Tuesday, July 17, 2012

Veneer - glue up and vacuum pressing process

I prepared the veneer skin by seaming the veneer with veneer tape. The side you see with the tape is the show side and the other side is the glue side. This particular glue up is destined to be the balancing veneer on the floor of my entertainment center. In other words, it will be on the bottom of the cabinet facing the floor, so all pressure is off to get this perfect!
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Cauls are prepared for both sides of the veneer. I use 3/4 inch MDF that I’ve pre covered with plastic to ensure that I don’t glue the panel to the caul.
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I’ll spread the glue with a paint roller. I’ve found these black rollers work very well.
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Gloves and blue tape need to be on hand.L1030373-2012-07-15-19-46.JPG

The glue is a two part glue consisting of a resin and a hardener mixed in a ratio of 4:1.L1030376-2012-07-15-19-46.JPG

I mix is slowly adding a little of the powdered hardener at a time, then stirring until it has been incorporated into the resin.
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Here is the glue mixed and ready to spread. It has the consistency of thick syrup.L1030378-2012-07-15-19-46.JPG

I pour some on the MDF panel that is the substrate for the veneer skin I’m applying.
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The paint roller is used to spread a thin coat of the glue evenly on the substrate.
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I carefully lay the veneer skin on the substrate with the glue face facing the glue. This may seem inherently obvious, but it is very easy to make a fatal mistake at this point (which I know from experience!)

I use clear packing tape in a few places around the substrate to fix the veneer skin to the substrate so it will not move as the vacuum press starts to apply pressure.
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I place the top caul over the panel and very carefully align it so the substrate is completely covered. I size the cauls so I end up with about a 1/4 inch overhang.
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I use blue tape to bind the sandwich together. The idea is to tape the entire assembly so it will not move as the vacuum press begins to apply pressure.
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The assembly is very heavy, so I’ve devised a very simple system so I can do this by myself. I’ve built the veneer sandwich on a movable cart that is slightly higher than my vacuum press. I can position the assembly in front of the press and carefully load it into the bag.
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I seal the bag and turn on the vacuum.L1030389-2012-07-17-08-46.JPG

Once the vacuum has removed all the air inside the bag, the pressing is underway with about 1400 pounds per square foot of pressure on the sandwich.
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After the glue has cured (how long this takes depends upon the temperature, but it takes a minimum of four hours) I remove the panel from the press. Now I must remove the veneer tape. I do this using a sponge to soak the veneer tape with water to reactivate the glue. Then it is a simple matter of carefully easing the tape off the panel.
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