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Projects / Programmes source: ARIS

Development and implementation of innovative machining technology for machining ZnO based ceramics with defined cutting geometry, in serial production, to increase the quality of varistors as final products

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Research activity

Code Science Field Subfield
2.10.00  Engineering sciences and technologies  Manufacturing technologies and systems   

Code Science Field
T130  Technological sciences  Production technology 

Code Science Field
2.03  Engineering and Technology  Mechanical engineering 
Keywords
Cutting, machining of ZnO ceramics, varistor, innovative machining technology, contact surfaces
Evaluation (rules)
source: COBISS
Evaluation of bibliographic research performance indicators according to ARIS methodology
Citations Citations for bibliographic records in COBIB.SI that are linked to records in citation databases
source: WoS source: Scopus source: COBISS
Researchers (17)
no. Code Name and surname Research area Role Period No. of publications
1.  38903  Jaka Dugar  Manufacturing technologies and systems  Researcher  2019 - 2022  43 
2.  30008  Matej Felicijan  Chemistry  Researcher  2019 - 2020  0 
3.  38150  PhD Damir Grguraš  Manufacturing technologies and systems  Researcher  2021 - 2022  95 
4.  35396  PhD David Homar  Manufacturing technologies and systems  Researcher  2019 - 2020  54 
5.  50688  PhD Awais Ikram  Manufacturing technologies and systems  Researcher  2020 - 2022  30 
6.  37944  Marija Jeretina    Technical associate  2019 - 2020  0 
7.  50820  Matjaž Kern  Manufacturing technologies and systems  Junior researcher  2019 - 2021  37 
8.  23470  PhD Peter Krajnik  Manufacturing technologies and systems  Researcher  2020 - 2022  235 
9.  17076  PhD Davorin Kramar  Manufacturing technologies and systems  Researcher  2019 - 2022  448 
10.  38555  Branko Lampret  Electronic components and technologies  Researcher  2019 - 2022  0 
11.  51384  Miha Mlakar  Electronic components and technologies  Researcher  2019 - 2020  0 
12.  06963  MSc Andrej Pirih  Telecommunications  Researcher  2019 - 2022  45 
13.  51330  Helena Podgoršek Dremel  Chemistry  Researcher  2019 - 2022  0 
14.  26559  PhD Franci Pušavec  Manufacturing technologies and systems  Head  2019 - 2022  610 
15.  18047  Vinko Rotar    Technical associate  2019 - 2022  38 
16.  30149  Saša Rustja-Kosec  Materials science and technology  Researcher  2019 - 2022  15 
17.  51385  Tine Tavčar  Electronic components and technologies  Researcher  2019 - 2022  0 
Organisations (3)
no. Code Research organisation City Registration number No. of publications
1.  0782  University of Ljubljana, Faculty of Mechanical Engineering  Ljubljana  1627031  29,252 
2.  3621  Razvojni center eNeM Novi Materiali d.o.o. (Slovene)  Zagorje ob Savi  3986365000  42 
3.  6399  Raycap, Surge Protective Devices, Ltd.  Komenda  5286948000  161 
Abstract
With surge protective devices (SPD) where the main component for the correct operation is varistor ceramics we protect the devices in the object from direct or indirect lightning strike into electricity and telecommunication lines. It should be noted that parts that are under voltage (electrical voltage conductors, telecommunication and information lines) can not be directly connected to a potential equalization collector. They can be connected via overvoltage conductors, which in their normal operating state do not represent a conductive connection. For the time of overvoltage surge, they represent very low resistance and practically for a short time, they short-circuit the conductors under voltage with a potential equalizer collector. When the voltage returns again to the operating voltage the initial state is restored and the network can operate normally. The essential element for which the overvoltage protection is working properly is a ceramic disk made of varistor ceramics, the manufacturing of which is the main topic of the mentioned project.   In general, for the manufacture of ceramics the sintering process is used for both oxide and non-oxide mixtures. For the ultimate functionality of products, both micro and macro geometry of contact surfaces are cruical. This requires subsequent finishing of sintered discs. Due to the high hardness of these materials even at elevated temperatures usually finishing cutting technologies with undefined cutting edge geometriy are used. A typical example of such conventional finishing is the use of the lapping process. Due to the need for high material removal rate and the requirements involving complex surface geometries of the product, the conventional lapping and grinding technology represents limited productivity, inability to produce the required geometries and frequent uncontrolled chipping or sharpening of the finished products' edges which are crucial for the uniform distribution of the electric field strength. As an alternative, the project will perform the analysis of the possibility of introducing cutting processes with defined cutting geometry (milling, turning) into the manufacturing of ceramic components. The problems that arise are connected with the chip formation mechanisms due to the material properties of ceramics (strenght and hardness). Therefore, the goal of this researh work will be oriented in the analysis of the mechanisms of cutting and chip formation. As a research contribution, it is expected to link the microstructure of the workpiece, the geometry (radius) of the tool cutting edges and the change in the geometry of the tool as a result of tool wear. Thus, the main goal and purpose of the project is the wider analysis of new production technologies of ceramic varistors based on milling and turning. Additionally, the goal is to implement the developed production technology into an industrial application and verify it on a specific product. In addition, the goal is to develop and raise the technology to the large-scale production of new high-quality varistors. In addition to the mentioned field, the acquisition of such an alternative of manufacturing technology would allow the application of the presented varistors to the wider areas of photovoltaic systems, telecommunications networks, the automotive industry (electric car chargers) and other electric power areas. The use of overvoltage protection with the mentioned ceramics promises significant economical savings as it enables protection of expensive electrical components against destruction or damage as a result of surge arrests. The primary objective of the project is related to the application development and industrial implementation of varistor ceramics manufacturing to achieve precise technical characteristics of the essential elements of surge protective devices. With a successfully completed project overvoltage protection devices will become widely available which will be reflected in the greater
Significance for science
Faculty of Mechanical Engineering UNI-LJ in the cooperation with Slovenian company Varsi d.o.o. in last year have shown with the development and testing of prototypes that the performance of varistor ceramics can be significantly improved by using cutting processes. Developed prototypes especially emphasize that the proposed alternative ensures that there is no adhesion of the workpiece material to the tool which is one of the reasons why it is possible to obtain extremely high-quality workpiece surfaces with the methods of defined cutting geometry in the case of a ceramic workpiece. These surfaces exhibit even higher quality compared to conventional finishing processes using undefined cutting geometry such as grinding or lapping. Therefore, the originality of this project is reflected in the possibility of application development and transfer of technology into the serial production, as well as the achievement of: (1) the required production parameters to achieve an extremely even distribution of the electric power of varistors (the biggest problem up to date); and (2) the installation of dedicated machining centers suitable for serial production. Thus, for situation in Slovenia the development of implementation would in itself be an original result. Additionally the new innovative solution with laser assisted machining which is in the discussion for patenting will also be tested on the specific issues of the participating industry. With the success of the project, it is expected to implement the first Slovenian industrial application of varistor ceramics processing with the precision cutting technology.   With such a project Varsi will have the opportunity to acquire so-called innovative and high-performance varistor ceramics production and ultimately set a new competitive edge in the global market. It is clear and expected that the potential impact of the results is high and that in the long run the results can have great significance for the Slovenian economy.
Significance for the country
The presented project problematics address the essence of overvoltage protective devices which are mainly suitable for the protection of devices and facilities where high operating currents (up to 12.5 kA) are present. The largest field of application of such devices is wind power plants where ceramic varistors must exhibit 100% reliability at a higher number of lightning strikes.   In addition to the mentioned field, the acquisition of such an alternative of manufacturing technology would allow the application of the presented varistors to the wider areas of photovoltaic systems, telecommunications networks, the automotive industry (electric car chargers) and other electric power areas. The use of overvoltage protection with the mentioned ceramics promises significant economical savings as it enables protection of expensive electrical components against destruction or damage and prevent losses of all those who were exploiting these devices.    Such high-tech overvoltage protection is from the production point of view a great challenge and an unexplored field of work which has been partially conquered only in Japan at the moment. At the moment it is the only manufacturer of such varistor ceramics. At the Faculty of Mechanical Engineering UNI-LJ we started researching and introducing a new production technology of the mentioned varistor ceramics. With the results obtained in the processing of prototype samples it is evident that we are competing with currently the only producer and we can gain an advantage over global competition.   The main economic and social contribution of this project is the development of technology and the implementation of varistor ceramics processing in the Slovenian industry. Through the development we will master new areas of work and at the same time take advantage of the fundamental advantages of such cutting methods in terms of increasing productivity and competitiveness in a demanding global market. This will be achieved through: +Ensuring the robustness of the technology that will achieve the manufacturing requirements for the production of varistor ceramics with cutting processes and will successfully replace the existing lapping or grinding process which proved to be inadequate after several years of experiments. +Increase of productivity and ensuring a 100% reliability in manufacturing of the varistor ceramics prescribed by IEC 61643 standard for surge protection devices. +Reducing the production costs and becoming independent from the current sole supplier of varistor components. +Making the process more flexible by a successful transition to a serial production would allow us to use it on a wide range of dedicated machining centres.   Through the behaviour analysis and the possibility of applying technology to serial production, the results of this project will contribute to a completely new dimension of understanding the processing of varistor ceramics. By doing so, the said company Varsi d.o.o. will become more competitive if not even a leader in the global market.
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