Povećanje kvalitete rezultata površinske hrapavosti kod obrade slobodnih površina temeljem neuronskih mreža

This paper concerns with free form surface reorganization and assessment of free form model complexity, grouping particular surface geometrical properties within patch boundaries, using self organized Kohonen neural network (SOKN). Neural network proved itself as an adequate tool for considering all topological non-linearities appearing in free form surfaces. Coordinate values of point cloud distributed at a particular surface were used as a surface property’s descriptor, which was led into SOKN where representative neurons for curvature, slope and spatial surface properties were established. On a basis of this approach, surface patch boundaries were reorganized in such a manner that finish machining strategies gave best possible surface roughness results. The patch boundaries were constructed regarding to the Gaussian and mean curvature, in order to achieve smooth transition between patches, and in this way preserve or even improve desired curve and surface continuities, (C2 and G2). It is shown that by reorganization of boundaries considering curvature, slope and spatial point distribution, the surface quality of machined free form surface is improved. Approach was experimentally verified on 22 free form surface models which were reorganized by SOKN and machined with finish milling tool-path strategies. Results showed rather good improvement of mean surface roughness profile Ra for reorganized surfaces, when comparing to unorganized free form surfaces.Ovaj se članak bavi reorganizacijom slobodnih površina i ocjenom kompleksnosti modela slobodnih površina, grupirajući određena površinska geometrijska svojstva unutar zatvorenih površina, koristeći samoorganizirajuću Kohonenovu neuronsku mrežu (SOKN). Neuronske mreže pokazale su se kao prikladan alat za razmatranje svih topoloških nelinearnosti koje se pojavljuju kod slobodnih površina. Vrijednosti koordinata oblaka točaka raspodijeljenih nad određenom površinom korišteni su kao svojstveni opis, što je nadalje vodilo prema SOKN-u, gdje su ustanovljeni reprezentativni neuroni za zakrivljenost, nagib i prostorno-površinska svojstva. Na temelju ovoga pristupa reorganizirane su granice zatvorenih površina na takav način da metode površinske obrade daju najbolje moguće rezultate spram površinske hrapavosti. Granice tih površina određene su prema Gaussovoj i prosječnoj zakrivljenosti kako bi se postigao glatki prijelaz između zatvorenih površina te kako bi se na taj način očuvala ili čak unaprijedila željena zakrivljenost i glatkoća površine, (C2 i G2). Pokazano je da se reorganizacijom granica s obzirom na zakrivljenost, nagib i prostornu raspodjelu točaka, poboljšava kvaliteta obrađene slobodne površine. Pristup je eksperimentalno potvrđen na 22 modela slobodne površine koji su reorganizirani SOKN-om i površinski obrađeni određenim metodama. Rezultati pokazuju poprilično dobro poboljšanje prosječne vrijednosti površinske hrapavosti Ra za reorganizirane strukture u usporedbi sa neorganiziranim slobodnim površinama

Application of Lean Methods into the Customised Product Development Process of Large Power Transformers

The study conducts research on lean product development (PD) methodology and presents a case study of its practical application into a specific one-of-a-kind development of large power transformers. The demonstrated framework is the result of a 5-year intensive research that led to an extensive transformation of a traditional PD environment into a highly efficient process according to lean principles. Paper explains how lean PD integrates with robust, concurrent and smart design strategies in highly individualized PD business. A generalized framework of PD and design process renovation is presented, comprising three main fields of interest: Process & Tools, People, and Knowledge. A direct consequence of implied renovation are significant savings. Case-study company cut down engineering changes by 32 % in three year test period and experienced performance improvement between 25 % and 83 % across designated process indicators

Dinamičko planiranje i terminiranje uz više kriterija u proizvodnji tokarenih dijelova

Technical innovations in the area of manufacturing logistics are being introduced partially and thus not exploiting their full potential. In order to optimise the efficiency of turning manufacturing processes, the process has been analysed and fundamentally re-engineered. All data from production (operations, quantities, date, time duration of operations, etc.) are now located in ERP system. It provided the necessary condition for the establishment of a robust dynamic planning model. An update was required for the whole lifecycle of products and means of work. The paper presents the information support and an algorithm for a dynamic planning model, based on a genetic algorithm. Continuous data capturing and planning in real time are a breakthrough in the management of the process. Presented are a generalised dynamic planning model and a case example from the production of turned parts, which take account of the singularities of a real environment. Production capacities have to be linked up with the supply chain and customers. The presented dynamic planning model can be adapted to various types of production.U području proizvodne logistike tehničke se inovacije uvode parcijalno te se ne koristi njihov puni potencijal. U cilju poboljšanja efikasnosti proizvodnih procesa tokarenja, postupak se analizirao i u potpunosti preradio. Svi se podaci iz proizvodnje (operacije, količine, datumi, vrijeme trajanja operacija itd.) sada nalaze u ERP sustavu. On je osigurao potrebne uvjete za stvaranje modela dinamičkog planiranja. Tražili su se ažurirani podaci o cijelom radnom vijeku proizvoda i sredstvima za rad. U članku se predstavlja informatička podrška i algoritam za dinamički model planiranja, zasnovan na genetskom algoritmu. Stalno dobivanje podataka i planiranje u realnom vremenu predstavljaju važan napredak u upravljanju tim procesom. Predstavljen je generalizirani model dinamičkog planiranja i primjer iz proizvodnje tokarenih dijelova gdje se uzimaju u obzir specifičnosti stvarnog okruženja. Proizvodni se kapaciteti moraju povezati s nabavnim lancem i kupcima. Ovaj se model dinamičkog planiranja može adaptirati različitim tipovima proizvodnje

Product Function Matrix and its Request Model

A developed model of the first structural shape of the matrix of product function and its requests model have been shown in practice. It relates functions of the product and its requests model, and technical systems that solve them. Functions are described by parameters, determined by physical laws. The technical systems and functions are related among themselves through correlations that fill the field of the matrix. The correlations are determined through winning parameters. Winning parameters are determined from the set of parameters of each function that have the greatest importance and influence on a specific function. The model is implemented into a developed prototype computer system. The first structural shape of the product function matrix and its requests model for the stator of the electrical motor of the intake unit have been generated through the prototype computer system. By implementing the product function matrix and its requests model in the process of product conceptual design, it becomes possible for a designer to examine himself by comparing the possibilities of implementation of new ideas with previously built products

Product Function Matrix and its Request Model

A developed model of the first structural shape of the matrix of product function and its requests model have been shown in practice. It relates functions of the product and its requests model, and technical systems that solve them. Functions are described by parameters, determined by physical laws. The technical systems and functions are related among themselves through correlations that fill the field of the matrix. The correlations are determined through winning parameters. Winning parameters are determined from the set of parameters of each function that have the greatest importance and influence on a specific function. The model is implemented into a developed prototype computer system. The first structural shape of the product function matrix and its requests model for the stator of the electrical motor of the intake unit have been generated through the prototype computer system. By implementing the product function matrix and its requests model in the process of product conceptual design, it becomes possible for a designer to examine himself by comparing the possibilities of implementation of new ideas with previously built products

Generiranje funkcijske strukture unutar više-strukturnih matričnih oblika

This paper aims at showing the possibility of improving the initial phase of design process using the matrix function multi-structured form of products and their requests. The developed matrix model is a tool which by using a mathematical model interconnects functions and technical systems that solve them. This is one of the main differences with regard to morphological matrix. By mutual linking of matrices the matrix structure is generated in which the whole functional structure of a product is stored. For the sake of uniformity the functions are described by parameters defined from physical laws. In this way the complete knowledge about a product is registered in matrices enabling the generation of the variant and new products. The model is implemented into a prototype computer Web application with the central relational data base. A higher quality, faster and cheaper management of the design process is thus made possible.Cilj ovoga rada je prikazati mogućnost poboljšanja inicijalne faze konstrukcijskog procesa korištenjem više-strukturnog oblika matrice funkcije proizvoda i njihovih zahtjeva. Razvijeni matrični model je alat koji korištenjem matematičkog modela dovodi u međusobne odnose funkcije i tehničke sustave koji ih rješavaju. To je jedna od bitnih razlika u odnosu na morfološku matricu. Međusobnim povezivanjem matrica generira se matrična struktura u kojoj je pohranjena cjelokupna funkcijska struktura proizvoda. Kako bi se postigla jednoznačnost, funkcije su opisane parametrima određenim iz fizikalnih zakona. Ovako je u matricama popisano cjelokupno znanje o proizvodu koje omogućuje generiranje varijantnih i novih proizvoda. Model je implementiran u prototipnu računalnu Web aplikaciju s centralnom relacijskom bazom podataka. Na ovakav način omogućeno je kvalitetnije, brže i jeftinije vođenje konstrukcijskog procesa

Thermal model of through flow universal motor by means of lumped parameter network

Biti u stanju predvidjeti porast temperature unutar stroja jednako je važno kao i predvidjeti njegovo djelovanje i radni vijek. Budući da mjerenja temperature i toplinske simulacije računalom mogu zahtijevati puno vremena, putovi topline unutar protočnog univerzalnog motora su opisani jednostavnom toplinskom mrežom skupnog (lumped) parametra. Jednom kad je model izgrađen, njegovi nepoznati koeficijenti konvekcije su usklađeni s alatom genetičkog algoritma u MatLab. Model je primijenjen i uspješno provjeren mjerenjima na dva različita tipa motora usisivača za prašinu. Uzimajući u obzir gibitke rotora kao jednog od ulaza modela, procjene temperature su točnije bez obzira na radni režim stroja.Being able to predict temperature rise inside a machine is as important as predicting its performance and life. Because temperature measurements and computational thermal simulations can be time consuming, thermal paths inside the through-flow universal motor were described by means of simple lumped parameter thermal network. Once the model was built, its unknown convection coefficients were tuned with the genetic algorithm tool in MatLab. The model has been applied and successfully verified with measurements on two different types of a vacuum cleaner motor. Taking account of impeller losses as one of the model inputs makes temperature estimates more accurate regardless of machine’s operational regime

Utjecaj upravljanja na kreativnost i transfer znanja u akademskom virtualnom poduzeću

In a competitive knowledge-based environment the role of creativity in new product development (NPD) has increased. The university as the provider of scientific and technological knowledge has become a key player in NPD, as a supplier of knowledge and human capital and as the physical space for new enterprises. The boundaries between science and technology, university and industry are in flux. This article therefore examines the environmental, strategic and organizational factors influencing innovation in NPD process on an example of an Academic Virtual Enterprise (AVE) that was applied in a design course called European Global Product Realization. AVE represents a creative working environment for students, where they act as real professionals in solving a real-life design problem.U konkurentnom okruženju utemeljenom na znanju povećana je uloga kreativnosti u razvoju novog proizvoda (RNP). Sveučilište kao pružatelj znanstvenog i tehnološkog znanja postalo je ključni igrač u RNP, kao dobavljač znanja i ljudskog kapitala i kao fizički prostor za nova poduzeća. Granice između znanosti i tehnologije, sveučilišta i industrije su fluidne. Ovaj članak istražuje stoga okolišne, strateške i organizacijske faktore koji utječu na inovacije u RNP procesu na primjeru akademskog virtualnog poduzeća (VP) koje je primijenjeno u oblikovanju kolegija Realizacija europskog globalnog proizvoda. VP predstavlja kreativnu radnu okolinu za studente, gdje oni djeluju kao pravi profesionalci u rješavanju stvarnog problema oblikovanja (konstruiranja)

A Mathematical Model and Numerical Simulation of the Static Stability of a Tractor

Tractor overturning remains a serious problem in agricultural activities. A detailed analysis of problems and causes leading to a tractor overturn have revealed that by improving tractor’s static stability we can positively influence the safety as early as during the concept phase. We designed a mathematical model and a numerical simulation of the static stability of a tractor with an oscillating front axle in relation to its position on a slope. It was followed by analysing the changes of individual parameters, such as the position of the centre of gravity, the wheelbase, the wheel track width and the height of the oscillating axle mounting point, and their impact on tractor’s static stability in relation to its position on a slope. Results show that manipulating these parameters can significantly increase tractor’s static stability. A better static stability is directly proportional to improved dynamic stability, resulting in a better safety in a view of the tractor overturn, particularly while working on a sloping terrain

Global optimization of freeform support structures

Postojeći su arhitektonski projekti usmjereni konstrukcijama slobodnih i neodređenih oblika. Veza između onoga što se želi postići projektom i izrade predstavlja izazov kod izvedbe potporne konstrukcije koja je geometrijski održiva, a trebala bi zadovoljiti određene estetske, izvedbene, toplinske zahtjeve i one koji se odnose na čvrstoću. Kako bi se osigurao kontakt rubova dodirnih izolacijskih panela cijelom njihovom debljinom, rubovi moraju biti odrezani pod različitim kutovima što dovodi do razlika u visini vrhova kuta te razlika u položaju unutarnjih metalnih ploča izolacijskih panela. Osnovni cilj predstavljenog istraživanja je razvoj postupka optimizacije pomoću kojega će se postići minimalna razlika u visini spoja kod svih spojišta, uzimajući u obzir sve površine slobodnog oblika pojedinog arhitektonskog projekta. Da bi se nadoknadile zaostale razlike u visini spojeva predlaže se korištenje držača razmaka različitih debljina. Mreže uglavnom četverokutne strukture konusnih svojstava zahtijevaju optimizaciju visine vrhova kutova kako bi se kod svih greda postigle približno minimalne razlike u visini spojeva. U članku se razmatra globalna minimizacija razlika u visini spojeva na uzorku arhitektonskog projekta slobodnog oblika, s mrežom uglavnom četverokutne strukture s konusnim svojstvima. Usporedba razlika u visini spojeva prije i poslije optimizacije pokazuje znatno poboljšanje.The trends in current architectural design are leading towards structures with free and irregular forms. The connection between the design intent and the fabrication presents a challenge when creating a support structure that is geometrically viable and should possess certain aesthetics, fabricational, thermal and strength requirements. To ensure the contact of edges of neighborhood insulation panels along their thickness, their edges must be cut under different angles which cause the differences in vertex heights and further the differences of the positions of the inner metal sheets of the insulation panels. The main goal of the presented research is the development of the optimization procedure by which the minimal joint height differences will be achieved in all the joints, taking into account all free form surfaces of the individual architectural design. To compensate for the residual joint height differences the usage of spacers of different thicknesses is proposed. Quad-dominant meshes with conical properties require optimization of the vertex heights to align all beams at approximately minimal joint height differences. The paper considers global minimization of joint height differences for a sample of free form architectural design, meshed with quad-dominant mesh with conical properties. The comparison of the joint height differences before and after the optimization shows the substantial improvement