Using a CNC Vacuum for a Glue Press

      You can use a CNC vacuum for laminate and veneer glue-ups or for laminating plywood sheets together. February 15, 2009

5x5 baltic birch is becoming harder to get in my area. What is the best way to laminate two sheets together and make sure the middle is secure. Clamping the outside is easy but the middle is what I'm worried about. We can get 5x5 in 1/2 and 1/4" but we need 3/4". Is there anyone who knows of a supplier in the southeast? Both of my suppliers say it will be a problem until the end of the year.

Forum Responses
(Laminate and Solid Surfacing Forum)
From contributor T:
A vacuum press would do it, but why not just switch to another product?

From the original questioner:
I need 5'x5' sheets. They are for round tables which get stained and finished. I would buy 5x10 if it were available from one of my suppliers. Do you have another product in mind that I could use? How much would it cost to set up a vacuum press? I have a vacuum pump on my CNC table that I might be able to use.

From contributor E:
If you have a vacuum table on your CNC, then you don't need anything else. You need some room around the edges of the part to seal down the plastic, so hopefully your table is a little bigger than the biggest part.

Lay your sheets on the table and cover them with a sheet of visqueen (heavy plastic film), hanging past the part 4-6 inches all around. Turn on your vacuum and it should suck down with adequate force. You might need to put a layer of fiberglass window screening between the part and the plastic for airflow. You can use a couple of pin nails or micro pins to keep things from sliding around, if you're sure you won't hit them later.

Sometimes I use duct tape or 2" blue painters tape around the edges if there is a leak. Depending on the size of your pump, there is a lot you can do with this. We have also put a petcock in the vacuum line to use with a smaller hose for other applications.

From the original questioner:
Yes the table has a 6x10 cutting area so this should work out just fine. How long should I leave the vacuum on, the set time it gives on the jug?

From contributor E:
Use the set time as a guide. I usually like to let things set in clamps for 3-4 hours minimum, depending on temperature and other factors. When using plastic bags and vacuum, there can be other variables like flow through on the table. You have to experiment and use your experience to determine the proper amount of glue, because you don't want too much squeeze out that will not dry under the plastic and make a mess, or too little that will not bond well. I have found that a medium nap paint roller will give good coverage when used on both sides of pieces. Play around with a few smaller pieces first, and you will start to find a lot of uses for your vacuum table - this also works well for curved work, where you have made the patterns on the machine.

Another thing you could try is to cut both circles out on the machine and drill locating holes for 1/4" dowel pins in the blanks; three pins would line up the two parts perfectly- apply glue and clamp. You would just have to determine whether you can make this work in the thicknesses you are using.

From the original questioner:
I can't wait to try it out. I'll take your advice and experiment with some smaller items and glue amount. I use mostly tightbond on ply, should I use something different? I have had good results with this type in the past.

From contributor E:
Titebond makes a cold-press veneer glue. It is just a slower setting glue with extended open time for when you are gluing up large areas. I have had good luck with it, and appreciate the extra set-up time it provides.

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