Improving wood surface form by modification of the rotary machining process—a mechatronic approach

Abstract

Rotary machining is extensively used for planing and moulding operations within the woodworking industry. Although the surface form produced by this machining method is acceptable, the rotary machining action produces cutter marks on the wood surface so that further finishing operations, such as sanding, are often required to generate a product of acceptable standard. It has been theorized that the surface finish of planed and moulded timber products may be improved by oscillation of the cutter block in either a vertical or horizontal plane. This paper describes the use of a rapid surface simulation algorithm to predict surface finish and the use of computer simulation to model cutterblock oscillation. The result is a tool for effective design and optimization of a hydraulic oscillation system in order to improve surface form. NOTATIONhydraulic ram area (m 2 ) A artificial neural network ANN bulk modulus (N/m 2 ) B capacitance (F) C C cv coefficient of viscous friction d strain developed/applied field (C/N) dielectric displacement (C/m 2 ) D field (V/m) E f d feed rate of workpiece (m/s) f k feed per knife (m) resonant frequency (Hz) f m f n antiresonant frequency (Hz) f r feed per revolution (m) F force (N) strain developed/applied charge density g (m 2 /C) depth of knife marking (m) h H original horizontal sample array I(t) x instantaneous cutter tip locus position (x axis) I(t) y instantaneous cutter tip locus position (y axis) k A drive amplifier constant (mA/V) k LE leakage coefficient (cm 3 /N m 2 ) spool displacement gain (mm/mA) k s M total ram, slideway and cutterblock mass (kg) n cutterhead rotational speed (rad/s) number of knives in the cutterhead produc-N ing a wave on the workpiece p hydraulic fluid pressure (N/m 2 ) P pitch of knife marking (mm) P f pressure required to overcome viscous friction hydraulic fluid flow, single acting ram input q (cm 3 /s) Q general hydraulic fluid flow (cm 3 /s) energy supplied/dissipated per cycle Q m radius of cutting circle (m) r ct s Laplace operator S d scallop depth: depth of knife marking (mm) mechanical compliance (m 2 /N) s E S strain surface simulation algorithm SSA t time (s) T stress (N/m 2 ) valve actuator time constant 6 m V volume of oil column (m 3 ) V v valve voltage (V) x hydraulic ram displacement (m) valve spool displacement (m) X s The MS was recei6ed on

Mechatronic approach towards surface quality improvement in rotary wood machining

“…In the first approach, models that predict the quantitative relationships between machining parameters (cutting speed and feed speed) and surface finish quality are used to select optimal machining parameters for obtaining a high quality surface finish. 6,7 In the second approach, surface finish quality is improved through real-time modification of process kinematics (cutter-path optimisation) [8][9][10][11][12] and active vibration control. 13 This first approach has been used to minimise surface roughness during milling of medium density fibreboard (MDF) in Gaitonde et al 6 and Davim et al 7 It is reported in both articles that the surface finish quality of milled MDF increases with an increase in cutting speed.…”

“…The first one is the introduction of additional horizontal cutterhead movement during the machining process. [8][9][10] The objective of the horizontal cutterhead movement introduction is to produce a surface finish with reduced waviness heights.…”

Waves on wood

“…The need for a generalized model for surface defect simulation was identi®ed. Recent work [25,29] has established and re®ned such a model environment currently implemented via MATLab TM [30].…”

Improving wood surface form by modification of the rotary machining process

“…The resultant surface is computed as a series of discrete points. A few authors [1,7,8] developed surface simulation algorithms specifically for wood machining. These algorithms only take into account the rotary machining process kinematics.…”

“…without increasing the number of knives or without increasing the cutterhead diameter) if the modified cutterhead movement is synchronized with the rotational position of the knives. For example, horizontal cutterhead movement, investigated in reference [1], reduces waviness height when synchronized with the position of the knives. This paper investigates the influence of vertical cutterhead movement.…”