MULTI-AXIS LINKED SERVO SYSTEM CONTOURING ERROR CONTROL APPROACH BASED ON NURBS CURVE INTERPOLATION

2011 ◽  
Vol 10 (01) ◽  
pp. 21-27 ◽  
Author(s):  
GUOYONG ZHAO ◽  
YUGANG ZHAO
Keyword(s):  
Error Control ◽  
Servo System ◽  
Numerical Control ◽  
Cnc Machine Tools ◽  
Cnc Machine ◽  
Nurbs Curve ◽  
Control Approach ◽  
Contouring Error ◽  
Curve Interpolation ◽  
Servo Controller

The contouring precision of computer numerical control (CNC) machine tools relates to whether the dynamic performances among all the axes match or not. In general, the cross-coupled controller (CCC) is a more efficient approach to enhance contouring precision than single-axis servo controller. Note that the contouring error CCC can not be separated from pathway programming in multi-axis linked servo system. In order to obtain satisfied contouring precision, the CCC approach connected with non-uniform rational basis spline (NURBS) curve interpolation is researched in detail in the paper. Above all, an "arc approximation algorithm" contouring error computing model is developed, according to the real cutter positions from each axis feedback and the interpolation dots stored in the interpolation buffer. Then the contouring error correction quantity PI control and distribution algorithm is put forward by introducing a zoom coefficient. The contrast experimental results on the CNC experiment table show that the developed CCC approach can reduce contouring error and improve tracking performance further.

scholarly journals Study of Machining of Gears with Regular and Modified Outline Using CNC Machine Tools

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2913
Author(s):  
Rafał Gołębski ◽  
Piotr Boral
Keyword(s):  
Machine Tools ◽  
Coordinate Measuring Machine ◽  
Optical Microscope ◽  
Numerical Control ◽  
Cnc Machine Tools ◽  
Cnc Milling ◽  
Cnc Machine ◽  
Cylindrical Gears ◽  
Measuring Machine ◽  
Five Axis

Classic methods of machining cylindrical gears, such as hobbing or circumferential chiseling, require the use of expensive special machine tools and dedicated tools, which makes production unprofitable, especially in small and medium series. Today, special attention is paid to the technology of making gears using universal CNC (computer numerical control) machine tools with standard cheap tools. On the basis of the presented mathematical model, a software was developed to generate a code that controls a machine tool for machining cylindrical gears with straight and modified tooth line using the multipass method. Made of steel 16MnCr5, gear wheels with a straight tooth line and with a longitudinally modified convex-convex tooth line were machined on a five-axis CNC milling machine DMG MORI CMX50U, using solid carbide milling cutters (cylindrical and ball end) for processing. The manufactured gears were inspected on a ZEISS coordinate measuring machine, using the software Gear Pro Involute. The conformity of the outline, the tooth line, and the gear pitch were assessed. The side surfaces of the teeth after machining according to the planned strategy were also assessed; the tests were carried out using the optical microscope Alicona Infinite Focus G5 and the contact profilographometer Taylor Hobson, Talysurf 120. The presented method is able to provide a very good quality of machined gears in relation to competing methods. The great advantage of this method is the use of a tool that is not geometrically related to the shape of the machined gear profile, which allows the production of cylindrical gears with a tooth and profile line other than the standard.

scholarly journals Practical method for the fast generation of a CAM model for jet engine parts

2021 ◽  
Vol 13 (3) ◽  
pp. 168781402110027
Author(s):  
Byung Chul Kim ◽  
Ilhwan Song ◽  
Duhwan Mun
Keyword(s):  
Computer Aided Design ◽  
Feature Recognition ◽  
Practical Method ◽  
Numerical Control ◽  
Cnc Machine Tools ◽  
Cnc Machine ◽  
Jet Engine ◽  
Computer Aided ◽  
Cad Models ◽  
Cam Model

Manufacturers of machine parts operate computerized numerical control (CNC) machine tools to produce parts precisely and accurately. They build computer-aided manufacturing (CAM) models using CAM software to generate code to control these machines from computer-aided design (CAD) models. However, creating a CAM model from CAD models is time-consuming, and is prone to errors because machining operations and their sequences are defined manually. To generate CAM models automatically, feature recognition methods have been studied for a long time. However, since the recognition range is limited, it is challenging to apply the feature recognition methods to parts having a complicated shape such as jet engine parts. Alternatively, this study proposes a practical method for the fast generation of a CAM model from CAD models using shape search. In the proposed method, when an operator selects one machining operation as a source machining operation, shapes having the same machining features are searched in the part, and the source machining operation is copied to the locations of the searched shapes. This is a semi-automatic method, but it can generate CAM models quickly and accurately when there are many identical shapes to be machined. In this study, we demonstrate the usefulness of the proposed method through experiments on an engine block and a jet engine compressor case.

FPGA-Based Intelligent Software Hardening Chip for Computer Numerical Control System

2011 ◽  
Vol 105-107 ◽  
pp. 2217-2220
Author(s):  
Mu Lan Wang ◽  
Jian Min Zuo ◽  
Kun Liu ◽  
Xing Hua Zhu
Keyword(s):  
High Speed ◽  
High Performance ◽  
Large Scale ◽  
Position Control ◽  
Computer Numerical Control ◽  
Numerical Control ◽  
Cnc Machine Tools ◽  
Cnc Machine ◽  
Cnc System ◽  
Intelligent Software

In order to meet the development demands for high-speed and high-precision of Computer Numerical Control (CNC) machine tools, the equipped CNC systems begin to employ the technical route of software hardening. Making full use of the advanced performance of Large Scale Integrated Circuits (LSIC), this paper puts forward using Field Programmable Gates Array (FPGA) for the functional modules of CNC system, which is called Intelligent Software Hardening Chip (ISHC). The CNC system architecture with high performance is constructed based on the open system thought and ISHCs. The corresponding programs can be designed with Very high speed integrate circuit Hardware Description Language (VHDL) and downloaded into the FPGA. These hardening modules, including the arithmetic module, contour interpolation module, position control module and so on, demonstrate that the proposed schemes are reasonable and feasibility.

An Equivalent-Plane Cross-Coupling Position Control for Contour-Accuracy Improvement in Three-Axis Free-Form Contour Following Tasks

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Jian-Wei Ma ◽  
De-Ning Song ◽  
Zhen-Yuan Jia ◽  
Wen-Wen Jiang ◽  
Fu-Ji Wang ◽  
...  
Keyword(s):  
Error Control ◽  
Position Control ◽  
Three Dimensional ◽  
Cross Coupling ◽  
Experimental Tests ◽  
Numerical Control ◽  
Free Form ◽  
Contouring Error ◽  
Contour Following ◽  
Better Than

To reduce the contouring errors in computer-numerical-control (CNC) contour-following tasks, the cross-coupling controller (CCC) is widely researched and used. However, most existing CCCs are well-designed for two-axis contouring and can hardly be generalized to compensate three-axis curved contour following errors. This paper proposes an equivalent-plane CCC scheme so that most of the two-axis CCCs or flexibly designed algorithms can be utilized for equal control of the three-axis contouring errors. An initial-value regeneration-based Newton method is first proposed to compute the foot point from the actual motion position to the desired contour with a high accuracy, so as to establish the equivalent plane where the estimated three-dimensional contouring-error vector is included. After that, the signed contouring error is computed in the equivalent plane, thus a typical two-axis proportional-integral-differential (PID)-based CCC is utilized for its control. Finally, the two-axis control commands generated by the typical CCC are coupled to three-axis control commands according to the geometry of the established equivalent plane. Experimental tests are conducted to verify the effectiveness of the presented method. The testing results illustrate that the proposed equivalent-plane CCC performs much better than conventional method in both error estimation and error control.

scholarly journals Dynamic Modeling and Experiment Research on Twin Ball Screw Feed System Considering the Joint Stiffness

Symmetry ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 686 ◽  
Author(s):  
Meng Duan ◽  
Hong Lu ◽  
Xinbao Zhang ◽  
Yongquan Zhang ◽  
Zhangjie Li ◽  
...  
Keyword(s):  
Dynamic Modeling ◽  
Dynamic Characteristics ◽  
Friction Model ◽  
Numerical Control ◽  
Ball Screw ◽  
Cnc Machine Tools ◽  
Axial Stiffness ◽  
Cnc Machine ◽  
Feed System ◽  
Lumped Mass

It is of great significance to study the dynamic characteristics of twin ball screw (TBS) feed system to improve the precision of gantry-type dual-driven computer numerical control (CNC) machine tools. In this paper, an equivalent dynamic model of the TBS feed system is established utilizing lumped mass method considering the stiffness of joints. Equivalent axial stiffness of screw-nut joints and bearing joints are both calculated by Hertz contact theory. Furthermore, a friction model is proposed because the friction force of the screw nut affects the stiffness of the joints. Then, the friction parameters are obtained by using the nonlinear system identification method. Meanwhile, a finite element model (FEM) is developed to assess the dynamic characteristics of TBS feed system under the stiffness of joints. Finally, validation experiments are conducted, and the results show that the positions of the nut and the velocities of worktable greatly affect the dynamic characteristics of the TBS feed system. Compared with the theoretical calculation, FEM and experiments indicate that the dynamic modeling proposed in this article can reach a higher accuracy.

An Analytical C3 Continuous Local Corner Smoothing Algorithm for Four-Axis Computer Numerical Control Machine Tools

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Qin Hu ◽  
Youping Chen ◽  
Jixiang Yang ◽  
Dailin Zhang
Keyword(s):  
Machine Tools ◽  
Numerical Control ◽  
Cnc Machine Tools ◽  
Smoothing Algorithm ◽  
Linear Motion ◽  
Tool Orientation ◽  
Cnc Machine ◽  
B Splines ◽  
Rotary Axes ◽  
Tip Position

Linear motion commands of multi-axis computer numerical control (CNC) machine tools need to be smoothed at the transition corners, because the velocity discontinuities at corners can result in fluctuations on machine tool motions and lead to poor surface quality. However, no research has been reported on local corner smoothing algorithm for four-axis CNC machine tools with two rotary axes by considering their special kinematic characteristics. To this end, this paper proposes an analytical C3 continuous local corner smoothing algorithm for four-axis CNC machines with two rotary axes. After coordinates transformation, the tool tip positions and tool orientations are smoothed by locally inserting specially designed three-dimensional (3D) quintic B-splines and one-dimensional (1D) quintic B-splines into the corners between linear motion segments, respectively. The smoothing algorithm guarantees C3 continuity of the tool tip position and C3 continuous synchronization of the tool orientation related to the tool tip position, through analytically evaluating control points of the inserted microsplines. The maximum error tolerances of the tool tip position and tool orientation are mathematically constrained. Experiments on an in-house developed four-axis machine verify the efficacy of the proposed algorithm, where maximal errors caused by the local corner smoothing algorithm are constrained, the synchronization of the tool orientation and the tool tip position are achieved, and the proposed C3 continuous corner smoothing algorithm has lower jerk and jounce but higher tracking and contour accuracy than C2 continuous algorithm.

Maintenance Strategy Optimization for Computer Numerical Control Machine Tools

2015 ◽  
Vol 809-810 ◽  
pp. 1504-1509 ◽  
Author(s):  
Ana Lacramioara Ungureanu ◽  
Gheorghe Stan ◽  
Paul Alin Butunoi
Keyword(s):  
Machine Tools ◽  
Computer Numerical Control ◽  
Numerical Control ◽  
Condition Based Maintenance ◽  
Financial Impact ◽  
Cnc Machine Tools ◽  
Cnc Machine ◽  
Maintenance Strategies ◽  
Time Period ◽  
A Company

In this paper are proposed two new approaches to maintenance strategies for Computer Numerical Control (CNC) machine tools. The analysis is done for different families of CNC machine tools from S.C. Elmet Bacau, a company specialized in aviation. In maintenance actions applied to CNC machine tools is very important to know the evolution of defects and critical state of electrical and mechanical components. The results of this analysis concludes that maintenance actions can be judged by the developing time period diagram, between failure appearance and interruptions in operation. It is also analyzed the financial impact, revealed from known maintenance strategies adopted on CNC machine tools, resulting in a positive approach of condition based maintenance.

scholarly journals Research on Deterministic Figuring of Ultra-Precision Shaft Parts Based on Analysis and Control of Figuring Ability

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2458
Author(s):  
Zizhou Sun ◽  
Yifan Dai ◽  
Hao Hu ◽  
Guipeng Tie ◽  
Chaoliang Guan ◽  
...  
Keyword(s):  
Machine Tools ◽  
Measured Data ◽  
Numerical Control ◽  
Cnc Machine Tools ◽  
Machining Efficiency ◽  
Air Bearing ◽  
Cnc Machine ◽  
Ultra Precision ◽  
Precision Machine Tools ◽  
And Control

The application of ultra-precision shaft parts is widely used, such as the spindle core of the air bearing spindle in ultra-precision machine tools. The precision of the spindle core is extremely high, and it is very difficult to obtain directly by traditional Computer Numerical Control (CNC) machine tools but is mostly obtained by manual grinding, whose machining efficiency is greatly limited. Based on the deterministic figuring theory, this paper focuses on the ultra-precision roundness, optimizing the filtering parameters of the measurement error data and studying the generation mechanism of the removal function morphology; the shape of the removal function is adjusted by combining the analysis of the figuring ability and positioning error. Finally, the optimized removal function is used on an experimental steel shaft, the average roundness convergence ratio is 72% higher than that of the original removal function, and the roundness reaches a 0.1 μm level. The result shows that a reasonable filtering of measured data and the removal function adjusted for the surface feature can improve the efficiency and precision of deterministic figuring on shaft parts.

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