主轴-切削交互过程建模与高速铣削参数优化

高速切削参数的合理选择是困扰企业的一个难题,过于保守的切削用量限制了高速机床性能的发挥和生产效率的提高.以高速铣削加工为对象,考虑高速旋转主轴的离心力和陀螺力矩效应,基于Timoshenko梁单元和Jones轴承模型建立高速主轴-刀具系统动力学模型.将主轴-刀具动态特性与高速铣削过程耦合,研究高速主轴-刀具系统动力学特性与切削过程之间交互机理,推导闭环动态铣削系统的特征方程.基于上述理论分析,提出基于主轴-切削交互过程模型的高速铣削切削参数优化方法,并应用于某型直升机的铝合金变速箱端盖加工中,通过选用最佳切削深度和主轴转速,使变速箱盖前端面内侧壁的加工效率提高了275％.     

基于主轴系统动力学的铣削稳定性建模与分析

高速切削技术具有加工精度高和表面质量好的特点,但在切削难加工材料时易发生颤振。基于主轴系统动力学进行铣削稳定性的建模与分析,采用有限元法建立主轴系统动力学模型,重点考虑主轴旋转时产生的离心力对结合面刚度的影响,分析主轴转速对结合面刚度和主轴系统频响函数的影响规律。结合主轴系统动力学特性和动态铣削过程建立铣削动力学模型,利用全离散法进行铣削稳定性预测,分析主轴转速、刀具直径和刀具悬伸量对铣削稳定域的影响规律。     

高速铣削稳定性的不确定性建模及实验预测

高速铣削加工过程的颤振不稳定性是制约刀具寿命和加工效率的主要因素。传统的颤振稳定性预测模型都假设系统参数是恒定的,但是在实际的高速铣削过程中,影响加工稳定性的参数会随着高主轴转速、高系统动态特性而发生变化。为提高铣削加工精度,以高速铣削加工稳定性为研究对象,考虑参数不确定性的影响,应用棱边定理和排零准则,建立高速铣削变参数稳定性预测数学模型。在此基础上,通过模态测试和辨识铣削力系数获得固有频率及切削系数的变动范围,然后采用数值分析和铣削实验相结合的方式,验证了建立的高速铣削变参数稳定性模型的正确性。     

铝合金铸造壳体高速铣削参数优化研究

在铝合金铸造壳体高速铣削的条件下,通过分析机床-刀具系统动态特性(颤振)与铣削参数合理的匹配关系,进而确定主轴转速和轴向切深的稳定颤振区域,在此基础上合理地选择非颤振铣削参数,为实际生产中铣削参数的选择提供科学依据。在具体实例中,通过对数控机床主轴进行数据采集,进而对数据进行解析,然后通过软件进行颤振稳定性仿真,获得稳定性叶瓣图,分析现场的实际工况,在叶瓣图非颤振区域选择合理的铣削参数,对优化的铣削参数进行了验证。结果表明,在主轴转速8 000r/min,切宽20mm的情况下,铣削加工过程稳定,切削效率提高了700%,表面粗糙度由原来的1.6μm降低至0.8μm。     

切削锥长度和主轴转速对干攻丝中径差的影响

中径差作为评价内螺纹质量的重要参数,对内螺纹的加工质量影响很大.为研究切削锥长度和主轴转速对内螺纹中径差的影响,采用高速钢直槽丝锥对45钢进行了干攻丝试验.试验结果表明:切削锥长度和主轴转速对中径差均有影响.在100 r/min的主轴转速下,使用切削锥长度为2.5 mm的丝锥进行切削可获得最佳的中径差,其中径向中径差的...     

高速切削和高速主轴

高速切削加工的应用领域在扩大，因而高速主轴系统的结构及与其相关联的主轴与刀具连接方式就至关重要本文介绍了选择高速主轴应考虑的各种参数与因素，以及ＨＳＫ连接的特点与优点。     

离心力效应对高速回转刀具系统松脱转速影响分析

1引言 在ISO标准下,切削加工中主轴转速超过8000r/min称为高速切削加工.随着转速的上升,刀具自身系统的离心力也逐渐增大,当转速达到一定程度时,这种离心力就成为了刀具系统的主要载荷.     

CAXA软件在加工中心准高速加工中的应用

准高速加工是既有的常速加工的延伸。其具体形式为：在确保机床床身、主轴刚度及刀具的正常磨损下,通过对现有设备进行技术改造和性能提升,一定程度上提高机床的主轴转速（最高约10000RPM）和加工进给速度（最大约1000-2000mm／min）,减少刀具在单位转速下的切削量和切削阻力。粗加工阶段,尽快切除工件毛胚的加工余量,提高工效并降低制造成本;精加工阶段,利用高转速的优势实现较高的加工精度和工件表面质量。这大大拓宽了现有设备的加工范围,使得过去无法实现的一些加工目标得以实现,提高了机床的使用价值。     

高速主轴过盈联结特性研究

高速主轴是高速切削技术的核心部件，其与电动机转子间的过盈量的大小是影响主轴的几何精度、运动精度、加工精度的关键因素。高速主轴与转子间的联结特性不仅受到初始装配公差的影响．还受到离心力的影响，且随着转速的提高。离心力的影响也越来越大。因此．设计过盈联结时．必须综合考虑接触应力、扭矩和转速对联结特性的影响。文章研究了高速主轴过盈联结的特性，分别推导出了高速主轴在静态和动态条件下过盈量和接触应力的理论公式。上述公式的推导有助于高速主轴过盈联结的设计。提高主轴的运动特性和加工特性。     

基于刀尖模态的Al-7075铣削颤振稳定性预测研究

针对切削加工中的颤振问题,以铣削加工Al-7075为例,通过刀尖模态分析、模态参数识别,获得了铣削加工Al-7075的颤振稳定性叶瓣图(Lobes图)。通过设计信号采集实验,对颤振电压信号和铣削力信号进行采集并对颤振进行实验表征,进而验证稳定域预测的准确性。研究表明,切削加工Al-7075过程中,颤振易发生在低转速区,提高主轴转速及合理加大轴向切深可提高生产率和加工质量,从而验证了Lobes图中稳定域预测的有效性。     

Analysis of cutting force coefficients in high-speed ball end milling at varying rotational speeds

In high-speed ball end milling, cutting forces influence machinability, dimensional accuracy, tool failure, tool deflection, machine tool chatter, vibration, etc. Thus, an accurate prediction of cutting forces before actual machining is essential for a good insight into the process to produce good quality machined parts. In this article, an attempt has been made to determine specific cutting force coefficients in ball end milling based on a linear mechanistic model at a higher range of rotational speeds. The force coefficients have been determined based on average cutting force. Cutting force in one revolution of the cutter was recorded to avoid the cutter run-out condition (radial). Milling experiments have been conducted on aluminum alloy of grade Al2014-T6 at different spindle speeds and feeds. Thus, the dependence of specific cutting force coefficients on cutting speeds has been studied and analyzed. It is found that specific cutting force coefficients change with change in rotational speed while keeping other cutting parameters unchanged. Hence, simulated cutting forces at higher range of rotational speed might have considerable errors if specific cutting force coefficients evaluated at lower rotational speed are used. The specific cutting force coefficients obtained analytically have been validated through experiments.     

Comprehensive measurement and evaluation system of high-speed motorized spindle

Reducing the manufacturing time is the trend of high-precision manufacturing, and the precision of a work-piece is very important for manufacturing industry. The high-speed motorized spindle is the most critical part and becoming more widely used in the machine tool at present, and its precision may affect the overall performance of high-speed cutting. Most of the studies on high-speed cutting are focused on the cutting force, the vibration of the spindle and effects of the spindle’s thermal deformations; hence, how to roundly measure and objectively evaluate high-speed spindle is an imminence question of it because the comprehensive dynamic properties and evaluation system of spindles directly affect the cutting ability of the whole machine tool before they are manufactured. This paper presents a comprehensive measurement and evaluation system of high-speed motorized spindle, which reflects the overall performance of motorized spindle and bases on international standard.     

主轴/刀柄7:24和1:10锥度联结系统性能分析

针对机床主轴/刀柄在高速切削离心力作用下的联接性能进行了分析,重点介绍了7:24和1:10锥度的结构,以及在高速切削时与锥孔配合的特性。因此,主轴/刀柄1:10锥度联结系统在高速加工、连接刚性和重合精度上均优于7:24,更适合高速切削加工。     

主轴系统的刚柔耦合接触动力学仿真分析

以高速数控铣床主轴多体系统为例,研究了主轴刚柔耦合多体系统的输出响应的动态特性。从柔性多体动力学的基本原理出发,系统地分析了主轴系统刚柔耦合的动力学模型的原理,提出基于修正的Craig-Bampton法建立主轴系统刚柔耦合的接触动力学模型的方法。基于虚拟样机模型,综合考虑齿轮传动的时变啮合刚度、间隙、摩擦和切削力等影响动态响应的接触因素,分析出轴承结合部、驱动转速和齿轮啮合等的时变特性对主轴系统动态响应的影响。仿真结果与理论和实验分析结果相一致。该仿真算法可以有效地解决考虑多动态参数激励的主轴系统的动态响应问题。     

考虑结合面和轴向力的主轴系统动力学特性

汽车覆盖件淬硬钢模具由于硬度高,在铣削过程中动态铣削力大,易发生颤振,而主轴系统动力学特性直接影响铣削稳定性。为了准确建立主轴系统动力学模型,考虑主轴系统铣削状态下产生的轴向铣削力和离心力对主轴结合面接触刚度的影响。通过分析得到,轴向铣削力对主轴结合面接触刚度有强化作用,使主轴系统固有频率有微小的增加;而离心力对结合面接触刚度有软化作用,随着主轴转速升高,系统的固有频率减小,尤其高转速时主轴系统的动力学特性偏差较大,对比而言离心力的软化作用多于轴向铣削力的强化作用,故主轴系统在铣削过程中动力学特性相比静止无载状态下仍是软化现象;分析结合面预紧力、刀具参数等因素对主轴系统动力学特性的影响规律,为准确分析主轴系统动力学特性和预测铣削稳定性提供理论参考。     

Chatter stability prediction for high-speed milling through a novel experimental-analytical approach

Chatter prediction is crucial in high-speed milling, since at high speed, a significant increase of productivity can be achieved by selecting optimal set of chatter-free cutting parameters. However, chatter predictive models show reduced accuracy at high speed due to machine dynamics, acquired in stationary condition (i.e., without spindle rotating), but changing with spindle speed. This paper proposes a hybrid experimental-analytical approach to identify tool-tip frequency response functions during cutting operations, with the aim of improving chatter prediction at high speed. The method is composed of an efficient test and an analytical identification technique based on the inversion of chatter predictive model. The proposed technique requires few cutting tests and a microphone to calculate speed-dependent chatter stability in a wide range of spindle speed, without the need of stationary frequency response function (FRF) identification. Numerical and experimental validations are presented to show the method implementation and assess its accuracy. As proven in the paper, computed speed-dependent tool-tip FRF in a specific configuration (i.e., slotting) can be used to predict chatter occurrence in any other conditions with the same tool.     

T/ R 组件封装用铝硅合金高速铣削试验研究

为解决T/ R 组件封装用铝硅合金材料普通铣削加工过程中效率较低、加工成本较高的问题,文中采用三刃硬质合金端面铣刀对某T/ R 组件封装用铝硅合金CE11 进行了高速铣削试验,探索了其在高速铣削过程中,切削量、主轴转速、背吃刀量等对切削力、切削温度的影响,分析了常用切削参数下切削力及切削温度的变化趋势及原因。通过试验得到了CE11 较为合理的高速铣削参数,对提高切削效率及加工质量有一定的指导意义。     

考虑极限切削宽度的45钢切削力仿真分析

以高速车削45钢为研究对象,针对高速车削颤振问题,通过绘制稳定性叶瓣图得到无颤切削参数。利用Third Wave AdvantEdge有限元分析软件,基于无颤切削参数设计正交试验,运用极差分析法得到切削用量对各切削力的影响主次顺序和最优组合。根据仿真试验结果,建立了车削力预测模型并检验了回归模型的可靠性。通过单因素试验法分析研究了各切削参数对车削力的影响规律,从减小车削力和提高高速车削加工稳定性方面出发,在所选参数范围内得出了高速车削45钢时的最优参数组合为:v=1200m/min,f=0.05mm/r,ap=0.2mm。     

Analysis of the machining stability of a milling machine considering the effect of machine frame structure and spindle bearings: experimental and finite element approaches

Chatter vibration has been a troublesome problem for a machine tool toward the high precision and high-speed machining. Essentially, the machining performance is determined by the dynamic characteristics of the machine tool structure and dynamics of cutting process of spindle tool. Prediction of the dynamic behavior at spindle tool tip is therefore of importance for assessing the machining stability of a machine tool at design stage. This study was aimed to evaluate the machining stability of a vertical milling system under the interactive influence of the spindle unit and the machine frame structure. To this end, a realistic finite element model of a vertical milling tool was generated by incorporating the spindle-bearing model into the head stock mounted on machine frame. The influences of the dynamics of spindle-bearing system and the machine frame structure were investigated respectively. Current results show that the machine tool spindle system demonstrates different dynamic behaviors at different frequency ranges, which are also characterized as structural modes and spindle modes, respectively. In particular, the maximum compliance of spindle tool tip was found to occur at the bending vibrations of spindle shaft and vary with the preload amount of spindle bearing. The machining stabilities were predicted to different extent, depending on the exciting modes which could be related to the influences of machine frame and spindle unit.     

Extension of process damping to milling with low radial immersion

This paper investigates the stabilizing effect of process damping at low cutting speeds for regenerative machine tool vibrations of milling processes. The process damping is induced by a velocity-dependent cutting force model, which takes into account that the actual cutting velocity is different from the nominal one during machine tool vibrations. The chip thickness and the cutting force are calculated according to the direction of the actual cutting velocity. This results in an additional damping term in the governing delay-differential equation, which is time-periodic for milling and inversely proportional to the cutting speed. In the literature, this term is often assumed to be constant and is considered to improve stability properties at low spindle speeds. In this paper, it is shown that the velocity-dependent cutting force model captures the improvement in the low-speed stability only for turning operations and milling with large radial immersion, while it results in a negative process damping term for low-immersion milling. Consequently, an extended process damping model is needed to explain the low-speed stability improvement for low radial immersion milling.