Employees of the Precision Engineering Laboratory visited the 17th International conference EUSPEN 2017, held from 29.05. to 02.06.2017. in Hannover, Germany.

In the session Applications of Precision Engineering in Biomedical Sciences, our team presented a poster:

• ‘Issues in validation of friction in the nanometric domain‘, by authors: M. Perčić, S. Zelenika and E. Kamenar

In the session Advances in Precision Engineering and Nanotechnologies, our team presented a poster:

• ‘Determination of efficiency of orthodontic treatment by using engineering tools‘ by authors M. Brumini, E. Kamenar, P. Gljušćić, S. Zelenika, S. Špalj

Our member prof. Saša Zelenika was a member of the International Scientific Committee as well as the Chair of the session “Advances in Precision Engineering and Nanotechnology”.

This year’s Science festival in Rijeka was held from April 24th to April 29th, 2017. The 15th festival was held in 22 Croatian cities at the same time. The theme of this year’s festival was weather/time.

Opening ceremony of this event was held at City Hall Korzo on Monday, April 24th, 2017 at 11:00.

As a part of the Science festival Precision engineering laboratory team members Prof. D. Sc. Saša Zelenika, D. Sc. Ervin Kamenar and M. Sc. Petar Gljušćić organized an open laboratory day for broader public on April 27th, 2017.

Our member D. Sc. Ervin Kamenar defended his doctoral thesis entitled “Ultra-high precision positioning via a mechatronics approach” on May 19th, 2016.

Doctoral thesis supervisor vas Prof. D. Sc. Saša Zelenika.

Our member D. Sc. Kristina Marković defended her doctoral thesis entitled “ANALYSIS OF INFLUENCING PARAMETERS IN THE DESIGN OF CROSS – SPRING PIVOTS” on March 20th, 2015.

Doctoral thesis supervisor vas Prof. D. Sc. Saša Zelenika.

Committee for the defense of the doctoral thesis:

1. Prof. D. Sc.Dubravka Siminiati, University of Rijeka, Croatia, Faculty of Engineering (Sveučilište u Rijeci, Tehnički fakultet) – Committee Chair
2. Prof. D. Sc. Saša Zelenika, University of Rijeka, Croatia, Faculty of Engineering (Sveučilište u Rijeci, Tehnički fakultet)
3. Prof. D. Sc. Nenad D. Pavlović, University of Niš, Serbia, Faculty of Mechanical Engineering (Mašinski fakultet Univerziteta u Nišu)

Thesis abstract:

Compliant mechanisms, that gain at least part of their mobility from the deflection of flexible members, are an alternative to conventional sliding and rolling mechanisms used to transfer motion, power or force. Compliant mechanisms are nowadays widely used in mechanical engineering design, precision engi neering as well as the micro- and nanosystems technologies. Parameters influencing the design of differ ent configurations of cross-spring pivots are analysed in this doctoral thesis. In fact, the main goals in their design are: achieving the highest possible accuracy and precision, achieving the lowest possible variability of rotational stiffness, stability, design simplicity and reliability. Since the considered mechanis ms are constituted by spring-strips, the prediction of their behaviour is to be based on the analysis of the characteristic parameters of the strips themselves. In order to analyse the influencing parameters in the design of symmetrical cross-spring pivots loaded by a pure couple, an analytical model of the behaviour of spring-strips in the field of large (geometrically nonlinear) deflections based on the Elastica method, as well as a numerical model based on the finite elements method, are hence developed in the thesis. In order to assess the applicability of the developed numerical model in predicting the stress-strain behaviour of the considered mechanisms, results obtained numer ically are compared with experimental data available in literature. With the goal of determining the limits of applicability of the approximated calculation methods depending on the needed accuracy, the results of the analytical calculations of the stress-strain behaviour of the cross-spring pivots are then compared with results obtained by using the finite element method. Numerical calculations are used next to optimise pivots’ design by assessing the influence of the angle and the position of the intersection as well as of the initial curvature of the spring-strips,. A design solution allowing the minimisation of the parasitic shifts, as well as the minimisation of variability of the rotational stiffness, even for large rotations of the pivot is thus obtained. At the end of the thesis, ananalysis of the influence of external loads on the variability of rotational stiffness and on the entity of the parasitic shifts is also performed. The results obtained in the doctoral thesis allow thus not only assessing the influence of the design parameters in the design of cross-spring pivots (i.e. the influence of these parameters on rotational stiffness and the accuracy of the considered mechanisms), but also creating the preconditions for the development of a new class of ultra-high precision rotational compliant mechanisms with potentially broad applications in industrial and design praxis.

     

Update (09-13-2014):

As a result of collaborative research between School of Medicine in Rijeka and Precision Engineering Laboratory of Faculty of Engineering in Rijeka,  an article has been published in The Korean Journal of Orthodonics and can be read here.

Colaboration with School of Medicine in Rijeka

The Precision Engineering Laboratory has established cooperation with the School of Medicine in Rijeka. Measurement of special screws with small dimensions which are used in orthodontics was conducted using the Optical Stereomicroscope Olympus SZX16.

Characteristic properties (size, pitch angle etc.) of the screws were measured since the manufacturer does not provide this information in their catalogs for this type of special screws. Measurements were carried out in order to further analyze the influence of the dimensions of the screws on the percentage of successful operations on patients.

Measurements and analysis were performed and the final report was made in March 2012. We wish to thank Prof. Stjepan Špalj and Prof. Barbara Mady Maričić from the School of Medicine in Rijeka, Chair of Pediatric Dentistry and Orthodontics for cooperation with the Precision Engineering Laboratory.

Also, we wish to thank to our students: Arian Karabegović, Jelena Srnec and Dražen Žužić for their assistance during the measurements.

Our member D. Sc. David Blažević defended his doctoral thesis entitled “Analysis of mechanical aspects in the design of vibration energy harvesters” on September 2nd, 2014.

Doctoral thesis supervisor vas Prof. D. Sc. Saša Zelenika.

Employees of the Precision Engineering Laboratory visited the 14th international science conference EUSPEN 2014, held from 02. to 06.06.2014. in Dubrovnik. The conference is run and organized by the European society for precision engineering and nanotechnology. It’s an international conference, visited by scientists and engineers from all over the world. The main science themes are:

• Renewable Energy Technologies
• Precision Engineering for Medical Products
• Additive Manufacturing for Precision Engineering
• Nano & Micro Metrology
• Ultra Precision Machines
• Ultra Precision Manufacturing & Assembly Processes
• Important/Novel Advances in Precision Engineering & Nano Technologies
• Motion Control in Precision Systems, Nano & Micro Manufacturing

In the theme Renewable Energy Technologies our team presented a poster:

• ‘River flow energy harvesting by employing piezoelectric eels‘, by authors: E. Kamenar, S. Zelenika, D. Blažević and student I Šamanić. Paper can be read here, poser can be found here.

In the theme Ultra Precision Machines, our team presented two posters:

• ‘Precision positioning system with high-speed FPGA-based closed loop control‘ by authors E. Kamenar, S. Zelenika and M. Franulović. Paper can be read here, poser can be found here.
• ‘Numerical modelling of piezoelectric vibration energy scavenging bimorphs‘ by authors D. Blažević and S. Zelenika. Paper can be read here, poser can be found here.

Employees of the Precision Engineering Laboratory participated on the 37th International Convention on Information and CommunicationTechnology, Electronics and Microelectronics (MIPRO) in Opatija, Croatia.

In the SP MIPRO Junior Student Papers section our team presented a work entitled ‘Comparison of different DC motor positioning control algorithms’, written by students  Nikola Baćac, Vedran Slukić, Miroslav Puškarić, Boris Štih, junior researcher Ervin Kamenar and professor Saša Zelenika.

The paper won the award for the best student paper!

The paper can be read here, and pptx presentation can be seen here.

David Blažević and Ervin Kamenar, Croatian national heat winners, participated at the Euspen Challenge event which was held in Copenhagen from 2nd till 4th July 2013, at the Otticon headquartes, and Technical University of Copenhagen. Otticon is one of the biggest producers of cutting edge hearing aids in the world.

Euspen Challenge is an international competition to identify outstanding students across Europe with potential to be future leaders in the field of precision engineering and Nanotechnology. It is a unique opportunity for young engineers to promote themselves at an international level  and to connect with industry.

This year’s Euspen Challenge involved 9 International teams of 3 students.

The main challenge was to develop and construct a prototype of an auxiliary tool for battery loading of small hearing aids. As hearing aids get smaller, grabbing and changing batteries becomes a serious problem mainly for elderly people. In that case an interface is needed. Production as well as impact considerations on economic welfare were integral parts of the challenge exercise.

David’s team won the award for the best presentation.

In a collaboration with prof. Zoran Jurković from the Department of industrial engineering and management, positioning accuracy and repeatability of the X axis of the CNC machine “Prvomajska TU360” were experimentally assessed. A Michelson-type laser Doppler interferometric system was employed to complete the assessment. Several different linear positioning experiments were conducted. In the first two experiments, positioning with a 5 mm step is performed for the 200 mm measuring range of the X axis. The measurements are repeated for the 20 and 40 mm steps in the same positioning range. The team is currently working on the analyses of the obtained data.