Production laminating -- is hot or cold press faster?
I had a salesman in the other day and he was telling me about a new white glue guys are using, all they are doing is applying the glue with a spreader and then pinch rolling the sheets? Sounds kind of iffy to me.
It is important to know the substrate and overlay material. HPL works well in a pinch roller, veneer does not.
The way I see shops work the pressing problem is like this:
Hot presses work on pressure and heat. The heat makes the glue work faster, so the press time is shorter. One panel at a time, press 3 to 5 minutes, and let set for 4 to 6 hours; then it's ready to use.
Cold presses works on pressure. The cold press is meant to get maximum pressure for a short period of time on a maximum amount of material. You can press 10 to 20 pieces of material at a time, for approximately 20 minuntes, then let set for 6 to 8 hours and the material is ready to use.
New glues are coming out all the time to help speed up this process. If you take your questions to the Adhesives Forum on this website I am sure Jeff can help you with.
The pressing you choose to do depends on a lot of factors. These include the application process, glue line requirements and material being glued.
When gluing veneer, the best possible bond is achieved with a hot press. Millions of board feet of plywood are produced this way every day. HPL, on the other hand, can be successfully glued with contact cement or PVA (white glue) using a pinch roller. Far from being a new method, it's actually been done for years by many skilled lay-up persons.
I will speak from experience and say that yes, PVA glue and a pinch roller works like a charm; we've been doing it for about six months.
We probably lay up 25-30 sheets per project, and it takes two guys about an hour to lay-up, and another hour to dry. We use Wilsonart 3000 PVA glue and apply it with two, 10-inch paint rollers. The laminate will not un-adhere from the substate, in fact that has been somewhat of a minor problem for us; sometimes when we ran short on material our guys would strip laminate off scraps of pre-layed sheets. They can't take it off with PVA glue once it's dry.
We have had a slight problem doing paper-backed veneers with PVA. It tends to pucker at the ends of the sheet. It's not really a concern to me, because veneer is a very small percentage of what we do.
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