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Just started Veneering our substrate with Hardwood veneers and we are having troubles keeping the 9" wide by 80" long maple veneer from Curling up before pressing. As soon as we place the veneer on the glued substrate we start to see them curl up like a canoe.
Any ideas on why this is happening. Veneer to dry and as soon as we put it on the glue its taking in moisture?
Thanks ahead for any info.
You are using a water based glue so as the veneer takes on moister it cures like a potato chip!
Place the veneer on the core just before you put it into the press, no lingering. You could even place the top veneer on in the the press as ir seems you have a manual feed press.
Make sure there is no direct hear flowing on the layup table. (a winter issue).
FYI (not related) I have 125" guillotine F/S in the Machinery exchange; if you can use one it's good deal. Really need it out of here.
Are you applying a coat of adhesive to the veneer? Or just substrate?
Simple solution been doing this for years. Take a clean spray bottle, fill it with clean water, distilled water if you feel more comfortable, doesn't matter. Hold the spray bottle about 2 feet above the veneer and with a sweeping motion, lightly mist the veneer. Doesn't take alot just mist it. The veneer will start to lay down before your eyes, it works trust me. What you're doing is basically counter balancing the moisture the veneer takes on from the glue. Works with all raw veneer. Learned this trick back in '89 from a man that was considered at the time, and was, one of the smartest veneer guys in the entire world.
One additional note, I would cross band and re-calibrate those hardwood edged boards, you're going to have a telegraph issue if you don't. Okume works well.
With PVA, I only do what can I spread and get into the press within 10min or so. I spread the glue, lay the veneer and lay the cover sheet(s) - a single process with three steps. I use a few short bits of tape, pre-applied to the veneer and cover sheet(s), to keep things from sliding around (better perimeter bond). Curl is unavoidable, but easily handled with tape, cover sheets or stacking (I prefer not to do the later). I would never introduce extra moisture by spraying the face of the veneer w/ water.
What kind of glue are you using, it looks like water based contact cement (not a good choice)?
I agree, unless you need it that big for an edge profile, the banding is way too big.
I guess if you have the time to go through all those steps as Dave does it, give it a try. A very light mist of water does the trick, it's quick it works and doesn't hurt a thing.Pressed thousands of sheets this way. But everyone has their own technique, find what works for you and run with it. Good luck with your project
Thanks Guys for all the info, ill try a few things and get back to you with what works for me. I am applying glue to the substrate and not the veneer. I also need this wide banding for profiling.
Based on the picture you are taking too long to get them in the press. You've got 4 double sided panels glued and nothing is in the press yet.
Also no cauls to hold the veneer flat. My veneer curls if I lay in on a fresh glued surface and don't do anything to hold it down, even 1/4" mdf will do the job.
Doesn't seem like a veneer problem but more of a process problem, change the process and the problem will go away.