scholarly journals Performances and Shapes of Acceleration-deceleration Curve of Kinematical Linkages

2020 ◽  
Vol 14 ◽  
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Mobile Element ◽  
Industrial Robots ◽  
Numerical Control ◽  
Design Stage ◽  
Contour Error ◽  
Maximum Acceleration ◽  
Positioning Accuracy ◽  
Acceleration And Deceleration

The transient duty has a very important role within the kinematical linkages of the numerical control machine tools and industrial robots. The acceleration and deceleration of the movable element of the kinematical linkage participates directly to achieving the positioning accuracy and to the path error. This work presents the main shapes of the acceleration- deceleration curve of the kinematical linkage, as well as their performances. Shapes of the acceleration-deceleration curve are presented for positioning linkages as well as for contouring linkages. The extent of influence upon the contour error in case of the linear and exponential acceleration-deceleration of kinematical linkage is also presented. The works is also giving recommendations on the way of choosing the type of curve being used in case of various transient processes, by the machine tool builders, with a view to obtaining high dynamical performances. In general, the recommendations are considering the inertia of the mobile element and the imposed path error. By knowing the acceleration shape, the machine tool designer and builder can know, even from the design stage, the area of the transient duty where the acceleration is maximal. The maximum acceleration imposes the rate of the impulsion torque of the drive servomotor based on which the kinematical linkage is sized, in terms of its components.

Accurate Estimation of Cutting Time Based on Control Principle of Machine Tool

2016 ◽  
Vol 10 (3) ◽  
pp. 429-437 ◽  
Author(s):  
Kosuke Saito ◽  
◽  
Hideki Aoyama ◽  
Noriaki Sano ◽  
◽  
...  
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Tool Path ◽  
Estimation Error ◽  
Numerical Control ◽  
Accurate Estimation ◽  
Flexible System ◽  
Acceleration And Deceleration ◽  
Nc Machine ◽  
Control Principle

The accurate estimation of cutting time before beginning a cutting process is necessary to improve the productivity of machining. Commercial computer-aided machining (CAM) systems estimate the cutting time by dividing the tool path length by the designated feed rate in a numerical control (NC) program. However, the actual cutting time generally exceeds the estimated cutting time for curved surfaces because of the acceleration and deceleration of the NC machine tool. There are systems that estimate cutting time while considering acceleration and deceleration along the controlled axes, but these are applicable only to particular machine tools. In this study, a flexible system for the accurate estimation of cutting time, based on the control principle of a machine tool, is developed. Experiments to estimate cutting time are conducted for the machining of complex shapes using two different NC machine tools. The actual cutting time is compared with the cutting time estimated by the developed system and that by a commercial CAM system. The estimation error of the proposed system is only 7%, while that of the commercial CAM system is 51%.

scholarly journals A Non-Delay Error Compensation Method for Dual-Driving Gantry-Type Machine Tool

Processes ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 748
Author(s):  
Qi Liu ◽  
Hong Lu ◽  
Xinbao Zhang ◽  
Yu Qiao ◽  
Qian Cheng ◽  
...  
Keyword(s):  
Machine Tool ◽  
Error Compensation ◽  
Prediction Method ◽  
Compensation Method ◽  
Industrial Robots ◽  
Numerical Control ◽  
Heavy Duty ◽  
Positioning Errors ◽  
Compensation Methods ◽  
Type Machine

The drive at the center of gravity (DCG) principle has been adopted in computer numerical control (CNC) machines and industrial robots that require heavy-duty and quick feeds. Using this principle requires accurate corrections of positioning errors. Conventional error compensation methods may cause vibrations and unstable control performances due to the delay between compensation and motor motion. This paper proposes a new method to reduce the positioning errors of the dual-driving gantry-type machine tool (DDGTMT), namely, a typical DCG-principle-based machine tool. An error prediction method is proposed to characterize errors online. An algorithm is proposed to quickly and accurately compensate the errors of the DDGTMT. Experiment results verify that the non-delay error compensation method proposed in this paper can effectively improve the accuracy of the DDGTMT.

Optimization of Control Gains in Numerical Control

2016 ◽  
Vol 1136 ◽  
pp. 651-654
Author(s):  
Hideki Aoyama ◽  
Duo Zhang
Keyword(s):  
Feed Rate ◽  
Machine Tools ◽  
Cutting Tool ◽  
Numerical Control ◽  
Machining Processes ◽  
Nc Program ◽  
Acceleration And Deceleration

It is frequently the case that the feed rate indicated in a numerical control (NC) program does not obtain in actual machining processes and the cutting tool does not path the points indicated in the NC. A reason underlying such problems is that control gains are not optimized, which causes issues with acceleration and deceleration in the control of machine tools. To address these problems, in this paper, we propose a method for the optimization of control gains using the MATLAB and Simulink software by considering the weight of the workpiece, the controlling distance, and the controlling speed. Simulations confirmed the effectiveness of our proposed optimization.

scholarly journals Assessment of the safety of use of portable machine tools

2018 ◽  
Vol 189 (3) ◽  
pp. 192-205
Author(s):  
Monika Nowak ◽  
Agnieszka Terelak-Tymczyna
Keyword(s):  
Machine Tool ◽  
Working Conditions ◽  
Machine Tools ◽  
Numerical Control ◽  
Milling Machine ◽  
Safety Issues ◽  
Large Size ◽  
Score Method ◽  
Characteristic Features ◽  
Risk Reducing

The article presents safety issues related to on-site machining with the use of portable machine tools. Their advantage is the possibility of machining elements at places in which they are used. This especially refers to large-size constructions, welded elements and any items whose disassembly is technically difficult. The authors present tasks performed by the operators of portable machining equipment, working conditions, construction and characteristic features of portable machine tools on the example of a portable boring machine, milling machine and flange facing machine. The presented characteristics can influence the safety of work with these machines. The information given in the article were used to asses risk at the position of a portable machine tool operator. The assessment was conducted using the Risk Score method taking into account four stages of using portable machine tools, i.e. transport, assembly/disassembly, machining and maintenance. The result of the conducted risk analysis is the proposal of possible risk reducing actions. Due to the specificity of the operation of portable machine tools which significantly impedes the development of a machine tool which would be safe in and of itself, the proposed actions refer mainly to organisational solutions. The work presents also the thesis that it is possible to decrease the risk at this position thanks to the use of numerical control in a portable machine tool. Such a solution may reduce exposure to some identified threats. The issue is presented on the example of a prototype of a portable flange facing machine developed in the Institute of Mechanical Technology ZUT in Szczecin.

Contour Controller Design for Cubic Parallel Machine Tool

Manufacturing ◽  
2003 ◽  
Author(s):  
Sungsoo Kim ◽  
Seung Hwan Lee ◽  
Daehie Hong ◽  
Woo Chun Choi ◽  
Jae-Bok Song
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Estimation Method ◽  
Parallel Machine ◽  
Control Algorithms ◽  
Contour Error ◽  
Contour Control ◽  
Contouring Accuracy ◽  
Parallel Machine Tools ◽  
Parallel Machine Tool

In machining processes, contouring accuracy is usually more important than tracking performance. In order to reduce the contour error, there have been many contour control algorithms for conventional machine tools, which noticeably improve their contouring accuracy. However, the available contour control algorithms cannot be directly applied to the parallel machine tools. The dynamic characteristics of the parallel machine tools are not consistent inside workspace and unsymmetrical disturbances can be imposed on any axis. Due to these, mismatched dynamics cause unwanted contour error. In this paper, we present a contour control algorithm for the cubic parallel machine tool that employs the parallel mechanism for its moving table, which can be also applied to a general parallel manipulator. The contour error estimation method for free-formed curve trajectory is proposed and the relation between the contour error vectors in joint and Cartesian spaces is considered. In order to show the validity of the algorithm, the contour control simulations and experiments are made for various contour trajectories with the cubic parallel machine tool. The results show that the proposed controller reduces the contour error considerably both in joint and Cartesian spaces.

A Reliability Analysis of NC Machine Tools Based on the Weibull Distribution

2015 ◽  
Vol 741 ◽  
pp. 763-767
Author(s):  
Hui Liang Li
Keyword(s):  
Weibull Distribution ◽  
Machine Tool ◽  
Machine Tools ◽  
Interval Estimation ◽  
Point Estimation ◽  
Numerical Control ◽  
Control Machine Tool ◽  
Failure Data ◽  
Nc Machine ◽  
Nc Machine Tools

In this paper, a series of numerical control machine tool truncated failure data collect.The data are assumed to be two parameter weibull distribution and related parameters is obtained and relevant inspection and test of hypothesis, it is concluded that the mathematical model of batch of nc machine tool failure interval time distribution.Relevant indicators to determine the reliability of nc machine tools, machine tool's observations, Machine tool observations, point estimation and interval estimation index value provide a theoretical basis for the research on reliability of machine tool.

MPCC-Based Set Point Optimisation for Machine Tools

2019 ◽  
Vol 13 (3) ◽  
pp. 407-418
Author(s):  
Titus Haas ◽  
Sascha Weikert ◽  
Konrad Wegener ◽  
◽  
Keyword(s):  
Machine Tools ◽  
State Of The Art ◽  
Linear Constraints ◽  
Numerical Control ◽  
Contour Error ◽  
Set Point ◽  
Dynamic Constraints ◽  
Control Code ◽  
Time Optimal ◽  
Optimal Set

Numerical control code is typically used for manufacturing a workpiece using machine tools. Most state-of-the-art approaches decouple the set point optimisation into two steps: the geometry and the feed rate optimisation that does not necessarily result in time-optimal set points for the desired geometry. Given the originally programmed geometry through the numerical control code, dynamic constraints of the machine tool, and maximum permissible contour error for the optimisation, a model predictive contouring control based set point optimisation approach is developed to generate time-optimal set points for machine tools globally. A suitable error definition and its linearisation are used whereby the optimisation problem can be represented by a quadratic programming problem with linear constraints. Compared to most state-of-the-art methods, a direct approach is presented and no previous geometry optimisation step is required. Depending on the demands of accuracy, different maximum contour error constraints and penalisation as well as various maximum permissible axis velocities and accelerations are presented and tested on a test bench. The method is shown to be adaptable to different demands on the set points, and the contour errors can be affected by either the constraints or penalising factors.

scholarly journals Modular design research of computer numerical control machine tools oriented to customer requirements

2020 ◽  
Vol 12 (4) ◽  
pp. 168781402091657
Author(s):  
Fei Li ◽  
Xudong Li ◽  
Hualong Xie
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Quality Function Deployment ◽  
Modular Design ◽  
Computer Numerical Control ◽  
Mapping Method ◽  
Numerical Control ◽  
Control Machine Tool ◽  
Control Machine ◽  
Customer Demands

In order to study the modular design of computer numerical control machine tools oriented to customer demands, the customer demand information model was established based on rough analytic hierarchy process and information entropy by analyzing and transforming customer demands. Based on the domain mapping method of axiomatic design and quality function deployment integration, the product function model and structure model of computer numerical control machine tools are established. Based on fuzzy clustering analysis, the module division of computer numerical control machine tools is studied, and the dynamic clustering diagram of computer numerical control machine tools is formed with MATLAB as the operating environment. Based on Technique for Order Preference by Similarity to Ideal Solution method, the scheme of computer numerical control machine tools module division is evaluated. Taking the horizontal computer numerical control machine tool products of Shenyang Machine Tool Group as an example, the module division is carried out. The example design and the result analysis prove that the module division system is very effective and fast.

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