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TAVAC

Introduction

The Portuguese moulds and special tools industry has been the forerunner for the introduction of new design and manufacturing technologies, such as the use of CAD/CAM systems, EDM, CNC machining, more specifically high speed machining and rapid prototyping.

However, despite the progress made, limitations persist in the manufacturing processes currently used, and difficulties continue in the introduction of recently developed advanced manufacturing processes. For example, it can be seen that the manufacturing time for a mould is heavily dependent on machine finishing time (both on the machine 50%, and manually 25%).

The finishing of moulds, dies, stamps and special tools is one of the operations, which requires greater human intervention and is very often carried out through the use of traditional, unsophisticated methods. This leads to excessively long manufacturing times, possible dimensional deviations, non-conformities and inescapably, the need for skilled labour.

It becomes important, therefore, to identify which advanced manufacturing technologies could contribute to the shortening of production times, and then demonstrate the qualitive and quantitive effect on productivity and quality of the introduction of these technologies.

Goals

  • To develop and implement advanced finishing technologies in the moulds, dies, stamps and special tools industries;
  • To initiate the re-engineering of conventional manufacturing processes based on the use of new finishing technologies;
  • To develop alternative chains of production dedicated to the following types of products:
    • Moulds for the injection of plastics;
    • Moulds for glass;
    • Progressive tools, matrixes and cutting, bending, fixing and stamping punches;
    • Special Tools in tungsten and cobalt carbides
  • To specify, develop and integrate systems with a view to introducing pilot - installations into the industrial companies based on the results obtained during the different stages of the project.

Development of Technologies

EDM

The materials used were those that are normally used in the manufacture of molding surfaces made in steel and other non-ferrous materials (copper/chromium alloys, aluminium alloys.

AGILTEC, INETI and CENTIMFE analyzed the effect of the chemical composition of the steels and the area polished by EDM with regard to surface integrity and polishing capability, measured as polishing time and lowest possible roughness obtainable.

Work was carried out to optimize process by varying electrical and washing parameters.

Methods and technologies were also partially developed to ensure greater stability of the polishing process as a means of reducing polishing time. It was concluded that time currently spent on polishing was uneconomic.

In particular, it was developed a system for monitoring the EDM polishing process, which permits the aforementioned instabilities to be diagnosed and eliminated, when possible.

We studied methods leading to the improvement of washing, we studied EDM technology for the roughing and finishing of other materials distinct from the steels of moulds and tools - copper and aluminium alloys, tungsten carbides, cast iron and stainless steel.

Finally, we studied the effect of introducing additives, in the form of semicondutor powder, into the EDM polishing process.

Abrasive Flow

The aim of the application of abrasive flow machining and polishing technology within the scope of the project was to polish dies, stamps and moulds.

Process parameters were identified and characterized. It was concluded that the type of abrasive paste used (viscosity and granulometry), extrusion pressure and control of the opening for abrasive paste to pass were factors of fundamental importance.

Preliminary tests allowed the effects of the different process parameters to be estimated with regard to roughness and dimensional accuracy. Also of crucial importance is the condition of surface finishing before the first abrasive flow run. The rheological behaviour of the abrasive paste was similary studied, which in the future, will provide information for sizing tools and reams.

The process was applied to the polishing of moulds for glass manufactured in grey cast iron, in accordance with Intermolde specifications. It was concluded that the process is not suitable for the processing of this type of material.

It was noted that initial surface finishing, as well as shape defects that are characteristic of wire EDM, play a critical role in the performance of this process. The need for integrated optimization of the wire EDM / abrasive flow sequence was clearly highlighted, as was seen in the PP2 project.

High Speed Machining

Bibliographic research was carried out and information was gathered on high speed machining. Research was also done into methodologies and high speed machining strategies, as applied to the complex surfaces, which characterize the moulds for plastics and glass industries.

The characteristics of high speed equipment were investigated with regard to type of spindle, control of axes and other aspects of construction.

Other tests were carried out on problems connected to the cutting process, more specifically, chip formation and the dynamic imbalance of tools, and how the eccentricities of mass can influence the forces and stability of the process.

As regards CNC programming, analyses were carried out on systems with regard to the transference of data to machine tools (DNC), on CAD/CAM tools and their respective post processors. Also analysed were the characteristics of the main CNC controls within a high speed-machining framework, which obviously require high-speed data processing.

Experimental studies were conducted into the turning of steels hardened by heat treatment. The tools used were made of cubic boron and ceramics mixed with titanium nitrides and titanium carbides and ceramics reinforced with silicon carbide fibres.

It was concluded that R&D efforts should be concentrated on the development of high speed milling technology for tempered steels, centred on the use of tools made of super hard materials. This research took place within the context of the consortium. Additionally, a system was developed to monitor and diagnose milling operations and their integration into the high-speed cell HISIM.

Information systems for integrated process planning, CNC programming and tool management

Some of the most important limitations at companies were identified in relation to the most modern support systems on the market for the creation and the manipulation of information for manufacture. In Portugal CAPP systems are not used in this industry and it was perhaps in this area, along with tool management systems (TMS), that the greatest deficiencies were apparent. CAPP, CAM, TMS and DNC systems were identified, which are commercially available and are of particular interest to the moulds and tools industry. Some of these products were selected and acquired. The Process Planning function integrated into CAPP systems was the object of special interest. Integrated system architecture was specified and developed based on these products. The need to develop routines and applications was demonstrated if performance is to be optimized, both for CAPP systems optimized machining trajectory and programme. An integrated system prototype was developed which is now on demonstration at AGILTEC.

Other Technologies

The possibility of using ultrasonic polishing for steel moulds was considered with the aim of developing a chain of production for some types of moulds for glass. At an initial stage, research personnel were trained to use this new technology and information was gathered on the process. The main applications were identified, as were the most important processing parameters. These parameters included static force, granulometry and type of abrasive and amplification, which is provided by an amplifier assembly.

Machining tests were carried out on some different materials: glass, ceramic, graphite and steel. It was proved that machinability decreased which demonstrates the nature of the cutting process produced by the impact of the abrasives suspended in the carrier fluid.

Tests for the polishing of cast iron and steel moulds demonstrated that the process can only be applied to very small areas and only to steel or aluminium moulds. This several restricts the type and dimension of moulds that can be economically processed using this technology.

As regards 5 axes milling, it was not possible to make as much progress as was hoped due to unexpected technical difficulties.

The CNC milling process with 3 axes control was analysed and critical process parameters were identified that would enable best possible finish. They include surface shape, overlay between consecutive cuts, mill geometry, cutting parameters, which influence cutting forces, and also machining strategies. More specifically, these strategies include cut approach, machining direction and variations in cutting conditions during machining. It was concluded that:

  • It is important to select strategies and machining methods to obtain highly accurate components, with reduced dimensional deviation and low levels of roughness;
  • Reductions in manual polishing time are subject to the extent of marks left by the mill. Reducing these marks, by reducing overlay, should be compensated by an increase in linear toll feed, which is consequence of the spindle rotation speed.
Other Activities

Meetings were held with industry specialists where the aim was to obtain a fuller understanding of the practical problems inherent in the use of this technology. This enabled us to gauge more comprehensively the areas to be investigated throughout the project.

Tangible and intangible investments were made to modernize and replace equipment at organizations within the scientific and technological community - INETI, Agiltec and Centimfe. A high speed milling machine was acquired for Centimfe.

As a result of research into high speed milling, another project was started within EUREKA - HISIM programme - Development of an intelligent high speed milling cell, in a consortium comprised of Fatronik, Tekniker, Goratu Machines Herramientas (SP) and FIDIA.

Conclusions

The experience acquired during the project can be considered very positive. In addition to successful results, some failures were also registered. The project allowed very important working relationships to be established between companies and institutions from the scientific and technological community.

Such relationships allowed the activities of each of these institutions to be adjusted to meet market requirements. This contributed greatly to improved relative positioning and created new areas of R&D as well as infrastructure capabilities that will be of interest to Portuguese industry.

Results

Other Activities

Meetings were held with industry specialists where the aim was to obtain a fuller understanding of the practical problems inherent in the use of this technology. This enabled us to gauge more comprehensively the areas to be investigated throughout the project.

Tangible and intangible investments were made to modernize and replace equipment at organizations within the scientific and technological community - INETI, Agiltec and Centimfe. A high speed milling machine was acquired for Centimfe.

As a result of research into high speed milling, another project was started within EUREKA - HISIM programme - Development of an intelligent high speed milling cell, in a consortium comprised of Fatronik, Tekniker, Goratu Machines Herramientas (SP) and FIDIA.

Conclusions

The experience acquired during the project can be considered very positive. In addition to successful results, some failures were also registered. The project allowed very important working relationships to be established between companies and institutions from the scientific and technological community.

Such relationships allowed the activities of each of these institutions to be adjusted to meet market requirements. This contributed greatly to improved relative positioning and created new areas of R&D as well as infrastructure capabilities that will be of interest to Portuguese industry.

Partners

The company Aníbal H. Abrantes was the promotor and leader of this project, and the consortium was formed by the following companies:

  • Intermolde
  • F. Ramada
  • Durit
  • A. Rigorosa

The technological infra-structures were:

  • INETI
  • CENTIMFE
  • ITEC (later substitued by Agiltec).
 

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