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

Održivi proces obrade – mit ili stvarnost

The industry is under increasing pressure of the financial crisis, global competition, stricter environmental legislation and supply-chain demand. To tackle these issues, a sustainable development trend has to be assured synergetically on all the levels/fields, including machining processes. This paper promotes sustainable production via an improvement of machining technologies through an alternative cryogenic machining process. Presented are comparative experimental results of cryogenic machining performances in accordance with conventional processes, through the analysis of: cutting forces, tool-wear, temperatures and costs. This work proves that the cryogenic machining technology has a high potential to cut costs and improve competitiveness by reducing resource consumption therefore, creating less waste, and has less of an environmental and social impact. The results of this work confirm that alternative sustainable cryogenic machining offers conditions for fulfilling the sustainability pillars: the economical, social and environmental one, over conventional machining processesIndustrija je pod sve većim pritiskom financijske krize, globalne konkurencije, strožih zakona o zaštiti okoliša, lanaca ponude i potražnje. Da rješavajući ova pitanja, održivi trend razvoja mora osigurati sinergiju na svim razinama / poljima, uključujući i obrade. Ovaj rad promovira održivu proizvodnju putem suvremene tehnologije u vidu alternativnog kriogenog procesa obrade. Prikazani su eksperimentalni rezultati komparativne kriogene obrade u odnosu na konvencionalne procese, kroz analizu: sila rezanja, trošenja alata, temperature i troškove. Ovaj rad dokazuje da kriogene tehnologije imaju visok potencijal za smanjenje troškova i poboljšanje konkurentnosti smanjenjem potrošnje resursa, dakle, omogućuje manje otpada, a ima manji ekološki i društveni utjecaj. Rezultati ovog rada potvrđuju da alternativna održiva kriogena obrada omogućava ispunjenje uvjeta za održivost: ekonomsku, socijalnu i ekološku, u odnosu na konvencionalnu obradu

Influencing Indicators Determination - Precondition for Successful Innovation Management in Mechanical Industry

The purpose of the study was to establish the most important influencing parameters concerning innovation processes aimed at achieving improved business performance in the machinery and equipment manufacturing industry in Slovenia. A five steps research methodology was applied. Initially, a group of variables among the statistical data was selected, and then some additional variables were defined. In the third step, the variables were dispersed among the following categories: input, process, indirect output and direct output variables. In the fourth step, reciprocal correlations among particular variables were calculated prior to the final selection of the most important correlations and their interpretation. The influential input and process variables were estimated, and these indicate not only the sequence of activities but also particular areas where additional effort needs to be invested in innovation. The research limitations are related to statistical methodology since the used correlation coefficient itself does not provide any information on the direction of the cause-effect relation. Further limitations are connected with statistical data failing to cover all the important topics related to the innovation performance within a company. There are also some misleading questions/definitions in the SURS/Eurostat which partially result in subjective results. The time delay factor also represents one of the limitations of the study. Namely, a change in certain influencing parameters (e.g. R&D expenditure) normally requires a certain period of time to actually come into effect. The findings also represent a set of suggested guidelines in which enterprises, national policy leaders and also supporting environment organisations should put their efforts. The way of analysing and interpreting the data deriving from the mechanical industry are new. Besides, the results and conclusion are also original and may be applied by the aforementioned target groups

Tool wear performance evaluationin MDF machining with anthropomorphic robot

Najnoviji napredak u robotici čini robote pogodne za različite potrebe. Osim manipulativnih i instalacijskih aplikacija, koje su najčešće za robotske manipulatore, može se obavljati i glodanje. U bliskoj budućnosti robotski manipulatori s integriranim vretenom, pravilnim reznim alatom i pravilno odabranima parametrima glodanja, mogli bi zamijeniti konvencionalne CNC strojeve kod srednjih tolerantnih strojnih obrada, pogotovo kod upotrebe mekanih materijala krajnjih proizvoda. U principu, trajanje alata i trošenje tijekom glodanja s robotima nije dostupno ili istraživano. Stoga, ovaj rad predstavlja analizu HSS trošenja alata tijekom obrade MDF (ploče srednje gustoće) materijala s antropomorfnim robotom. Težište je na međuodnosu trošenja alata i položaja izratka u području rada robota. Za tu analizu, ispitivanja su provedena u četiri različita položaja prema udaljenosti između baze robota i ispitivanog položaja glodanja. Rezultati pokazuju da porast udaljenosti značajno utječe na trošenje alata, zbog vibracija, što pokazuje sasvim drugačije ponašanje od krutih konvencionalnih CNC strojeva.Recent progress in robotics makes robots suitable for many different applications. Beside manipulative and installation applications, which are the most common for robot manipulator, milling can be performed as well. In the near future, robot manipulators, integrated with spindle, proper cutting tool and milling parameters could replace conventional CNC middle toleranced machining, especially for soft material end products. In general, tool life behaviour in milling with robots is not available or studied. Therefore, this work presents the analysis of HSS tool wear in milling MDF (medium density fibreboard) with an anthropomorphic robot. The focus is on the correlation of the tool wear and the workpiece position in the robot operation area. To analyse this, tests were performed in four different positions according to the distance between robot base and test milling position. Results show that increasing distance significantly affects tool wear, on account of vibrations, what shows completely different behaviour than stiff conventional CNC machine tools

Measurements and analyses of lateral acceleration in traffic of vehicles

Ubrzanja i kočenja su potrebna u prometu kako bi se omogućilo vozilu da putuje iz jednog mjesta na drugo. Tijekom vožnje prisutna su bočna ubrzanja, koja djeluju u zavojima. Ubrzanja i kočenja prisutni tijekom vožnje su obično u rasponu od jedne petine do jedne trećine maksimalne vrijednosti. U kritičnim i neočekivanim situacijama, ubrzanja i kočenja se povećavaju do maksimalne vrijednosti. Maksimalne vrijednosti ubrzanja i kočenja ovise o hrapavosti tla, tipa tla, kvalitete guma, kvalitete kočnice vozila, itd. Zbog kritičnih i neočekivanih situacija, postoje mnoge nesreće na cestama. U tim slučajevima, ubrzanja ili kočenja dostižu granične vrijednosti i mnogo puta vozilo postaje nekontrolirano. U ovom radu prikazan je sustav za mjerenje i analizu ubrzanja i kočenja u prometu vozila. Ti sustavi su neophodni za analize različitih nesreća u prometu i definiranju maksimalnih ubrzanja, maksimalnih bočnih ubrzanja te maksimalne vrijednosti kočenja u različitim situacijama. U ovom članku su također prikazana praktična mjerenja i analize maksimalnog ubrzanja i kočenja za odabrane automobile, koje su izmjerene na ravnoj cesti, te usporedbe tih mjerenja s podatcima proizvođača i ubrzanja i kočenja izmjerenih na pisti.Accelerations and braking are needed in traffic to allow a vehicle to travel from one place to another. Also present during the drive are lateral accelerations, which are active in curves. The accelerations and braking active during the drive are usually in the range of one fifth to one third of maximum value. In critical and unexpected situations, the accelerations and braking are increased up to maximum values. Maximum values of acceleration and braking depend on roughness of ground, type of ground, quality of tires, quality of vehicle brakes, etc. Because of critical and unexpected situations, there are many accidents on the roads. In these cases, accelerations or braking reach their limit values and many times the vehicle becomes uncontrollable. In this paper the system for measurement and analyses of accelerations and braking in traffic of vehicles is presented. These systems are necessary for analyses of different accidents in traffic and to define maximal longitudinal accelerations, maximal lateral accelerations and maximal braking in different situations. Also presented in this article are practical measurements and analyses of maximal accelerations and braking for selected cars, which were measured on a straight road, and comparisons of these measurements with the producer data and accelerations and braking measured on a racetrack

Kinematic constraints and offline programming in robotic machining applications

Robotski obradni programi postaju sve učestaliji u svijetu industrijskih robota. Međutim, njihova kinematička složenost još uvijek nudi mnogo izazova. Ovaj rad daje pregled kinematičkih ograničenja, koja su važna za izvanmrežno programiranje industrijskih robota za uporabu kod obradnih programa. Prikazana su tri moguća rješenja za prevladavanje kinematičkih ograničenja (end-effector rotacija, djelomična translacija i djelomična rotacija). Razvijen je računalni algoritam za izbjegavanje takvih ograničenja, programiran i testirani analizom slučaja. Rezultati pokazuju da kinematička ograničenja mogu biti automatski izbjegnuta primjenom razvijenog algoritma izbjegavanja kod izvanmrežnog programiranja softvera za robotsku obradu odvajanjem čestica.Robotic machining applications are becoming more and more frequent in the world of industrial robots. However, their kinematic complexity still offers many challenges. This work presents an overview of kinematic constraints, which are important for the offline programming of industrial robots for the use in machining applications. The three possible solutions for overcoming kinematic constraints (end-effector rotation, part translation, and part rotation) are presented. The computer algorithm for avoiding such constraints was developed, programmed and tested with a case study. Results show that kinematic constraints can be automatically avoided by implementation of developed avoidance algorithm into the offline programming software for robotic machining

Kinematic constraints and offline programming in robotic machining applications

Robotski obradni programi postaju sve učestaliji u svijetu industrijskih robota. Međutim, njihova kinematička složenost još uvijek nudi mnogo izazova. Ovaj rad daje pregled kinematičkih ograničenja, koja su važna za izvanmrežno programiranje industrijskih robota za uporabu kod obradnih programa. Prikazana su tri moguća rješenja za prevladavanje kinematičkih ograničenja (end-effector rotacija, djelomična translacija i djelomična rotacija). Razvijen je računalni algoritam za izbjegavanje takvih ograničenja, programiran i testirani analizom slučaja. Rezultati pokazuju da kinematička ograničenja mogu biti automatski izbjegnuta primjenom razvijenog algoritma izbjegavanja kod izvanmrežnog programiranja softvera za robotsku obradu odvajanjem čestica.Robotic machining applications are becoming more and more frequent in the world of industrial robots. However, their kinematic complexity still offers many challenges. This work presents an overview of kinematic constraints, which are important for the offline programming of industrial robots for the use in machining applications. The three possible solutions for overcoming kinematic constraints (end-effector rotation, part translation, and part rotation) are presented. The computer algorithm for avoiding such constraints was developed, programmed and tested with a case study. Results show that kinematic constraints can be automatically avoided by implementation of developed avoidance algorithm into the offline programming software for robotic machining

Framework proposition and technical guidelines for manufacturers of custom made tools, machinery and special equipment

U radu se daje pregled najnovijih dostignuća u modernim oblicima organizacije, suradnje i fleksibilnosti, trendovima i predviđanjima u automobilskoj industriji kao reprezentativnom kupcu alata, strojeva i specijalne opreme, kao i upravljanje vijekom trajanja, održivosti i mogućnosti stvaranja nove vrijednosti u tim industrijskim sektorima. Na temelju toga predlaže se okvirno načelo nazvano "pametni alat, stroj i specijalna oprema". Daje se dio istraživanja provedenog na slovenskim proizvođačima kod kojih su prepoznati tehnološki indikatori važni za implementaciju predloženog načela, te su rangirani u skladu s njihovom važnosti. Daju se i dodatne primjedbe koje su stavili proizvođači, te kritička analiza i rasprava rezultata.This paper overviews the state-of-the-art in modern forms of organization, collaboration and flexibility, trends and forecasts of the automotive industry as a representative buyer of tools, machines and special equipment, as well as life cycle management, sustainability and possibility for added value creation in these industry sectors. Based on this, a framework called "smart tool, machine, and special equipment" is proposed. A part of the research done on Slovene manufacturers is presented, where the technological indicators important in the implementation of the proposed framework are identified and ranked regarding to their importance. Additional suggestions by the manufacturers are also provided, as well as critical analysis and discussion of the findings

Uloga kriogenika u postupcima strojne obrade

The purpose of this work is to present some guidelines in the sustainable machining processes, using cryogenic conditions and gaining higher performances, lower environmental and health influences, increased safety, etc. The study presents the details about cryogenic fluids and their use in machining processes as an alternative to oil-based emulsions. The details of liquid nitrogen and the ways of their application in the machining processes, known as cryogenic machining process, are given. The research is upgraded with experimental case study on high temperature alloy machining – tungsten, and so presenting an important scientific and sustainability contribution in production processes. Experimental and analytical results are proving that the cryogenic machining technology has a high potential to cut costs and improve competitiveness, by reducing resource consumption and creating less waste and have less of an environmental and social impact, fulfilling the sustainability pillars: economical, social and environmental one, over conventional machining processes.Cilj je ovog rada dati prikaz smjernica u ostvarenju održive proizvodnje stvaranjem kriogenih uvjeta radi postizanja viših perfomansi u obradi, manjeg utjecaja na okolinu i ljude, povećanja sigurnosti itd. Istraživanjem se prikazuju pojedinosti o kriogenim fluidima i njihovoj upotrebi u postupcima strojne obrade kao alternativno sredstvo emulzijama na bazi ulja. U radu su dane pojedinosti o tekućem dušiku i načinima njegove primjene u strojnoj obradi, poznatim kao kriogeni procesi strojne obrade. Istraživanje je provedeno eksperimentalno pri obradi legura za rad na visokim temeperama na bazi volframa i na taj način dan značajan znanstveni doprinos u postupcima održive proizvodnje. Eksperimentalni i analitički rezultati potvrđuju da kriogena tehnologija strojne obrade ima dobar potencijal za smanjenje troškova i poboljšanje konkurentnosti, smanjenje potrošnje sirovina, smanjenje otpada, manji utjecaj na okolinu i ljude, ispunjavajući uvjete održivosti: ekonomske, socijalne i okoliš u odnosu na konvencionalne postupke strojne obrade