Plywood: The Production Process
Plywood is a wood-based panel product comprised of a collection of veneers that are glued together with a resin. To sum up the production process; logs are peeled into veneers, the veneers are lathered in glue, laid up so that the grain direction of each veneer is perpendicular to its adjacent veneer, pressed together, trimmed and sanded. plywood_870 But there is more to the production process than just that...

Step 1: The Forest

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It's important to us that all raw logs used in our plywood are sourced from legal and sustainable forest concessions. We only use mills who use the Timber Trade Federation's Responsible Purchasing Policy to ensure this.

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Once trees reach an acceptable level of maturity, they are felled by trained harvesters. Depending on the operation of the mill, vehicles like those in the image above can be used to select and fell trees using satellite imagery.

Step 2: Transport to the Mill

Logs are transported from the forest concession to the mill to be processed.

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Transportation comes with its own environmental issues in some instances, as forest areas are cleared to make room for roads and therefore new trees cannot grow.

Step 3: The Log Pond

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On arrival at the mill, logs are stored in the Log Yard. Mills will use various methods to retain the moisture in the logs, many opting for sprinkler systems. Logs will then eventually make their way to the Log Pond. Logs are submerged in water for an extended period of time so that they are easier to cut down to size and easier to peel. Some mills in colder climates have heated log ponds as the heat also improves the quality of the peeling; they refer to this as hydro-thermal processing.

Step 4: De-barking the Logs

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Before the logs are cut and peeled, the bark must be removed. Mills use industrial machines such as this to de-bark logs as they continue along the production line.

Step 5: Cutting the Logs

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De-barked logs then move on to be cut to size. The size that the logs are cut to is usually dependent on the production at the time of cutting; finished panel size & grain direction play a part in the cutting of logs.

Step 6: Peeling the Logs

  Logs are peeled using a rotary lathe. This peels the log in a manner similar to that of a pencil sharpener except the blade is completely parallel to the log at the time of cutting. You can see this process in action in the video above, and see them coming out of the back of the peeling machine straight onto a conveyor in the video below.
 

Step 7: Sizing and Grading

Once they've been peeled the resultant sheets are fed to the next step on a conveyor, as in the image below.

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Following peeling, the veneers are moved along the production line in long streams. They need to be cut to size and go through an initial grading process. Grading is especially important in regards to Birch Plywood so the majority of mills use scanning technology to check for defects in the veneers, cutting to the required sizes and then separating potential face veneers from core veneers.
  Unlike mills from Eastern Europe and the Baltics, countries like China will peel the veneers in smaller squares and then stitch them to the appropriate size as a more cost effective (but quality reducing) method.

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Step 8: Drying the Veneers

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At this point, the veneers are still wet from being soaked in the log pond. The veneers must be dried for a variety of reasons; from protecting the wood from fungal decay to increasing the mechanical properties of the finished board. Most mills use large, industrial dryers, often connecting to the log peeler via conveyor belt; however, more frugal methods can also be used. For example, some log peelers in China leave the veneers out in the open to dry throughout the day.

Step 9: Repairing Defects

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Once dry, veneers need to be repaired where defects exist. In the case of Birch Plywood for example, open knots (where branches used to be) can be 'plugged' in. Splits in veneers on plywood can also be filled in and mis-sized veneers can be finger-jointed together (see above). Some mills have a machine that scans the veneers and automatically plugs open holes or knots. (See below).
 

Step 10: Application of Glue and Lay-Up

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Veneers are run through a gluing machine which essentially rolls the glue onto the face and back of the veneer. They are then placed on top of an unglued veneer so that the stack alternates; Glued, Unglued, Glued, Unglued and so on.

Step 11: Cold Pressing

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Cold Pressing occurs after glue has been applied in order to prepare the veneers for Hot Pressing. This works to flatten out the veneers and ensure the glue is distributed across the veneers evenly.

Step 12: Hot Pressing (Daylight Press)

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This part of the production process is where the actual panels begin to take shape. Multiple panels are loaded into the daylight press. The Daylight Press then compresses and maintains heated pressure on the boards for a long period of time. This creates and maintains required contact between the glue and veneers. It also decreases tension in the glue line and the thickness of glue layer.

Step 13: Trimming, Sanding and Finishing

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Following Hot Pressing, the board is left to stabilise and cool down before further processing. Then it is a case of trimming down any excess veneer so the board has square edges, then the boards are most commonly sanded using a large, industrial sander.

Step 14: Quality Control

The final product has to be assessed for quality but it wouldn't be very efficient just to wait until the end of the process to find a large problem with production. For this reason, mills control their production by carrying out a number of tests on different sections of the production process e.g. testing moisture levels, formaldehyde release, durability, etc.

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Many mills have what is called a Factory Production Control certificate which means they have been audited by a third party and had their production process approved to relevant European standards.

Step 15: Packaging

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Finished products are then stacked up and banded together. Any relevant CE marks are printed on the packaging.

Step 16: Delivery

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We take delivery of plywood weekly, ready to despatch to you!

22 comments

Mark Donnison

Mark Donnison

Hi Darjan, we don't operate a Mill as we are only a supplier. Your best bet would be to contact a mill directly.

darjan

darjan

How much timber is needed to made 1m3 of plywood?

Mark Donnison

Mark Donnison

Do you have an offcut piece that you could use to see how deep the marks go?

REBECCA J HOKE-MENTZER

REBECCA J HOKE-MENTZER

Please please tell me how to get rid of I think vine marks..I have tried sanding to no avail..please email me if you are able to help.

Mark Donnison

Mark Donnison

Hi, as we don't personally manufacture plywood products, like you we rely on what we are told by our suppliers/mills for information. You will see similar price disparities in the Ply's we sell. Our suppliers have told us that making the thicker cuts is easier and marrying up the three ply pieces and keeping it within tolerance is MUCH easier with the larger pieces. With the thinner cuts, the precision required is much greater, there is a lot more unusable output and it is very difficult to join together 3 pieces and have the result within tolerance.

Mr G Larkin

Mr G Larkin

Dear Kitronik. I'm a builder using many different kinds and types of plywood. I've had a debate with my local timber yard about plywood! Could you tell me if it is harder to make good 20 mm plywood or harder to make good 5mm plywood? Can you see where i'm going with this? Because the 5mm plywood that i buy costs twice as much as 20mm identical material plywood: based on thickness. E.G. the 5mm is £20 per sheet and the 20mm ply costs me £10 per 5mm. Can you please explain? Shipping costs based on density and weight are identical. Yours sincerely

Mark Donnison

Mark Donnison

Hi Russel, this is not something we have any experience of. Your best bet would be to contact a Mill/Factory or Joiners for information.

Russel Lee

Russel Lee

Good Day, is it possible to get a floorplan or plan layout for a wood manufacturing area? thanks!

Mark Donnison

Mark Donnison

Hi Fakhr, please contact our sales team via email, they will be happy to help you with your enquiry: sales@kitronik.co.uk

Vahid Khosroshahi

Vahid Khosroshahi

Dear sir/madam, Hello, Good day, This is Fakhr from Khosroshahi Trading. We are going to purchase raw mdf about 1050 cubic meter in these details: size:1220*2800*16 mm, E1 , +740 kg/m3 The port is BANDAR IMAM in CIF mode I would appreciate if you give me proforma with the unit and total price of 1050 cubic meter in DOLLAR and EURO. Im looking forward to hearing from you. I would be glad if you contact me via whats app: 0098 935 1867691 Best Regards, Khosroshahi Trading

Mark Donnison

Mark Donnison

Hi Grace, without being directly a part of the production process it is difficult to say. If you were to contact a mill I'm sure they could better answer your question.

Grace K

Grace K

Hi! Thank you for this info. What would you estimate the length of time from Forest to Quality Control is?

Mark Donnison

Mark Donnison

Hi, your best bet would be to speak directly to a mill as we are only a supplier. I hope this helps.

Zxen Loong

Zxen Loong

Hi, I have an asignment to do about current Plywood production management. Can you tell me about it ??

Mark Donnison

Mark Donnison

Hi Louis, thanks for getting in touch. Your best bet is to contact a Mill directly as we deal with distributors and not the Mills directly.

Louis

Louis

Hi, thank you for your enriching ideas. Am a forestry student specialised in wood transformation. Please can i have more details on the type of machines and or engines used along the production chain(from forest to delivery).Regards

Mark Donnison

Mark Donnison

Hi Debbie, there are a lot of things to consider which make it difficult to say with any certainty. Things like the type of fixings, the weights involved and the heat generated by the radiators etc. This probably isn't the advice you wanted but I would suggest consulting with a builder, just to be on the safe side. Sorry I couldn't be more help.

Debbie L Taylor

Debbie L Taylor

Hi i was wondering if you could help me if could you tell me if the Ply Boards could be used un painted,unstained just secured to the wall to hold up radiator brackets and a large radiator as my walls are plaster board and not very strong ? Or will i need to paint or stain also if the formaldehyde glue is safe for this purpose Thanks Debbie

Mark Donnison

Mark Donnison

Hi Aren, your best bet would be to contact a Mill directly. We don't have access to any further information than the info we posted as we deal with suppliers rather than mills.

Aren Brown

Aren Brown

Hi, I like the way you present your information. I'm doing a report on wood products and I would like to know if you can help me out, with little more in dept on the difference process? For example: (“Mills will use various methods to retain the moisture in the logs” ). What are the various methods exactly? I would really appreciate it very much. Thank You!

Mark Donnison

Mark Donnison

Hi Jean, it's certainly something we could look to doing but in the meantime the manufacturer datasheets contain a lot of good information of this type.

Jean Lariviere

Jean Lariviere

Hello, very good presentation. Good learning tool. Would it be possible to get a list of generic chemicals used during the process of plywood? Like low formaldehyde resin, anti-fungal products? Also, do some producers use surfactants or wetting agents to get better wetting of glue on layer of veneer. Regards Jean Lariviere

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