region resulting from elements diffusion. Meanwhile, the wear degree of the rake face of tools is aggravated by the mutual promotion of diffusion wear and adhesive wear. In the normal wear stage, the degree of looseness and brittleness of the rake face of the original turning tool is greater than the one of the micro groove turning tool. In the severe wear stage, cobalt elements in the rake face of the two turning tools are dissolved and diffused in varying degrees, which further aggravates the brittle-weakening of materials in the region. But the degree of loose brittleness of the rake face of the original turning tool is still greater than the one of the micro groove turning tool. It can be concluded that the micro groove on the rake face of the new turning tool can improve the rake face wear to a certain extent.     

带卷屑槽刀具最大前角的数学模型与求解

由于现代数控刀具都设计有卷屑槽,从而使其前刀面不是平面,而是曲面。本文针对前刀面为圆柱面的一部分时,采用向量矩阵法建立最大前角计算的数学模型,应用该模型可以在给定条件下,计算曲面型前刀面车刀的最大前角和其它重要的几何参数。最后,给出了计算实例。     

曲面型前刀面实际切削前角的建模与分析

采用向量矩阵的方法，建立了曲面型前刀面车刀实际前角计算的数学模型，利用该模型可以计算出法剖面、主剖面和流屑剖面内前角的大小，从而为车刀的结构设计和卷屑槽槽型的研究提供了基础数据。最后给出了计算实例并进行了分析。     

On the contribution of primary deformation zone-generated chip temperature to heat partition in machining

In machining, the percentage of heat flux that enters the cutting tool can have a critical impact on tool wear especially in dry cutting or high speed machining. In previous work, heat partition was evaluated by iteratively reducing the secondary deformation zone heat flux to the tool until the finite element simulated temperatures matched the experimental measured rake face temperatures. This follow-on work quantifies the contribution of primary zone heat flux to heat partition in machining. In this study, an analytical model was used to evaluate the rise in chip temperature due to primary deformation zone heat source. The heat partition and thermal modelling on the rake face was then conducted with an appropriate initial rake face temperature. Thus primary zone heat loads and shear-force-derived secondary zone heat flux were applied in finite element transient heat transfer analysis to evaluate heat flux into the cutting tool. External dry turning of AISI/SAE 4140 with tungsten carbide-based multilayer TiCN/Al₂O₃-coated tools was conducted for a wide range of cutting speeds between 314 and 879 m/min. Results further support the dominance of secondary zone heat flux on heat partition. The contribution of primary zone heat generation to the cutting tool heat flux in machining was less than 9.5 %. These findings suggest that, to address the thermal problem in machining, research and development should also focus on reducing friction on the rake face (e.g. coating innovations) and reducing contact areas (e.g. rake face design) in addition to the modification of shear angle and hence primary zone heat intensity.     

纯钒车削刀具磨损表面形态及机理研究

对金刚石刀具、涂层刀具及硬质合金刀具车削纯钒时刀具磨损形态及其磨损机理进行观察和分析.结果表明,在所选取条件下,不同刀具材料对工件材料切削时表现出的刀具磨损形态主要为前刀面磨损、后刀面磨损、微崩刃、剥落和粘结等.刀具的前刀面主要是沿切屑流出方向的沟槽形月牙洼磨损,而后刀面以粘结磨损为主.CD10刀具和H10非涂层刀具具有较佳的切削性能,而H13A非涂层刀具和GC1025涂层刀具不适于纯钒车削.     

Prediction of cutting temperature distributions on rake face of coated cutting tools

Coated cutting tools have been widely employed in metal cutting operations owing to its excellent abrasion resistance and heat transfer performances. Rake face temperature is the primary factor that determines the temperature distribution in the cutting tool body. Based on the heat source theory, a new prediction model is proposed in this paper to forecast the temperature distribution on the rake face. Infrared image is used to develop a new turning experimental apparatus to measure the rake face temperature of coated tool during the cutting process. Rake face temperature measurement results are used to verify the proposed model prediction results of temperature distribution. Several cutting tests are carried out with monolayer coated tools in the machining of H13 hardened steel. The rake face temperature in monolayer coated tool for machining H13 shows an increase trend as the cutting speed increases. The influence parameters including thermo-physical properties and tool/workpiece frictional coefficient of coating material on temperature distribution in coated tools are discussed and illustrated. The research results presented in this paper can help to access the potential of coated tools used in the hardened steel machining.     

平面铣削刀具前刀面瞬态切削温度的研究

刀具切削温度对刀具寿命、刀具磨损等有重要影响。因此在实际加工之前预测出刀具温度,对合理选择切削参数、优化数控程序等均具有重要意义。平面铣削等断续切削过程的热条件不同于车削等连续切削过程。用数学物理方法建立了平面铣削过程刀具的一维传热学模型,用解析的方法预测平面铣削过程中刀具前刀面的温度分布,考虑了刀具切出时空气强化对流散热对刀具前刀面温度的影响。结果表明,刀具切入时间和切出时间对刀具温度有较大影响。用文献中断续车削刀具温度实验数据对铣削刀具前刀面温度的传热学预测模型进行了验证,结果表明二者趋势一致,但平面铣削预测的刀具温度略低于断续车削的刀具温度。     

涂层刀具车削淬硬钢时前刀面摩擦系数的自组织特征

采用四种硬质合金涂层刀片对45和T10A淬硬钢两种材料进行了正交切削试验,通过所测得的三向切削力计算了前刀面平均摩擦系数,详细分析了前刀面摩擦系数随切削过程的变化情况,以及切削参数对摩擦系数的影响。结果表明前刀面摩擦系数随切削过程的进行迅速减小并趋于稳定,表征了涂层刀具切削淬硬钢时的自组织现象。     

CN35硬质合金涂层刀具高速车削淬硬钢的磨损与破损形态

借助于扫描电镜照片和能谱分析,对高速车削淬硬45钢时CN35硬质合金涂层刀具的失效形态及其机理进行了观察和分析。结果显示,在高速切削条件下,涂层刀具的失效形态主要分为破损与磨损两种,刀具正常磨损失效过程仍然遵循常规切削条件下三个阶段的程序。刀具破损失效发生在低速切削阶段,且随着切削速度的提高,破损部位由后刀面转移到前刀面;高速切削时,刀具失效形式倾向于后刀面磨损、边界磨损和切削刃斜面磨损,因高热、粘结、疲劳、氧化、扩散和热裂等原因造成刀具切削功能丧失。     

Improving waviness of bore in precision hard turning by pressurized coolant

Precision hard turning is an emerging innovated machining technology for machining hardened workpiece (60~62 HRC) with characteristic of better flexibility, high production rate, and cost saving. However, one of problem in this process is that it is difficult to remove the thermal distortion of the workpiece induced by the heat generated during the process, especially in the case of precision hard turning of bore. In this paper, pressurized coolant was used in a precision hard turning of bore, with polycrystalline cubic boron nitride as the tool materials, to reduce the thermal distortion of the machined part such as form error and to improve its waviness. The pressurized coolant jet was directly delivered under the chip on the rake face. Experimental result indicated that form error induced by the heat has been reduced, and waviness of the bore was improved with use of pressurized coolant. Crater wear is smaller under pressurized coolant compared to dry cut due to lower rake face temperature and shorter contact length between chip and workpiece.