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Interior door veneer splitting3/16
We are having some issues this winter with some hardwood door veneers splitting on site. We lay 1/8" Eastern White Maple over a 32lb particle board core. All my material is sitting @ about 9% moisture in my BC warehouse. We are shipping finished doors to cold dry Alberta with strict handling instructions to ensure they don't dry out to fast. Obviously I can't control what they do on there end much. I had 1 customer measure their moisture @4.5%. Is there anything we can do to avoid these issues in the dead of winter with these 2 different climates? Somehow slowly lower our moisture content. Obviously not shipping for 2 months isn't an option. Glue is not failing as the veneer is actually pulling the core material apart as it shrinks.
Since it's radiating from the hole in the particle board, I'd say the core of the particle board is wetter than the surface.
You are making the case for 'locally produced millwork" and not shipping long distances or into areas that vary much from the area the doors were produced.
I saw the subject arise and be dissected at a tooling conference where some white pine 6 panel door guys were having problems with their Oklahoma assembled doors made with rails/stiles from Northern CA and panels from Iowa. They could not understand why they had problems.
You might check to see what 4.5% MC means for EMC and Relative Humidity. I suspect it is not even healthy for humans.
I see you have a panel shrinkage issue as well. I had no idea you could get a home humidity so low the wood got to 4.5% The occupants must have skin cracking and falling off!
What if you were to reduce the thickness of the maple and add a cross-band veneer. Sorry if I sound like an idiot if this can't be practicality done for production.
I had to fly to Alaska a few years ago because a cabinet door package that we made in WA state ended up in the ultra-low (unconditioned) indoor humidity of AK in December/January. I took along a few select pages of "Understanding Wood" and a humidity gauge to show them why the doors were shrinking and splitting. We ended up replacing about 1/3 of the doors at no cost with the understanding that a humidification unit would be added to their central heat. Originally, we had no idea where this job was shipping, since we only do the doors. I kept our solid cabinet shop relationship intact, but said no warranty ever on any job going to unconditioned space.
Is your maple plain sawn? If so, go to quarter sawn as it has half the seasonal movement of plain sawn. I don't know what the seasonal movement is for particle board, but MDF is around 3%. Sugar maple shrinks 9.9% for plain sawn and 4.8% for QS from green to oven dry. Of course, you aren't starting with green wood, but it's clear QS is the way to go. If you already are using QS then something is really strange. What glue are you using between the veneer and core?
There appears to be some confusion about what I meant by MDF having a 3% shrinkage. You have to use that value with the formula in Hoadley's book "Understanding Wood", page 140 in my edition. If your door stile was 5" wide and the moisture content in it changed from 8% to 4.5% MDF would shrink:
5 x 0.03 (which is 3%) x (0.08 - 0.045/0.28) = 0.0188"
Plain sawn hard maple with a shrinkage of 9.9% would shrink 0.062", which is 0.043" more than the core. If you used QS hard maple, the difference would only be 0.011"
As I said before, I don't know what the shrinkage/expansion of particle board is, but if it's similar to MDF it could explain the problem the OP is having if he is using plain sawn hard maple with a very rigid glue.