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Articles by Manfred Gronalt

Category : Research article

article id 23032, category Research article

Maria Anna Gartner, Matthias Kaltenbrunner, Manfred Gronalt. (2024). Dynamic box assignment planning in log yards. Silva Fennica vol. 58 no. 1 article id 23032. https://doi.org/10.14214/sf.23032

Keywords: storage assignment; seasonality; binary integer program; optimisation model; sawmill storage

Highlights: Seasonal change of assortments calls for dynamic box assignment planning in log yards; Multi-period planning better suited for dynamic problem, however period per period planning improves with decreasing capacity on the log yard; Rearrangement of assortment amounts to 8–11% of total transportation distance (loaded travelled distances of transportation vehicle); Considering separate box allocation (storage and ejection), which results in double stage planning of box allocation, benefits most if 10% additional volume may be cut in to clear the box.

Abstract | Full text in HTML | Full text in PDF | Author Info

The situation on the log yard changes seasonally and also over the years. The quantities of assortments to be stored, their number and also the type of wood can change. To respond to this, we have developed a dynamic log yard planning model for assigning roundwood to specific ejection boxes and storage areas in order to minimise the overall transport distances of the loaded transportation vehicles on the log yard, including any possible re-allocation of assortments. The study centres on the log yard of a medium-sized hardwood sawmill in Europe, with actual cutting data from a six-month period. We are comparing a multi-period binary integer program with a model that operates on a period per period basis and a solution approach that splits the problem into two subproblems and solves them sequentially. The models undergo testing with decreasing space capacities at the storage boxes on the log yard and are compared. If capacity is continuously decreasing from 100% to 80%, then period per period planning is on average 13% worse than multi-period planning. We also investigate how the solutions change when twice as many or half as many assortments are stored at the log yard. In addition, we study how much the solutions improve when logs can be removed from the storage boxes to clear them and release them for other material in the following period.

Gartner, University of Natural Resources and Life Sciences, Department of Economics and Social Sciences, Institute of Production and Logistics, Feistmantelstrasse 4, 1180 Vienna, Austria https://orcid.org/0000-0001-8547-718X E-mail: maria.gartner@boku.ac.at
Kaltenbrunner, improvem GmbH, Holzinnovationszentrum 1a, 8740 Zeltweg, Austria https://orcid.org/0000-0002-1178-0087 E-mail: matthias.kaltenbrunner@improvem.at
Gronalt, University of Natural Resources and Life Sciences, Department of Economics and Social Sciences, Institute of Production and Logistics, Feistmantelstrasse 4, 1180 Vienna, Austria https://orcid.org/0000-0003-0944-4911 E-mail: manfred.gronalt@boku.ac.at

article id 10074, category Research article

Sebastian Kühle, Alfred Teischinger, Manfred Gronalt. (2019). Optimal location of laminated beech production plants within the solid hardwood supply network in Austria. Silva Fennica vol. 53 no. 3 article id 10074. https://doi.org/10.14214/sf.10074

Keywords: decision support system; facility location; laminated timber products; mixed integer linear programming; supply chain network design

Highlights: This paper provides data to the solid hardwood business and develops a mixed integer linear program model to design a laminated beech wood supply network; It covers the strategic decision where to locate a new production facility within the existing supply network with the lowest supply network cost; Sufficient sawn wood suppliers and potential facility locations are provided.

Abstract | Full text in HTML | Full text in PDF | Author Info

Due to changes in forest management in various European countries, hardwood forest areas and amounts will increase. Sustainable and individual utilization concepts have to be developed for the upcoming available resource. Studies conclude that there is low potential for hardwoods in the traditional appearance market thus the application areas have to be extended to new structural innovative products. This paper examines the extension to a future laminated beech wood supply network which would be a combination of already existing and new production facilities. For a better future use of hardwood raw materials it is necessary to consider the entire supply chain. This also better shows a total hardwood value chain. Therefore, this paper provides data to the solid hardwood business and develops a mixed integer linear programming to design a laminated beech wood supply network. The model is applied to Austria as the sample region. It covers the important strategic decisions where to locate a downstream facility within the existing production network with the lowest supply network cost. Fourteen scenarios are developed to examine various future network configurations. Results about optimal material flows and used sawmills as well as downstream production facilities are presented in form of material and financial performances. Two optimal laminated beech production locations are determined by the calculated scenarios results, and the impact of a new sawmill is analyzed which is focused on beech.

Kühle, BOKU - University of Natural Resources and Life Sciences, Vienna, Department of Material Science and Process Engineering, and Renewable Institute of Wood Technology Materials, Konrad-Lorenz-Straße 24, 3430 Tulln, Austria E-mail: skuehle@boku.ac.at
Teischinger, BOKU - University of Natural Resources and Life Sciences, Vienna, Department of Material Science and Process Engineering, and Renewable Institute of Wood Technology Materials, Konrad-Lorenz-Straße 24, 3430 Tulln, Austria E-mail: alfred.teischinger@boku.ac.at
Gronalt, BOKU - University of Natural Resources and Life Sciences, Vienna, Department of Economics and Social Sciences, Institute of Production and Logistics, Feistmantelstraße 4, 1180 Vienna, Austria E-mail: manfred.gronalt@boku.ac.at

article id 1006, category Research article

Jörn Rathke, Maria A. Huka, Manfred Gronalt. (2013). The box assignment problem in log yards. Silva Fennica vol. 47 no. 3 article id 1006. https://doi.org/10.14214/sf.1006

Keywords: log yard planning; sawmill; linear optimization

Highlights: Logistic approach for the optimization of log yard in terms of arrangement of storage boxes and ejection boxes reduced transportation time by 16 percent compared with the original solution.

Abstract | Full text in HTML | Full text in PDF | Author Info

This paper presents an optimization approach to minimizing log yard round wood transportation time for a medium sized hardwood sawmill. The log yard, which has to ensure a smooth raw material supply to the entire production process, is the first processing step in a sawmill. The log yard also serves as an internal round wood sorting and storing capacity. Thus, an optimal assignment of ejection boxes, storage boxes and feeding carriages is required to minimize transportation time at a log yard. The main contribution of this paper is to present an integrated approach which simultaneously takes into account log transportation time, storage capacity and yard crane deployment. The approach is based on two steps: a) defining storage spaces per batch and calculating distances and b) determining optimum box assignments in the log yard in order to minimize overall transportation distance. The solution in step b) is compared with the results obtained by random box assignment as well as a spreadsheet based planning method. We have been able to show that our approach is much more flexible and results are more than 16 percent better than the corresponding real life solution.

Rathke, University of Natural Resources and Life Sciences, Institute of Production and Logistics, Feistmantelstraße 4, 1180 Vienna, Austria E-mail: joern.rathke@boku.ac.at
Huka, University of Natural Resources and Life Sciences, Institute of Production and Logistics, Feistmantelstraße 4, 1180 Vienna, Austria E-mail: maria.huka@boku.ac.at
Gronalt, University of Natural Resources and Life Sciences, Institute of Production and Logistics, Feistmantelstraße 4, 1180 Vienna, Austria E-mail: manfred.gronalt@boku.ac.at

article id 267, category Research article

Manfred Gronalt, Peter Rauch. (2008). Vendor managed inventory in wood processing industries – a case study. Silva Fennica vol. 42 no. 1 article id 267. https://doi.org/10.14214/sf.267

Keywords: building materials; service level; solid structure timber; SST; wood construction

Abstract | View details | Full text in PDF | Author Info

Solid structure timber (SST) is an important building material in the wood construction business, in which its production volume is largely related to that respective business. Due to the large variability in the demand and seasonal factors, SST producers’ inventories are likely to be simultaneously overstocked for one type of timber and out of stock of another. An inventory policy that ensures a high service level and relatively low stocks is required. In the present paper, we propose the vendor managed inventory (VMI) approach for controlling the stock of deals that are produced at a sawmill and delivered as raw material for SST-production. We evaluate two VMI implementations against the actual inventory management for three different market scenarios. Furthermore, we layout the necessities for reconfiguring the business processes, and subsequently set up an organisational framework within VMI, which is indeed applicable in this segment of the woodworking industry. In our application background, VMI as an inventory control system is able to reduce the overall raw material stock by more than 37% by simultaneously increasing the SST service level.

Gronalt, BOKU – University of Natural Resources and Applied Life Sciences, Feistmantelstr. 4, 1180 Vienna, Austria E-mail: mg@nn.at
Rauch, BOKU – University of Natural Resources and Applied Life Sciences, Feistmantelstr. 4, 1180 Vienna, Austria E-mail: peter.rauch@boku.ac.at

Category : Review article

article id 7760, category Review article

Maria A. Huka, Manfred Gronalt. (2018). Log yard logistics. Silva Fennica vol. 52 no. 4 article id 7760. https://doi.org/10.14214/sf.7760

Keywords: log yard; tactical structural and operational problems; material flow; facility layout planning; storage assignment; vehicle movement; seasonality

Highlights: Characteristics of log yard logistics; Classification into tactical structural and operational problems in the wood industry; Different solution methods such as optimisation, heuristics and simulations and their possible application within the log yard with an overview of existing literature which includes several different case studies with varying emphases, problem analysis and solution methods.

Abstract | Full text in HTML | Full text in PDF | Author Info

For sawmills, paper mills, particleboard, oriented strand board (OSB), fiberboard and other wood production factories, the log yard is the first step, where raw materials are sorted and stored before production begins. Due to the size of these production sites great potential exists for the optimisation of internal logistics. In this paper the different planning problems of the log yard are introduced and existing literature examined. Beginning with the tactical problems of structure, such as assessing material flow, planning facility layout and assigning storage areas, it continues with operational problems such as vehicle movement planning within the log yard, empty trip minimisation and the seasonality of raw material availability. Data derived from this study reveals a variety of possible solution methods, the applicability of which depends on the precise nature of the log yard operations. Additionally, several real life examples are provided which illustrate the potential for operational improvement.

Huka, University of Natural Resources and Life Sciences, Institute of Production and Logistics, Feistmantelstraße 4, 1180 Vienna, Austria E-mail: maria.huka@boku.ac.at
Gronalt, University of Natural Resources and Life Sciences, Institute of Production and Logistics, Feistmantelstraße 4, 1180 Vienna, Austria E-mail: manfred.gronalt@boku.ac.at

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