Search

Gravity has huge impact on the accuracy of heavy-duty machine tools. To investigate errors caused by gravity, it is essential to figure out the most influential factor. This paper presents a geometric error modeling for heavy-duty CNC machine tools. Regarding a machine tool as a rigid multi-body system (MBS), the geometric error model has been established by utilizing kinematics chain and homogeneous transfer matrix (HTM). By analyzing the Jacobi matrix, the influence of all the geometric error parameters has been calculated to find out the key geometric error that affect the accuracy most. It is revealed that gravity of beam and tool affect the accuracy of the machine tool most through the ANSYS simulation. It supports a theoretical basis for the further research on error compensation of the key component of a machine tool.

Automatic tape laying is a widely-used fabricating process for fiber-reinforced composite materials in aerospace and aviation industry. To fulfill the tape laying process, it is necessary to cut the prepreg tape into designated shape accurately and promptly. In this paper, a scheme of ultrasonic cutting bench is put forward to investigate the parameters of ultrasonic cutting process. The functional requirements are analyzed and the key components of ultrasonic cutting bench, such as transverse feed mechanism of cutter, revolving gear of cutter, and mechanism for precision positioning of cutting depth, are presented in detail, which lays a solid foundation for future experimental research.

A review of methods used for fault recognition of the rolling elements in gearbox, namely gear and bearing, is presented in this paper. The procedure of the fault recognition can be classified into three phases, which are data acquisition, data processing or important features extraction, and the fault mode detection. Many different methods have been developed in dealing with each phase, so that the arrangement of the entire process has different strategies. This paper summarizes some general used and recently popular developed methods of each phase, and makes comparison between them. This work also aims at giving a perspective in such area in the future, based on the known researches.

The size of pulse compression gratings (PCG) is very big in the ICF system, so we obtained a large size grating by mechanically stitching small caliber gratings. And we design the splicing mechanism to be a 5-DOF Parallel Mechanism with macro/micro dual feed drive control to meet the requirements of large travel, high precision, high stability and 5-DOF of the grating tiling. The macro-moving part is designed to be the 5PTS-1PPS parallel mechanism, using the Feed Mechanism of ballscrew with Stepper Motor Drive.The micro-moving part is designed to be 5TSP-1PPS parallel mechanism, using the feed mechanism of Flexure Hinge with Piezoelectric Ceramic Actuator. We derived control algorithm of parallel mechanism by the method of the Kinematics of parallel mechanism. We analyzed the systematic error and put forward the error correction method in order to improve the positioning accuracy. At last, we designed an optical detecting system to evaluate the feasibility of this scheme, the positioning accuracy and the Stability of parallel Splicing structure. The results showed that the mechanism performance can meet the requirements of grating tiling work.

For automated fiber placement machine, tensioner is one of the important modules, which precisely generates and controls the tension of fibers.This paper performs a system analysis and synthesis of the key technologies of tensioner in recent years by summing up the development course of the tensioner. A new type of tensioner specially designed for fiber placment technology is presented. Experiments results prove the feasibility of the proposed mechanism and control algorithm. In addition, this paper also aims at giving a perspective in such area in the future.

Form grinding is one of the most efficient processes for finish machining of gear wheels. This paper investigates the method of system development for wheel modification of involute cylindrical gear based on SINUMERIK 840D system and its OEM development package. The control software developed for form grinding is applied to dress form grinding wheel by using the numerical control dresser, and normal projection is adopted as the method to calculate the sectional shape of grinding wheel. The friendly interface of control software, edited by Visual Basic was developed to meet needs of users. Finally, personalized interface and processing methods are integrated and embedded in Siemens CNC system through Dynamic Link Library to implement parameterized automatic processing, which is more efficient in programming and machining.

Error compensation can improve the accuracy of machine tools effectively. Among the error sources affecting the accuracy of CNC machine tool, geometric error is always set as a key performance criterion. This paper summarizes several methods of geometric error modeling and reviews the characteristics of different methods. Furthermore, available methods for measuring geometric errors have been reviewed also based on the advanced instruments. This work aims at enhancing the efficiency of error detection and give a perspective for the application of error compensation in the future.

To overcome the difficult in modeling the mode theory for magnetic flywheel, by non-parametric frequency domain identification method for identification of system model, this paper select the PID neural network nonlinear intelligent control methods based on GA. Used a method based on iterative process to suppress the resonance, combined with zero-pole theory, this research designed a GA-based PID neural network identification controller to address the modal vibration suppression problems in the external rotor flywheel .The experiments for this paper proved the effectiveness of iterative process, and the controller can restrain the system mode vibration well.

The magnetic flywheel is widely used in energy storage and spacecraft, and it needs to reduce the system’s power consumption effectively when designing the controller. Always, the magnetic bearing system’s performance depends on the tracking performance of the desired force signal. In order to balance the two goals between reducing magnetic system’s power consumption and guaranteeing its performance, a current power allocation way was proposed, and a static current optimization was given based on the way. According to the simulation and experimental results, this method can reduce the magnetic bearing system’s power consumption significantly and keep the tracking performance of force signal well on the same time.

This paper outlines a conceptual framework of STEP-NC manufacturing system, which integrates the entire manufacturing process including CAD, CAPP, CAM and CNC, to make full use of the advantages of the new generation of data model. The STEP-NC manufacturing system consists of five parts and the STEP-NC standard is used to transport the complete product information. The intelligent CNC in this system can parse STEP-NC program directly so that no translation is needed and the part programs are reusable. Networked manufacturing can be realized by implementing this new framework of STEP-NC manufacturing system.

Micro-end-milling tools are suitable for machining miniature parts which have complex shape. As the diameters of tools are too small, cannot directly obtain the frequency response functions (FRFs) through impact hammer test at tool tip. This paper employs Receptance Coupling method (RC), couple the tool tip’s FRFs with machine-toolholder system’s FRF, and then get the micro-end-milling tool’s FRF. Establish the coupling model, then finite element and hammer test of the blank gauge tools are used to obtain the coupling transfer functions (TFs). Then analyze the tool tip model by finite element, couple with the machine-toolholder system hammer test result and coupling transfer functions, finally the micro-end-milling tool’s FRFs are obtained. Through the hammer test of blank gauge tool, the effectiveness and feasibility of RC method are verified. The result shows that the RC method is accurate at micro-end-milling tool in steady state milling.

The micro crowled integral impeller is one of the key parts of aeroengine. It is difficult to machine for its complex structure and small dimension. In this paper, the tool path planning scheme of micro crowled integral impeller is researched, which lays foundation for the numerical control machining of the part. To begin with, considering the feature of impeller’s structure, a kind of processing route is proposed and the processing regions are divided, which satisfy the demand of accuracy and efficiency. Then, the tool path planning scheme of the impeller is put forward, which is regular and is more suitable for a large-diameter tool to fulfill the machining process. Finally, machining simulation is carried out to prove the feasibility and correctness of the proposed path planning scheme.

To improve production quality and reduce machining time, machining parameters need to be monitored and adjusted automatically in milling. An integrated controller which is modular, configurable and based on OMAC, is established. The hardware platform, resultant cutting force constraint and its fuzzy control rules have been introduced in detail. In the fuzzy controller designed, two inputs and one output are used with five fuzzy sets for the controller, and the output rate of feed-rate can be changed from 50% to 200%. This controller has the abilities of reducing fluctuation range of cutting force, adjusting feed-rate intelligently, which is a part of CNC system. The experiment results show it can realize the real time status monitoring with this system, reduce the cutting force fluctuation, and adjust the feed-rate intelligently during machining.

The influence of preheating adopted and preheating unadopted on manufacturing speed during the automated fiber placement process has been analyzed. According to Fourier heat equation and assuming the towpreg with uniform material properties, a heat transfer model of towpreg has been established. The boundary conditions and initial conditions of this model at different stages have been given based on energy exchange principle. The research chooses thermoplastic composite APC-2(carbon/PEEK) as the towpreg material and utilizes the finite element method to investigate the temperature history of the fiber placement process. Since fiber placement speed is related with the response time of temperature, it can be obtained by the temperature history. Finally, the results demonstrate preheating can significantly improve the fiber placement speed.

Based on the principle of axial active magnetic bearing rotor-system with single degree of freedom, magnetic rotor-system vibration mode was described. A 3D finite element model of active magnetic bearing rotor-system was established by ANSYS11. Initial six order natural frequencies and vibration mode were calculated by the module of modal analysis of ANSYS11, and compared with the results of system identification. Analysis shows that there was a certain difference between the results, but the difference was small. The analysis result indicates that it is an effective method to apply FEA in the design of the active magnetic bearing. It provided the foundation for structure optimal design of the system and theoretical basis for flexible system design.

The numerical simulation of hot-stamping process was carried out for UHSS square-cup parts, and the influence of dies temperature on the hot-stamping process was anlysised. Besides, through the microstructure analysis and mechanical properties testing of the formed parts, effects of dies temperature on microstructures and mechanical properties of hot-stamping square-cup parts were obtained. The experiment and simulation results showed that the mechanical properties of the UHSS are strongly dependent on the temperature, so the dies temperature is one of the most important parameters that have to be taken into account in designing the hot-forming dies and the hot-forming process.

In order to overcome the system nonlinear instability and uncertainty inherent in magnetic bearing systems, two PID neural network controllers (BP-based and GA-based) are designed and trained to emulate the operation of a complete system. Through the theoretical deduction and simulation results, the principles for the parameters choice of two neural network controllers are given. The feasibility of using the neural network to control nonlinear magnetic bearing systems with un-known dynamics is demonstrated. The robust performance and reinforcement learning capability in controlling magnetic bearing systems are compared between two PID neural network controllers.

Currently machine tools and strategies researched in micro-milling field universally cannot be applied to 3D meso-scale parts machining directly, so great importance should be attached to the research on 5-axis machine tools and the suitable strategies for 3D meso-scale machining. This paper introduced a self-made 5-axis machine tool and several micro-milling strategies which were applicable to 3D meso-scale parts machining. Using these strategies, a mini impeller was successfully machined on the 5-axis machine tool developed independently. The experiment result showed the machine tool and the strategies were suitable for machining meso-scale 3D parts.

The numerical control (NC) program files need re-generating if there is any tool dimension change or tool wear for multi-axis machining. If the tool is replaced to adapt this change there will be increased cost. To solute this problem, 3D cutter radius compensation method for 5-axis computer numerical control (CNC) machining is deeply researched. Taking five axes linkage machine tools of X, Y, Z, B, C form with rotary tables B and C as an example, coordinate transformation matrix (CTM) and the cutter compensation vector for 3D cutter radius compensation are derived. The discrimination methods for path joint pattern (PJP) are given. A controller with 3D cutter radius compensation function for 5-axis linkage CNC machine tools is developed based on this method. The controller is allocated to a 5-axis milling machine tool and experiments are done. The proposed algorithm is demonstrated using a practical example.

When using meshing creating method of FP (fiber placement) track, once the track point falls at some vertex point of mesh element, in the meantime the vertex point happens to be shared by several mesh elements, there needs a reasonable calculation method to select next mesh element which the FP track will pass through. Then it comes to the problem on linking of FP tracks. In order to solve it, in this paper, the author puts forward a new method, in which parallel projection theory is used, project need analytical mesh element and FP reference vector to a sound projective plane, on which the mesh element be selected and the FP track be calculated, then the FP track would be projected back to the placement surface. Program using this method realized a reasonable joint at the shared vertex point of meshing elements, which the FP direction has little change, and the mutation of track doesn’t come forth. So, the correctness of the method, which putted forward in this paper, is proved.

For the application of STEP-NC in NC system, an STEP-NC code translator is exploited. Firstly, summarizes the limitation of conventional standard ISO6983 and the superiority of STEP-NC. After an analysis on two different generating methods of STEP-NC program, introduces the exploited STEP-NC code translator based on ISO14649. According to inner logical relation, the code translator is composed by six functional modules, an operating principle chart is presented, function and realizing method of every module is disserted on. At last, exampled with a program which includes planar face, pocket, slot, Bezier surface and replicate feature of round hole, planning the whole toolpath of the program using extracted information about workingstep, feature and operation by the exploited STEP-NC code translator. A cutting simulation is made to the toolpath and the workpiece model. The result proves the feasibility of the STEP-NC code translator.

The theory of composite material patch winding is proposed to determine the winding trajectory by a meshed data model. The bridge condition on the concave surface is considered in this work. This paper puts forward the judgmental principles and corresponsive solutions by applying differential geometry theory and space geometry theory. To validate the feasibility of the patch winding method, the winding control code is programmed. Furthermore, the airplane inlet winding experiments are carried out.

To meet the need of advanced manufacturing technique, an open computer numerical control (CNC) software package for CNC machining is developed. Module library of the software package was of tree structure with a depth of 5. Terminal nodes of the tree were module units with unambiguous functions. Module units which dealt with real-time tasks were developed adopting real-time dynamical linked library (RTDLL), and non-real-time module units were developed with component object model (COM). CNC controllers for various machine tools could be built with the software package. The controllers’ external interfaces were coincident with the serial real-time communication system (SERCOS) international standards, and the internal interfaces followed the open modular architecture controller (OMAC) agreement. Motion controllers for 3-axis linkage milling machine tools and for 5-axis linkage milling machine tools were built using the software package. It is shown by experiments that controllers built can be used for motion control of CNC machine tools and CNC machine tools with the controllers have good processing performances.

The current 5-axis coordinated linear interpolation method results in low-speed, low-accuracy and enormous numerical control (NC) files in sculptured surface machining. An instruction format with AKIMA spline curves suitable for 5-axis coordinated real-time interpolation is presented by making use of the advantages of AKIMA curves to represent spatial curves. Curve through position vectors in the machining path is constructed using AKIMA spline method. The related orientation vector to each position vector is calculated by angles of the machine tool rotation axis. Then curve through orientation vectors is achieved by AKIMA method too. Real-time interpolation of these curves is accomplished with a method of truncated Taylor series expansion. A controller with this interpolation method is developed in an open computer numerical control (CNC) system developed by ourselves. The performance of the proposed controller is demonstrated using a practical example.