CNC Kernel Research Articles

Real-time compensation of tool deflection using a sensor embedded boring bar with wireless signal feedback to the machine tool controller

Boring bar deflection is a generic problem when machining deep holes to high dimensional tolerances. Reaching the final dimension can be tricky and time consuming because the deflection varies with cutting parameters, insert, and material. Here we use embedded strain sensors to determine the tool deflection, and we compensate for it by adding an overlaid movement to the machine tool x-axis. The compensating value from the tool is sent via Bluetooth to an IPC that communicates with the CNC kernel via the PLC. We investigate and discuss the accuracy and dynamics of this machining system installed in our largest lathe.

Approach to development of HMI screens for CNC with dynamic kinematics

Adaptation of the user interface of the CNC system to work with machines with dynamic kinematics is considered in this paper. The method of changing the kinematic processing scheme “on the fly” should also allow switching user screens “on the fly”, changing them to the option that is currently needed. For these purposes, the basic functionality of the system is expanded by processing events from the CNC kernel.

ESPRIT- and HMM-based real-time monitoring and suppression of machining chatter in smart CNC milling system

Suppression of machining chatter during milling processes is of great significance for surface finish and tool life. In this paper, a smart CNC milling system integrating the function of signal processing, monitoring, and intelligent control is presented with the aim of real-time chatter monitoring and suppression. The algorithm of estimation of signal parameters via rotational invariance techniques (ESPRIT) is adopted to extract the frequency characteristics of acceleration signals, and then, cutting state is categorized as stable state, chatter germination state, and chatter state based on amplitude-frequency characteristics of identified acceleration signals. The model of chatter identification is acquired by training a hidden Markov model (HMM), which combines acceleration signals and labeled cutting state. To implement real-time chatter suppression, the algorithm of fuzzy control is integrated into a smart CNC kernel to determine the relationship between cutting force and spindle speed. Furthermore, spindle speed of machine tool could be adjusted timely in the presented system once the chatter is identified. Finally, the effectiveness of the proposed real-time chatter monitoring and suppression system is experimentally validated.

Dynamic performance of industrial robot with CNC controller

As the application of industrial robots in machining is constantly increasing, many techniques have been developed to make this use more efficient and accurate. The robot controller is one of the key factors to influence the robot performance. This paper discusses the performance of a CNC kernel which is directly integrated into the industrial robot. The dynamic motion of the robot is thoroughly analyzed. A conventional robot controller is carefully evaluated to make a clear comparison.

An ARM-based Multi-channel CNC Solution for Multi-tasking Turning and Milling Machines

ARM-based CNC systems are used as a low-cost solution for controlling 2-3 axis machines. The increase of computing power of ARM processors facilitated their application to controlling multi-tasking and multi-axis machines with several independent control channels. The paper presents the results of the exploratory investigation of the transition from the PC-based to the ARM-based CNC solution. The cross-platform architecture of CNC systems, the porting of CNC kernel software to the single-board computers Raspberry Pi 2 with the Linux operating system and the control of servo drives and PLC I/O over EtherCAT fieldbus with cycle time of 2ms are investigated as well.The dual-channel configuration of ARM-based CNC designed to control the multi-tasking turning and milling machine with inclined layout is presented. The paper illustrates the kinematic scheme and the network architecture of NAKLON 535 machining center for ARM-based CNC solution.

Implementation of Real-Time Machining Process Control Based on Fuzzy Logic in a New STEP-NC Compatible System

Implementing real-time machining process control at shop floor has great significance on raising the efficiency and quality of product manufacturing. A framework and implementation methods of real-time machining process control based on STEP-NC are presented in this paper. Data model compatible with ISO 14649 standard is built to transfer high-level real-time machining process control information between CAPP systems and CNC systems, in which EXPRESS language is used to define new STEP-NC entities. Methods for implementing real-time machining process control at shop floor are studied and realized on an open STEP-NC controller, which is developed using object-oriented, multithread, and shared memory technologies conjunctively. Cutting force at specific direction of machining feature in side mill is chosen to be controlled object, and a fuzzy control algorithm with self-adjusting factor is designed and embedded in the software CNC kernel of STEP-NC controller. Experiments are carried out to verify the proposed framework, STEP-NC data model, and implementation methods for real-time machining process control. The results of experiments prove that real-time machining process control tasks can be interpreted and executed correctly by the STEP-NC controller at shop floor, in which actual cutting force is kept around ideal value, whether axial cutting depth changes suddenly or continuously.

An Open Modular Architecture Controller Based Online Chatter Suppression System for CNC Milling

In milling processes, chatter is a kind of sudden relative vibration appearing between the cutter and the workpiece, which results in poor part quality, accelerated tool wear, and shortened spindle life. In this paper, an open modular architecture controller (OMAC) of machine tool which integrates the algorithms including chatter recognition, compensation command generation, and execution is proposed with the aim of providing an integrated solution for milling chatter suppression in CNC kernel. To effectively identify chatter, experiments are designed to determine the optimal installation place of accelerometer and then triaxial cutting forces and acceleration signals are compared to see which are more sensitive to chatter onset. In terms of data processing, 16 sampling points in time domain are chosen to perform online fast Fourier transform (FFT) in consideration of signal effectiveness and computational efficiency. To implement real-time chatter suppression in CNC kernel, a simplified dynamic model of milling system is used to obtain the relationship between chatter frequency and spindle speed. Finally, an adaptive control module which completes force signal extraction and processing by FFT and has the ability to modify related cutting parameters is designed to interact with other modules in OMAC where data acquisition thread and interpolation thread are synchronized. The proposed system is experimentally validated.

Research and Development of a Cross-platform CNC Kernel for Multi-axis Machine Tool

The demand for cross-platform solutions for real-time control systems is determined by the necessity to reduce the development cycle time, to provide broad opportunities of configuring the CNC system for multi-axis machine tools and to simplify the implementation of application solutions for shop floor. The paper proposes an approach of building a portable CNC kernel based on platform independent libraries. Open architecture CNC system offers levels of abstraction in the kernel for implementing various HMIs, accepting different part program language versions and using different fieldbuses. An example of adapting cross-platform CNC kernel for multi-channel and multi-axis machine tool is illustrated.

CNC 기계의 원격 에너지 모니터링을 위한 온라인 시스템 구조

Enhancing energy efficiency of machine tools causes substantial impacts on the manufacturing industries, to cope with the competitive introduction of the total energy management strategies. Real-time energy monitoring is essential to identify energy consumption patterns of the machine tools and correlate them with the energy management strategy. Integrated analysis of machine tool’s operation status and the corresponding energy usage is most important to accurately evaluate the energy efficiency under the various machining process environments. This paper proposes a system architecture to realize the online energy monitoring system and the embedded energy monitoring approach interconnected with the CNC kernel. The shop-floor operation management system is presented to integrate the proposed online energy monitoring approach.

Scalable Open Cross-Platform Kernel of PCNC System for Multi-Axis Machine Tool

Creating the basis of numerical control is demanded by ensuring the invariance of the applied solution, reducing the development cycle and preserving investments made in software development through cross-platform solution for real-time, the component approach and code reusing. Open architecture is implemented with the help of allocating the levels of abstraction in the CNC kernel, which provides transparence kernel algorithms according to the specifics of the hardware solution, the flow program language version, and the way of implementing the operator interface. The paper illustrates the approach of the invariant CNC kernel layout and the scaling of the control channels inside the pipeline data processing, according to the multi-axis machine requirements. The prospects of development in the direction of using web-technologies and creating remote terminals for controlling, monitoring and adjusting machine tools are defined. The right choice of the control system architecture reduces the interpolation and PLC cycle time, which is the determining factor in the high-speed cutting for multi-axis machine tools. It results in reducing data processing time in CNC enhance the manufacturing performance.

A framework and data processing for interfacing CNC with AP238

Tomorrow's manufacturing workstation will be autonomous and intelligent with the ability to interpret geometric and manufacturing knowledge and automatically to manufacture components. STEP-NC is one of the building blocks that will support this endeavour for a new paradigm of the intelligent autonomous manufacturing. This paper outlines a framework for a STEP-NC controller, which represents one of the building blocks for tomorrow's manufacturing workstation. The conceptual controller consists of an interpreting module (interpreter), a planning module (planner), a simulation module and a CNC kernel. The interpreter reads an AP238 file and converts it into internal data, which the planner utilizes to sequence the specific machining operations and processes. The work illustrates the feasibility of the framework for interpreting STEP-NC information in an AP238 format and storing the data within a STEP compliant data structure for use in machine planning. The implementation tools and methods for interpreting the AP238 file are outlined through an example part/case study to demonstrate the STEP-NC conversion process.

Study on a reconfigurable model of an open CNC kernel

Based on a behavioral model, in this paper a new dynamic modeling method is presented and used to analyze the life cycle of application objects and their interactions in an open-architecture CNC controller model. Since a CNC kernel has a high capability real-time multi-task controller, it is important to develop CNC software based on non-real-time preempt multi-task operating system (Windows NT). A proper method for software high capability real-time control is employed when open on CNC kernel is designed. Further, the paper develops a solution for how to realize reconfigurable structures in CNC systems and seamless connection between function modules and a system.

Developing an integrated STEP-compliant CNC prototype

Abstract STEP-compliant CNC is the next-generation CNC controller, taking the STEP-NC data model as the interface scheme between CAM and CNC and carrying out various intelligent functions. At the moment, efforts are being made worldwide to establish an international standard for the new interface scheme (so-called STEP-NC), formalized as ISO 14649. In the near future, the new interface scheme will be completed and announced as the international standard. Upon completion, the standard will replace the conventional scheme based on ISO 6983, so-called M&G codes. Further, the new interface scheme will impact the CAD-CAM-CNC process chain and the advancement of the CNC controller. This paper develops an integrated STEP-compliant CNC system (or STEP-CNC) based on the new interface scheme. The system is composed of five modules: (1) Shop Floor Programming System (PosSFP), (2) Tool Path Generator (PosTPG), (3) Tool Path Viewer (PosTPV), (4) Man Machine Interface (PosMMI), and (5) CNC Kernel (PosCNC). The developed system is a prototype but very comprehensive, including all the modules required for realizing “art-to-part” through the new CAD-CAM-CNC chain. Architecture and functional details are presented together with a realistic demonstration.