Ri Liang Liu

Networked Connection of NC Machine Tools Based on MTConnect

MTConnect is a technical standard recently proposed to facilitate the organized retrieval of process information mainly from numerically controlled machine tools. In this paper, core components such as agent, client, adapter etc are overviewed. Considering the difference in manufacturing devices openness and capabilities, different application schemes of agent and adapter are designed according to MTConnect protocol. Agent is designed for data acquisition in different situations and different ways to use Adapters are mainly discussed. Finally, the client, a software function in the application is developed by using C#. And the application is applied to a NC machine tool. In terms of data request, collecting, transmission and detection from a working NC machine tool, the proposed architecture in this paper is verified successfully.

An Agent-Based Framework for STEP-NC Controllers of CNC Machine Tools

STEP-NC is a promising data interface for CNC, by which a comprehensive set of information regarding the product to be manufactured can be conveyed for the first time to the shop floor. In this paper, the new data model is briefly overviewed and analyzed. Then functionalities and considerations as for implementation of STEP-NC controllers are identified, followed by a conceptual framework proposed for such STEP-NC controllers for a new breed of CNC machine tools featuring autonomy and cooperation. The proposed system is constituted with a planning agent and a machining agent. The former is designed to take responsibility to cooperate with the external systems, to prepare all the data needed in machining and schedule them into unit tasks, while the latter, as one of the planning agent’s local control modules in light of an excellent combination of functionality and reliability, controls the machine tools adaptively. The working mechanism of the whole system is also introduced with an illustration of the operational flow.

Study on the Simulation System Based on STEP-NC

This paper presents a simulation system based on STEP-NC that can verify STEP-NC program and demonstrate the running of STEP-NC system (CNC system based on STEP-NC). NC Programs used in the STEP-NC system are in XML format. The overall architecture of the system which consists of feature extraction module, graphical modeling module, movement modeling module, feature library, simulation drive module and user interface is established. Some key technologies to implement simulation system are discussed in details. The simulation system shows great potential to the development and popularization of STEP-NC system.

A STEP Compliant Framework for Cutting Force Prediction for NC Turning Operations

With STEP-NC (ISO 14649) being gradually accepted as new standard for programming computerized numerical control (CNC) machine tools, new technologies and computer systems in the design and manufacturing process chain are emerging, and conventional systems are reshaping, to support interoperable and intelligent manufacturing. This paper addresses issues and solutions for the adaptation. In the first place, a strategy for adapting legacy CNC turning machine tools to the emerging standard is presented. In the second place, the new data model is analyzed and a practical way to retrieve and extract manufacturing information from the STEP-NC part program for turning process is presented. In the third place a workable approach to calculating the cutting force and chip load in turning operations is presented based on the mechanistic modeling method. Finally the proposed approach is implemented in a prototype system and tested with an example STEP-NC program for turning, which shows not only the feasibility of the proposed approach for information extraction and process evaluation, but also the possibility of using simple transitional systems to bridge the gap between the sophisticated STEP-NC part program and conventional CNC machines.

Tool-Path Calculation for NC Machining the Helical Surface of Screw Shaft Based on the End Section

With the increasingly wide use of screw components in industry, technologies for efficiently fabricating the complex helical surfaces on these components play an important role in modern metal-working. In this paper, the helical surface of a screw shaft is mathematically modeled based on the profile of its end section, and the whirlwind milling process and its requirements for machining the screw using standard cutter blades are overviewed. Then a theoretical approach to calculating the tool path and the corresponding movements of the machine axes for producing such a helical surface are presented. Finally a case study is provided with an example screw whose end section is described using sampled points.

Generating STEP-NC Files for a Circuit Board Milling System

Since G-codes have been proved limiting the modern manufacturing industry, ISO14649 was put forward. This paper presents a solution to generate ISO14649 files for circuit board milling. The process planning is given, and all the processes needed are contained in the ISO14649 file. Features and machining operations are identified for each process, such as the closed pocket having a “General_closed_profile” attribute and bosses, round holes, slots, the planar face, contour parallel strategy, contour bidirectional strategy and etc. The scenario of one feature with multi tools are put forward to promote the milling efficiency and an entity “Combined_Machining_workingsteps” is proposed. Besides, some other extensions are made, such as entities for representing circuit geometries in machining features. Algorithms for tool paths generation are demonstrated for contour parallel milling and bidirectional milling, where a new algorithm based on pixels is used. The new algorithm can be used in other functions such as detecting uncut regions.

A Feature-Based Approach to Path Planning for in-Process Probing Operations in STEP-Compliant NC Manufacture

With STEP-NC providing a way for seamless integration of the design, manufacturing, and quality control processes, the implementation of in-process measurement in this context has become a necessity for STEP-compliant NC manufacture. In the light of current research and development trends in this field, this paper proposes an approach to on-machine planning for in-process measurement, focusing on touch probing operations. Issues about the measured elements and the probing path planning are mainly addressed, and a prototype system is designed and implemented, which generates probing paths based on the information contained in the STEP-NC part program. The feasibility of the proposed approach is demonstrated with an example STEP-NC file.

A Circuit Milling System with Pixel Based Algorithms

This paper presents a circuit milling system, which integrates CAM functions and gives a good performance for flexibility and changeability. Gerber format files are described and read into some data structures that support centerline shape representation. The pixel based algorithms are used to get contours, get contour-parallel tool paths, detecting uncut regions, and also used to calculate the tool radial compensation. The precision is discussed and is proved feasible for circuit milling. The milling operation is divided into isolating and hollowing operations to make the process planning more flexible. The detailed algorithms of isolating and hollowing are given, which contain contour-parallel offset and direction-parallel tool paths. Hollowing supports multi tools to promote the efficiency. All the processes such as drilling, isolating, hollowing and cutting off are given in detail.

Design and Implementation of a Data Processing and Visualization System for STEP-NC Programs

Over the last decade a new data interface for CAM/CNC integration has been established to replace ISO 6983. The new standard, ISO 14649 (STEP-NC), provides a comprehensive data model that describes both geometrical and technological information in an object-oriented way. In order to bridge the gap between such rich-information programs and the legacy CNC systems, this paper presents a framework for manipulating the manufacturing data in STEP-NC part programs. The proposed system provides a basic platform for STEP-NC program interpretation, geometry visualization, micro-process planning and program re-generation. Major issues relating to the realization of manufacturing information extraction and shop-floor-level process planning are addressed in particular, and a prototype for STEP-NC turning process is implemented to demonstrate the feasibility of the approach.

Intelligent Control of CNC System Based on STEP-NC

In this paper, Data model used in intelligent CNC system based on STEP-NC is presented. A multi-agent architecture of the intelligent CNC system based on STEP-NC is proposed. The architecture consists of fourteen functional agents, such as interpreter agent, process planning agent, simulation agent, tool path planning agent, monitoring agent, expert system agent, etc. Some key technologies to implement the intelligent control including simulation, online inspection and expert system are discussed detailed. As a result, the architecture and key technologies proposed in this paper will aid the development work of the intelligent STEP-NC system.