Wet Glued Wood Article Surface Drying
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Solution Overview
Problem
The uneven initial moisture content of freshly sawn wood and the deformations caused by kiln drying lead to unreliable wet gluing processes and the need for extensive planing and profiling to achieve level faces and edges, resulting in faulty glue lines and inefficiencies in wood article manufacturing.
Innovation Solution
A method involving the drying of the superficial layer of freshly sawn wood pieces to below the fibre saturation point, followed by application of a polyurethane glue, to create a reliable wet gluing process that minimizes the need for planing and profiling, using controlled low-temperature drying and specific moisture content ranges to ensure consistent glue lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If kiln drying process is used to dry wood pieces, then moisture content is reduced, but face evenness is lost causing cupping, bowing, and twisting deformations
Solution Approach 1:
The drying process is segmented into two distinct stages: (1) initial drying of freshly sawn wood to reduce moisture content to fibre saturation point while maintaining face evenness, and (2) subsequent kiln drying or air drying to achieve final moisture content. This segmentation allows the first stage to remove free water without causing deformations, while the second stage handles bound water removal with controlled conditions.
Solution Approach 2:
The invention applies preliminary action by drying the wood surfaces to fibre saturation point immediately after sawing, before kiln drying. This preliminary drying removes free water from cell lumens without creating the steep moisture gradients that cause cupping and bowing, thereby preserving face evenness while preparing the wood for subsequent drying stages.
2Manufacturing precision
If extensive planing and profiling is performed to re-establish level faces and edges, then gluing quality is improved, but material loss and processing time increase
Solution Approach 1:
The invention performs preliminary action by maintaining face evenness during the initial drying stage before gluing. By drying to fibre saturation point immediately after sawing without allowing kiln drying deformations to occur, the wood surfaces remain sufficiently level for direct wet gluing, eliminating or minimizing the need for subsequent planing and profiling operations.
Solution Approach 2:
The invention changes the moisture content parameter to fibre saturation point (approximately 30%) for the initial drying stage, which is higher than traditional kiln drying targets. This parameter change allows the wood to dry without creating the steep internal moisture gradients that cause deformations, thereby preserving surface flatness and reducing material removal requirements.
3Loss of time
If wet gluing is applied to freshly sawn wood with uneven moisture content, then processing time is reduced, but glue line reliability deteriorates due to high free water levels
Solution Approach 1:
The invention applies preliminary action by drying the wood surfaces to fibre saturation point immediately after sawing, before applying wet glue. This preliminary drying removes excess free water from the wood surfaces, creating optimal conditions for wet gluing by reducing free water competition with the glue adhesive, thereby ensuring reliable glue lines while maintaining the efficiency benefits of wet gluing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables the production of glue lines comparable to dry gluing, reducing faulty glue lines and eliminating the need for extensive surface preparation, thereby enhancing the reliability and efficiency of the wet gluing process for wood articles.
Implementation Method 1
drying the surface of said wood piece so that the moisture content of said superficial layer, up to a depth of from 0.15 mm to 0.3 mm in said wood piece, is below the fibre saturation point
Data Source
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AI summary
The present invention relates to a method for manufacturing a wet glued wood article, as well as a wet glued article obtainable by said method and also uses of a wet glued artice, wherein the method comprises the following steps: a) providing two actively never-dried or slightly dried wood pieces comprising at least one surface each which has a superficial layer having a thickness of least 2 - 3 wood cells; b) drying said surfaces of said wood pieces so that the moisture content of said superficial layer is below the fibre saturation point, providing a dried surface on each of the said wood pieces; c) applying a gluing agent on said dried surface of one of the wood pieces, thus providing a glue surface; d) bringing the dried surfaces together so that said glue surface touches the dried surface on the other wood piece, thus providing a wet glued wood article.