Research on optimization of milling performance of V-groove micro-texture ball-end milling cutter

Journal of Mechanical Science and Technology - Titanium alloys generally have problems such as sticking, large cutting force, and poor heat dissipation during the cutting process., research shows...     

木工硬质合金S曲线球头镂铣刀的研究

如果用一般方法加工不带导向柱球头镂铣刀的刃部,其基准精度低,很难保证刃部圆跳动公差,因此设计了以中心孔和预留反顶尖为定位基准精磨柄部,再以精磨后的柄部为基准;加工刃部的机加工艺,满足了该镂铣刀产品性能的要求。     

Accessible regions of tool orientations in multi-axis milling of blisks with a ball-end mill

Noninterference tool orientations are hard to be determined in multi-axis milling of blisks, because the integrated structure of blisks introduces more geometrical constraints. To address this problem, an original approach without interference detection is proposed to solve accessible regions of tool orientations in milling of blisks. Based on the visibility of checking surfaces, only critical points on surface profiles are searched and processed to construct the accessible regions. In this approach, the start point of each profile is sought on boundaries of the main surface with a constant step length. From this point, a new critical point is first searched along a specified direction and then adjusted iteratively until it locates on a profile. When all critical points on profiles are searched like this, the searched points on each checking surface are reordered to form one or more than one closed curve to present the accessible region related to this checking surface. These curves are then mapped onto a unit sphere and divided into nonintersecting segments. After that, a concise approach is proposed to combine accessible regions of all checking surfaces into simply connected regions. This algorithm is finally verified with two kinds of blisks and compared with a referenced method. The results show that the proposed method can efficiently solve accessible regions in multi-axis milling of blisks with an expected accuracy.     

四轴数控重磨球头立铣刀端刃的实现问题研究

球头立铣刀的应用越来越广泛，其质量好坏直接影响到加工对象的表面质量、精度及加工效率。目前，刀具用户对球头立铣刀用钝后的重新修磨，依靠手工进行，其精度无法保证，如何有效解决它的修磨问题十分迫切。本文从工作实际出发，就如何进行快速、准确、高质量的刀具修磨工艺和编程技术进行研究，对具体地如何实现球头立铣刀端刃的重磨和夹具设计问题进行讨论。     

The effects of cutter eccentricity on the cutting force in the ball-end finish milling

Ball-end mill are usually used for finish machining with multi-axis CNC milling centers. Cutter eccentricity (offset magnitude e _c, angular location of the offset vector λ _c) is very important when predicting cutting forces accurately. In the process of cutting force modeling, not only the e _c, but also the λ _c, affects the cutting forces by associating with the rotation angle, the chip thickness, and the entry and exit angles of the cutting forces. The e _c affects the values of the cutting forces, while λ _c causes the delay phenomenon of the cutting forces mainly. Experiment results show that the cutting forces, considering the cutter eccentricity, more especially considering the influence of the λ _c, agree better with the measured cutting forces than the cutting forces without considering the cutter eccentricity.     

A novel mathematical model for grinding ball-end milling cutter with equal rake and clearance angle

In this paper, new mathematical models and grinding methods of ball-end milling cutter were proposed based on the orthogonal spiral cutting edge curve. In order to avoid interference, a conical wheel was also designed and employed to grind the rake and rear faces of ball-end milling cutter on a five-axis grinder. Mathematical models of both rake face with equal rake angle and rear face with equal clearance angle were established to improve the machining characteristics of ball-end milling cutter. The design and simulation software of ball-end milling cutter was developed to design and optimize different shapes of both rake face and rear face. Furthermore, grinding experiment of the new ball-end milling cutter was carried out to confirm the validation of the mathematical models.     

Tool path generation method for multi-axis machining of helical milling cutter with specific cross-section profile

The geometry of helical milling cutter with specific cross-section profile is normally generated with form cutter by the toolpath generating method. The general purpose CAD/CAM software can generate the cutter location file of this class of product only by the sculpturing method. To obtain the flexibility of machining process, this paper presents an interference-free toolpath generating method for semi-finish and finish machining of the helical milling cutter. The method for design and machining of the helical milling cutter is established based on the differential geometry and the enveloping theory. In the finish machining of helical milling cutter, the form grinding wheel profile is firstly derived. To reduce the cost and lead time of the generating method with the form-mill cutter for semi-finish machining, a toolpath generating method which combines the advantages of the generating method and sculpturing method was presented. The cutter location uses ball-nose conical end mill is derived according to the geometric characteristics of the enveloping element. The cutting simulations with solid model were performed to verify the proposed toolpath generation method.     

Increasing the sensitivity of the X-ray testing of hollow fan blades

A method for improving the parameters of the X-ray testing of hollow turbine fan blades is proposed.     

Active suppression of chatter in peripheral milling. Part II. Application of fuzzy control

In this paper, a feasibility study is conducted where fuzzy logic control is investigated to actively vary spindle speed modulation parameters for chatter suppression. A justification for using fuzzy control is given, as well as a brief synopsis of the fuzzy inferencing mechanism. Proportional and proportional-integral fuzzy control algorithms are developed. The set point in these controllers is established from experimental observations and measurements of the machined surfaces. Controller performance is tested by simulating changes in the axial depth of cut from a stable depth to 20% and 50% beyond the stable limit for constant speed cutting. It was found that both controllers were able to regulate the vibration in the milling process, however, the proportional-integral controller generally exhibited more desirable performance characteristics.     

ESPRIT- and HMM-based real-time monitoring and suppression of machining chatter in smart CNC milling system

Suppression of machining chatter during milling processes is of great significance for surface finish and tool life. In this paper, a smart CNC milling system integrating the function of signal processing, monitoring, and intelligent control is presented with the aim of real-time chatter monitoring and suppression. The algorithm of estimation of signal parameters via rotational invariance techniques (ESPRIT) is adopted to extract the frequency characteristics of acceleration signals, and then, cutting state is categorized as stable state, chatter germination state, and chatter state based on amplitude-frequency characteristics of identified acceleration signals. The model of chatter identification is acquired by training a hidden Markov model (HMM), which combines acceleration signals and labeled cutting state. To implement real-time chatter suppression, the algorithm of fuzzy control is integrated into a smart CNC kernel to determine the relationship between cutting force and spindle speed. Furthermore, spindle speed of machine tool could be adjusted timely in the presented system once the chatter is identified. Finally, the effectiveness of the proposed real-time chatter monitoring and suppression system is experimentally validated.     

轮槽加工中铣削力与铣削温度分布规律研究

轮槽铣刀的改进往往是推动轮槽加工技术进步的最直接动力,而轮槽铣刀不同点的切削用量不同,很难测量出刀具不同点的力和温度。基于微元思想并利用标准盘铣刀和等效方法进行了铣削试验,得到了轮槽铣刀相应型线上铣削力与铣削温度的分布曲线并关注了危险点。     

Development of chatter detection in milling processes

The aim of this research is to develop an in-process detection of the chatter for the actual milling processes regardless of any cutting condition within the small data processing time by utilizing the dynamic cutting forces obtained during cutting. The proposed method introduces three parameters, which are calculated and obtained by taking the ratio of the average variances of the dynamic cutting forces of three force components, to identify the chatter. The algorithm was developed and implemented on five-axis computer numerical control machining center to detect the chatter in ball-end milling and end milling processes. The chatter and the nonchatter can be simply detected during the in-process cutting by mapping the obtained values of three parameters in the reference feature spaces regarding the determined threshold values. The experimental results showed that the proposed method can be effectively used to detect the chatter during cutting even though the cutting conditions are changed.     

多轴NC加工中刀具运动包络面的计算

数控加工的干涉检查及仿真是检查数控代码正确性的一种十分有效和可行的方法.根据五轴加工机床的特点推导出了刀具运动包络面的计算公式,并对该方法的计算机应用进行了分析,结果表明该方法具有一定的理论意义和使用价值.     

The avoidance of cutter gouging in five-axis machining with a fillet-end milling cutter

This paper proposes a new method of automatic detection and elimination of cutter gouging when using the fillet-end milling cutter to produce a complex surface on the five-axis computer numerical control machine tool. To avoid local cutter gouging at the point where the cutter and part surface make contact with each other, the method of exact curvature matching between the cutter and part surface is presented. The size of cutter radii is more easily determined by this method. To detect if a rear cutter gouging occurs near the contact point, a square grid with horizontal and vertical points is used for illustrating the checking area and checking points. The technique of automatic generation of the square grid points and the method of detection and avoidance of rear cutter gouging are investigated throughout this article. In the end, the studied methodology and algorithms are inspected and verified by using an example of nonuniform rational B spline surface.     

装配式圆磨圆柱形铣刀的设计

提出利用刀体自身圆磨反装设计大直径圆柱形铣刀的方法 ,并推导了装配式圆磨圆柱形铣刀有关参数的设计公式。     

Form error estimation in ball-end milling of sculptured surface with z-level contouring tool path

This paper presents a flexible model for estimating the form error in three-axis ball-end milling of sculptured surface with z-level contouring tool path. At an interval of feed per tooth, the whole process of sculptured surface machining is treated as a combination of sequential small inclined surface milling. For ball-end milling of the inclined surface with z-level contouring tool path, at surface generation position, an analytical model is proposed to identify the feedback effect of tool deflection on cutting edge engagement. The deflection-dependent cutting edge engagement is determined by using an iterative procedure. And ultimately, the form error is obtained from the balanced tool deflection and associated surface inclination angle. In a validation experiment, the estimated form errors are compared with both the measurements and the predictions of a rigid model. It is shown that the proposed flexible model gives significant better predictions of the form error than rigid model. Good agreement between the predicted and measured form errors is demonstrated for the ball-end milling of sculptured surface with z-level contouring tool path.     

Cutting force prediction in ball-end milling with inclined feed by means of geometrical analysis

A geometrical model for the analysis of cutting forces in ball-end milling has been presented in a previous work (Tsai CL, Liao YS, J Mater Process Technol 205:24–33, 10), which can be used to analyze cutting forces in vertical or horizontal feed. In this paper, the three-dimensional geometrical analysis is depicted with different interacting relations among cutting edge, undeformed chip and shear zone along nonhorizontal cutting direction, and a general geometrical model of inclined feed in ball-end milling is presented. According to the geometrical analysis, the cutting directions of horizontal, vertical, inclined downward, and inclined upward feed are defined with a feed angle. A general force model is derived, and the three-dimensional cutting forces are predicted. Experiments are conducted to verify the geometric force model. The influences of different feed angle and helix angle on cutting forces in inclined downward and inclined upward feed are discussed and simulated.     

数控铣削加工中的精确对刀方法

数控加工中,为了保证加工精度和不损伤已加工表面,常常要借助对刀工具来对刀。介绍采用寻边器等三种常见的对刀工具在已加工表面的对刀操作应用,并分析每种方法的特点和应用技巧。