Tuesday, January 30, 2018

Plywood and Fiberboard Sheet Goods

This post discusses many different types of plywood and fiberboard sheet goods.  These are engineered wood products made out of wood plies or wood fibers. Types of fiberboard include particle board, medium-density fiberboard (MDF), and hardboard.

The great majority of the material featured on this page are available from Fingerle Lumber in Ann Arbor, Michigan. Others can be purchased from All American Plywood in Detroit, Michigan.

Note: For information on hardwoods and veneer please see Wood Basics.

Plywood

Plywood is a composite material made up of thin layers or "plies" of wood veneer. The plies are glued together with the wood grain of adjacent layers rotated relative to one another. There are several important benefits to the cross-grain orientation of the layers:
  • It reduces expansion and contraction of the panels due to moisture changes in the atmosphere. This provides much improved dimensional stability over hardwood.
  • The strength of the panel is consistent across all directions. 
  • The wood is less likely to split when nailed or screwed near the edges of the parts. 
Below are some videos describing the process of making plywood:

Plywood Grading

Plywood grades are established by the APA – The Engineered Wood Association (the initials APA come from the associations previous name of the American Plywood Association). In the United States, there are four basic plywood veneer grades: A, B, C and D.

Each plywood sheet will have two grades, for example AC. The first letter is the grade of the face veneer, and the second is for the back veneer grade. Some plywood sheets have a third letter, X, that designates them for exterior use.

A Grade: This material is the highest quality. It is sanded smooth, and is paintable. Some neatly made manufacturer repairs are acceptable, however you can generally expect the material to be free of repairs and knots.

B Grade: This material is a solid surface with some repairs, usually football-shaped patches and/or wood filler. It may contain tight knots up to 1 inch in diameter, however no chunks of wood are missing. There may be some minor splits.

C Grade: Contains tight knots to 1-1/2 inches in diameter with knotholes to 1 inches in diameter. There may be some splits and discoloration.

D Grade: This is the lowest grade and the material may contains knots and knotholes up to 2-1/2 inches in diameter. Some splits are likely present. Generally no repairs have been made to the material.

Baltic Birch Plywood

This material is commonly used in CNC routed projects. The wood species is Birch and it is sourced from the regions surrounding the Baltic Sea. In the case of the material we get in the Taubman Fab Lab it comes from Russia.

It's a veneer core material meaning all the plies in the sheet are free of voids. Well in theory... as you can see in the examples below there are sometimes small defects which you can see in the cut edges. In general however you won't find any large voids as you would in lesser grade stock.

There is often a superior face side and a lesser side. The non-face side may contain what are known as footballs. You can see one in the lower right of the piece below. It is a patch placed into a defect area of the veneer. It looks better than seeing a knot, but it does break the flow of the grain across the sheet. Keep this in mind as you are designing - if both faces are visible in your final product you may want to position your parts on the sheet for cutting as to avoid the area with footballs.

Paint Grade Birch Plywood

This is a low-cost product which accepts paint well. Generally the face veneers are not as clean in terms of the grain but they are free of defects so the paint application will be smooth.

CDX Plywood

CDX refers to "C-D Exposure 1". The faces are graded C and D and the glue used in the plywood is exterior glue. While the material is moisture resistant it cannot be exposed to outdoor conditions for an extended period of time. This is a low-cost material commonly used in construction. 

Radiata AC Plywood

This is a 7 ply material with thick exterior plies. The A grade side is high quality and has a marked grain pattern to it, similar in appearance to Pine.

Face Veneer Plywood

Below are a few examples of plywood with pre-finished veneers or lower quality material in the internal plies with high quality hardwood face veneers.

Pre-Finished Baltic Birch Plywood

This is a very high quality material composed of 13 thin plies. Both faces are pre-finished so it is ready for use immediately after cutting. The edges are free of any significant defects (voids).

Red Oak Veneer Plywood

This material has 5 plies and a Red Oak veneer on both sides.

Birch Veneer Particle Board

This material has 5 plies and a Birch veneer on both sides.

MDO (Medium Density Overlay) Fir Plywood

MDO is an exterior grade plywood with smooth, brown medium-density plasticized overlay. It's good for accepting paint and resisting exposure to moisture. The painted surface won't show any grain.
This material is available with the overlay on one side or two. 

Other Sheet Materials


Below are some videos describing the process of making Medium Density Fiberboard (MDF) and Oriented Strand Board (OSB):

Medium Density Fiberboard (MDF)

MDF is an engineered wood product made by breaking down hardwood or softwood into wood fibres, combining it with resin binder and a small amount of wax, and forming panels by applying high temperature and pressure. MDF is generally denser than other sheet goods such as plywood and particle board. This material is heavily used in the furniture industry.

Ultralight Medium Density Fiberboard (UDF)

This material is a light-weight version of MDF. It is much more porous than MDF and so is often used as spoilboard material in CNC routing applications. UDF allows the vacuum pressure from the CNC machine's vacuum table to be transferred right through itself to hold down the material resting on it. It can be planed flat over and over to restore a smooth surface. 

Melamine

Melamine has a compressed wood core, similar to particle board, which is covered with a resin and paper finish. Melamine is often used for cabinetry when a durable, smooth, wear resistant finish is needed.  The top coat is smooth and resists moisture. It's not as durable as a layer of plastic laminate (the melamine surface is much thinner) but is often used as a low-cost substitute. Sharp cutters are needed as edge chipping is sometimes an issue.

Particle Board

This is an engineered wood product manufactured from sawdust, small shavings or wood chips combined with a binder, which is then pressed and extruded. Particle board is cheaper, denser and more uniform than plywood and is used when cost is more important than strength and appearance. Particleboard can be painting or covered with wood veneers to improve the appearance. Though it is denser than conventional wood, it is the lightest and weakest type of fiberboard.

Birch Veneer Particle Board

A singly layer of Birch veneer is applied to a particle board core.

Maple Veneer Particle Board

This material has 5 plies and a Maple veneer on both sides. 

Oriented Strand Board (OSB)

Oriented strand board (OSB) is an engineered lumber formed by compressing layers of wood strands in combination with an adhesive (usually a resin that has been coated onto the flakes). OSB has desirable mechanical properties that make it suitable for load-bearing applications in construction. It is also sometimes used in furniture construction where a strong, low cost material is needed.

Cedar Flake Board

Flake board is another name for oriented strand board. This material is composed of strands from Cedar trees. It's strong and has the pleasant smell of cedar. It is used in closet lining or chest lining applications.

Sound Deadening Board

This fiberboard product is lightweight and porous. It is used as wall and ceiling material in noisy environments to absorb reflected sound waves to decrease the overall volume level in a space. 

PVC Azek

This material is different from all the other materials in this post because it does not contain wood fibers which can promote mold growth. It is strong and lightweight. It can be cleaned with soap and water. The material is color-fast and stain resistant and is extremely scratch resistant.

Bending Material 

Some types of plywood or fiberboard are designed to be used in applications where the material needs to follow curves or be bent into shapes. The material is classified into barrel type (4' edges bend) or column type (8' edges bend).

Bending Plywood

1/4'' Neatform Bendy MDF


No comments:

Post a Comment