OSB flakes are pitched from a bunker and fall through rotating discs or rotating paddle wheels. Surface layers use spinning discs with gaps in between to orient the flakes in the machine direction (parallel). Core layers use paddle wheels to orient the flakes in the perpendicular direction. Mills have two surface and two core but Broken Bow has four surface and two core. QA managers can adjust formers to balance the parallel and perpendicular values. Then it goes to a mulit-opening or continuous press.
Using a Multi-Opening Press to Create OSB Flooring
Then the formed mat is cut into 8'X24" mats and each are loaded individually into multiple levels of the press. The press acts a batch process that treats each loaded mat equally. A 12" mat is compressed to 0.750" within 30-50 seconds and the mat is cooked at 400F at this thickness for 160 seconds. The buildup of steam requires that the press open slowly to prevent the OSB panels from "blowing" apart. (about 60 secs).
Multi-Opening Press Advantages
- Lower density to fast closing
- Slightly lower edge swell
- Better panel to panel consistency
Multi-Opening Press Disadvantages
- Limited to 8' X 24" dimension
- Less theoretical capacity
- Any press problems lead to 100% downgrade of loaded panels
Using a Continuous Press to Create OSB Flooring
The alternative to the multi-opening press approach is to use a continuous press. The formed OSB mat travels continuously through press and is not cut to length until trim & grade. The press acts as a continuous process that gradually compresses the mat to thickness. Steam pre-heats the core to help achieve the theoretical lower cook time of 60-80 seconds. Mat reaches thickness gradually as enters press in 30-50 secs but steamed mat is softer and does not have same density profile as multi opening. Like multi, the continuous press "raises" top platen slowly to allow steam to escape.
Continuous Press Advantages
- Any length product can be made.
- Greater theoretical capacity
- Press problems do not create as much downgrade.
- Produce thicker products (e.g., 1'1/8")
Continuous Press Disadvantages
- Belt tracking is major process concern because corrections impact the product being pressed.
- Higher density and slightly higher edge swell.
- Potential of greater panel to panel variation if press changes occur.
Final Stage Before Creating OSB Floors
The final stage is sanding which is important for creating OSB floors. Bottom sanding provides flat surface for joist and excellent glue surface for flooring adhesive. Top sanding provides a flat OSB floor surface for hardwood and tile. Sanding both sides provides thickness tolerance of +/- .010 which is equal to sanded plywood. 30-60% less thickness variation than leading OSB competitors.
See how AdvanTech flooring compares to other plywood and OSB flooring