Determining the Minimum Waiting Times in a Hybrid Flow Shop Using Simulation-Optimization Approach

Planning the order and size of batches is an extremely complex task especially if these tasks are related to production companies in a real environment. This research deals with the problem of determining the entry order and size of product batches in order to optimize inter-operational waits, in the form of waiting in queues for processing and waiting due to the setting-up of the workplace. In real environment, these waits represent a large share of the time spent in the production of a unit of product in a hybrid flow shop. This problem is almost impossible to be solved with analytical models because they may require many simplifying assumptions. Therefore, a simulation-optimization approach is used to solve this problem. Discrete event simulation allows greater flexibility in the representation of the real production system, while the integrated optimization tool, a genetic algorithm, serves to find the optimal solution relatively quickly. To ensure simpler production management, batch size is defined as a fixed value with the exception of a different first or last batch which represents the difference to the required production volume. Therefore, two optimization cases are presented in the paper. Although both cases show improvements, the case when a different batch is the first batch shows better results. In that case, the share of setup time in the total production time of the product unit was reduced from 4% to 3%, and the share of waiting time in the queue for processing was reduced from 76% to 32%

A simulation framework for determining the optimal time utilization of a hybrid flow shop : doctoral dissertation

Planiranjem proizvodnje osigurava se postojanje i konkurentnost proizvodnih poduzeća na tržištu. Osobito su važni poslovi operativne pripreme temeljem kojih se definira vremenski plan odvijanja proizvodnje i osiguravaju svi potrebni resursi. Kod proizvodnje tehnološki složenih obitelji proizvoda u modelu višepredmetnoga linijskoga proizvodnog sustava ograničene fleksibilnosti s proizvodnim procesom koji se odvija u više segmenata uobičajena je visoka iskorištenost proizvodnog sustava što sužava mogućnost pronalaska ekonomičnog rješenja. Iz toga proizlazi potreba za razvojem simulacijskog okvira za određivanje veličine jedinične serije i redoslijeda ulaza jedinične serije u proizvodni proces, dva glavna područja poboljšanja mjera uspješnosti. Razlog razmatranja ovih dviju veličina leži u tome što različite vrijednosti veličine jedinične serije i redoslijeda ulaza proizvoda direktno utječu na vrijeme potrebno za odvijanje proizvodnog procesa. Rješavanje problema određivanja veličine jedinične serije i redoslijeda ulaza jedinične serije među najtežim je zadacima planiranja proizvodnje. Pogotovo ako se posebna pozornost posveti utjecaju pripremno-završnog vremena ovisnog o slijedu, kao i raspoloživosti proizvodnih kapaciteta te dostupnosti transportne opreme na konačan rezultat. Implementiranjem izrađenog matematičkog modela u razvijeni simulacijski okvir stvorena je podloga za razvoj znanstveno zasnovane metode. Takav simulacijski okvir omogućava eksperimentiranje s računalnim matematičkim modelom fizikalnog sustava. Proizvodni proces prikazan je kao diskretna simulacija događaja podržana genetskim algoritmom. Primjenom i razvijanjem procedura unutar genetskog algoritma omogućeno je određivanje optimalnoga vremenskog iskorištenja višepredmetnoga linijskoga proizvodnog sustava. Razvijeni računalom potpomognuti simulacijski okvir provjeren je na konkretnom primjeru iz realnog sektora te na jednostavan i vizualno jasan način služi kao potpora pri planiranju proizvodnje. Simulacijski okvir primjenjiv je u raznim proizvodnim okruženjima, pogotovo onim koji se bave proizvodnjom širokog asortimana tehnološki složenih proizvoda.Production planning ensures the existence and competitiveness in the market, with particularly important tasks of operational preparation on the basis of which the production schedule is defined and all the necessary resources are provided. In the production of technologically complex product families in a hybrid flowshop system with limited flexibility and multi-stages production process, the high utilization of the production system is common, which limits the possibility of finding an economical solution. This implies the need to develop a simulation framework for determining the size and entry-sequence of batches into the production process, a two main areas for improving performance measures. The reason for considering these two values lies in the fact that different values of batch size and entry-sequence of batches directly affect the duration of the production process. Solving the problem of determining batch size and schedule is among the most difficult tasks of production planning. Especially if special attention is paid to the influence of sequence-dependent setup times, the availability of production capacities and the availability of transport equipment on the final result. Implementing the created mathematical model in the developed simulation framework, a basis for the development of a scientifically based method was created. Such a simulation framework allows experimentation with a computer mathematical model of a physical system. The production process is presented as a discrete event simulation supported by a genetic algorithm. Applying and developing procedures within the genetic algorithm will allow determining optimal time utilization of a hybrid flow shop. The developed computer-assisted simulation framework has been tested on a concrete example from the real sector and serves as a support in production planning in a simple and visually clear way. The simulation framework is applicable in various production environments, especially those engaged in the production of a wide range of technologically complex products

A simulation framework for determining the optimal time utilization of a hybrid flow shop : doctoral dissertation

Planiranjem proizvodnje osigurava se postojanje i konkurentnost proizvodnih poduzeća na tržištu. Osobito su važni poslovi operativne pripreme temeljem kojih se definira vremenski plan odvijanja proizvodnje i osiguravaju svi potrebni resursi. Kod proizvodnje tehnološki složenih obitelji proizvoda u modelu višepredmetnoga linijskoga proizvodnog sustava ograničene fleksibilnosti s proizvodnim procesom koji se odvija u više segmenata uobičajena je visoka iskorištenost proizvodnog sustava što sužava mogućnost pronalaska ekonomičnog rješenja. Iz toga proizlazi potreba za razvojem simulacijskog okvira za određivanje veličine jedinične serije i redoslijeda ulaza jedinične serije u proizvodni proces, dva glavna područja poboljšanja mjera uspješnosti. Razlog razmatranja ovih dviju veličina leži u tome što različite vrijednosti veličine jedinične serije i redoslijeda ulaza proizvoda direktno utječu na vrijeme potrebno za odvijanje proizvodnog procesa. Rješavanje problema određivanja veličine jedinične serije i redoslijeda ulaza jedinične serije među najtežim je zadacima planiranja proizvodnje. Pogotovo ako se posebna pozornost posveti utjecaju pripremno-završnog vremena ovisnog o slijedu, kao i raspoloživosti proizvodnih kapaciteta te dostupnosti transportne opreme na konačan rezultat. Implementiranjem izrađenog matematičkog modela u razvijeni simulacijski okvir stvorena je podloga za razvoj znanstveno zasnovane metode. Takav simulacijski okvir omogućava eksperimentiranje s računalnim matematičkim modelom fizikalnog sustava. Proizvodni proces prikazan je kao diskretna simulacija događaja podržana genetskim algoritmom. Primjenom i razvijanjem procedura unutar genetskog algoritma omogućeno je određivanje optimalnoga vremenskog iskorištenja višepredmetnoga linijskoga proizvodnog sustava. Razvijeni računalom potpomognuti simulacijski okvir provjeren je na konkretnom primjeru iz realnog sektora te na jednostavan i vizualno jasan način služi kao potpora pri planiranju proizvodnje. Simulacijski okvir primjenjiv je u raznim proizvodnim okruženjima, pogotovo onim koji se bave proizvodnjom širokog asortimana tehnološki složenih proizvoda.Production planning ensures the existence and competitiveness in the market, with particularly important tasks of operational preparation on the basis of which the production schedule is defined and all the necessary resources are provided. In the production of technologically complex product families in a hybrid flowshop system with limited flexibility and multi-stages production process, the high utilization of the production system is common, which limits the possibility of finding an economical solution. This implies the need to develop a simulation framework for determining the size and entry-sequence of batches into the production process, a two main areas for improving performance measures. The reason for considering these two values lies in the fact that different values of batch size and entry-sequence of batches directly affect the duration of the production process. Solving the problem of determining batch size and schedule is among the most difficult tasks of production planning. Especially if special attention is paid to the influence of sequence-dependent setup times, the availability of production capacities and the availability of transport equipment on the final result. Implementing the created mathematical model in the developed simulation framework, a basis for the development of a scientifically based method was created. Such a simulation framework allows experimentation with a computer mathematical model of a physical system. The production process is presented as a discrete event simulation supported by a genetic algorithm. Applying and developing procedures within the genetic algorithm will allow determining optimal time utilization of a hybrid flow shop. The developed computer-assisted simulation framework has been tested on a concrete example from the real sector and serves as a support in production planning in a simple and visually clear way. The simulation framework is applicable in various production environments, especially those engaged in the production of a wide range of technologically complex products

IDEJNI PROJEKT PROIZVODNOG SUSTAVA STROJNE OBRADE

Ovim diplomskim radom je izrađen idejni projekt proizvodnog sustava strojne obrade za sljedeće izratke u zadanim količinama: osovina (30 000 komada), pogonski zupčanik (20 000 komada), osovina sa zupčanikom (20 000 komada). Analizom proizvodnih, tehnoloških i konstrukcijskih karakteristika izrađen je plan obrade za svaki proizvod. S obzirom na karakteristike izradaka i zadane količine te mogućnosti promjena u budućnosti koristit će se fleksibilna proizvodna oprema. Procesnom metodom je izvršeno grupiranje izradaka, te je određen tropredmetni proizvodni sustav za grupu izradaka ABC. Izborom transportnog sustava, redoslijedom obrade i grafičkim prikazom ciklusa izrade određuje se prostorni raspored te hodogrami obrade svakog izratka. Odabran je dvoredni prostorni raspored proizvodne opreme s dvosmjerno-prolaznim hodom. Na taj način je omogućen tok izratka bez međutransporta. Izradom ovog idejnog projekta uviđena je sva problematika projektiranja proizvodnog sustava te mogućnost rješavanja problema na više načina sa ciljem postizanja optimalnog proizvodnog sustava.With these diploma thesis was created conceptual project of manufacturing system for machining workpieces in the following set amounts: shaft (30 000 pieces), driving gear (20 000 pieces), integral pinion shaft (20 000 pieces). The analysis of manufactural, technological and constructional characteristic made treatement plan for each workpiece. Taking into account the characteristic of the workpieces and the default amount and possibility of changes in the future, will use flexible manufacturing equipment. Using process method were grouped parts workpieces and is determined three-subject manufacturing system for a group of a workpieces ABC. By selecting the transport system, order processing and graphic display cycle, development is determined by the spatial arrangement and workflow manufacturing of each workpiece. It is selected the double row spatial arrangement of manufacturing equipment with two-way-passing stroke. This enables workpiece flow without transport between two operations. This preliminary project shows all the problems of designing the manufacturing system and the ability to solve problems in different ways in order to achieve an optimal manufacturing system

IDEJNI PROJEKT PROIZVODNOG SUSTAVA STROJNE OBRADE

Ovim diplomskim radom je izrađen idejni projekt proizvodnog sustava strojne obrade za sljedeće izratke u zadanim količinama: osovina (30 000 komada), pogonski zupčanik (20 000 komada), osovina sa zupčanikom (20 000 komada). Analizom proizvodnih, tehnoloških i konstrukcijskih karakteristika izrađen je plan obrade za svaki proizvod. S obzirom na karakteristike izradaka i zadane količine te mogućnosti promjena u budućnosti koristit će se fleksibilna proizvodna oprema. Procesnom metodom je izvršeno grupiranje izradaka, te je određen tropredmetni proizvodni sustav za grupu izradaka ABC. Izborom transportnog sustava, redoslijedom obrade i grafičkim prikazom ciklusa izrade određuje se prostorni raspored te hodogrami obrade svakog izratka. Odabran je dvoredni prostorni raspored proizvodne opreme s dvosmjerno-prolaznim hodom. Na taj način je omogućen tok izratka bez međutransporta. Izradom ovog idejnog projekta uviđena je sva problematika projektiranja proizvodnog sustava te mogućnost rješavanja problema na više načina sa ciljem postizanja optimalnog proizvodnog sustava.With these diploma thesis was created conceptual project of manufacturing system for machining workpieces in the following set amounts: shaft (30 000 pieces), driving gear (20 000 pieces), integral pinion shaft (20 000 pieces). The analysis of manufactural, technological and constructional characteristic made treatement plan for each workpiece. Taking into account the characteristic of the workpieces and the default amount and possibility of changes in the future, will use flexible manufacturing equipment. Using process method were grouped parts workpieces and is determined three-subject manufacturing system for a group of a workpieces ABC. By selecting the transport system, order processing and graphic display cycle, development is determined by the spatial arrangement and workflow manufacturing of each workpiece. It is selected the double row spatial arrangement of manufacturing equipment with two-way-passing stroke. This enables workpiece flow without transport between two operations. This preliminary project shows all the problems of designing the manufacturing system and the ability to solve problems in different ways in order to achieve an optimal manufacturing system

IDEJNI PROJEKT PROIZVODNOG SUSTAVA STROJNE OBRADE

Ovim diplomskim radom je izrađen idejni projekt proizvodnog sustava strojne obrade za sljedeće izratke u zadanim količinama: osovina (30 000 komada), pogonski zupčanik (20 000 komada), osovina sa zupčanikom (20 000 komada). Analizom proizvodnih, tehnoloških i konstrukcijskih karakteristika izrađen je plan obrade za svaki proizvod. S obzirom na karakteristike izradaka i zadane količine te mogućnosti promjena u budućnosti koristit će se fleksibilna proizvodna oprema. Procesnom metodom je izvršeno grupiranje izradaka, te je određen tropredmetni proizvodni sustav za grupu izradaka ABC. Izborom transportnog sustava, redoslijedom obrade i grafičkim prikazom ciklusa izrade određuje se prostorni raspored te hodogrami obrade svakog izratka. Odabran je dvoredni prostorni raspored proizvodne opreme s dvosmjerno-prolaznim hodom. Na taj način je omogućen tok izratka bez međutransporta. Izradom ovog idejnog projekta uviđena je sva problematika projektiranja proizvodnog sustava te mogućnost rješavanja problema na više načina sa ciljem postizanja optimalnog proizvodnog sustava.With these diploma thesis was created conceptual project of manufacturing system for machining workpieces in the following set amounts: shaft (30 000 pieces), driving gear (20 000 pieces), integral pinion shaft (20 000 pieces). The analysis of manufactural, technological and constructional characteristic made treatement plan for each workpiece. Taking into account the characteristic of the workpieces and the default amount and possibility of changes in the future, will use flexible manufacturing equipment. Using process method were grouped parts workpieces and is determined three-subject manufacturing system for a group of a workpieces ABC. By selecting the transport system, order processing and graphic display cycle, development is determined by the spatial arrangement and workflow manufacturing of each workpiece. It is selected the double row spatial arrangement of manufacturing equipment with two-way-passing stroke. This enables workpiece flow without transport between two operations. This preliminary project shows all the problems of designing the manufacturing system and the ability to solve problems in different ways in order to achieve an optimal manufacturing system

A simulation framework for determining the optimal time utilization of a hybrid flow shop : doctoral dissertation

Planiranjem proizvodnje osigurava se postojanje i konkurentnost proizvodnih poduzeća na tržištu. Osobito su važni poslovi operativne pripreme temeljem kojih se definira vremenski plan odvijanja proizvodnje i osiguravaju svi potrebni resursi. Kod proizvodnje tehnološki složenih obitelji proizvoda u modelu višepredmetnoga linijskoga proizvodnog sustava ograničene fleksibilnosti s proizvodnim procesom koji se odvija u više segmenata uobičajena je visoka iskorištenost proizvodnog sustava što sužava mogućnost pronalaska ekonomičnog rješenja. Iz toga proizlazi potreba za razvojem simulacijskog okvira za određivanje veličine jedinične serije i redoslijeda ulaza jedinične serije u proizvodni proces, dva glavna područja poboljšanja mjera uspješnosti. Razlog razmatranja ovih dviju veličina leži u tome što različite vrijednosti veličine jedinične serije i redoslijeda ulaza proizvoda direktno utječu na vrijeme potrebno za odvijanje proizvodnog procesa. Rješavanje problema određivanja veličine jedinične serije i redoslijeda ulaza jedinične serije među najtežim je zadacima planiranja proizvodnje. Pogotovo ako se posebna pozornost posveti utjecaju pripremno-završnog vremena ovisnog o slijedu, kao i raspoloživosti proizvodnih kapaciteta te dostupnosti transportne opreme na konačan rezultat. Implementiranjem izrađenog matematičkog modela u razvijeni simulacijski okvir stvorena je podloga za razvoj znanstveno zasnovane metode. Takav simulacijski okvir omogućava eksperimentiranje s računalnim matematičkim modelom fizikalnog sustava. Proizvodni proces prikazan je kao diskretna simulacija događaja podržana genetskim algoritmom. Primjenom i razvijanjem procedura unutar genetskog algoritma omogućeno je određivanje optimalnoga vremenskog iskorištenja višepredmetnoga linijskoga proizvodnog sustava. Razvijeni računalom potpomognuti simulacijski okvir provjeren je na konkretnom primjeru iz realnog sektora te na jednostavan i vizualno jasan način služi kao potpora pri planiranju proizvodnje. Simulacijski okvir primjenjiv je u raznim proizvodnim okruženjima, pogotovo onim koji se bave proizvodnjom širokog asortimana tehnološki složenih proizvoda.Production planning ensures the existence and competitiveness in the market, with particularly important tasks of operational preparation on the basis of which the production schedule is defined and all the necessary resources are provided. In the production of technologically complex product families in a hybrid flowshop system with limited flexibility and multi-stages production process, the high utilization of the production system is common, which limits the possibility of finding an economical solution. This implies the need to develop a simulation framework for determining the size and entry-sequence of batches into the production process, a two main areas for improving performance measures. The reason for considering these two values lies in the fact that different values of batch size and entry-sequence of batches directly affect the duration of the production process. Solving the problem of determining batch size and schedule is among the most difficult tasks of production planning. Especially if special attention is paid to the influence of sequence-dependent setup times, the availability of production capacities and the availability of transport equipment on the final result. Implementing the created mathematical model in the developed simulation framework, a basis for the development of a scientifically based method was created. Such a simulation framework allows experimentation with a computer mathematical model of a physical system. The production process is presented as a discrete event simulation supported by a genetic algorithm. Applying and developing procedures within the genetic algorithm will allow determining optimal time utilization of a hybrid flow shop. The developed computer-assisted simulation framework has been tested on a concrete example from the real sector and serves as a support in production planning in a simple and visually clear way. The simulation framework is applicable in various production environments, especially those engaged in the production of a wide range of technologically complex products

IDEJNI PROJEKT PROIZVODNOG SUSTAVA STROJNE OBRADE

Ovim diplomskim radom je izrađen idejni projekt proizvodnog sustava strojne obrade za sljedeće izratke u zadanim količinama: osovina (30 000 komada), pogonski zupčanik (20 000 komada), osovina sa zupčanikom (20 000 komada). Analizom proizvodnih, tehnoloških i konstrukcijskih karakteristika izrađen je plan obrade za svaki proizvod. S obzirom na karakteristike izradaka i zadane količine te mogućnosti promjena u budućnosti koristit će se fleksibilna proizvodna oprema. Procesnom metodom je izvršeno grupiranje izradaka, te je određen tropredmetni proizvodni sustav za grupu izradaka ABC. Izborom transportnog sustava, redoslijedom obrade i grafičkim prikazom ciklusa izrade određuje se prostorni raspored te hodogrami obrade svakog izratka. Odabran je dvoredni prostorni raspored proizvodne opreme s dvosmjerno-prolaznim hodom. Na taj način je omogućen tok izratka bez međutransporta. Izradom ovog idejnog projekta uviđena je sva problematika projektiranja proizvodnog sustava te mogućnost rješavanja problema na više načina sa ciljem postizanja optimalnog proizvodnog sustava.With these diploma thesis was created conceptual project of manufacturing system for machining workpieces in the following set amounts: shaft (30 000 pieces), driving gear (20 000 pieces), integral pinion shaft (20 000 pieces). The analysis of manufactural, technological and constructional characteristic made treatement plan for each workpiece. Taking into account the characteristic of the workpieces and the default amount and possibility of changes in the future, will use flexible manufacturing equipment. Using process method were grouped parts workpieces and is determined three-subject manufacturing system for a group of a workpieces ABC. By selecting the transport system, order processing and graphic display cycle, development is determined by the spatial arrangement and workflow manufacturing of each workpiece. It is selected the double row spatial arrangement of manufacturing equipment with two-way-passing stroke. This enables workpiece flow without transport between two operations. This preliminary project shows all the problems of designing the manufacturing system and the ability to solve problems in different ways in order to achieve an optimal manufacturing system

A Combined Discrete Event Simulation and Factorial Design Experiment for the Scheduling Problem in a Hybrid Flow Shop

Production plants have always been confronted with the problem of scheduling, as this has a direct impact on production time and therefore on production costs. This is especially true in today's world, where it is necessary to produce a quality product at a low price and in a short time, while at the same time responding flexibly to customer demands. Due to the complexity and for economic reasons, testing different variants in a real production environment is insufficient and ineffective. For this reason, this paper proposes a new method that combines discrete event simulation and factorial design experiment to find the optimal schedule in hybrid flow shop. It was tested with the goal of achieving the minimum makespan. The results show that this method makes it possible to find improved solution very quickly. Compared to the original production schedule, the makespan could be reduced by 3 hours and 31 minutes which is reduction of 16.3%. The proposed methodology can be used in many discrete and process production plants

Application of Modified Steady-State Genetic Algorithm for Batch Sizing and Scheduling Problem with Limited Buffers

Batch sizing and scheduling problems are usually tough to solve because they seek solutions in a vast combinatorial space of possible solutions. This research aimed to test and further develop a scheduling method based on a modified steady-state genetic algorithm and test its performance, in both the speed (low computational time) and quality of the final results as low makespan values. This paper explores the problem of determining the order and size of the product batches in a hybrid flow shop with a limited buffer according to the problem that is faced in real-life. Another goal of this research was to develop a new reliable software/computer program tool in c# that can also be used in production, and as result, obtain a flexible software solution for further research. In all of the optimizations, the initial population of the genetic algorithm was randomly generated. The quality of the obtained results, and the short computation time, together with the flexibility of the genetic paradigm prove the effectiveness of the proposed algorithm and method to solve this problem