Advances on indirect methods to evaluate tool wear for Radiata pine solid wood molding A. Aguilera a,n , P.J. Méausoone b , A. Rolleri a , J.L. Barros c , F. Burgos a , C. Aguilar d a Forest Products Laboratory, Universidad Austral de Chile, Valdivia, Chile b LERMAB, Laboratoire d’Études et de Recherche sur le Matériau Bois, Lorraine University, Epinal, France c Acoustic Institute, Universidad Austral de Chile, Valdivia, Chile d Department of Metallurgical Engineering and Materials, Universidad Técnica Federico Santa María, Valparaíso, Chile article info Article history: Received 18 September 2015 Received in revised form 24 December 2015 Accepted 27 December 2015 Available online 7 January 2016 Keywords: Radiata pine Sound pressure Electrical current Tool wear Molding abstract The final quality of solid wood molding depends on several factors, where the choice of cutting condi- tions and consequently the tool performance are key points when processing this type of material because tool wear affects physical–chemical and thermodynamic behavior of the surface submitted to coating. One of the main problems at the production line is to achieve an adequate monitoring system of the cutting process to prevent and detect operational problems or loss of productivity. The objective of this research is to evaluate results from two different control process methods, such as sound pressure and electrical current measurement submitted during different cutting conditions and to determine the cutting distance increase, as innovative methods to estimate tool wear when appearance grade products are being produced. & 2016 Elsevier B.V. All rights reserved. 1. Introduction Currently, added value wood based products such as the appearance grade of decorative moldings, reach increasingly demanding markets. These wood products are not free from defects, produced either from raw material or as a result of mis- matches in the production process. Several processing variables can produce these defects, the most important being surface quality. In the industrial context of molding production, comprehensive selection and classification controls of raw material are applied, using infrared scanning technology and X-ray vision [26,27], cou- pled to highly efficient and accurate analysis. The twain system prevents raw material losses that may compromise process effi- ciency. Quality appreciation is undergone by machine operators but this process lacks sensors that evaluate processed wood quality. Surface quality influences the coating or the adhesion between surfaces, where the evolution of tool wear will affect to some extent these properties. In this sense, when cutting distance is regularly increased with production, we observe a gradual increase of cutting power and a progressive deterioration of sur- face quality. Tool wear phenomena may raise production costs because of the loss of raw material and ultimately the loss of markets and lack of consumer confidence, with the principal reason being the late replacement of the cutting tool. Although, tool wear estimation is essential for online process control and optimization: in fact, many technicians eliminate the used tool, in fear of producing damaged surfaces. Tool wear prediction methods have been extensively studied in metal machining [28,29] but not as much for wood machining. Therefore metal research has used, for example, tool life models like Taylor's equation and also temperature based equations. These are considered as a function of input cutting parameters and tool wear rate models as a function of output state variables (cutting temperature and speed, normal stress, etc.) using Takeyama and Murata's [1] wear model or Usui's wear model [2], both based on physical considerations such as abrasive and diffusion phenomena. Tool life is primarily affected by edge wear until the point of cut- ting refusal. It is well known that the limiting factor is the dimensional accuracy of the machine piece, the roughness or when the tool wear is such that the edge is no longer reliable. From the mechanical point of view, tool life comes to its end when the edge breaks [3] or once it has met a defined value. It is necessary to set up strong definitions to identify when the cutting edge is worn out by different operations, criteria and tools. Clearly, if a cutting edge does not produce the required finish or if it does not maintain certain tolerances, it can no longer be used for the operation. The risk of rupture increases with the level of edge wear, mainly once it exceeds a certain value. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/wear Wear http://dx.doi.org/10.1016/j.wear.2015.12.011 0043-1648/& 2016 Elsevier B.V. All rights reserved. n Corresponding author. Tel.: þ56 632221717; fax: þ56 632221224. E-mail address: aguilera@uach.cl (A. Aguilera). Wear 350-351 (2016) 27–34