Optimization of delamination factor in drilling medium-density fiberboards (MDF) using desirability-based approach

Medium-density fiberboards are finding increased applications in furniture and domestic industries. Drilling of these materials cannot be avoided. Delamination associated in drilling is the serious problem and this problem should be addressed further. This paper presents the systematic experimental investigation, analysis and optimization of delamination factor in drilling of medium-density fiberboards (MDF). Experiments were conducted on CNC drilling machine at various cutting conditions. The parameters considered for the experiments are cutting speed, feed rate and drill diameter. An empirical model has been developed for predicting the delamination factor at entry and exit of the holes in drilling of MDF boards. Desirability function based approach is employed for the optimization drilling parameters for minimizing the delamination factor at entry and exit in drilling of MDF boards. The influences of different parameters and their interactions are studied in detail and presented in this study.     

用高转速微电极电解钻削深小孔

针对难切削材料的深小孔加工,提出一种有效排屑、迅速补充电解液的新工艺——高转速微螺旋电极电解钻削加工工艺,并对该工艺进行了机理分析与试验研究。研究了电极转速、电压、脉冲频率、进给速度等工艺参数对深小孔电解钻削加工精度和稳定性的影响,提出合理匹配上述参数可在较高加工效率下获得高的加工精度和加工稳定性。基于硬质合金微螺旋电极用自行研制的高精度微细电解系统成功地在高温镍基合金GH4169上加工出了一组孔径小于0.5mm、深径比大于10、形貌较好,锥度较小,侧壁陡直,进出口边缘锐利的深小孔。试验结果表明,高速电解钻削加工工艺在深小孔加工方面很有潜力。     

高速透平单斜齿轮弹热变形及其修形研究

针对高速透平单斜齿轮传动在啮合过程中产生的啮入冲击大、齿向偏载明显的问题,对造成上述现象的单斜齿轮弹性变形和热变形进行了研究,提出了适合高速透平单斜齿轮的修形措施。对齿廓修形中的齿顶修形高度通过二种不同的计算方法进行了比较,确定了比较合适的齿顶修形高度计算方法;对计算齿顶修形量时要考虑的基节偏差,齿形误差等作了量化处理;从而确定了高速透平单斜齿轮的齿廓修形和齿向修形方法;应用该方法对一台高速齿轮箱产品的单斜齿轮实施了修形,并与同等线速度未修形的高速齿轮箱进行了空负荷试车数据对比。研究结果表明,修形齿轮箱的噪声下降了3 d B(A)~4 d B(A),振动降低了2μm~3μm;可见通过修形能有效地改善轮齿的啮合性能,降低振动和噪声。     

Effect of tool wear on delamination in drilling composite materials

Among all machining operations, drilling using twist drill is the most frequently applied for secondary machining of composite materials owing to the need for structure joining. Delamination is mostly considered as the principal failure model in drilling of composite materials. Drill wear is a serious concern in hole-making industry, as it is necessary to prevent damage of cutting tools, machine tools and workpieces. The industrial experience shows the worn drill causes more delamination. This paper presents a comprehensive analysis of delamination caused by the drill wear for twist drill in drilling carbon fiber-reinforced composite materials. The critical thrust force at the onset of delamination for worn drill is predicted and compared with that of ideal drill. The experimental results demonstrate that though the critical thrust force is higher with increasing wear ratio, the delamination becomes more liable to occur because the actual thrust force increases to larger extent, as the thrust factor (Z) illustrates. Compared to sharp drill, the worn twist drill allows for lower feed rate below which the delamination damage can be avoided.     

高速渐开线斜齿圆柱齿轮齿廓修形技术研究

高速渐开线斜齿圆柱齿轮啮合频率高且传递功率大,为使高速齿轮箱平稳运行,减少由于轮齿受载变形和制造安装误差引起的啮入、啮出冲击,降低齿轮箱运行噪声并改善其润滑状态,齿廓修形十分重要.利用Pro/E软件建立斜齿轮啮合模型,通过接口程序,将模型导入ANSYS-Workbench软件中进行仿真分析,得出齿廓修形的各项参数.经验证,修形后的齿轮等效应力峰值略有上升,而接触应力峰值大幅降低,且消除了干涉,提高了高速齿轮传动的平稳性.     

变质M2高速钢稀土离子硫碳氮共渗研究

对Y-K-Na复合变质的M2高速钢进行离子硫碳氮共渗和稀土离子硫碳氮共渗处理,研究稀土元素对复合变质M2高速钢离子硫碳氮共渗组织和性能的影响。试验结果表明:稀土元素改善变质M2高速钢渗层组织,提高表面硬度,使渗层硬度梯度平缓,可有效地提高其抗摩擦磨损的能力。     

全液压钻机调速方案的探讨

全液压钻机的速度调节有多种方法,每种方法都有各自的特点,调节方式的可靠性和实用性对全液压钻机的性能有较大的影响.介绍了全液压钻机在施工过程中,实现钻具进给和回转执行部件调速系统的几种方案,分析了各种调节方法的优点及存在的问题,并提出钻机应采用的较合理的调速方式.     

Realization of micro EDM drilling with high machining speed and accuracy by using mist deionized water jet

In electrical discharge machining, both the gas and liquid dielectric have unique advantages and inevitable disadvantages. The mist medium with a special property between gas with liquid is expected to have a better performance in EDM. In this paper, the performance of mist deionized water jet has been studied based on the disadvantages of deionized water in deep micro hole drilling: electrolysis action, electrophoresis action and gap-contamination by debris. Based on the analyzation on the advantages of mist jet, three projects of experiments have been done to verify its performance on the suppressing of electrolysis action and improving the debris exhaust. The results show that the micro EDM drilling with high machining speed and accuracy can be realized with mist jet. This method is particularly effective in deep micro hole drilling, since deeper holes can be obtained at faster machining speed with mist jet due to its significant improvement in debris exhaust.     

A preliminary assessment of high speed tool steels manufactured from powder for rolling bearing materials

High speed tool steels manufactured from powder were assessed under arduous conditions of rolling contact and compared with conventional materials using an accelerated service simulation test. Metallographic investigations revealed factors influencing performance. Material manufactured from powder was generally found to be inferior to vacuum-remelted material due to poor structure, porosity, high interstitial nitrogen content and other manufacturing variables. Sound homogeneous material with uniform fine carbide distribution and gas content comparable with those of conventionally cast material appears potentially suitable for rolling bearings. The improved performance at elevated temperature may be due to metallographic changes, deleterious interstitial nitrogen content being reduced by a precipitation process.     

高速钻削碳纤维复合材料加工参数对入口分层的影响研究

高速切削技术一直以来都是提高生产效率和节约成本的关键技术。碳纤维复合材料以其耐磨性、耐腐蚀性等一系列优点倍受人们的青睐。研究了碳纤维复合材料在高速钻削过程中切削速度、进给速度和钻头刀尖角对钻削入口分层的影响;利用三水平的全因子分析法进行钻削试验,同时将得到的分层因子建立二元非线性回归模型,并进行方差分析和响应面分析。研究结果表明:分层对进给速度的敏感性更强;随着切削速度的提高,分层因子逐渐减小;小的刀尖角更有助于获得好的加工孔质量。所构造回归模型的预测结果与试验结果基本一致,表明该模型可以有效地预测钻削表面的分层状况。     

高速装备前瞻自适应速度优化算法

为了实现高速加工中进给速度的高速衔接,避免因加速度突变导致对数控设备的冲击,提出了一种基于插补前S曲线加减速的前瞻自适应速度优化算法。该算法能够根据加工段的过渡情况自动调节预读段数。以进给速度最大化为目标,在预读段衔接进给速度限制和加工过程平滑减速的约束条件下,根据离散化S曲线加减速规律求解最优衔接进给速度。将求得的最优衔接进给速度作为相应加工段的实际末速度,来实现加工段的速度控制。给出了该算法在高速数控系统中的实现方法,并在管切割数控系统中得到了应用。实验结果表明,该算法能够实现进给速度的高速、平滑衔接,满足高速加工的要求。     

高速高加速堆垛机速度控制曲线研究与优化

将以高速高加速堆垛机作为研究对象,采用动力学分析并利用叠加原理得到立柱动态挠曲变形公式,分析影响立柱变形的因素。提出一种新型速度曲线优化控制方案,当进行长距离作业,堆垛机速度可以到达最大设计速度时选择S型速度控制曲线,当运行短距离作业,堆垛机速度无法达到最大设计速度即需减速制动时选择三角函数型速度控制曲线。此方案使堆垛机速度加速度变化连续平滑,抑制立柱变形而产生摆动,提高堆垛机稳定性。     

高速切削技术及高速切削可转位铣刀的研究

高速切削是先进制造技术中最重要的加工工艺之一，而切削刀具是实现这一工艺的关键。论文介绍了高速切削技术，以及高速切削技术要求的高速切削刀具，特别说明的是高速切削铣刀；论述了高速切削的可转位铣刀的特点、切削刀具材料和刀体结构。     

高速切削技术的发展与展望

结合国内外高速切削技术的研究现状,介绍高速切削的概念、国内外发展动态及其相关技术的发展;探讨高速切削的应用领域;分析高速切削研究现存问题并展望高速切削的发展趋势和未来研究方向。     

A study of the effect of palm oil as MQL lubricant on high speed drilling of titanium alloys

The main objective was to study the potency of MQL palm oil (MQLPO) as a lubricant in the high speed drilling of Ti-6Al-4V. For the comparison, MQL synthetic ester (MQLSE), air blow and flood conditions were selected. Uniform flank wear, micro-chipping, thermal cracking and flaking were the dominant tool failure modes. It was found that MQLSE and MQLPO gave comparable performance with the flood conditions. In addition, MQLPO outperformed MQLSE on the cutting forces, temperature, power and specific cutting energy. This shows that palm oil can be used as a viable alternative to synthetic ester for MQL lubricant.     

Effect of drilling speed on the required torque and thrust force for non-ferrous materials

Constant-feed-rate drilling tests under conditions of dry cutting were performed on three non-ferrous materials, namely free machining brass, aluminium and lead. The tests covered a wide range of cutting speeds. Both thrust forces and torques were affected by the drill diameter and by speed variations. Empirical relationships between the thrust force, the torque and the cutting parameters were derived for the materials used.     

高速加工必须具备的条件

以生产精密机床见长的瑞士MIKRON公司近年来开发的高速、高精密加工中心深受中国用户的青睐。在CIMT2003展会上，他们展出了多台技术水平高的精密高速加工中心。本刊采访了MIKRON公司中国代表处的陈民先生，请他谈谈MIKRON展品的特点和高速加工技术。     

高速切削机床进给系统

介绍了高速切削机床的直线进给系统,包括电-机伺服进给和直线电机驱动的两种进给系统的结构组成、工作原理、精度和性能要求、应用范围,以及进行改进和提高的措施。     

Components for high speed atomic force microscopy

Many applications in materials science, life science and process control would benefit from atomic force microscopes (AFM) with higher scan speeds. To achieve this, the performance of many of the AFM components has to be increased. In this work, we focus on the cantilever sensor, the scanning unit and the data acquisition. We manufactured 10 microm wide cantilevers which combine high resonance frequencies with low spring constants (160-360 kHz with spring constants of 1-5 pN/nm). For the scanning unit, we developed a new scanner principle, based on stack piezos, which allows the construction of a scanner with 15 microm scan range while retaining high resonance frequencies (>10 kHz). To drive the AFM at high scan speeds and record the height and error signal, we implemented a fast Data Acquisition (DAQ) system based on a commercial DAQ card and a LabView user interface capable of recording 30 frames per second at 150 x 150 pixels.