Quality Control for Veneered MDF Panels with Solid Wood Edgebanding

      Here's a complicated discussion about whether veneered MDF panels require multiple plies of veneer, and whether or not they must be laid up oversized and then trimmed to fit. October 15, 2012

Question
Our veneer pressing company advises that for 6mm (1/4") solid wood edgebanded panels we must first apply an oversized edge to each panel in order that it can be trimmed after the veneer is applied. Can we not get the same precision with CNC'd panels which are then edgebanded with a machine that can apply 1/4" solid wood edging?

Also, they say the veneer must be applied in two layers (the first 90 degrees to the other) in order to increase the stability of the veneer as the two different substrates move differently. Even so there is the rare possibility that the edgeband could telegraph through (which nothing can be done about) and the veneer sometimes delaminates along the solid wood edges later (which is dealt with by our shop gluing and clamping according to the veneer company's instructions). Is this advice correct? Money is not the issue, quality and not doing unnecessary steps is.

Forum Responses
(Cabinetmaking Forum)
From contributor D:
I do not know the use for these panels, so I hope I am not out of line. I don't know of a feed-through edgebander that will apply edges to material that thin. That leans me toward your component supplier's method.

If the banding is internal, then the crossband, or two plied veneer face is the correct method. He is also correct about the solid wood banding telegraphing through. Delamination along the edges is another concern. The success rate for repairing these is fair, at best.

My concern is the thickness. You would have to start off with 3/8" material, glue on the solid edges, and plane down somewhere 1/8" to compensate for the veneer face thicknesses. I would think the panels would warp or bow like crazy.



From the original questioner:
I forgot to provide some info. These are 3/4" thick MDF CNC'd blanks that we are using for drawer and door panels, edgebanding with 3/4" hardwood, pressing first a C-grade American black walnut veneer onto both sides to balance the veneer (or a synthetic backer like Polybak BP42), then pressing an A-grade ABW veneer onto both sides at a 90 degree angle to the first veneer, then trimming the hardwood edges down to 1/4", then easing the edges by hand and finishing with a clear coat finish. We are not using a pre-made 2-ply cross-back veneer because we are hand-picking the ABW veneer from a single log and very carefully sequence matching and numbering (SMN'd) the panels to achieve the desired look.


From contributor D:
Upon reading your response, I see that I completely misread your post. I was reading that the panel thickness was 1/4" thick. I think you are going down the right path as far as the how to make these panels. It will be a much cleaner look to the door/drawers. With the edgebanding externally applied, I think it would be hard to get the color uniform.


From contributor O:
I would not say that the advice you have received is incorrect, but I would say that I disagree. First, the issue of whether you have to oversize the edgebanding. I have heard of other companies doing this. We do not. The only reason to do this is because of how the trimming is done. They want to be able to saw cut the panel after pressing, so they need to have enough solid material on there to do that.

Veneer faces can also be trimmed with router- or shaper-type machines (we have specialized machines for this) after pressing, in which case you do not need to put on an oversized edgeband before pressing. If your vendor is trimming with a saw, are they sanding the edges? I have heard of people receiving panels that need a lot of handwork to remove kerf marks - look before you leap.

Next; the need to crossband over an internally-banded panel. If you only have 1/4" wide banding, I would think crossbanding would not be necessary in most cases. Is there a possibility of telegraphing? Yes, but we have veneered many square miles of panels over many years with edgebands that wide without telegraphing issues. With wider bands (1/2"+) I would start to be concerned, or in horizontal applications with high-gloss finishes. I would not be concerned for your application.

However, this is also related to flushness tolerances. Hearing that there is some concern (or has it already happened?) with veneer delaminating at the edgebanding makes me wonder if there are tolerance issues. We have also never had delamination at edgebands, but we hold extremely tight tolerances for flushness. I would think it would be more of a problem where an oversized edgeband is being applied to allow for saw trimming. I can't imagine telling a customer that they should be prepared to repair panels that are shipped faulty. All of this is just another opinion, albeit from someone who does veneer pressing full-time.



From the original questioner:
It was actually the veneer pressing company that informed us that telegraphing was possible on a 1/4" solid edgeband. I pressed them on this issue (no pun intended) as to why this would happen and how to avoid it and they stressed that calibration sanding helped to avoid it but stopped short of saying the chances were almost nil. They said that telegraphing is possible and has happened in the past. They were also the ones suggesting that we oversize the edgeband by 1/2". I talked to some designers about this and they suggested that the veneer pressing company was only approaching it in this manner because of the guarantee they have to provide on the workmanship, but I have no desire to do extra steps that are not required.

I have talked to people who have edgebanded 1/4" solid wood onto MDF and wrapped the surface with only one layer of veneer with no issues at all, so I am obviously a bit confused about all of this and the differing views I am hearing. Maybe the next veneer should be very thick. I don't think, though, that not crossbanding is something I am prepared to attempt in this situation. The panels will be coming back to us for trimming off the extra 1/2".



From contributor O:
Sure, telegraphing of a 1/4" edgeband is possible. It's also possible to win the Tri-State Lottery, but extremely unlikely. For what it's worth, it's also possible to have telegraphing with a crossband. Also, this is dimensionally-stable wood correct?

It strikes me that unnecessary complexity has been added here and when you add complexity you add cost and more importantly increased risk of problems, not decreased risk of problems. I see absolutely no reason why you should not be able to order panels made to net size with a 1/4" edgeband and one layer of standard-thickness (0.5-0.6 mm)face veneer and get perfect results, unless there is some issue with tolerance, or they are oversanding the faces.



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