Computer Numerical Control Controller Research Articles

Development of Pitch Cycle-Based Iterative Learning Contour Control for Thread Milling Operations in CNC Machine Tools

The helical contour motion accuracy of feed drive axes is important for thread milling operations in computer numerical control (CNC) machine tools. However, the motion dynamics and external disturbances significantly affect the contour motion results, while the feed drive axes perform helical motions in thread milling operations. Although existing iterative learning contour control (ILCC) methods can improve contour motion accuracy, the problems of data recording and processing on memory usage and computational burden in control systems, wasted materials, and increased costs in thread manufacturing still limit the practical applications of ILCC. Therefore, considering the similar motion dynamics and external disturbances of the feed drive axes during the pitch cycle motions of a helical path, this study developed a pitch cycle-based iterative learning contour control (PCB-ILCC) method to address the control system and thread manufacturing problems caused by the use of ILCC. For PCB-ILCC, this study adopted contour error vector estimation by referring to the interpolated positions on the pitch cycle of the helical path to simplify the computational complexity and designed the ILCC using the cycle learning method to easily implement the ILCC structure. Thus, this study developed a permanent magnet synchronous motor (PMSM) driving control utilizing the robust control method to mitigate the problems of motion dynamics and external disturbances on the feed drive axes. Thread milling experiments performed on a five-axis CNC machining center demonstrated the feasibility of the PCB-ILCC and validated that it can significantly improve the helical contour motion accuracy of the feed drive axes and achieve an 80% contour error reduction rate in comparison with the proportional–proportional–integral control, which is extensively used in commercialized PMSM drivers and CNC controllers.

Dynamic behavior and path accuracy of an industrial robot with a CNC controller

The application of industrial robots in the field of machining is gradually increasing, but their low absolute position accuracy and low stiffness affect the improvement of machining accuracy. Computer numerical control (CNC) has good performance to control the motion accuracy in the machine tool. Therefore, it is proposed to improve the motion accuracy of robots. This article utilizes a stereo high-speed camera to track robot motion. Circular paths running under the CNC system are planned to evaluate its performance, which includes path accuracy, motion velocity, and acceleration. The performance of identical paths running in a conventional robot controller is evaluated for comparison. Based on the experimental analysis, the CNC system, which has more functionalities for acceleration regulation, can get better path accuracy and stability. It indicates that acceleration control has a significant effect on path accuracy and motion velocity. The acceleration profile in a conventional robot controller resembles a triangle. By default, the maximum acceleration value is adopted for the motion planning. Therefore, its accelerating and decelerating phase is much shorter than that of the CNC system, which could lead to instability. Both Step-shaped and trapezoidal acceleration profiles in the CNC system improve the dynamic behavior of the robot. Considering the trade-off between path accuracy and motion velocity, the Step-shaped acceleration profile can be applied to the optimization of the traditional robot motion control.

Design and Development of IIoT Dashboard for Overall Equipment Effectiveness Monitoring of CNC Machine Tools

Abstract: Smart Manufacturing systems are regarded as the fourth revolution in the manufacturing industry, which is shaped by widespread deployment of sensors and Internet of Things. The present work constitutes of ‘Development of Industrial Internet of Things (IIoT) Dashboard for ‘Overall Equipment Effectiveness’ (OEE) Monitoring of CNC Machine Tools’ for a legacy CNC machine which is converted to smart machine. Data fetched from the CNC controllers through OPCUA is sent to the connected cloud database which will be imported into PowerBI desktop and the data has been classified and processed according to the requirement to develop a data modelling architecture of OEE, the Working status of the machine is visualized by Creating Monitoring and Performance charts and graphs of different design in Microsoft PowerBI Desktop. The Advanced visualizations constitutes od various features along with different analysing capabilities that results is creating reports which enumerates the state of OEE as a Key Performance Indicator (KPI). As Microsoft Power BI pertains a set of pre-established steps for data processing, the situation designated may constitute a limitation to automatic data refresh, leading to a do-over to verify, the specific interval of time, the conformity of data so they can be imported into the system. Keywords: Industrial Internet of Things (IIoT), Open Platform Communications United Architecture (OPCUA), Computer Numerical Control (CNC), Overall Equipment Effectiveness (OEE), Key Performance Indicator (KPI).

Generation Method of Cutting Tool Paths for High-Speed and High-Quality Machining of Free-Form Surfaces

In general, NC programs for machining free-form surfaces using a computer numerical control (CNC) machine tool are generated using a computer-aided manufacturing (CAM) system. The tool paths (CL data) generated by a CAM system are approximated straight-line segments based on tolerance (allowable error). As a result, the tolerance affects the machining accuracy and time. If the tolerance is set to a small value, the lengths of the segments are shortened, and the machining accuracy is improved. The process in which a CNC machine tool reads and analyzes an NC program and controls the motors requires a minimum processing time of an NC program block (block-processing time). Therefore, if the lengths of the approximated straight-line segments are too small, it will be impossible to reach the indicated feed speed, and the machining time will be longer. In this study, by identifying the block-processing time of a CNC controller and deriving the appropriate length of the approximated straight-line segment based on the block-processing time, a CL data creation method that is capable of high-speed and high-accuracy free-form surface machining is proposed. In addition, experimental verification tests of the method are conducted.

Interpreting the G-code of drilling machining to use in open CNC controller machine

Computer numerical control (CNC) software is the “brain” of a machine tool as it controls the machine tool’s movement. The development of open CNC controller systems is one of the most popular topics in the last three decades due to the current CNC remains exclusive and costly. However, there is no open-source system that can use with an open CNC controller. In this developed system, the drilling G-code was analyzed to extract the points before simulating and sending it to any open CNC controller machine. Among the machining processes used most extensively is drilling. The used modules and functions are created by LabVIEW. The results show the system’s extracted points are similar to the draw drilling point in Solid work.

Study of CNC System for PCB Design using Proteus

A Computer Numerical Control (CNC) system for Printed Circuit Board (PCB) design using Proteus Design Suite has been presented. A schematic diagram and single-sided PCB layout of a high voltage circuit for Geiger– Muller (GM) tube is designed using Proteus software. Subsequently, the PCB layout of the circuit is converted into Gerber files that are decoded into G-code through Flat CAM software. The G-code is introduced to the CNC system consisting of a computer, a CNC controller and a CNC machine. The code is stored in the memory of the computer and is uploaded to the CNC controller byMach3 software. The controller operates the CNC machine to perform isolation routing, drilling and milling for PCB as per the instructed design. It is noticed that the CNC system associated with Proteus makes the PCB designing process automated and easier by reducing the process of printing as well as etching. This study reveals that the proposed system can eliminate human error to achieve better accuracy and higher productivity as compared to the conventional methods of PCB design.

Real-Time Local Optimal Bézier Corner Smoothing for CNC Machine Tools

A straight line or G01 is the most common path in computer numerical control (CNC) contour machining. However, non-smooth corners introduce discontinuous movement along each axis during machining. The commonly used strategy is to redesign a corner into a smooth corner path. Therefore, optimal corner smoothing should simultaneously find an optimal corner path and a corner speed that satisfied the axis motion limits. To achieve this goal, we use particle swarm optimization (PSO) to find the optimal Bezier curve and the optimal corner speed, then convert the axis constraints into polynomial inequalities and use fitness selection to deal with axis acceleration and jerk limits. For real-time operation, we establish a look-up table with the optimal corner speed and corner path models for use by a CNC controller. In the experiment, the YCM NXV560A vertical machining center was used to conduct a real machining test on a Taiwan contour, and the feasibility of the controller to generate the optimal corner strategy for various linear paths was verified.

Development of an Analyzing and Tuning Methodology for the CNC Parameters Based on Machining Performance

This paper proposes the development of a tuning methodology which can set the proper values of the Computer Numerical Control (CNC) parameters to achieve the required machining performance. For the conventional operators of machine tools, the CNC parameters were hard to be adjusted to optimal settings, which was a complicated and time-consuming task. To save time in finding optimal CNC parameters, the objective of this research was to develop a practical methodology to tune the CNC parameters effectively for easy implementation in the commercial CNC controller. Firstly, the effect of the CNC parameters in the CNC controller on the tool-path planning was analyzed via experiments. The machining performance was defined in the high-speed (HS) mode, the high-accuracy (HP) mode, and the high-surface-quality (HQ) mode, according to the dynamic errors of several specified paths. Due to the CNC parameters that have a particularly critical effect on the dynamic errors, the relationship between the CNC parameters and the dynamic errors was validated by the measured data. Finally, the tuning procedure defined the anticipated dynamic errors for the three machining modes with the actual machine. The CNC parameters will correspond with anticipated dynamics errors based on several specified paths. The experimental results showed that the HS mode was the fastest to complete the path, and the completion time of the HP and HQ modes were increased by 37% and 6%, respectively. The HP mode had the smallest dynamic errors than other modes, and the dynamic errors of the HS and HQ modes are increased by 66% and 16%. In the HQ mode, the motion oscillation was reduce significantly, and the tracking error of the HS and HP modes were increased by 85% and 28%. The advantage of the methodology is that it simplifies set-up steps of the CNC parameters, making it suitable for practical machine applications.

Analytical modeling of the CNC machine axis motion in high-speed milling with local smoothing

In high-speed milling (HSM) of free-form surfaces, the tool path is mainly characterized by a set of short discontinuous segments in tangency. These discontinuities bring an intense kinematic parameter fluctuation of the computer numerical control (CNC) machine axes. The smoothing of the programmed tool path and the optimal choice of the manufacturing process parameters ensure a high productivity with the required quality of the machined surfaces. Precise estimation of the machining time allows an accurate evaluation of the machined product cost. Thereby, this is achieved by studying the effect of the tool path smoothing and the CNC controller parameters on the axis kinematics and the following errors. This paper focuses on the geometrical modeling of the local smoothing block adopted by Sinumerik CNC. Further, a kinematic model is proposed to simulate the axis motion in linear interpolation mode with local smoothing. The identification of the interpolator reduction effect on the programmed tolerance leads to the identification of the smoothing model adopted by the CNC unit. Then, the axis kinematic behavior is modeled while taking into account the drive parameter axes defined by the manufacturer of the CNC unit. The experimental results showed a smooth variation of the axis feed rate along the smoothing blocks and a good correlation with the proposed models.

A computer numerical control (CNC) multi-pass spinning solution to a center lathe retrofit

This paper suggests a typical scheme for substantially low cost machine upgrading with regard to research and manufacturing activities through the integration of mechanical, electronic and software technologies. Computer numerical controlled (CNC) multi-pass spinning process is considered state-of-the-art nowadays in critical applications such as aerospace and automotive industries but equipment cost is still an issue. For the sake of novelty, accuracy and repeatability of spun products, a conventional lathe machine has been converted into CNC spin-forming machine by retrofitting to generate automatic tool paths in two axes for multi-pass spinning. Actuators and sensors necessary to provide controlled motion of mechanical elements such as mandrel, roller, and holder are selected to cope with the requirements of this incremental metal forming process. A CNC controller is integrated to the system with software to generate the tool path and G-code required for producing cups using the retrofitted machine. Rotational speeds together with longitudinal and transverse axes movements are calibrated. Backlash in power screws is evaluated and considered in the displacement control. Different tool paths including involute path can be generated using the developed control system. The machine has been used successfully to produce cups with high processing speeds and superior surface quality to that reported in the available literature. Based on experimental investigation under lubricated condition, the geometrical and surface quality with productivity was improved and an optimum exists at 0.6 mm/rev. feed ratio, 200 RPM mandrel rotational speed, and seven spin-forming passes.

Three-axis CNC machining feedrate scheduling based on the feedrate restricted interval identification with sliding arc tube

In the computer numerical control (CNC) machining for free form surfaces, the time-optimized and smooth feedrate profile plays an essential role in the high-speed and high-precision machining. For the traditional feedrate scheduling method (e.g., the “bang-bang” control method), there may be many fluctuations in the planned feedrate profile, especially in region of large curvature, which results in poor quality of machining surface. To address this issue, a novel concept called sliding arc tube (SAT) is proposed in this paper, from which the trajectory is partitioned as feedrate restricted intervals (FRIs) determining the target feedrate and the positions of tool acceleration and deceleration on the tool path. The SAT is built based on the local geometric information of tool paths. As the SAT is constructed in the tube-shaping process and then sliding on the tool path and finally blocked by it, the breaking point for generating the FRI is found on the trajectory curve. For the proposed FRI identification method, it is computational efficient and it can be implemented in the real-time manner in the CNC controller. Results from both simulation and real machining experiments validate that, with the proposed SAT, the FRIs can be precisely and efficiently identified for the given trajectory curve, the frequent acceleration and deceleration of machine tool is alleviated, and the machining quality can be improved in this way.

A knowledge based intelligent process planning method for controller of computer numerical control machine tools

The development of computer, internet and information technology puts forward higher demands for Computer Numerical Control (CNC) machine tools to improve the intelligence in many aspects. Among these aspects, intelligent process planning plays an important role in current changeable market and customized product promotion by shortening production cycle and providing more stable process planning ability. To realize intelligent process planning, a CNC controller with cloud knowledge base support is proposed with ability of making process planning autonomously based on workpiece design. Previous work of knowledge model and cloud knowledge base framework design is introduced, and then this paper focuses on the complete process planning method within the intelligent CNC controller. Both interactivity between knowledge base and CNC controller, and query/infer mechanism in knowledge base are illustrated in detail. A case study of two shafts process planning is shown to demonstrate the feasibility of the intelligent process planning method.

On-machine quasi-3D scanning measurement of bevel gears on a five-axis CNC machine

Most commercialized measuring machines for bevel gears have a four-axis structure plus a 3D scanning probe. Because these probes are highly efficient, a large number of high-precision gear grinding and complex machines now apply them to detect tooth surface contour error. Nevertheless, such probes are still too expensive to implement on a milling machine. This paper, therefore, proposes a quasi-3D probe as a better solution for cost reduction. More specifically, the study develops an on-machine measurement system on five-axis machines which are needed for producing bevel gears. It employs a quasi-3D scanning probe whose sensor can detect in xyz directions while outputting only a one-dimensional (1D) deviation. This novel method enables measurement using solely a four-axis movement, meaning that only four coordinates are needed to measure pitch and topography. These coordinates are derived by first establishing mathematical models of bevel gear measurement. Also developed is an evaluation program that communicates between the PC and CNC controller. The proposed mathematical models are then applied to a five-axis CNC (computer numerical control) machine equipped with a Siemens 840Dsl controller and verified by comparing the results of this measurement and evaluation with the accuracy report for the same gear measured on a dedicated gear measurement machine.

Development of Client-Server Application by Using UDP Socket Programming for Remotely Monitoring CNC Machine Environment in Fixture Process

The use of computer technology in manufacturing industries can improve manufacturing flexibility significantly, especially in manufacturing processes; many software applications have been utilized to improve machining performance. However, none of them has discussed the abilities to perform direct machining. In this paper, an integrated system for remote operation and monitoring of Computer Numerical Control (CNC) machines is put into consideration. The integrated system includes computerization, network technology, and improved holding mechanism. The work proposed by this research is mainly on the software development for such integrated system. It uses Java three-dimensional (3D) programming and Virtual Reality Modeling Language (VRML) at the client side for visualization of machining environment. This research is aimed at developing a control system to remotely operate and monitor a self-reconfiguration fixture mechanism of a CNC milling machine through internet connection and integration of Personal Computer (PC)-based CNC controller, a server side, a client side and CNC milling. The performance of the developed system was evaluated by testing with one type of common protocols particularly User Datagram Protocol (UDP). Using UDP, the developed system requires 3.9 seconds to complete the close clamping, less than 1 second to release the clamping and it can deliver 463 KiloByte.

Design and development of a CNC machining process knowledge base using cloud technology

Nowadays, computer numerical control (CNC) machine tool undertakes more processing tasks than other common machine tools because of its highly automated machining ability and high performance. However, due to the lack of intelligence in machining process planning, machining procedure of products mostly depends on process planners rather than CNC machine tools. To make product quality less dependable on process planner’s ability and improve the efficiency of process planning in order to fulfill changeable market, this paper presents an approach to design and develop CNC machining process knowledge base using cloud technology. The general standard STEP-NC is mapped to web ontology language (OWL) to describe machining process-related knowledge in a readable and comprehensible way. This mapping relation also makes knowledge suitable for storage in HBase. Through this ontology model, descriptive and logical knowledge can be collected. Hadoop platform is used in this approach to provide the NoSQL database HBase for large-scale knowledge storage and MapReduce programming model for large-scale knowledge processing. Taking advantage of MapReduce, knowledge query engine and reasoning engine can be developed. Users can submit task and resource descriptive files to the cloud through CNC controller and get machining process solutions from knowledge base. Evaluation mechanism is also adopted to filter low-quality knoweldge.

Methods of In-Process On-Machine Auto-Inspection of Dimensional Error and Auto-Compensation of Tool Wear for Precision Turning

The purpose of this study is mainly to develop an information and communication technology (ICT)-based intelligent dimension inspection and tool wear compensation method for precision tuning. With the use of vibration signal processing/characteristics analysis technology combined with ICT, statistical analysis, and diagnosis algorithms, the method can be used to proceed with an on-line dimension inspection and on-machine tool wear auto-compensation for the turning process. Meanwhile, the method can also monitor critical tool life to identify the appropriate time for cutter replacement to reduce machining costs and improve the production efficiency of the turning process. Compared to the traditional ways, the method offers the advantages of requiring less manpower, and having better production efficiency, high tool life, fewer scrap parts, and low costs for inspection instruments. Algorithms and diagnosis threshold values for the detection, cutter wear compensation, and cutter life monitoring were developed. In addition, a bilateral communication module utilizing FANUC Open CNC (computer numerical control) Application Programming Interface (API) Spec was developed for the on-line extraction of instant NC (numerical control) codes for monitoring and transmit commands to CNC controllers for cutter wear compensation. With use of local area networks (LAN) to deliver the detection and correction information, the proposed method was able to remotely control the on-machine monitoring process and upload the machining and inspection data to a remote central platform for further production optimization. The verification experiments were conducted on a turning production line. The results showed that the system provided 93% correction for size inspection and 100% correction for cutter wear compensation.

Development of Cutting Force Prediction Method Using Motion Information from CNC Controller

Five-axis machines and multi-tasking machines are widely used because they facilitate integration of work processes and simplification of jigs and set-ups. Along with effective machine use, development of optimum machining such as research on tools and cutting methods to achieve high-speed cutting and increase of material removal rate is being investigated. While these efforts have greatly contributed to furthering of automation and cost reduction at the manufacturing site, complex machine motions and increased demanding work processes can lead to unexpected collisions and tool breakages. To prevent tool breakage caused by unexpected overloading or to improve the inefficient feed rate on the basis of safety considerations, simulations based on numerical control (NC) data are usually performed in advance to evaluate the cutting force. In high-speed, high-efficiency machining, however, the machine does not always execute movements as instructed by the NC data and the predicted cutting force does not always agree with the actual cutting forces. In this study, therefore, we developed an off-line system in which the motion information of each axis of an actual machine is acquired from a computer numerical control (CNC) controller, and is then used to predict the cutting force. The effects of using the proposed method are described in this article.

A novel ISO 6983 interpreter for open architecture CNC systems

Computer numerical control (CNC) technology is a key technology in machine tools and is also the base of industrial unit computerization. CNC machines are operated by controllers, which have a software module inside known as interpreter. The function of an interpreter is to extract data from computer-aided manufacturing (CAM) system-generated code and convert it to controller motion commands. However, with the development of numerical control technology, existing CNC systems are limited with interpreter lacking in expandibility, modularity, and openness. In order to overcome these problems, open architecture technology (OAC) was employed in CNC controller. In this paper, a new technique is presented for the interpretation of the International Standards Organization (ISO) 6983 data interface model. The proposed technique is able to interpret ISO 6983 data and translate it to the internal structure required by the CNC machine. It takes an input file in text format and extracts position, feed rate, tool, spindle, and other data. It is also able to generate output in text and EXtensible Markup Language (XML) files as per user defined file structure. The use of .txt and .xml files enables shop floor data modification and internet accessibility facilities in CNC system. The paper includes an introduction, brief description of the architecture, algorithm design, operational pattern, and validation of the system through experimental studies. The output of these experiments illustrated satisfactory performance of the interpreter with an OAC CNC system.

New technique for the interpretation of ISO 14649 and 6983 based on open CNC technology

Computer numerical control (CNC) controller is the termination organiser, which is located at the end of the manufacturing process chain. The CNC controller is composed of two modules: software and hardware. The software module of the controller is known as interpreter that translates International Standards Organization (ISO) data interface model instructions to the hardware parts of the controller in the required structure of the machine. The aim of next-generation CNC is to be portable, interoperable, flexible, open, intelligent and adoptable. In the progression towards the development of next-generation CNC systems, the problems of current ISO data interface model limitation and CNC machine vendor dependency were faced. In order to overcome these issues, the ISO standard (ISO 14649) and open architecture control (OAC) technology were introduced. In this paper, a new technique for the interpretation of both ISO data interface models has been presented. The developed module is specially designed for the OAC-based CNC systems that translate the ISO 14649-21 and ISO 6983 information to the CNC machine in required structure. The module also provides a shop floor editing facility and is also able to generate the physical file output in user-defined structure of .txt and .xml formats.

ISO 6983 Translator for PC Based CNC Systems

Computer Numerical Control (CNC) controller is an important part of machine, composed of hardware and software models. Software model, usually called an interpreter translates input code as per internal structure of CNC machine. Now a day’s traditional controllers of CNC machine are found to be closed in nature, because they are depended of vendor’s specifications. Due to that dependence they do not facilitate access to the inner features of machine. In order to overcome these problems open architecture controllers were introduced. In this article a new ISO 6983 translator for open architecture CNC controller is being proposed. The developed software model is able to read commercially available Computer Aided Design (CAD) /Computer Aided Manufacturing (CAM) system generated International Standards Organization (ISO) 6983 file and extracts position, feed rate, spindle speed, tool etc data and translates to OAC machine. At the same time it is also able to generate output in user defined text and EXtensible Markup Language (.xml) formats. Further design of paper includes development of translator, followed by case study experiment and finally ends with conclusion.