Robustness evaluation of cutting tool maintenance planning for soft ground tunneling projects

Tunnel boring machines require extensive maintenance and inspection effort to provide a high availability.The cutting tools of the cutting wheel must be changed timely upon reaching a critical condition.While one possible maintenance strategy is to change tools only when it is absolutely necessary,tools can also be changed preventively to avoid further damages.Such different maintenance strategies influence the maintenance duration and the overall project performance.However,determine downtime related to a particular mainte-nance strategy is still a challenging task.This paper shows an analysis of the robustness to achieve the planned project performance of a maintenance strategy considering uncertainties of wear behavior of the cutting tools.A simulation based analysis is presented,imple-menting an empirical wear prediction model.Different strategies of maintenance planning are compared by performing a parameter vari-ation study including Monte-Carlo simulations.The maintenance costs are calculated and evaluated with respect to their robustness.Finally,an improved and robust maintenance strategy has been determined.

Point-Based Data Analysis for Extracting Parameters of Cutting Tools

Various types of cutting tools are known and are in use for machining parts. The dimensional parameters associated with cutting tools need to be estimated and compared to the desired values for determining their cutting performance. In this paper, a data analysis methodology for extracting parameters from a measured point set corresponding to the surface of a cutting tool is provided. We propose that the 3-D data can be simplified into 2-D data or regular data by virtually slicing it at a predetermined section or by projecting it onto a same axial plane after a simple fixed-axis rotation. A plurality of curves can be generated and optimized based on the obtained 2-D points on a cross section for calculating the section parameters, including radial (axial) rake angle, relief angle, and land width. Other dimensional parameters can also be extracted from the contour of the presented rotary axial projection data. The experimental results have shown that the approaches elaborated in this paper are effective and robust, which can be potentially extended to other applications such as the inspection of similar parts and their parameters extraction.

CPS Modeling of CNC Machine Tool Work Processes Using an Instruction-Domain Based Approach

Building cyber-physical system(CPS) models of machine tools is a key technology for intelligent manufacturing. The massive electronic data from a computer numerical control(CNC) system during the work processes of a CNC machine tool is the main source of the big data on which a CPS model is established. In this work-process model, a method based on instruction domain is applied to analyze the electronic big data, and a quantitative description of the numerical control(NC) processes is built according to the G code of the processes. Utilizing the instruction domain, a work-process CPS model is established on the basis of the accurate, real-time mapping of the manufacturing tasks, resources, and status of the CNC machine tool. Using such models, case studies are conducted on intelligent-machining applications, such as the optimization of NC processing parameters and the health assurance of CNC machine tools.

Repair Effect of Hot Work Tool Steel by Laser-Melting Process

Both wear and crack due to heat checking in hot work tool steel are major failure modes.It is desirable to find amethod to lengthen the tool life while reducing manufacturing cost.This paper suggests a method to improve toollife for hot work tool steel(SKD6)with crack by laser-melting process.The method has been evaluated using theimpact and fatigue test results.It is demonstrated that a repair of the crack by a laser-melting process is effectivefor life extension of the damaged tool.

Prediction Model for Net Cutting Specific Energy in CNC Turning

A prediction model for net cutting specific energy in computer numerical control(CNC)turning based on turning parameters and tool wear is developed.The model can predict the net cutting energy consumption before turning.The prediction accuracy of the model is verified in AISI 1045 steel turning.The comparative experimental results show that the prediction accuracy of the model is significantly improved because the influence of tool wear is taken into account.Finally,the influences of turning parameters and tool wear on net cutting specific energy are studied.With the increase of cutting depth,the net cutting specific energy decreases.With the increase of spindle speed,the additional load loss power of spindle drive system increases,so the net cutting specific energy increases.The net cutting specific energy increases approximately linearly with tool wear.The results are helpful to formulate efficient and energy-saving CNC turning schemes and realize low‑carbon manufacturing.

基于VMD-SSA-LSTM考虑刀具磨损的数控铣床切削功率预测模型研究

传统的切削过程功率获取需要基于复杂的切削功率模型且很少考虑刀具磨损的影响,针对此设计了一种基于变分模态分解(VMD)、麻雀搜索算法(SSA)、长短时记忆(LSTM)神经网络的考虑刀具磨损的数控铣床切削功率预测模型,该模型无需解构数控铣床运行过程的能耗机理,基于一次性的历史实验数据即可实现数控铣床切削过程功率的高精度预测。首先,采用人工智能机器视觉技术对刀具磨损图片进行分析处理,获取刀具磨损图像的数字化特征,从而得到刀具最大磨损量;然后,建立基于VMD-SSA-LSTM考虑刀具磨损的数控铣床切削功率预测模型,利用VMD对数控铣床运行数据进行分解,采用SSA算法对LSTM神经网络超参数进行寻优,并将分解出的铣床运行数据分量输入到LSTM神经网络中,接着将每个分量的预测值相加,得到切削功率预测值;最后以面铣加工为例,将所提出的预测模型与BP神经网络、LSTM神经网络和传统模型进行对比分析,验证了所提模型的有效性和优越性。

机床封闭空间内切削声场分布有限元分析

声音传感器具有易安装、无需粘附传感器和不干扰加工过程等特点,在加工过程刀具磨损在线监测中具有广泛的应用前景。但是,在机床封闭空间内声音传播过程受机床内壁、主轴和工作台等结构影响,将产生反射、衍射等现象,导致声场分布具有较大差异性,为声音传感器的合理布置带来困扰。为此,以数控铣床为研究对象,基于声学有限元理论建立铣削加工声场仿真模型,采用压力声学瞬态分析方法,建立正弦加速度声源信号在机床内的传播模型,采用傅里叶变换对机床内声场进行频谱分析。结果表明,在距声源0.4 m和壁面的位置,声压较大,在机床中部,声压随声源距离的增大而减小。本模型为基于声信号的刀具磨损监测奠定了基础。

燃油调节器壳体深孔加工复合刀具设计与试验研究

燃油调节器壳体类零件是航空发动机产品中的关键构件,其典型特征是孔系众多,呈现孔径小、深径比大等特点。针对燃油调节器壳体复杂高精度腔孔加工周期长、刀具利用率高、加工效率低和成本高等问题,本研究根据腔孔结构特点及精度要求,设计并制备了专用内冷式复合成型刀具。通过改进应用场景加工工艺方案和优化切削参数,并在零件上进行生产验证,实现了对复杂腔孔的高效率、高质量和高精度的稳定切削。

金刚石涂层刀具高速铣铝合金平面切削毛刺研究

采用热丝CVD法制备纳米与微米金刚石薄膜涂层刀具,利用场发射扫描电镜表征其薄膜表面形貌。用已制备的CVD金刚石涂层刀具,在无润滑干切条件下高速顺、逆端铣铝合金平面,研究CVD金刚石涂层刀具切削时的棱边毛刺特点与大小;并对纳米金刚石涂层刀具高速顺铣切削工艺参数进行正交试验,探究取得少无切削毛刺的切削参数与切削工艺。结果表明:工件铣削后棱边毛刺分布不均匀,顺铣毛刺稀疏,尺寸较小,其中纳米金刚石涂层刀具顺铣棱边毛刺高度平均值为32.08μm,仅为微米金刚石涂层刀具顺铣毛刺高度的46.5%。纳米金刚石涂层刀具高速顺铣平面,对棱边毛刺影响最大的是v_(c),其次为v_(f),ae的影响最小,最优参数组合为a_(e)=4 mm、v_(f)=2000 mm/min、v_(c)=400 m/min,铣削后毛刺高度平均值为21.29μm。当金刚石涂层刀具端铣铝合金平面时,为取得较小的棱边毛刺,优选纳米金刚石涂层刀具,采用顺铣棱边的切削方式与切削工艺,以及相应的高速切削参数。

渐开线圆柱齿轮的通用型滚插刀设计方法

针对渐开线圆柱齿轮的滚插加工,基于交错轴渐开螺旋面线接触啮合,提出一种通用型滚插刀设计方法,适用于任意结构前刀面。简述滚插加工原理,分析计算交错轴渐开螺旋面线接触啮合的条件;从渐开螺旋面出发,给出切削刃的计算方法,以重磨后刃形精度不变为要求,构建后刀面模型;分析并给出了滚插加工参数的计算方法;基于滚插刀设计实例和VERICUT软件对不同参数的工件进行仿真加工,验证了所设计滚插刀的通用性与可行性,为通用型滚插刀设计提供了一种简单、无刃形误差的方法。

技能型社会建设背景下职业技能倾向测试的构建流程与策略

在技能型社会建设中,完善的职业技能倾向测试不可或缺。本研究以工作过程系统化理论为指导,探讨了职业技能倾向测试构建过程中的测试内容、结构、流程和工具等问题。在内容层,通过企业调研,明确职业技能倾向测试的内容来源;在结构层,按照“技能元-技能簇-情境簇-岗位簇”自下而上的测试逻辑,搭建职业技能倾向测试的四级结构;在实施层,按照界定测试范畴、选定参照模型、筛选测试工具、输出测试结果、实现结果应用五大环节,确定职业技能倾向测试的研制流程;在结果层,设计七种测试表单观测被测职业技能发展水平,最终形成职业技能倾向测试工具。

硬料螺纹孔铣削加工技术研究

Cr12MoV材料经热处理后硬度达到56~62 HRC,切削性能差,切削难度大,以热处理后Cr12MoV材料的模具零件螺纹孔为例,传统的加工方式一般采用电火花机床进行螺纹孔加工,加工效率低,为提高加工效率采用铣刀铣削加工。经加工测试,得出铣削加工硬料螺纹孔提升了加工效率,降低了加工成本,在加工过程中更加安全环保。

数控车床加工的产品质量控制

使用数控车床在加工过程中,经常会碰到尺寸精度不稳定、位置精度不稳定、表面粗糙度不稳定等产品质量难以控制的问题,甚至会碰到不明原因的振刀、断刀、缠屑、零件变形等问题,本文主要从三个大方面阐述数控车床加工的产品质量控制方法,数控车床设备,工艺方法、刀杆、刀片的选择和切削用量。

数控刀具技术与应用探析

数控刀具是切削加工的基础工艺装备,在制造过程中与数控机床相互配合承载不同的加工工艺,共同完成材料切削加工。针对数控刀具的选用,探讨了选用要点,并以具体数控车加工为例进行了刀具的选用,以促进数控刀具更好地发展与应用。

镍基高温合金切削加工研究现状及发展趋势

镍基高温合金因其优异的性能在航空航天等领域得到了广泛应用,但其在切削加工过程中会表现出切削力大、切削温度高、刀具磨损严重、加工硬化严重以及加工精度低等问题。该文重点介绍了切削参数、新型切削液技术和切削刀具类型对于切削加工工艺的影响,简要阐述了镍基高温合金表面完整性的研究现状,且总结了超声振动切削加工对镍基高温合金切削性能的影响,最后对镍基高温合金未来的发展趋势进行了展望,为后续切削加工提供了重要参考依据。

数控机床切削过程中的振动分析与控制策略研究

数控机床切削过程中振动问题成因复杂且对切削加工精度、质量、效率等有较大影响。梳理了数控机床切削的振动的影响因素、振动机理、振动衡量等基础概念,以及金属切削过程的主动、被动和半主动颤振控制技术;从数控机床切削颤振控制技术发展、控制逻辑以及基于数理模型的控制模型建构逻辑角度等探讨颤振的控制策略,并从系统动力学、多元数据融合、智能控制等角度予解释。

数控机床切削控制能力对机械加工精度的影响分析

数控机床是现代制造业中广泛应用的重要设备之一,具有高效、精确、灵活等优点,在机械加工领域发挥着关键性作用。数控机床的切削控制能力和机械加工精度具有密不可分的联系,为进一步提高数控机床机械加工精度,从切削速度、走刀量、切线深度等方面分析对机械加工精度的影响,提出加强数控机床切削控制,提高机械加工精度的具体措施,以期为相关工作人员提供借鉴,进而提高机械加工质量。

Effect of cutting process on machine tool noise

Based on the principle of Statistical Energy Analysis (SEA) for non-conservatively coupled systems under general excitations, relationship between noise radiated from and excitations on coupled complex structures is studied, which lays a foundation for the determination of noise/vibration energy by evaluation of exciting forces, and from that the quantitative analysis of the effects of an excitation on sound power from a sub-structure can be done. With extending of the relationship to the study of cutting noise, regression analysis method for evaluating the effects of cutting process on machine tool noise is established. Results show that cutting process has generally negligible effects on machine tool noise, and there is no apparent difference between machine tool noise in cutting condition and in idle one.

高速切削综合技术

详细描述了高速切削相关技术的研究内容 ,主要包括高速切削机床、高速切削刀具、高速切削工艺、高速切削机理等 ;提出了高速切削技术的发展趋势。

高速高效加工领域科学技术发展研究

高速高效加工是近年来迅速发展起来的集高效、优质和低耗于一身的先进制造工艺技术,是机械加工技术的重要发展方向。在航空、航天、汽车、模具、高速机车等行业中应用已取得重大经济效益,对提高加工技术水平,推动机械制造技术的进步具有深远的意义。高速高效加工的研发主要包括加工机理、加工机床、刀具磨具和加工工艺等方面。给出高速切削磨削机理、刀具磨具、机床功能部件及整机设计等方面的新理论、新原理、新观点、新方法、新成果和新技术,介绍高速切削磨削技术在产业发展中的重大应用和重大成果。以汽车制造业为例指出高速加工技术的发展趋势,预测2015～2025年中型高速加工中心的技术指标,结合我国未来几年的战略需求和重点发展方向,提出高速加工技术发展路线,展望未来几年我国高速加工技术的发展重点。