12-04-2013, 02:58 PM
RECENT DEVELOPMENT IN TOOL ENGINEERING
RECENT DEVELOPMENT.pdf (Size: 114.12 KB / Downloads: 40)
INTRODUCTION
The twentieth century has witnessed, far reaching developments in all aspects of machining technology including machines, design of machines, control technology, new machining operations, ancillary operations, and above all, the use of computers in integrating the various sub-systems of a machining enterprise. Nowadays, the use of CAD/CAM and CNC machines are no longer marked as an added feature, rather it has become a necessity for all the manufacturing operations. Also, in the present era of globalization, manufacturing operations are not restricted to any geographical boundaries and manufacturing firms are facing stiff competition from potential competitors for survival in the global market in regard to quality and cost effectiveness of their products. For this, it is necessary to adopt world class manufacturing technologies, which will help them to improve productivity and profitability. Emergence of distributed computing, i.e. use of Internet and Intranet, has changed the whole scenario. It has enabled the manufacturers to opt for global manufacturing, which is based on the tenets of network based manufacturing. Augmentation of Internet technology and tool engineering enhances the productivity and profit of a manufacturing plant, which otherwise is quite difficult to gain. In next section, one such powerful methodology is described. It is known as Web-based Virtual Machine Tool operation (WVMT). Owing to its flexible and generic applicability, it has gained a wide popularity.
WEB-BASED VIRTUAL MACHINE TOOL (WVMT) OPERATION
Technical advancement in data handling, synchronization, and animation through the internet, together with ultra speed ISDN have motivated the development of Web-based Virtual Machine Tool operation (WVMT) by which CNC machine tool operation and the machined results can be visualized on the internet. To develop such a system, various methodologies, such as machine tool modeling, CAD/CAM, and Information Technology(IT) are required. WVMT technology involves bringing CNC machine tool operation and off-line CAM function into an internet environment. The effectiveness of WVMT system is largely dependent on the accuracy of modeling, speed of visualization and functionality of system.
STEP-NC
The last half century has seen a number of revolutionary changes to manufacturing system’s configurations. The traditional configuration of manufacturing systems was the dedicated transfer (machine) line. It enables mass production at high efficiency and low cost. A major drawback associated with the transfer lines was their inability to cope with the situations that demanded the production of different parts with similar efficiency. During the 1980’s, flexible manufacturing was developed to meet the need for the production of smaller batches of different parts. These systems used groups of computer numerically controlled (CNC) machines that could be reprogrammed to make different parts. These CNC machines became the central elements in systems such as flexible transfer lines, flexible manufacturing system (FMS) and flexible manufacturing cells (FMC).
Impediments of Current CNC Technologies
Over the last 50 years machine tools have evolved from simple machines with controllers that have no memory, driven by punched tape to today’s highly sophisticated CNC multi-process workstations. The year 1970 saw birth of the first machining center together with Direct Numerical Control (DNC). Today’s CNC machine designs are well developed with capabilities such as multi-axis control, error compensation, and multi process manufacture (e.g. combined mill/turn/laser and grinding machines).
Some efforts have been made to increase today’s CNC systems adaptability and reconfigurability, in particularly, the trend towards open architecture control, based on OSACA and OMAC (Open Modular Architecture Controller) where third party software can be used at the controller, working within a standard operating system. One further recognizable industrial development is the application of software controllers, where PLC logic is captured in software rather than in hardware. Although these developments have improved software tools and the architecture of CNC systems, vendors and users are still seeking a common language for CAD, CAPP, CAM and CNC, which will give compatibility and interoperability to CNC machine tools
The STEP-NC Standard
Today a new standard namely ISO 14649 recognized informally as STEP-NC is being developed by vendors, users, and academic institutions world wide to provide a data model for a new breed of intelligent CNCs. The data model represents a common standard specifically aimed at NC programming, making the goal of standardized CNC controller and NC code generation facility a reality. Currently two versions of STEP-NC are being developed by ISO. The first is the Application Reference Model (ARM) of ISO 14649 (i.e. ISO 14649 itself) and the other Application Interpreted Model (AIM) of ISO 14649 (i.e. ISO 10303 AP238). At present, the ISO 14649 standard consists of part 1 (overview), part 10 (general process data), parts 11 and 111 (milling and milling tools) together with parts 12 and 121 (turning and turning tools), which are still being developed and tested.