深孔镗杆在推镗和拉镗时的ANSYS受力分析

深孔镗削是提高深孔加工精度的一种方法,它能校正己有孔上的缺陷,如圆度误差、直线度误差,从而获得良好的几何精度和表面粗糙度。深孔镗削的加工方式、运动形式、镗刀的轨迹方程和对镗削的受力分析是深孔镗削加工中各不稳定因素的渊源,在深孔镗削过程中,运用合适的镗削方式可以减小切削系统的振动。针对多刃均布式深孔镗刀,在推镗和拉镗方式下进行受力分析,并利用PRO/E建立镗杆几何模型并生成中性几何文件,通过ANSYS有限元法,计算出推镗和拉镗时镗杆产生的挠度以及最大应力应变曲线,将二者结果进行比较,证明在细长管时拉镗加工的优势。     

Improvement of chatter stability in boring operations with passive vibration absorbers

This paper is focused on the behavior of boring bars with a passive dynamic vibration absorber (DVA) for chatter suppression. The boring bar was modeled as a cantilever Euler-Bernoulli beam and only its first mode of vibration was considered. The stability of the two-degree-of-freedom model was analyzed constructing the stability diagram, dependent on the bar characteristics and on the absorber parameters (mass, stiffness, damping, and position). Two analytical approaches for tuning the absorber parameters were compared. The selection criterion consisted on the maximization of the minimum values of the stability-lobes diagram. Subsequent analysis performed in this work, allowed formulating of new analytical expressions for the tuning frequency improving the behavior of the system against chatter.     

实用化振动切削技术——椭圆振动车镗工艺及装备

椭圆振动车镗技术是一种主要应用在精密切削领域内的特种加工技术，特别是在提高工件的表面质量、刀具的使用寿命和薄壁零件的加工精度等方面效果显著。我们最新研制了椭圆超声波振动车镗系统，并对不同材料进行了切削试验，取得了很好的工艺结果，充分体现了超声波振动车镗技术在实际切削加工中的优势。     

超声振动精密深孔镗削试验研究

通过超声振动深孔镗削试验,研究了超声振动镗削时切削速度、进给量和背吃刀量对加工精度和表面粗糙度的影响规律,分析了精密深孔超声振动镗削时的切削机制.     

Analysis of the vibration characteristics and adjustment method of boring bar with a variable stiffness vibration absorber

In deep hole boring process, long and flexible boring bars are often used. Due to the large length-to-diameter ratio, the stiffness of the boring bars is inevitably reduced, where the boring bars’ vibration effects will occur. The influences of vibration will significantly degrade the accuracy and the surface quality, or even lead failure of the production. Therefore, it is of significant importance to develop techniques to reduce vibration in deep hole boring. In this paper, a new boring bar with a variable stiffness dynamic vibration absorber (VSDVA) is presented, where the basic parameters of the proposed boring bar are measured. Based on the proposed dynamic model, the vibration characteristics of the proposed boring bar are analyzed, and the change laws of the vibration reduction performance are obtained under different excitation frequencies. A new vibration reduction method is proposed, where best vibration reduction performance can be achieved by adjusting the stiffness of the VSDVA. Finally, the vibration reduction performance of the proposed boring bar is validated and evaluated by boring experiments. These works could provide guidance for designing new types of boring bars, selecting cutting parameters, and adjusting the vibration reduction performance of the proposed boring bar, and as a result, it provides a new design idea for the design of boring bar.     

超声波振动镗孔镗刀的设计

设计了一种满足超声波振动镗孔要求的镗刀。阐述了设计方法,介绍了镗刀的结构形式、刀具材料、切削刃几何参数等的选用方法,并对结构尺寸进行了计算。     

Influence of magnetorheological elastomer on tool vibration and cutting performance during boring of hardened AISI4340 steel

During boring process, tool vibration is a major concern due to its overhanging length, which results in high cutting force, poor surface finish, and increase in tool wear. To suppress tool vibration and improve cutting performance, a novel technique in rheological fluid was designed and developed. In this work, a magnetorheological elastomer (MRE) was developed, and parameters, such as piston location, current intensity, and coil winding direction, were considered. Cutting experiments were conducted to obtain a set of parameters that can efficiently control vibration during boring of hardened AISI 4340 steel. Taguchi method was used to optimize the cutting condition, and findings show that the cutting tool embedded with the MRE reduced tool vibration and effectively increased cutting performance.

     

Dynamic cutting force modeling and experimental study of industrial robotic boring

In this paper, a new approach based on industrial robotic boring is proposed to solve problems associated with intersection holes during aircraft assembly. A model is established to predict the dynamic cutting force of a robotic machining system. The robot stiffness coupling, chip deformation, and plowing interference affecting the cutting force are considered using the principles of cutting mechanics and the Oxley orthogonal cutting model. By solving a numerical solution of motion differential equation, the cutting force components in the radial, tangential, and feed directions are obtained by the model. In addition, an advanced curve intersection method is developed to identify the instantaneous uncut chip area and cutting edge contact length. Verification tests were performed on an ABB-IRB6600-175/2.55 robot for titanium alloy TC4 to determine the accuracy of the predictions. The results show that the simulated and measured cutting forces were in good agreement under different cutting conditions. By analyzing simulated and experimental results, we show that the model can be applied to predict the occurrence of vibration and has application value in terms of suppressing vibration during robotic boring.     

Cutting tool condition monitoring by analyzing surface roughness,work piece vibration and volume of metal removed for AISI 1040 steel in boring

The vibration is one of the intensive problems in boring process. Machining and tool wear are affected more by vibration of tool due to length of boring bar. The present work is to estimate the effect of cutting parameters on work piece vibration, roughness on machined surface and volume of metal removed in boring of steel (AISI1040). A laser Doppler vibrometer (LDV) was used for online data acquisition and a high-speed FFT analyzer used to process the AOE signals for work piece vibration. A design of experiments was prepared with eight experiments with two levels of cutting parameters such as spindle rotational speed, feed rate and tool nose radius. Taguchi method has been used to optimize the cutting parameters and a multiple regression analysis is done to obtain the empirical relation of Tool life with roughness of machined surface, volume of metal removed and amplitude of work piece vibrations.     

Stabilization of high frequency chatter vibration in fine boring by friction damper

Friction damper has been found successful to prevent high frequency chatter occurring at more than 10,000Hz, and causing problem of reduced tool life in fine boring operation. The new damper is characterized by simple structure that consists of an additional mass attached to the main vibrating structure with small piece of permanent magnet. The principle is straightforward in which Coulomb and viscous frictions dissipate vibration energy at the interface between the damper and main vibrating structure. The damper needs no tuning, and is effective at high frequency. The paper first introduces a typical design of the friction damper with experimental proof by cutting tests of its effectiveness in eliminating the high frequency chatter in fine boring, and assuring normal tool life of the cutting edge. Theoretical and experimental analyses are introduced for understanding the fundamental principle and characteristics of the new damper. The new damper is effective for boring tools, which vibrate at frequency more than 5,000Hz.     

Analysis of dynamic properties of boring bars concerning different clamping conditions

Boring bars are frequently used in the manufacturing industry to turn deep cavities in workpieces and are usually associated with vibration problems. This paper focuses on the clamping properties’ influence on the dynamic properties of clamped boring bars. A standard clamping housing of the variety commonly used in industry today has been used. Both a standard boring bar and a modified boring bar have been considered. Two methods have been used: Euler–Bernoulli beam modeling and experimental modal analysis. It is demonstrated that the number of clamping screws, the clamping screw diameter sizes, the screw tightening torques, the order the screws are tightened has a significant influence on a clamped boring bars eigenfrequencies and its mode shapes orientation in the cutting speed—cutting depth plane. Also, the damping of the modes is influenced. The results indicate that multi-span Euler–Bernoulli beam models with pinned boundary condition or elastic boundary condition modeling the clamping are preferable as compared to a fixed-free Euler–Bernoulli beam for modeling dynamic properties of a clamped boring bar. It is also demonstrated that a standard clamping housing clamping a boring bar with clamping screws imposes non-linear dynamic boring bar behavior.     

二十辊轧机机架镗床镗削头结构设计

二十辊轧机的整体机架孔系复杂、加工深度长,要求精度高,需要采用专用的加工设备来完成孔系的加工。为此,针对整体机架孔系的特点,设计了一款二十辊轧机机架镗床镗削头,成功解决了非整圆深孔孔系加工中容易出现的孔径大小超差、孔系直线度及平行度超差、内孔粗糙度低及孔系整体加工精度不稳定等问题。     

Identification of dynamic properties of boring bar vibrations in a continuous boring operation

Vibrations in internal turning operations are usually a cumbersome part of the manufacturing process. This article focuses on the boring bar vibrations. Boring bar vibrations in alloyed steel, stainless steel and cast iron have been measured in both the cutting speed direction and the cutting depth direction with the aid of accelerometers. The dynamic response of a boring bar seem to be a time varying process that exhibits non-linear behaviour. The process is influenced by non-stationary parameters that are not under the control of the operator or experimenter. The vibrations are clearly dominated by the first resonance frequency in one of the two directions of the boring bar. The problem with force modulation in rotary machinery, which appears as side band terms in the spectrum, is also addressed. Furthermore, the resonance frequencies of the boring bar are correlated to an Euler–Bernoulli beam model.     

Blade geometry effects on the boring of valve seats of internal combustion engines

The boring of valve seats of internal combustion engines is done approximately 25 million times per year in Brazil. Excessive vibrations during this operation are common and can adversely affect dimensional and geometrical tolerances of the valve seats. The sealing of the combustion chamber is prejudiced, resulting in loss of power and higher emission of pollutant gases, harming the environment. The raw material of the valve seats is sintered steel of 370–410 HB hardness and is machined with expensive polycrystalline cubic boron nitride blades. In order to avoid the generation of excessive vibration or chatter during machining, operators reduce cutting speed and feed rate, which consequently causes reduction of productivity. In this context, investigation of the process was performed with the objective of minimizing the vibrations during the valve seat boring through changes in the tool holder design and in geometry of the cutting blades. The proposed modifications resulted in a remarkable reduction in magnitude of the resultant cutting force, vibrations, and roundness deviations of the valve seat. Hence, the sealing between the valve and the seat was improved and the emission of gases from the motor could be reduced, with gains in efficiency. The results also showed that the cutting blade edge must have a 60-μm honing, and the best cutting parameters are in the range: cutting speed 80–100 m/min and feed rate 0.04–0.08 mm/rev/tooth.     

Development of a novel boring tool with anisotropic dynamic stiffness to avoid chatter vibration in cutting: Part 1: Design of anisotropic structure to attain infinite dynamic stiffness

This paper presents a novel design method of the anisotropic structure to attain infinite dynamic stiffness to avoid chatter vibration in boring operations. Because a long and slender tool is used for boring operations, the stiffness of the tool holder is likely to decrease, resulting in low chatter stability. Although it is difficult to improve the stiffness of the boring holder itself, the nominal dynamic stiffness for the cutting process can be improved by designing an appropriate anisotropy in the dynamic stiffness of the boring tool. In this study, we formulate a theoretical relationship between the mechanical structural dynamics and chatter stability in boring operation and present the basic concept of tool design with anisotropic structure. In the actual tool design, ideal anisotropy may not be realized because of the influence of design error. Therefore, an analytical study was conducted to clarify the influence of the design error on the vibration suppression effect. Analytical investigations verified that the similarity of the frequency response functions in the modal coordinate system and the design of the compliance ratio according to the machining conditions are important. Furthermore, we designed a boring tool with an anisotropic structure which can achieve the proposed anisotropic dynamics. The frequency response function was evaluated utilizing FEM analysis. The estimated anisotropic dynamics of the proposed structure could significantly improve the nominal dynamics for boring operations.     

如何消除镗床镗杆轴向窜动

介绍镗床使用过程中消除镗杆轴向窜动造成的加工精度降低的方法.     

High speed electrochemical boring

Electrochemical machining (ECM) is widely used nowadays in a great variety of processes, especially in the aero and auto industries. The main machining processes, where high tool feed rates are required, are drilling, cavity sinking, broaching and grinding. In addition, the non-equilibrium machining processes, where stationary electrodes are utilized, have important practical applications in the fields of deburring and embossing. Electrochemical honing is a non-equilibrium process. EC honing is a new technique which, in spite of being used in some industrial plants, is still not fully described, requiring more information about the process. This work presents a comparative study, between rotating and non-rotating electrodes for the enlargement of conventionally pre-drilled holes. The comparison covers the rate of metal removal, dimensional accuracy, surface finish and power consumption. The beneficial advantages of using high rotational speeds on component accuracy are verified. The results emphasize that each process has its own particular characterization, appropriate field of application and tooling system.     

电子镗头

任何金属零件镗孔中,保持微米级误差永不是件容易的事。通常在孔的最后加工工序时必须人工介入,进行测量和校正。然而,有一个理想的装置,在加工过程中能自动测量并校正公差。     

镗杆和镗套烧结咬死后的快速修复方法

仅从镗杆镗套烧结咬死后修复的角度有针对性地提出了几种快速、适用的修复方法,这些方法在生产实际中已经过多次验证,采用这些方法可有效地解决镗杆和镗套烧结后快速恢复使用精度的问题,保证组合镗床在使用过程中不会因局部零件失效而长期影响生产.