Advanced Materials Research Vols. 542-543

Abstract: In order to solve the problems of the cam servo grinding motion control and the contour error detection method and dedicated program development, by the online measurement technology and SINUMERIK 840D system of interpolation table and electronic gear function, Coaxial movement superimposed on the control principle and the specific NC program to achieve high-speed precision grinding cam with discrete error compensation data. The grinding tests on engineering prototype, the experimental results show that the motion control and error compensation method can to compensate for the camshaft rotational speed difference, the servo system response deviation, hardware manufacturing errors repetitive impact factors.

Abstract: This paper emphasize the importance of informatization technology in NC machine tools field. Networking is playing an essential role in marketing research and analysis to make a new management system and more opportunities and profits.

Abstract: A method and prototype system have been developed to assess manufacturability of a machining job with a known machine tool. The data for describing the machining task confirms to STEP-NC data model, i.e. ISO 14649. A group of manufacturability indices have been suggested used in the system. They are called “Key Manufacturability Indicators” (KMIs). Examples of KMIs are workpiece clamping data, machine tool’s capability and cutting tool information. To assist the evaluation process, a machine tool data model is used. The prototype system is validated through an example.

Abstract: Setup datum of fixture design is an important factor of Numerical Control (NC) machining process planning. Using graph theory of FTG (Feature Tolerance relationship Graph) and DMG (Datum and Machining feature relationship Graph) technology, the feature relationship was proposed to construct a relational table of DMMT (Datum and Machining and Machine Tools) in NC machining setup process. The degree of graph as a discriminant evidence of the machining setup datum was given, so that the machining setup process planning was correctly designed. Combined with the capability of NC machine tools, the unit normal vector of feature facet between the feature datum and machining facet were multiplied to determine the fixture capability, which provide a reasonable proposal of machining setup process for multi-position rotation and multi-piece fixture design. Finally, a case study of machining setup process planning and multi-piece fixture equipment design from corporation was presented to verify the feasibility of the method that was based on the graph theory.

Abstract: In order to improve product manufacturing efficiency and quality, the paper brings up a method of building automatic programming template for the parts in same category with the help of an excellent programming platform --Unigraphics NX. It relieves automatic programming staff from repetitive work and improves the product manufacturing efficiency. The actual application result indicates that the method has certain practicality. Meanwhile, it also provides general design method for these similar parts.

Abstract: The point maximum likelihood and interval estimators of the parameters, as well as two reliability indices of the log-linear process model, including cumulative mean time between failures and reliability at given time are given. In tests for failure time trends, both the graphical methods include the mean cumulative function versus time plot and the total-time-on-test plot, and the analytical methods include the Laplace, the military handbook, and the Lewis-Robinson tests are used. A real case of failure dada with time truncation for multiple numerical control (NC) machine tools is given to illustrate the use of the proposed model.

Abstract: During the process of conventional DDA circular interpolation, the synthesis feed rate fluctuations often, the machining errors are large also. A new efficient arc interpolation method is proposed in this paper, which uses the principle of DDA circular interpolation, it’s function is optimized and improved, Radius is used as the basis of interpolation feed, the left normalized data and pre-loaded are used also. The simulation result of VB program show that efficient circular interpolation method not only has high efficiency,but also has high accuracy.

Abstract: In this paper, a new numerical control system(CNC) based on ARM9 and STC12C5410 is studied. The ARM9 core microprocessor, Samsung S3C2440A microprocessor, is the main operation core. It treats the flowing tasks: response to keyboard inputting, display contents on LCD, interpretive the NC codes, output crude interpolations and so on. The secondary CPU, STC12C5410, as the assisting microprocessor is only to realize fine interpolation. The system can be connected an 8-inches display in order to display more information and it has an interface to a four-axis hand wheel. It has a communication interface and can receive CNC codes form other computer. The system can drive four step-servo motors or servo-actuators and realize turning, milling, grinding and combination machining. That is that the system is a multifunction system.

Abstract: Parametric spline interpolation has been widely used in CNC machining because of its advantages over linear and circular interpolation. However, the acceleration/decleration (ACC/DEC) may easily change beyond the machine tool drive’s ability due to abrupt change in feedrate profile. In this paper, an adaptive non-uniform rational B-spling (NURBS) interpolation with S-shape ACC/DEC control algorithm is proposed. In the proposed algorithm, the commanded feedrate is kept constant for most time and adaptively adjusted at the sharp corners to confine the chord error within a specified tolerance range during the interpolation process. The S-shape ACC/DEC profile is adopted to generate a smooth feedrate and satisfy the machine acceleration and deceleration capability. Simulation results for NURBS example are provided to verify the feasibility and advantages of the proposed scheme.

Abstract: According to the required interval estimation precision of mean time between failures (MTBF) and reliability for numerical control (NC) machine tools, where failure processes can be described by the power law process model, the minimal testing truncated time and sample size of the reliability assessment test are given using Fisher information matrix method. The results show that there are two main factors which affect the truncated time and sample size. They are the log ratio of upper bound to lower bound and confidence of interval estimation for reliability indices, respectively. Among them, the minimal sample size increases significantly as the improvement of required precision of interval estimation for reliability indices and confidence increases, but the minimal testing truncated time is less affected by these two factors.