Plywood QC Inspection Checklist : Part 14 Production PROCESS (One time ,two times ,three times )
In order to make it easier for readers to understand the production process of plywood, I try to explain the whole process in simple English.
In China ,especially in the film faced plywood production process ,we always say one time hot pressing ,two times hot pressing ,or three times hot pressing .But I prefer to say 1 step production ,2 steps production or 3 steps production .Actually they are the same things .
The main differences between 1 Step and 2 step is the production process; and depending on the plywood application needs, the benefits of one over the other is more evident.
1 Step Plywood is produced by hot pressing the veneer and overlay film at the same time. It is important to remember that the platform substrate face veneer is not sanded. The potential for grain and patch transfer is present.
2 Step Plywood, however, is produced by hot pressing the platform substrate and overlay paper or veneers or film separately. The platform substrate top face veneer is fully sanded and repaired. Because of this, the risk of grain and patch transfer for plywood is greatly reduced. The benefits of 2 Step are how it is used for architectural purposes: smooth, textured or coated plywood. Balanced construction ensures panel stability
In the plywood industry ,also have other types of production process ,Technologies are always innovative, costs are always lowered as far as possible, quality is always improved, and resources are always used more reasonably.
Standard One-Step — Comprised poplar or eucalyptus in a line-by-line construction. This traditional veneer core construction is predominantly used for commodity structural uses panels and is suitable for use with faces of dark colored commodity ,non-appearance grade plywood .
Premium One-Step — Combination of sanded core with smooth grade outer crossbands selected for uniform color and surface smoothness next to the face and back, assembled in a line-by-line construction. Recommended for commercial grade plywood for low quality plywood .
Standard Two-Step — Platforms comprised of regular sanded core .Sanded before they are assembled with the face and back. Pre-sanding gives two-step panels a tighter thickness tolerance than one-step. Suitable for use with faces of darker premium sliced woods where color variation from outer crossbands is not a concern, such as bingtangor ,okoume ,pine ,pencil cedar ,film ,birch .
Premium Two-Step — Platforms comprised of the sanded core with good grade outer crossbands are selected for uniform color and surface smoothness and then sanded before they are assembled with the face and back,suitable for cherry, alder, red oak, walnut and hickory, Works well for high-grade rotary UV panels and dark sliced UV panels .
Pre-sanding gives two-step panels a tighter thickness tolerance than one-step, Suitable for use with faces of lighter-colored premium sliced woods such as high-end maple, anigre, bamboo, sycamore and sap birch.
A step means the panel has gone through the entire manufacturing process: lay-up, press, trim and sanding. For one-step, the panel goes through the manufacturing process and is then graded and delivered. Two-step means the core is pressed in the first step and is then patched and sanded, before being returned to have the front and back veneers applied by the press during the second step. Finally, it is finished, graded and delivered.
The one-step process costs less, which is an important factor for many applications. It uses a thicker rotary cut veneer, great for common, less expensive wood species such as okoume,bingtangor ,pine ,birch ,pencil cedar ,film ,HPL. With thicker outer veneers, the core does not need to be as smooth and uniform and there is a slimmer possibility of telegraphing (where the core color and surface finish show through).
Many factoriesl use the two-step process if the panel requirements call for a high-end wood species, a higher quality face and/or a tighter thickness tolerance. Being able to sand and repair the core prior to adding the final veneers creates considerable process control. Using a more exotic veneer costs more, therefore the veneer is cut thinner using a slicer instead of a rotary cutter. With the rotary cutter, a less expensive veneer is used, but better control of the core is required.