Determining the coefficient of friction of wood-based materals for furniture panels in the aspect of modelling their shredding process

In order to improve the power selection of the drive unit for the shredding machines, the authors determine the values of friction coefficients used in the cutting force models. These values consider the friction between steel and such wood-based materials as chipboard, MDF and OSB. The tests concern laminated and non-laminated external surfaces and surfaces subjected to cutting processes. The value of the coefficient of friction for the tested materials is in the range: for the static coefficient of friction 0.77-0.33, and for the kinetic coefficient of friction 0.68-0.25. The highest values of the static and kinematic coefficient of friction were recorded for MDF (non-laminated external surface) and they were equal respectively: 0.77 and 0.68. In turn, the smallest values of the discussed coefficients were recorded for chipboard (laminated external wood-base surface), which were at the level of 0.33 and 0.25, resp.

Cutting forces in quasi-orthogonal CNC milling

The paper is focused on the analysis of cutting forces in milling of MDF on the CNC machine (SCM Tech 99 L, SCM Group, Italy). The measurement of the forces was realized by a three-axis piezoelectric dynamometer Kistler 9257B (Kistler Holding AG, Switzerland). The forces were examined and analysed during quasi-orthogonal milling with a single-edged blade. The resulting forces were compared to each other depending on the conventional and climb milling of the edge of the MDF at changing feed speeds from 1.5 to 4.5 m∙min-1 with steps of 0.75 m∙min-1. The experimental values of cutting forces were also used for the first assessment of the fracture toughness and shear yield strength, main parameters of computational model based on Ernst-Merchant theory and on fracture mechanics. These values were input data for the calculation of the specific cutting resistance for CNC machining. The experimental data confirmed that the cutting force increases and the specific cutting resistance decreases with the increasing chip thickness.

Determination of maximum torque during carpentry waste comminution

In order to elaborate design guidelines for developing efficient and possibly most energy saving mills for comminuting carpentry, OSB and MDF waste, there have been performed some tests aimed at torque demand on the working unit of the machinery participating in that process. The tests were carried out on a cylindrical wood chipper. There were indicated the maximum, minimum and average values of the torque, indispensable for the comminution of boards with defined geometric sizes (5 – 50 mm wide ) and thickness (3 – 28 mm). The value of torque required in the comminution of carpentry waste increases with growing cross section, and the torque vs. cross section relation is approximately linear. The presented values may constitute not only a set of input data indispensable for modeling the power which is necessary for the comminution process, but they can also enable the validation of the existing cutting models with a single cylinder cutter.