The widespread adaption in the window and door industry of hydro planing with industrial moulding machines promises very smooth and even wooden surfaces. But the more uneven the growth rings are and the higher the difference in hardness of early wood vs. late wood and the duller the tool, the more unsatisfying the planing results become.
The flaws in the moulder's machined surface become clearly visible viewed against the light. You can see chatter marks as well as burnished areas that can appear shinier or duller. Pigmented water-based varnishes that are quite commonly used today are absorbed by the wood differently. This may cause a considerable difference in the colour or a «splotchy» effect, especially when darker colours are used. And after applying water soluble finishes, the wood fibres that were initially pressed down, straighten up again, causing «raised grain». This causes a rough surface which makes additional hand sanding necessary.
Approximately 20% of the manufacturing costs for windows consist of intermediate sanding work. And every time this has to be done, a little bit of the surface protection is removed. In most conventional work environments, this often also causes the emission of hazardous fi ne dust particles into the working area.
Cross grain machining instead of sanding offers the solution. This is where the «Quality Finishing» process sets in. By finely cross cutting the work piece, the wood fibres that run lengthwise are cut microscopically at a right angle against the hard growth rings. A precision like this cannot be achieved with conventional sanding techniques. And what's impressive - when the water-based wood preservatives are applied subsequently, the fibres do not straighten up anymore. No matter what kind of wood, optical imperfections that window manufacturers are normally used to, are replaced by smooth, homogenous, dull and uniformly fine surface structures with diffused light reflection.