Browsing by Subject "Production planning"
Now showing 1 - 5 of 5
Results Per Page
Sort Options
Item Open Access Concurrent consideration of product design, process planning and production planning activities(1998) Adil, Gajendra KumarIn manufacturing engineering, product design, process planning and production planning activities are often considered independently. However, in order to effectively respond to changes in business situations, such as changes in demand forecast, product mix and technology, it is desirable to consider them concurrently. For this purpose, a large-scale linear programming model has been developed. The model considers minimization of the sum of processing cost, late shipment cost and inventory holding cost as the objective, and concurrently selects product designs, and generates process plans and production plans. The number of columns in the formulation can be large and, hence, an efficient column generation scheme is developed to solve the model. The model and solution procedure are illustrated with examples.Item Open Access The effect of economies-of-scale on the performance of lot-sizing heuristics in rolling horizon basis(Taylor & Francis, 2020-02-26) Kian, R.; Berk, Emre; Gürler, Ülkü; Rezazadeh, H.; Yazdani, B.In this article, we consider the production planning problem in the presence of (dis)economies-of-scale in production costs on a rolling horizon basis with a fixed forecast horizon. We propose variants of three well-known and commonly used heuristics (Wagner–Whitin, Silver–Meal and Least Unit Cost) adapted for this particular setting. In an extensive numerical study with demands exhibiting stationary, increasing and decreasing trends and seasonality, we demonstrate that having longer forecast horizon is less effective in obtaining more cost effective production plans when the production cost function is convex and also when fixed setup cost is lower, which both are proxy to lack of economies-of-scale.Item Open Access A hierarchical model for the cell loading problem of cellular manufacturing systems(Taylor & Francis, 1998) Aktürk, M. S.; Wilson, G. R.A hierarchical cell loading approach is proposed to solve the production planning problem in cellular manufacturing systems. Our aim is to minimize the variable cost of production subject to production and inventory balance constraints for families and items, and capacity feasibility constraints for group technology cells and resources over the planning horizon. The computational results indicated that the proposed algorithm was very efficient in finding an optimum solution for a set of randomly generated problems.Item Open Access Production decisions with convex costs and carbon emission constraints(Bilkent University, 2016-03) Kian, RamezIn this thesis, di erent variants of the production planning problem are considered. We rst study an uncapacitated deterministic lot sizing model with a nonlinear convex production cost function. The nonlinearity and convexity of the cost function may arise due to the extra nes paid by a manufacturer for environmental regulations or it may originate from some production functions. In particular, we have considered the Cobb-Douglas production function which is applied in sectors such as energy, agriculture and cement industry. We demonstrate that this problem can be reformulated as a lot sizing problem with nonlinear production cost which is convex under certain assumptions. To solve the problem we have developed a polynomial time dynamic programming based algorithm and nine fast heuristics which rest on some well known lot sizing rules such as Silver-Meal, Least Unit Cost and Economic Order Quantity. We compare the performances of the heuristics with extensive numerical tests. Next, motivated from the rst problem, we consider a lot sizing problem with convex nonlinear production and holding costs for decaying items. The problem is investigated from mathematical programming perspective and di erent formulations are provided. We propose a structural procedure to reformulate the problem in the form of second order cone programming and employ some optimality and valid cuts to strengthen the model. We conduct an extensive computational test to see the e ect of cuts in di erent formulations. We also study the performance of our heuristics on a rolling horizon setting. We conduct an extensive numerical study to compare the performance of heuristics and to see the e ect of forecast horizon length on their dominance order and to see when they outperform exact solution approaches. Finally, we study the lot sizing problem with carbon emission constraints. We propose two Lagrangian heuristics when the emission constraint is cumulative over periods. We extend the model with possibility of lost sales and examine several carbon emission cap policies for a cost minimizing manufacturer and conduct a cost-emission Pareto analysis for each policy.Item Open Access Tepe Mobilya' da hücresel üretimle teslimat sürelerinin kısaltılması(TMMOB, 2006) Bozkurt, C. Halil; Çınar, Yüce; Kayayurt, Bade; Sevinçli, Berna; Tamer, Ş. Okan; Usluoğlu, A. Deniz; Aktürk, M. SelimTepe Mobilya Fabrikası'nda döşemeli ürünlerin teslimat sürelerinin azaltılması fabrika ve ürünlerin satışlarını gerçekleştiren Tepe Home için büyük önem taşımaktadır. Bu projede fabrikanın hücresel üretime geçişi için bir yöntembilim geliştirildikten sonra, hücreler arası ve hücre içi değişkenliği enazlayacak işçi atama probleminin çözümü için bir matematiksel model geliştirilmiş ve bu modelin çözümüyle en iyi hücre sayısı ve her bir hücreye atanacak makine ve işçi sayıları belirlenmiştir. Önerilen çözüm setinden alınan bir hücre ve işçi atama sonucu belirlenen bir pilot hücrede uygulanmış, olumlu sonuçlar alınmış ve bu yöntembilimi destekleyen web tabanlı olarak çalışabilen PHP programlama dili ve Oracle 9.2 veritabanının kullanıldığı "Üretim Takip ve Bilgilendirme Sistemi" programı hazırlanmıştır. Geliştirilen bu yöntembilim ile döşemeli ürünlerin teslimat sürelerinde İstanbul siparişleri için %14,5'lik, Ankara siparişleri içinse %8,29'luk bir azalma sağlanabileceği gösterilmiştir.