APPLICATION OF GROUP TECHNOLOGY FOR PRODUCTION TIME ESTIMATION

The development of industry, transport, communications and technology results in tougher competition, i.e. the process of globalization takes place. Small and medium enterprises (SMEs), which are greatly affected by this process, are expected to accept or to refuse the received offer in a very short period of time. Consequently, it is impossible for a small enterprise to create a technological process in order to calculate production times. The idea of the authors of this paper is to develop a system of part classification by means of group technologies. The classifier is used to classify parts into similar groups. So, if we have a new part, we can find a similar part and adopt its technological process to the new part. In the next step, an application to enable the production time estimation, and consequently the production cost estimation for each family of parts will be developed

Odabir procesa, redosljed operacija i složenost oblika - kriterij unapređenja procesa

The problem of the workpiece shape recognition, and technological process selection and optimization always includes the possibility of shape complexity assessment, and selection of primary process and sequence of operations. The process plans for mechanical products include selection of manufacturing processes: a primary process, and subsequent processes. In the first part, the objective of our research was to investigate the relation between requirements of the design, production quantity and material on one hand and capability of particular process on the other hand in order to be able to consider only the processes that make sense. Also, production costs, quality, lead-times and ecological aspects had to be considered. Our intention was to research and to give some guidance in classifying these requirements, to find a way how to deal with overlapping capabilities of the processes and to explore methods of dealing with numerous data that would facilitate decisions regarding “best” process selection. In the second part, our research explains the procedure for calculating shape complexity. The possibility to express it as an exact value is useful because it enables distinction on the quantitative level. This is needed for research of shape influence on process planning. In the third part, the focus of our research is creation of learning materials for defining the main criteria for selection of primary processes and types of operations in production. The selection of a primary process is based on material nature, quantity, shape complexity, part size and some other factors. Type and sequence of operations are the result of the influence of different factors such as product shape, surface roughness and tolerance. The application enables users to fully understand the procedure of primary process and operation sequence selection through step by step tutorials. The base programming language of E-Lapp application is Visual Basic.Net, the tools used to create e-learning materials are Microsoft PowerPoint 2007 and iSpring Presenter (Adobe Flash).Problem prepoznavanja oblika izratka, odabir tehnološkog procesa te optimizacija uvijek uključuju mogućnost procjene složenosti oblika, odabir primarnog procesa te redoslijeda operacija. Plan procesa za proizvode u strojogradnji uključuje odabir strojarskih procesa: primarnog procesa i redoslijeda operacija. U prvom dijelu, cilj istraživanja bio je istraživanje relacije između zahtjeva designa, proizvodne količine i materijala s jedne strane te prikladnosti određenog procesa s druge strane kako bi bili u stanju razmatrati samo odgovarajuće procese. Također, bili su razmatrani i proizvodni troškovi, kvaliteta, vodeća vremena te ekološki aspekti. Namjera je bila istražiti i dati naputak u klasifikaciji tih zahtjeva, pronaći način kako se baviti sa preklapanjem mogućnosti procesa te se baviti metodama prikladnim za obradu numeričkih podataka koji će olakšati donošenje odluka koje pomažu kod odabira “najboljeg’’ procesa. U drugom dijelu istraživanje objašnjava proceduru za proračun složenosti oblika izratka. Mogućnost njegova izdvajanja kao egzaktne veličine korisno je jer omogućuje razlikovanje na kvanitativnoj razini. Potrebno je to u istraživanju utjecaja oblika u procesu planiranja. U trećem dijelu , fokus našeg istraživanja je kreiranje materijala za učenje kako bi se kreirao glavni kriterij u odabiru primarnih procesa i vrste operacija u proizvodnji. Odabir primarnog procesa temeljeno je na materijalu, količini, složenosti oblika, veličini dijela te neih drugih faktora. Tip i redoslijed operacija su rezultat utjecaja različitih faktora kao što su oblik izratka, površinska hrapavost i tolerancija. Aplikacija omogućuje korisnicima potpuno razumijevanje procedure odabira primarnog procesa i redoslijeda operacija korak po korak u priručniku. Osnovni programski jezik e-Lapp aplikacije je Visual Basic.Net, a alati korišteni za kreiranje e-learning materijala su Microsoft Power Point 2007 te iSpring Presenter (Adobe Flash)

Selection of an Optimal Supplier

The paper describes the selection of an optimal supplier from China based on three obtained bids to produce 120,000 forged pieces, which is the primary process for shaft production. The choice was made using the AHP method based on the Expert Choice software program and Multiple-Criteria Decision-Making (MCDM). The key information when choosing the optimal supplier of large number of forgings is to define the objective of the task, decision tree with weighted criteria and sub-criteria, consistency checking and possible reconsideration using brain storming when defining the strength of criteria/sub-criteria. To some extent, this may reduce initial subjectivity in the decision-making process in the Decision Support System