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Why We Don’t Use Glue Pots on Our Veneer Splicers

It’s the silver bullet of veneer splicing: an all-in-one splicer that doesn’t require a separate glue area. Although the idea sounds great, we decided not to add a glue pot on our splicer. We admit it wouldn’t be hard to add one. So why don’t we offer it?

Glue Pot Research

Prior to introducing our splicer, we had a good deal of experience servicing machines with glue pots. We also talked with people around the world who run these machines to gather their thoughts. Those we interviewed formed two distinct groups.

The first group simply could not make glue pots work and returned to applying glue outside the machine. The second group did use a glue pot but with limitations: they changed the glue religiously every 30 minutes or so before it started to dry in the pot, or they only mixed a small batch, which they used up before it started to dry. If you only needed to splice 15 to 30 minutes per day, you also would find a way to make the pots work for you.

But why don’t glue pots work? For that answer, we talked to glue suppliers.

UF glue is the only glue that can be used with a longitudinal splicer. The glue powder is mixed with water so it can be spread evenly on the edge of the veneer and penetrate the edges. The water acts as a carrier for the glue only. UF glue is a thermoset glue; that is, it requires reaching a certain heat level to completely cure and set. For the thermoset action to occur, the water must be completely removed from the process first. It must either be evaporated off or cooked off.

In our system, we apply the glue in a separate step prior to splicing so that the glue has the maximum amount of time to penetrate the fibers before the water is evaporated. Then when the veneer enters the splicing heating area, the heat is being used 100% for the purpose of setting the glue.

In a system with a glue pot which applies the glue just ahead of the splicing heating area, the glue has no time to penetrate the fibers to strengthen the joint. It is applied and boiled until dry. In a system with glue pots, the glue enters the heating area with all the water still in the mixture of glue. As we said before, the water must be removed before the thermoset glue can work. This means the first part of the heating area is being used to cook the water from the glue. Therefore, the machine is losing splicing efficiency since the first section of the heating portion is actually used to dry the glue, not to splice the veneer. You must run the machine slower, so that the remaining area of the heaters has enough time to set the glue.

It’s no wonder then that glue suppliers receive more complaints about gluing quality when manufacturers use glue pots: their customers demand a different glue mixture that works better for the pots, and they complain about glue getting “all over my machine.” Suppliers have at times lost business to other glue suppliers who have claimed to have developed a “special mixture” for the glue pots, though these competitors cannot say what is special about it.

Glue Pot Production Issues

This process of drying the glue (removing the water) creates steam that is vented into the machine. This steam can distort the veneer edges, reducing the quality of the glue line and sometimes even causing buckle.

This steam that is vented escapes around the heater plates and enters moving parts of the machine, such as the chains and bearings. It carries with it some amount of suspended glue, which then dries and begins to coat the splicer parts. Although the amount is small enough to be barely visible, it is there and it accumulates.

You know how hard this glue dries. Now imagine what that hard glue can do to moving parts. Consider this: suppose you mix enough glue to require one gallon of water per shift. That water is now being removed by your splicer because you are not allowing it to evaporate before splicing. It’s as if you’re taking a spray bottle of water, mixing in a little glue, opening the side cover of the machine, and spraying away until the bottle empties, refilling, and spraying again until you have covered the machine with a gallon of water and glue.

Of course, you would never consider doing such a foolish thing, and no manufacturer would suggest you do that (unless he wants to sell you more parts).

Production Losses

For those who are determined to make the glue pots work, you are a singularly strong group to whom I take my hat off because I know how hard you are working. You stop the machine about every 30 minutes, throw away the remaining glue in the pots, clean the pots and the applicators, mix new glue, and start over.

But you lose at least 10 minutes every half hour for this process. That’s a third of your production time. Plus, you have to endure the double or triple amount of wear and repair on your machine.

Now really, what do you save by not having a separate glue area?

In this case there simply is NO SILVER BULLET. If you want the highest quality joints, the proper amount of glue application, the lowest glue usage, the fastest splicing speeds, the most production, the lowest maintenance, and no time spent cleaning glue from your splicer, you must apply the glue prior to splicing and let it dry.


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