Modeling and multicriterial optimization of the mortise forming process in pine wood blanks

The forming of the joint profile is an important stage in the technological process of manufacturing joints for wood splicing. A promising direction for improving this technology stage is the development of waste-free methods for the formation of high-quality finger joints using the technique of local pressing in the longitudinal direction. The introduction of technology into the production process requires a reasonable choice of the parameters of technological modes. One of the most important output parameter of the pressing process is the hardness of the mortise bottom, together with the pressing force and the depth of the densified zone. The first task of the research is the development of a model describing the impact of the technological modes on the hardness of the mortise bottom. The second task is the determination of the modes at which the resulting process parameters, or output functions (pressing force, depth of the densified zone, hardness of the mortise bottom) acquire optimal values. Data processing, their statistical analysis, and obtaining a regression model for determining hardness were carried out using the Statistica software package. The search for the extreme values of the output functions and the search for a compromise solution for finding rational values of the technological modes were carried out using the generalized reduced gradient method realized in the Excel Solver add-in. A predictive model was obtained for the hardness of the mortise bottom depending on the state of the wood and the parameters of the pressed mortise. Rational values of the input factors (moisture content, depth and width of the mortises) and the expected values of the output parameters for pine wood blanks were determined. The obtained values make it possible to recommend the technological modes of end local pressing of mortises in an industrial environment. The objective function has the potential to decrease the width of the mortises and to increase their length. This result can be used to improve the strength characteristics of adhesive joints on multiple pressed mortises and tenons.