29-10-2012, 12:09 PM
TOOL HEALTH MONITORING
TOOL HEALTH.ppt (Size: 1.03 MB / Downloads: 50)
INTRODUCTION
Flexible machining, flexible assembly, computer-aided inspection and associated manufacturing systems are proving to be superior to conventional production systems.
It is the concept of CIM that will lead us to the unmanned factory of the future. Within the CIM philosophy, the entire operation, from design through production to marketing and service, will be integrated together as a global system.
The objective of this paper is to (a) highlight the importance of tool health monitoring in an automated manufacturing system, (b) summarize, and critically examine, the state-of-the-art in this area, and © discuss the micro computer-based tool wear monitoring system that has been developed at the University of Windsor, Canada.
ROLE OF TOOL MANAGEMENT IN FMS
As a subsystem of CIM, FMS integrated machine tools and automated storage and retrieval system (AS/RS) to provide flexibility for meeting varied demands
Each of the machine centers within a machining cell is normally equipped with a tool magazine consisting of a large number of different tools for a variety of operations.
The principal function of TMS is to ensure the availability of the right tool at the right time and at the right station for carrying out the required machining operation.
The TMS itself includes tool health monitoring (THM) of which acoustic emission (AE), or any such method, is one of the elements.
Most subsystems within FMS including tool management are centered around manufacturing process.
Non-availability of a tool or its improper replacement within the subsystem will halt machining operations and other dependent process, there by hindering the smooth flow of work-in- process.
TOOL HEALTH MONITORING
An interruption of TMS due to excessive tool wear/fracture could be detrimental to the entire operation.
The cutting tool could very well become the weakest link in the long and complicated chain of FMS. Tool monitoring is concerned with assessing the condition of the tool as machining progresses.
It involves measuring direct or indirect parameter(s) that affect tool condition and comparing with pre-set levels to initial changes in the system.
Benefits of tool health monitoring include effect tool replacement policies, improved product quality and lower tool costs.
RELATIVE ADVANTAGE OF AE
Changes in AE signal level occur almost at the instant of tool fracture where as that in the force level occurs only after the tool has broken or chipped-off. Because of this, AE based methods can detect tool fracture quickly, thus being suitable for timely action.
The frequency range of AE signals is well above that of mechanical vibrations and noises, and therefore, no chance of contamination by the latter. This is, probably the biggest attraction of AE method over others.
Besides the tool wear, AE technique can also detect tool fracture. AE can show through its signature whether a chipping or fracture has taken place.