Planetary vertical concrete mixers: Simulation and predicting useful life in steady states and in perturbed conditions M.C. Valigi a, * , I. Gasperini b a Department of Industrial Engineering (DIIN), University of Perugia, Via G. Duranti, 63 06125 Perugia, Italy b SICOMA – Societa ` Italiana Costruzione Macchine, Via Brenta, 16 06078 Ponte Valleceppi (PG), Italy Received 9 March 2006; received in revised form 30 May 2007; accepted 23 July 2007 Available online 25 August 2007 Abstract A simulation environment for the dynamics of planetary concrete mixers has been developed, it is a model based method using the lumped parameters analysis and integrating the theory of classical mechanics and life analysis. The aim of this work is to give a fast and easy to use tool capable of predicting the behaviour and the useful life of concrete mixers through geometrical and physical parameters. Simulations were conducted in steady states and in per- turbed conditions. The gear reduction unit is the part of the mixer under most stress. Results were compared with data obtained from costumers on building sites. Ó 2007 Elsevier B.V. All rights reserved. Keywords: Simulation; Lumped parameter model; Gear reduction unit; Concrete mixer; Useful life 1. Introduction The two main categories of mixers are: batch mixers and continuous mixers. The first type produces con- crete one batch at a time, while the second produces concrete at a constant rate. The first type needs to be emptied completely after each mixing cycle, cleaned and then reloaded with the raw materials for the next batch. In the second type, as the name indicates, the raw materials are continuously loaded at one end as the fresh concrete exits the other end. Batch mixers are the most common type. Different types of batch mixers can be distinguished by looking at the orientation of the axis rotation: horizontal or inclined (drum mixers) or vertical (pan mixes) [1]. Long term usage of a mixer leads to wear on the blades and/or scraper, the build-up of materials (hardened mortar or cement paste) on the blades, the container, and/or the scraper. To avoid this situation, the concrete mixer should be thoroughly cleaned at the end of each day of opera- tion and the blades and scraper should be changed on a regular basis. 1569-190X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.simpat.2007.07.010 * Corresponding author. Tel.: +390755753724. E-mail address: mc.valigi@unipg.it (M.C. Valigi). Available online at www.sciencedirect.com Simulation Modelling Practice and Theory 15 (2007) 1211–1223 www.elsevier.com/locate/simpat