Clamping intelligent modular systems for cutting process.

Nita, Raluca ; Avramescu, Valeriu ; Craciunoiu, Stefan 等

1. INTRODUCTION

The evolution of modern society, marked by widespread of the technological innovation has accelerated products and demands diversification regarding their performances and imposed precision, reliability and productivity of manufacturing processes expectations, systems development in order to be capable to ensure the new requirements.(Nita & Craciunoiu, 2009) In order to have the possibility to process all kind of technological operations on multifunctional machine tools it is important to design modular structures for pieces clamping. (Paunescu et al., 2006). For answering to the technological and functional needs of the processing process the developed structures are equipped with sensors, drive systems, command and control assets, so the developed fixing systems are able to respond in real time requirements of the technological process, changing them functional characteristics depending to the changes occurred in the process and in the initial working sets.

2. GENERAL INFORMATION

Principal component of a production process is represented from technically point of view by the technological process, which includes various activities not only at the organizational level, but also at the economic, managerial, etc... In order to achieve for pieces with complex geometrical shapes high dimensional precision, roughness according to imposed technical specifications, it is necessary to adapt the technological processing to ensure the full complexity of technical requirements, technological and functional.

Improving the processing technologies is determined by the evolution of processing, assembly or control equipments. The device, in general, represents an important component that aims to ensure the products quality level, work productivity, systems flexibility and economic efficiency. This objective is achieved by ensuring the piece positioning accuracy in order to reduce the influence of external parameters processing, under orientation precision aspect, geometrical precision, functional precision and adaptability to the product changes and costs of the process.

Because of the multiple processing posibilities turning, milling, drilling, broaching, slotting, toothing and plane, exterior and interior cylindrical, rectification, and spiral, clamping systems it is necessary to be desing in modular variant, for an easy adaptation to any working conditions. (Paunescu et al., 2006).

An intelligent clamping device is necessary to respond to the specific processing needs and to be capable to addapt relatively easy to any kind of technological process.

Technological and functional needs of working are different from process to process so that the structures of the developed devices in order to respond in real time to the effective problems appeared during the technological process, are equipped with sensors, drive systems, command and active. (Nita & Craciunoiu, 2009)

Intelligent devices have the possibility to change their behavior as an adaptation to changes in the internal and external medium, through intelligence being understood by the ability of a system to achieve a particular purpose or to have a desired behavior under conditions of uncertainty, namely the emergence unexpected events and unexpected and incomplete and insufficient information to decide what to do. They are able to take decisions in these circumstances of uncertainty, being different of those that are scheduled to perform repetitive operations, also capable of changing their own behavior but on the basis of orders given by a human operator.

3. DATA ACQUISITION SYSTEM--INTEGRANT PART OF AN INTELLIGENT DEVICE

Data acquisition represents the process of obtaining data from an external source of computing system, through the measuring process some the systems parameters, in the frame of supervision and management of industrial processes; because the measurement and recording of data not satisfies the requirements of leadership, were imposed multiple functions required for the data acquisition systems, namely:

* Converting the physical phenomenon in a measure that can be measured.

* Getting signals from sensors for the purpose of extracting information.

* Data analysis and presentation in a useful form.

* Command signals generation for the exectoin elements from the adjustment loops coupled with the data acquisition system.

While a classical measurement system process throughout the whole measurement chain the signal received from the transducers only in analog form, a computerized measurement system transform the signal in a measured value from an analog to a digital form. After this transformation, all the respectively signal processing are actually numerical processing, performed in a system based on microprocessor (computer).

[FIGURE 1 OMITTED]

4. TECHNICAL AND FUNCTIONAL

CHARACTERISTICS OF THE INTELLIGENT MODULAR DEVICES

Dominant feature of a flexible fixing system also refers to the possibility of easy adaptation to the type of process: the process of cutting (turning, milling, drilling, grinding etc.). It should ensure a high level of work productivity and of the product quality and economic efficiency (Costea & Rachieru, 2005).The modular fixing elements offers the possibility of constructing a variety of devices for orientation and fixing, multifunctional (Costea & Rachieru, 2005), through some families of products in which construction to retrieve assemblies or identical parts, taking into consideration the concept of "Baukasten" games, (Costea & Rachieru, 2005) being possible to achieve such complex structures of elements of fixing devices by combining in a multitude of variations of the same components called modules (Costea & Rachieru, 1998; Prospectes, 2009).

In order to achieve the most accurate operating conditions for the machine tools processing devices, concerning the orientation, the geometry, the size and the functionality, these devices have been supplied with sensors meant to deliver accurate information during the processing procedure.

Cutting forces size are influenced by cutting regimes, the mechanical properties of the material of the half finished product, and have percussive nature at the first contact with the tool and variable during the cutting process as a result of the material unevenness and tools wear. Since there is no precise mathematical model to express tool shape depreciation, we use sensors that provide information about the size of the cutting forces, because they reflect the state of wear of the tool. (Nita & Craciunoiu, 2009)

Data collected at the sensors level are transmitted to a computer, which aims to ensure the active command of the processing. Signals can be taken directly by measuring tool geometry, the distance between the tool and the piece, the vibrations of the tool and also of the part, clamping force, and cutting forces. The data are compared with normal values, typical for work conditions, and for the given results of the clamping force and cutting force can be adjusted, up to complete hold of working process, to ensure the processing conditions of geometrical, orientation, dimensional and functional precision.(Nita & Craciunoiu, 2009). The novelty of fixing devices, besides the high degree of modularization, flexibility, automatically adjusting to the effective work condition appeared during the technological process with the help of sensors, drives systems, command and active control.

The construction of modular fixing devices ensure them the maximum flexibility, so that by combining different modules can be obtained different types and constructive variants corresponding to a variety of technological needs, by fast converting a variant of the device to another and a type of production to another in case of changing the production type. (Paunescu & Bulea, 2006)

Depending on the data collected by sensors, after their analysis through a program in which optimal values are recorded as such that process to take place in conditions of optimal safety, from the functional point of view and of the work parameters, is done an active command system based on control loop, which allows control of the device. In this way it is realized the connection between the process and the intelligent clamping device, through a feedback of control, based on the signals acquired by the sensors. After the signals are compared with values which are predefinited, thanks to the system of active control, the variable parameters of the device (such as clamping force, tools rotation) are modified in order to achieve even pieces with complex geometrical shapes at high dimensional precision, roughness according to imposed technical specifications.

[FIGURE 2 OMITTED]

For obtaining systems with higher performances that the classic ones, the typical performance of the command software should include: the command of the informational flux, the command of the processing process, monitoring and command of the performances, visualization the system functional stage.

5. CONCLUSIONS

Designed devices must have a high level of modularization, productivity, flexibility and adaptation, both for flexible configuration of processing systems and for guidelines and systems for specialized processing.

Dominant feature of a flexible fixing system also refers to the possibility of easy adaptation to the type of process: the process of cutting (turning, milling, drilling, grinding etc in the conditions of the small and medium production requirements. Because the fixing system it's designed from modular elements that can be combined depending on the type of process and of the imposed fixing restrictions can be used in most of the activities domains. In order to answer to the technological and functional needs of specific process the developed structures are equipped with sensors, drive systems, command and control assets, in order to be able to respond in real time requirements of the technological process, changing them functional characteristics depending to the changes occurred in the process and in the initial working sets.

6. REFERENCES

Costea, A. & Rachieru, N. (2005). Flexibilitatea si performanftle echipamentelor de prelucrare. Optimizarea proiectarii dispozitivelor, Bren Publishing, ISBN 973-648-391-63, Bucharest

Costea, A. & Rachieru, N. (1998). The increase of performances and technological flexibility of multi-purpose machines through the equipment with multi-functional modules. ICMaS'98, Technical Publishing, ISBN 973-311236-4, Bucharest

Nita, R.; Craciunoiu, S.; Avramescu, V. & Marin, G. (2009). Inteligent fixing sistems on multifunctional machine tools, Proceedings of the 13th International Conference ModernTechnologies, Quality and Innovation, ISSN 2066-3919 Iasi, 2009

Paunescu, T.; Bulea, H. & Paunescu, R. (2006). Dispozitive Modulare. Construcfie, Exploatare, vol. I. Technical Publishing of Transilvania University, ISBN (10) 973-635723-6, Brasov

Prospectes of the firmes (2009). Hohenstein--Germania, Mauser-Werk Oberndorf GmbH Germania, Helge F. Mara Prazizionswerkzeuge--Austria, Norelem Franca