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

Open innovation and business performance improvement in strategic business alliances

The purpose of the research was to investigate whether the companies involved in strategic business alliances (henceforth referred to as the SBA) have a higher level of open innovation and better business results in the metal industry in the EU country, namely Slovenia. The survey was carried out in 115 companies, where the aforementioned relations and their influence were studied applying appropriate statistical methods (e.g. the Mann-Whitney test, Chi-Square statistics, t-test, etc.). The sample encompassed four clusters and R&D centres from metal-processing industry. The results showed that SBA have a significantly strong impact on companies’ open innovation as well as more efficient cooperation with universities and research institutions. Among the companies involved in SBA, the portion of innovations generated in cooperation with their business partners accounted for 57.7%, while those, not involved in SBA, the same indicator amounts to 19%. In addition, the results showed that the majority of business results, in companies involved in SBA, were above average, compared to the industry sector average values. The value added per employee within companies involved in the SBA was significantly higher than the industry average, as well as the profits; difference was more than threefold. It may be concluded that SBA represent an important bridge in the transformation from a closed innovation model to a model of open innovation, resulting in better business performance. Important implication for companies is related to the message that cooperation with competitors may bring value added to all companies involved

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

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

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

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

Influence of milling process on machined surface of porous polyurethane (PU) foam

U ovo doba poliuretanske pjene za modeliranje uspješno zamjenjuju izvorne materijale u mnogim aplikacijama zbog određenih komparativnih prednosti, tako i kod kopiranja artefakta. Glodanje je temeljna strojna operacija koja se često koristi u obradi proizvoda od PU pjene. Ova eksperimentalna studija usredotočuje se na površinsku hrapavost glodane PU pjene. Ocijenjeni su utjecaji parametara obrade na hrapavost površine u procesu glodanja PU pjene. Linearne i površinske procjene hrapavosti nakon CNC glodanja su uspoređene i procijenjene za uporabu u budućim istraživanjima. Isto tako vrijednosti hrapavosti površina povećavaju se s brzinom punjenja po zubu i smanjuju se s povećanjem brzine vretena. Testovi glodanja pokazali su značajan utjecaj gustoće PU pjena za modeliranje na konačnu hrapavost površine. Dodatno su ocijenjene vrijednosti hrapavosti površina.Nowadays polyurethane modelling foams are successfully replacing original materials in many applications due to certain comparative advantages also in copying artefacts. Milling is a fundamental machining operation frequently used in transforming products of PU foam. This experimental study focuses on surface roughness of milled PU foam. The influences of machining parameters on surface roughness in PU foam milling were assessed. Linear and area surface roughness evaluations after CNC milling are compared and estimated for the use in future research. Additionally the surface roughness values increase with a feed rate per tooth and decrease with an increase of spindle speed. The milling tests showed significant influence of modelling board density on the final surface roughness. Additional area surface roughness values have been evaluated

Spark plasma sintering as an effective texturing tool for reprocessing recycled HDDR Nd-Fe-B magnets with lossless coercivity

The low-pressure hot-deformation methodology was applied to reprocess the nanocrystalline hydrogenation–disproportionation–desorption–recombination (HDDR) Nd-Fe-B powders from end-of-life (EOL) permanent magnets’ waste to determine the mechanism of texture development and the resultant improvement in remanence (and BH$_{max}$) in the recycled material. Both the hot-pressed and hot-deformed magnets produced via spark plasma sintering (SPS) were compared in terms of their magnetic properties with respect to forging pressures. Also, a comparison was established with the microstructure to cite the effectiveness of texture development at low deformation rates and pressures which is pivotal for retaining high coercivity. The hot-pressed magnets maintain the high coercivity (better than 100%) of the original recycled powder due to the control of SPS conditions. The hot deformation pressure was varied from 100–150 MPa at 750 °C processing temperature to identify the optimal texture development in the sintered HDDR Nd-Fe-B magnets. The effect of post-hot-deformation thermal treatment was also investigated, which helped in boosting the overall magnetic properties and better than the recycled feedstock. This low-pressure hot deformation process improved the remanence of the hot-pressed magnet by 11% over the starting recycled powder. The M$_r$/M$_S$ ratio which was 0.5 for the hot-pressed magnets increased to 0.64 for the magnets hot-deformed at 150 MPa. Also, a 55% reduction in height of the sample was achieved with the c-axis texture, indicating approximately 23% higher remanence over the isotropic hot-pressed magnets. After hot deformation, the intrinsic coercivity (H$_{Ci}$) of 960 kA/m and the remanence (B$_r$) value of 1.01 T at 150 MPa is indicative that the controlled SPS reprocessing technique can prevent microstructure related losses in the magnetic properties of the recycled materials. This route also suggests that the scrap Nd-Fe-B magnets can be treated with recoverable magnetic properties subsequently via HDDR technique and controlled hot deformation with a follow-up annealing

Influence of friction riveting parameters on the dissimilar joint formation and strength

Friction riveting represents a promising technology for joining similar and/or dissimilar materials of light-weight components. However, the main drawback of the technology is that it is primarily used only with special machines for friction welding that have a force control. In this study we used accessible CNC machines with a position control. A set of friction riveting experiments was performed to establish the relationship between the processing parameters, the rivet formation and its mechanical strength. During the manufacturing process, the axial force and torque were constantly measured. The fabricated joints were examined using an X-ray imaging technique, microstructural analyses, and mechanical tests. The samples were subjected to the pull-out test to analyse the joints’ strength and determine the failure mode type. In addition, a correlation between the friction riveting processing parameters, the rivet penetration depth, the rivet shape and the joint strength was established. The results depict that a higher axial force in the first production phase at the higher feeding rate increases the penetration depth, while in the second phase at lower feeding rate, an anchoring shape of a rivet forms

Ocena trajnosti naprednih tehnologij odrezavanja

Efficient cooling and lubrication techniques are required to obtain sustainable machining of difficult-to-cut materials, which are the pillars of aerospace, automotive, medical and nuclear industries. Cryogenic machining with the assistance of lubricated Liquid Carbon Dioxide (LCO2) is a novel approach for sustainable manufacturing without the use of harmful water-based metalworking fluids (MWFs). In case of unavoidable use of MWFs under high pressure, such as turning finishing processes of difficult-to-cut materials, the pulsating high pressure delivery of MWFs prolongs the tool life and enables the control over chip length to prevent surface damage of high value-added parts. In this paper, sustainability assessment of both advanced principles was carried out, considering overall costs and operational safety. Experimental tests were executed on difficult-to-cut materials in comparison to conventional flood lubrication. For both techniques, longer tool life compared to flood lubrication was observed additional cleaner production and higher part quality led to reduced long-term overall costs. These advanced machining technologies are also operation safe, proving to be a sustainable alternative to conventional machining