We often receive questions from customers when they want information or have problems with their laminated wood projects. These include panel-on-frame, veneer/solid core, or high-pressure lamination type of projects. We are going to discuss several issues that can arise, probable causes, and recommended solutions.
Uneven panels, plant temperatures, glue application, improper stock preparation, press time, and/or pressure can compromise the quality of the final laminated wood product. Here are the five most common problems, and what you can do to avoid them.
Cause #1 – Wood Stock is Uneven
Sometimes irregularities of an inner layer are transmitted to the surface, causing a spotty bond across the panel. The problem is often inconsistent stock thickness. Core thickness should not vary more than +\- 0.005 inches across the gluing area. Irregular glue spread can also cause spotty bonds and may indicate that your spreader roll is due for replacement or a re-groove. Also, if sanding the stock becomes necessary, use sandpaper with at least a 60 grit.
Cause #2 – Plant, Wood and/or Glue Too Cold
We receive many calls in the winter when customers seem to have seasonal issues. Materials that can not be stored inside, and are not given time to rise to indoor temperatures, can impact laminating quality. If your glue is "chalking" it's possible that the ambient temperature is lower than the recommended usage temperature - resulting in bright white squeeze out and a weak bond. As stated above, minimum temperatures guidelines include the laminating stock. Datasheets are your friend. Always read the adhesive data sheet before every project. Temperature is a significant factor in the success of your projects. So, for a proper cure, make sure the air, stock, and adhesive are all above the minimum recommended use temperature.
Cause #3 – Improper or Poor Adhesive Spread
Applying too much adhesive can cause problems with your project. Veneer laminations may warp pr have bleed through on the face. Not enough adhesive, on the other hand, can cause a pre-cure. A simple rule is to apply 30-45 pounds of adhesive per 1,000 square feet of glue line. You can verify that there is adequate coverage by looking for squeeze out as the panels are put under pressure. A mechanical glue spreader is going to be the best tool to achieve an even coating on the substrate. Use the Franklin Adhesives web-based spread calculator to help with your next project.
Cause #4 – Improper or Non-Contacting Substrates
For a proper bond, surface contact is a must, and pressure plays a vital role as well. However, the amount of force needed will vary from material to material and surface area. For high-pressure laminates 30-80 psi of pressure should be applied, solid core stock and all-veneer constructions should receive 110-150 psi and 100-250 psi respectively. Wood species is a significant factor in the varying degrees of pressure needed on all-veneer construction.
Cause #5 – Insufficient Press Time
Press times usually range from 30 minutes to two hours. How long you press your panels varies with the adhesive you use, the type of wood species, plant environmental conditions, and the moisture content of the stock. You can minimize the times through climate control in the plant and wood storage area. Keeping the moisture content of wood substrates between six and eight percent before and after pressing is recommended.
Choosing the Right Wood Glue
Franklin has a wide selection of glues for laminated wood. In addition to outstanding products, we have years of experience solving a wide variety of wood laminating problems. Call us at 303-515-2345 if you have any questions about wood glue issues and finding the right Franklin products for your application.