6-Axis control cutting of overhanging curved grooves by means of non-rotational tool with application of ultrasonic vibrations

This paper presents a new machining method that efficiently cuts overhanging curve grooves on wall surfaces without causing a collision between the tool and the workpiece. It also describes the development of software for 6-axis control grooving and the effect of applied ultrasonic vibrations (USV) in cutting overhanging grooves (OHG). In general, rotational tools are used to produce grooves, thus resulting in long circular arc segments at the cutting end points, as well as placing restrictions on the manufacture of grooves with continuous change in curvature, while ensuring that they do not overshoot the side clearance angle of the cutting edge with the groove. The study aims at machining OHGs presently impossible to machine by conventional methods. From the experimental results, it was found that the new machining method, which is 6-axis control cutting using a non-rotational tool with the application of USV, is capable of cutting an OHG on wall surfaces correctly.     

Creation of V-shaped microgrooves with flat-ends by 6-axis control ultraprecision machining

The use of diffractive optics having surface appearance like diffraction grating or Fresnel lens, which consist of a number of microgrooves with various shapes is analyzed. One of them is flat-end microgrooves having no slope at the end. The existence of a slope limits the design of microgrooves and causes unnecessary diffraction of light and losses. Thus, the slope must be eliminated. The study deals with the creation of curved V-shaped microgrooves with two flat-ends on a curved surface by using 6-axis control non-rotational cutting tools. The proposed method shows the effectiveness in creating flat-ended curved microgrooves on curved surfaces.     

Creation of Flat-End V-Shaped Microgrooves by Non-Rotational Cutting Tools

The study deals with the creation of V-shaped microgrooves with flat-end, which play an important role in case of generating intermittent grooves. Microgrooves by use of rotational cutting tool have a long radius in disengagement from the workpiece. Thus, two cutting methods by use of non-rotational cutting tool are devised so that V-shaped microgrooves with flat-end can be created. The first method makes use of straight chips generated under some cutting condition. Non-rotational cutting tool compresses the chips at the groove end and cuts the excessive parts of chips over the plane. The second method is to transcribe the surface of a tool indented vertically into a workpiece. As a result, it is experimentally found that the methods enable the creation of flat-end microgrooves.     

基于不旋转轴肩的铝镁异种材料搅拌摩擦焊

焊具是搅拌摩擦焊的核心,对焊接质量起至关重要的作用. 利用不旋转轴肩焊接系统对6061-T6铝和AZ31B镁合金进行连接,重点分析传统和不旋转轴肩焊接系统下接头成形和力学性能等. 结果表明,与传统工艺相比,采用不旋转轴肩工艺的接头表面成形更加光滑,焊核区以典型铝镁混合的叠层结构为主,且铝镁冶金结合界面呈弯曲状,有效地增强了铝镁异种材料的机械咬合效果;焊缝区金属间化合物层明显减小,其主要是由不旋转轴肩增强焊核区材料的搅拌效果并起到“热沉”的作用所致. 采用不旋转轴肩的接头最大抗拉强度为137 MPa,较传统工艺提高了28%.     

超声振动超精密车削Ti6Al4V的表面质量研究

为研究超声振动辅助超精密车削Ti6Al4V切削性能,使用Son-x公司的UTS one设备使单晶金刚石刀具在切削方向振动,使用350FG摩尔Nanotech 4轴机床进行加工,采用四因素三水平正交试验,试验因素为切削速度、切削深度、进给速度和刀具振幅,切削力、表面粗糙度为评价指标。采用Zygo的Nexview 8050三维光学表面轮廓仪测量表面粗糙度;采用Kistler 9256B三相测力仪测量主切削力、进给抗力、切深抗力;采用日立TM3000扫描电镜对切屑进行观察。结果表明：切削速度对表面粗糙度和切削力的影响最大,切削深度和刀具振幅影响次之,进给速度对表面粗糙度和切削力均无显著影响;提高刀具振幅从总体趋势上可以降低切削力和表面粗糙度;随着切削速度的提高,即使切削速度远低于传统公式中计算出来的临界切削速度,切屑也会从平整带状变为两侧呈规律性锯齿状的带状,进而成为散裂状并且中间出现裂纹的切屑,在刀具振幅下降的过程中,以上现象更为明显。     

机器学习辅助下的五轴数控铣削刀轨优化

针对铣削加工过程中刀具挠度变形的自动补偿问题,提出了一种用于五轴数控加工的刀轨自优化方法.首先,该方法从铣削加工材料去除仿真中获得工艺条件,且将计算出的切削条件与相应的形状误差测量相关联;其次,采用基于统计学习理论的支持向量回归(Support Vector Regression,SVR)来预测所产生的形状误差,并进行...     

Cutting force prediction in ball end milling of sculptured surface with Z-level contouring tool path

This paper presents an approach to predict cutting force in 3-axis ball end milling of sculptured surface with Z-level contouring tool path. The variable feed turning angle is proposed to denote the angular position of feed direction within tool axis perpendicular plane. In order to precisely describe the variation of feed turning angle and cutter engagement, the whole process of sculptured surface milling is discretized at intervals of feed per tooth along tool path. Each segmented process is considered as a small steady-state cutting. For each segmented cutting, the feed turning angle is determined according to the position of its start/end points, and the cutter engagement is obtained using a new efficient Z-map method. Both the chip thickness model and cutting force model for steady-state machining are improved for involving the effect of varying feed turning angle and cutter engagement in sculptured surface machining. In validation experiment, a practical 3-axis ball end milling of sculptured surface with Z-level contouring tool path is operated. Comparisons of the predicted cutting forces and the measurements show the reliability of the proposed approach.     

Predictive force model for ball-end milling and experimental validation with a wavelike form machining test

This paper presents a predictive force model for ball-end milling based on thermomechanical modelling of oblique cutting. The tool geometry is decomposed into a series of axial elementary cutting edges. At any active tooth element, the chip formation is obtained from an oblique cutting process characterised by local undeformed chip section and local cutting angles. This method predicts accurately the cutting force distribution on the helical ball-end mill flutes from the tool geometry, the pre-form surface, the tool path, the cutting conditions, the material behaviour and the friction at the tool-chip interface. The model is applied for a complex surface which is a wavelike form used as a validation machining test. The results are compared with experimental data obtained from ball-end milling tests performed on a 3-axis CNC equipped with a Kistler dynamometer.     

High-precision machining by measurement and compensation of motion error

This paper describes a systematic method to model and compensate geometric errors of machine tools. In order to separate geometric errors from other errors, measured errors are analyzed in the frequency domain by using the Fourier series. Then, the frequency components corresponding to geometric errors are selected based on the repeatability of their wavelength. Finally, the components are reconstructed and forwarded for the compensation by a fine motion drive. A CNC machine tool with a fine motion mechanism on the Z-axis was developed to compensate the error components in the Z direction on the XY plane. A flat surface machining with non-rotational cutting tools was tested to validate our approach. On the plane of 45 mm×70 mm, the fluctuation of the relative displacement was reduced from 1.3 to 0.5 μm P-V. Machining experiments with a single-crystal diamond tool were also carried out and the straightness of the profile curve was reduced from 1.0 to 0.4 μm. The result of the experiments showed that the geometric errors were compensated separately from the vibration due to the bending mode of the machine column.     

5-axis Control Ultra-precision Machining of Complex-shaped Mirrors for Extreme Ultraviolet Lithography System

The study deals with the manufacture of novel mirrors, an arc-shaped fly-eye mirror and a rectangular fly-eye one, for an extreme ultraviolet lithography system. Both mirrors have a complex reflective surface consisting of many small spherical mirror elements. A method is proposed to accurately realize such mirrors, using ultra-precision 5-axis control machining. The method enables to manufacture spherical surfaces with any radius, without changing the tool shape. Furthermore, another advantage of the method is that the sphericity of the resulting surfaces is independent of tool shape accuracy. By using this method, two kinds of fly-eye mirror with sixteen mirror elements are successfully fabricated.     

大型龙门式五轴加工中心仿真系统在UGNX7．5上的建立和应用

对数控编程计算机碰撞仿真加工系统进行分析和研究。通过在UGNX7．5中进行二次开发,研究了在UGNX7．5中开发五轴数控机床切削仿真加工环境,并以T35龙门五轴联动加工中心为例,详细介绍了在UGNX7．5中对大型龙门结构的数控五轴加工中心机床的切削仿真加工系统进行开发的方法与过程,开发了T35在UGNX7．5中的碰撞仿真加工系统。T35机床的仿真系统,对在其上加工的复杂零件刀具路径及机床运动可以进行精确的模拟加工,真实地反映和再现实际的加工过程,大大减少了机床的试切时间,提高了CAM程序的安全性和可靠性,降低了产品研发的成本。     

低速走丝电火花线切割加工复杂直纹面的运动轨迹分析

构建了低速走丝电火花线切割机4轴联动的运动分析模型,在此基础上提出了4轴联动实现扭转锥度型面线切割加工的运动控制方法,最后给出了加工实例并进行了计算机图形仿真.     

The form error prediction in side wall machining considering tool deflection

In this research, an effective method for the form error prediction in side wall machining with a flat end mill is suggested. The form error is predicted directly from the tool deflection without surface generation by cutting edge locus with time simulation. The developed model can predict the surface form error accurately about 300 times faster than the previous method. Cutting forces and tool deflection are calculated considering tool geometry, tool setting error and machine tool stiffness. The characteristics and the difference of generated surface shape in up milling and down milling are discussed. The usefulness of the presented method is verified from a set of experiments under various cutting conditions generally used in die and mold manufacturing. This study contributes to real time surface shape estimation and cutting process planning for the improvement of form accuracy.     

High-efficiency swinging-rotating diamond shaping of Fresnel lenses on roller molds

Direct diamond cutting of complex optical features, like Fresnel lens, on a roller mold is time-consuming and costly, due to the fixed tool setting angle and slow imitated turning motion. In this paper, a high-efficiency 5-axis machining process is proposed, namely swinging-rotating diamond shaping (SDS). A special tool positioning attachment is developed to precisely swing the tool for shaping the annular rings with varying facet angles. This process is experimentally verified, with the machining efficiency enhanced by an order of magnitude compared to the conventional way, thus making Fresnel lenses machining on roller cost-efficient and hence applicable to industry.     

Mathematical model and sensitivity analysis for helical groove machining

In any drill design, the helical groove shape plays a key role in ensuring an adequate flute space and an efficient chip removal capability. Moreover, the shape of the helical groove determines the principal drill angles. This study establishes a mathematical model of the helical groove and conducts a sensitivity analysis for helical groove machining performed on a 6-axis tool-grinding machine. Combining homogenous coordinate transformation and conjugate surface theory, a kinematic model is developed to facilitate the design of the helical groove shape (a direct problem). In determining the tool profile required to generate a desired helical groove (an inverse problem), this study exploits the condition that the common normal at the contact point between the tool and the helical groove surface must intersect the axis of the tool. The sensitivity of the helical groove profile with respect to the machining parameters is investigated. Finally, numerical examples are provided to demonstrate the validity of the developed models and algorithms. The numerical results reveal that the current design and sensitivity analysis methodology is comprehensive, simple and applicable to a wide range of helical groove machining applications.     

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。     

高精度复杂型线刀具制造工艺与装备研究

以高精度复杂型线刀具制造工艺与装备为研究对象，以菌形叶片叶根型线加工专用刀具为切入点，通过分析叶根型线的特点及加工工艺的优劣，确认以单边两次成型加工作为刀具加工工艺方案；并在此基础上确定刀具的轮廓度精度、前后刀面表面粗糙度等各项参数及精度要求。通过分析专用刀具的加工要求，确定专用磨床的整体布局及结构方案，并对机床的关键部件磨削装置的结构做了具体设计与阐述。分析磨削点在B轴回转轴线延伸线上的结构优点可知，B轴回转的角度误差未使磨削点位置发生偏差，可有效提升刀具的加工精度。为验证设计的合理性，通过制造与装配机床，利用雷尼绍XK10激光校准仪检测可知，几何精度均达到设计要求。最后，采用设计的刀具加工工艺方案及专用磨床对某菌形型线刀具进行加工，Zoller检测仪检测结果表明：刀具轮廓公差为工作面±0.005 mm,其余面±0.015 mm。     

五坐标加工中使用坐标内插法控制刀具轴向研究

在五坐标加工中,刀具轴向的剧烈变化很容易伤到被加工零件的曲面,因此对刀具轴向的控制就变得尤为重要.为了解决这个问题,文章提出一种控制刀具轴向光顺变化的方法,使得刀具轴向对被加工曲面几何的表现不敏感,避免刀具轴向的剧烈变化,从而达到了提高加工精度和效率的目的.最后通过实验验证了本方法在曲面加工精度上的有效性,以及达到避免刀具与零件之间干涉的目的.     

Tool setting on a B-axis rotary table of a precision lathe

A method has been developed for setting a single-point cutting tool on the axis of rotation of a B-axis rotary table on a precision lathe. The method requires that three grooves be machined in the face of a workpiece with the B-axis set at three different angles. The depths of each of the grooves are then measured, and the measured values are used to calculate the tool offset vector. Experiments on a four-axis diamond turning machine have verified the precision of this method. This method has a significant advantage over commercially available touch probe tool set stations, because touch probes are well known to damage the cutting edges of fragile tools, such as single-point diamond tools with a small nose radius and a large primary clearance angle. The method developed in this study does not subject the cutting edge of the tool to any stress beyond that of its intended purpose of machining workpiece material. Therefore, this method can be used to set extremely fragile single-point cutting tools without the risk of damaging the tools.     

An experimental study of the effect of high-pressure water jet assisted turning (HPWJAT) on the surface integrity

This study deals with the effect of High-Pressure Water Jet Assisted Turning (HPWJAT) of austenitic stainless steels on chip shape and residual stresses. The machining of the austenitic stainless steels represents several difficulties. Recently, research has shown that the introduction of a high-pressure water jet into the gap between the tool and the chip interface is a very satisfactory method for machining applications. In this article, the effect of a high-pressure water jet, directed into the tool-chip interface, on chip shapes breakage and surface integrity in face turning operations of AISI 316L steel has been investigated. Tests have been carried out with a standard cutting tool. The cutting speeds used were 80 and 150 m/min, with a constant feed rate of 0.1 mm/rev and a constant cutting depth of 1 mm. Three jet pressures were used: 20, 50 and 80 MPa. Residual stress profiles have been analysed using the X-ray diffraction method in both longitudinal and transversal directions. The results show that jet pressure and cutting parameters influence the residual stresses and the chip shapes. Using a high-pressure jet, it is possible to create a well fragmented chip in contrast to the continuous chip formed using dry turning. It is also possible to control the chip shape and increase tool life. When the jet pressure is increased the residual stress at the surface decreases; however it is increased by an increase in cutting speed. It can be concluded that surface residual stresses can be reduced by the introduction of a high-pressure water jet.