Yanlong Cao

Study on functional specification scheme on interface based on positioning features

This article proposes a scheme for functional specification in accordance with the new generation of geometrical product specification. The scheme is to decompose a geometrical functional requirement on a complex mechanism into geometric specifications defined on key parts. The assembly is analyzed by graph theory. The general geometrical functional requirement is analyzed and decomposed if necessary, with geometrical tolerances specified on ending parts. Then geometric variation model is built according to the invariant degree of freedom of both datum reference system and tolerance zone, which is subsequently used to validate the sufficiency of the datum reference frame on positioning features, thereby inferring joints that perform key roles in affecting function. After a series of topological rules formulated and validation algorithm applied, datum reference system is validated and detailed specifications are generated on joint surfaces. Those specifications on underlying parts or subassemblies are then defined as new geometrical functional requirements and should be further developed. Therefore, the designer can carry out an effective recursive approach capable of realizing each geometric specification on key features while ensuring functional tolerancing of the entire assembly. A case study is given to validate the proposed method.

Multi-scale prediction of the geometrical deviations of the surface finished by five-axis ball-end milling

Surface quality and accuracy are the main factors which affect the performance and life cycle of the products. Due to the complexity of the machining process, it is difficult to evaluate the machined surface real time. Simulation of the machining process became the main method to predict and control the quality of the machined surface. This article developed a multi-scale simulation system to predict the overall geometrical features of the milled surface. The effects of locating errors, geometrical errors of the machine tool and tool deflections on the quality of the machined surface are included in the proposed model. Also, different strategies are employed to evaluate the macro-scale and micro-scale geometrical deviations of the machined surface to balance the time cost and accuracy. In comparison with the traditional method, both the form deviations and roughness feature of the machined surface can be predicted. Since the static and dynamic properties of the machining system were considered, both the stable and unstable cutting conditions can be analyzed by using the proposed method. At the end of this article, case studies are carried out to validate the proposed method. The effects of the locating errors, geometrical errors of the machine tool and cutting parameters on the quality of the machined surface are analyzed. The significance of their influences on the quality of the machined surface was investigated.

EOQ principle analysis of benefit consistency of supply and demand based on comprehensive cost of quality

This paper presents a conceptual framework for economics of quality (EOQ) principle analysis based on comprehensive cost of quality (CCQ) which improved the traditional cost of quality (COQ) model. Firstly, the paper establishes the CCQ model. Then, relationship schemes between quality level and relevant costs are given. At last, the value engineering is introduced into the process of EOQ principle analysis and the mathematical model of EOQ principle analysis is established by compositing the value orientation from both enterprise and customer. The most appropriate quality level interval can be gotten by the EQQ model which is helpful for enterprises to select the most suitable quality level in market competition environment, and maximise revenue for both sides of supply and demand.

A novel tool-path generation method for five-axis flank machining of centrifugal impeller with arbitrary surface blades

The centrifugal impeller with arbitrary surface blades is a very important component in automobile, ships, and aircraft industry, and it is one of the most difficult parts to process. Focusing on the machining efficiency improvement, combining the geometric advantages of ruled surface and arbitrary surface, and utilizing the efficient and accurate advantages of flank machining and point machining, this article presents a novel and targeted tool-path generation method and algorithm for five-axis flank machining of centrifugal impeller with arbitrary surface blades. In light of specific characters of different surfaces, the analyses of two different impeller blades are proposed first, the more characteristic and complex geometrical structures of the arbitrary blade are achieved. In rough machining, an approximate ruled surface blade is obtained, and a simple channel is achieved; the flank milling of the centrifugal impeller with ruled surface blades is achieved relative to the point milling of the centrifugal impeller with arbitrary surface blades; and the triangle tool path planning method is added in this process to save the machining time and cost collectively. Furthermore, in semi-finish machining, the approximate sub-ruled blade surfaces are calculated, and a new flank milling method of the sub-ruled blade surfaces is achieved; a new solution for tool interference is achieved in this process and the generation of non-interference tool paths becomes easy. Machining experiments of two different impellers are presented as a test of the proposed methods.

Study on extraction of electrical runout in eddy current measurement using finite element method

Electrical runout is a bottleneck problem of eddy current sensor, which is caused by the maldistribution/variation of material electromagnetic properties of measurement target. However, extraction methods of electrical runout in eddy current displacement measurement remain ambiguous. Here, a 2D finite element model for the influence analysis of conductivity and permeability of ferromagnetic material on coil impedance of eddy current sensor is reported, which will be beneficial for detecting material properties and guiding manufacturing process. The relationships between the real and imaginary part of coil impedance with the varied material conductivity, relative permeability and the lift-off, which indicates the detecting distance, are investigated. When the conductivity, relative permeability of ferromagnetic material and the lift-off vary within a certain range, the relationships between the real and imaginary part of coil impedance are all nearly linear. This paper further shows that the character of distribution of resistance and reactance in diagram under different material properties and same measuring distance is linear. Furthermore, these lines under different measuring distances are parallel. Also the character under different measuring distances and same material property is linear, but these lines under different material properties are diffuse with same intercept. Altogether, the study shows that this method based on redesign of signal processing and its circuit is feasible and instructive in separating electrical runout from the output of eddy current sensor.

A method for estimating impact location of loose part using HHT

A method for estimating the impact location of a loose part is described in this paper, which uses Hilbert-Huang Transform (HHT) and dispersion characteristics of bending waves propagated in a plate. The power propagation velocity and arrival time difference of bending waves related to the dispersion characteristics can be obtained through the transformation of impact signals using Hilbert-Huang Transform. The distance from the impact location to the signal measuring point can be estimated using the information on the power propagation velocity and the arrival time difference of two bending waves. The experimental results show that the proposed method estimates the impact location with average relative percentage error in 7.68% compared with the actual impact location.

Planar straightness error evaluation based on particle swarm optimization

The straightness error generally refers to the deviation between an actual line and an ideal line. According to the characteristics of planar straightness error evaluation, a novel method to evaluate planar straightness errors based on the particle swarm optimization (PSO) is proposed. The planar straightness error evaluation problem is formulated as a nonlinear optimization problem. According to minimum zone condition the mathematical model of planar straightness together with the optimal objective function and fitness function is developed. Compared with the genetic algorithm (GA), the PSO algorithm has some advantages. It is not only implemented without crossover and mutation but also has fast congruence speed. Moreover fewer parameters are needed to set up. The results show that the PSO method is very suitable for nonlinear optimization problems and provides a promising new method for straightness error evaluation. It can be applied to deal with the measured data of planar straightness obtained by the three-coordinates measuring machines.

Tolerance specification of the plane feature based on the axiomatic design

Tolerance specification involves selecting tolerance types for functional or assembly features to control the variation of features. General methods tend to formulate a frame to specify all the features of part, while the specification methods or reasoning rules for specific feature (point, line, plane, cylinder, etc.) are less studied. This paper focuses on the tolerance-type selection of the plane feature. The theory of axiomatic design is introduced to select the tolerance type for the plane feature, and the problem is interpreted as a redundant decoupled design. To achieve the functional requirements, design parameters and constraints of physics domain are determined. The mapping rules, which are between design parameters and functional requirements, are generated based on the independent axiom. Considering the large number of solutions of the design, the constraints such as cost and inspection methods are introduced to reduce the number of solutions. The minimum information axiom is introduced for the optimum mapping rules and the tolerance types are selected by the optimum mapping rules for the plane feature. Finally, the specification process is concluded and demonstrated by means of an example.

A novel tolerance analysis method for three-dimensional assembly

Three-dimensional tolerance analysis is increasingly becoming an innovative method for computer-aided tolerancing. Its aim is to support the design, manufacturing, and inspection by providing a quantitative analysis of the effects of multi-tolerances on final functional key characteristics and predict the quality level. This article proposes a novel approach for three-dimensional assembly analysis—a hybridization of vector loop and quasi-Monte Carlo method. The former is used to establish the three-dimensional assembly chain and obtain the assembly function. The latter is adopted to generate n sets of dimensional values according to the distribution of each dimension in chain. The new method is shown to inherit many of the best features of classical vector loop and quasi-Monte Carlo, combining easy-to-obtain assembly function with accurate statistical analysis. For every set of dimensional values, one sample value of a functional requirement can be computed with the Newton–Raphson iterative procedure. A crank slider mechanical assembly is shown as an example to illustrate the proposed method.

Influence of tool rotation errors on flank machined surface

In flank milling, the machined metal surface is formed by the edge of the cutting tool and is thus affected by tool errors. Cutting tool rotation errors affect the movement of the tool teeth and thus change the trajectory of the tool edge. This change will also affect the cutting force, which will result in deformation in the cutting process. Previous studies focus mostly on the cutting tool runout error and ignore the effect of tool deformation. In this article, we built a mathematical model of the machining process that considers not only the tool runout error but also the tool tilt deformation error. Using this model, we analyzed how the tool rotation error will influence workpiece surface quality and surface frequency. Results show that feed rate and rotation errors will affect surface roughness, geometric error, and surface energy distribution.