Many concerns assess wood calibration on a regular basis. The huge economies of scale limit the number of samples that can be analysed. This limitation has a practical implication in wood product and forestry-related industries. We do not have a complete understanding of the variability of the wood within a given species and how environmental factors determine the changes in the qualities and properties of the wood. Determination of the genetic patterns for the wood properties also plays an important role in the assessment of the quality.
Measuring moisture in the wood
Moisture in the wood makes it expand and shrink. This is the biggest when it goes from “green lumber” to the normal humidity levels. This is also a measure of the humidity of the season as it is drier in the winter than during the summer. You can see some amount of wood movement during the transition period from winter to summer. Wood does not show a change in the length so that if you have a joint that is angled, there is bound to be some shrinkage during winter.
To measure this shrinkage or do the Wood calibration, one must hold the wood rigidly in place so that the movement of the wood is stopped. That is what we do with plywood. Most of the joints such as the mortise and tenon joints also work similarly.
If you have long pieces in the overlapping joints that are cross-grained, it will end to keep the wood from shrinking. We see that the wood has a certain amount of flexibility perpendicular to the grain. So, when the grains are perpendicular to the force applied, they will not shrink or change in length. But, if the tenon is huge, then it will shrink and expand and break the glue holding it on all sides.
Sanding to finish wood
Sanding is the process of finishing any wood product. In the automated sanding process, there are six types of processes. They are as follows:
- Calibration sanding
- Sealer sanding
- Orbital sanding
- Veneer sanding
- Brush sanding
- Profile sanding
The main aspects that determine the quality of the Wood calibration sanding include workpiece width, feed speed, abrasive belt, chip load, and type of material to be removed. We try to make all the faces flat in sanding.
Types of sanding
When we can achieve perfect flatness, we can apply the finish more easily. By sanding it, we prepare the surface for staining or finishing. We get rid of the material handling marks, defects in the wood, along with fibres and other organic residues in the wood. There are prominent kinds of finish sanding – cross belt and soft rubber drum.
Short fibres can be removed easily using a cross belt. It helps to avoid a washed-out appearance and helps remove tape more effectively. It also removes deep scratch marks aggressively. Before removing the topcoat, sealer sanding needs a fine-grit sequence and slower belt speed. We do brush sanding for two reasons – the edge braking to soften the edge and fibre removal. Edge braking helps us apply the sealer more evenly and by removing the fibre the surface quality is improved.
