Cabinet building - warping due to humidity

[Kodi Crescent]

I'm making a second attempt at building some frameless cabinets for a home office.  My first attempt used 18mm Baltic Birch from a local "open air", but covered lumberyard.  After building the carcasses, I could not get them fully squared, as the bit of warp pulled things the gables out of square.  Trying to install them was a nightmare, so I gave up and decided to try again.

This time I used 3/4" MDF faced Garnica from a local supplier that stored the sheets in a temperature controlled warehouse.  The sheets were nice and flat when I broke them down.  Now having spent some time in the humidity of my garage, they have a bit of warp to them - in some cases worse than previously.

I'm assuming there is no way to really prevent the humidity warping in a practical shop application unless the shop has an HVAC system.  How do those of you in high humidity areas deal with the warp and continue with the build?

 

[waho6o9]

3/4" backs help.

Good luck now.

 

[Kodi Crescent]

It turns out that most pieces weren't as bad as I thought.  It appears I can wrangle the panels fairly straight by applying trim during assembly.  I learned a lesson about gang clamping stock flat for storage and to not panic after inspecting just a single piece.

 

[kevinculle]

If you know there are large humidity differences between where the sheets previously lived and your shop it helps to give some time to acclimate before cutting the sheet into cabinet parts.

 

[Sparktrician]

It turns out that most pieces weren't as bad as I thought.  It appears I can wrangle the panels fairly straight by applying trim during assembly.  I learned a lesson about gang clamping stock flat for storage and to not panic after inspecting just a single piece.

Yup.  Gang clamping the sheets with cauls is one way you can do it.  Another is to order only what you can use in the next 24-48 hours and cut it immediately upon arrival.  [smile]

 

[James Biddle]

Using construction methods like dados' rabbits, dowels and such will help straighten parts during assembly.  But, quality materials reign supreme.

 

[Kodi Crescent]

I ended up reviewing my panels for straightness, labeled them, and used the straightest ones for the gables.  The more warped ones were reserved for the tops and bottoms.  These panels were shorter so that the warping was less pronounced.

I oriented the warps inwards, and then clamped and dominoed on a 2" trim "backer" to the tops, bottoms, and wall-mating sides to pull things back into alignment.  I used dadoes for my joints, and then glued and screwed things together.

Cabinets that butt against each other will have the gables clamped and screwed together to pull those warps out.

I've been checking the diagonals all along, and they seem to match (?).  There's maybe is a 1mm difference between diagonals on a 960mm x 560mm cabinet opening.  I'm assuming this is close enough for frameless construction, especially since these are going into my house.

I learned a lesson though - gang clamp panels flat early! (and save painting for after assembly, at least for me.)

 

[lwoirhaye]

For frameless, inset doors are the least forgiving. 1mm out is pretty darn square though.  There may be bowing of the panels so the distance between the sides of the cabinet at the center is lesser or greater than at the top or bottom.  Perfection is an unattainable ideal but with melamine panels and some large equipment like a carcase clamp remarkably consistent boxes can be turned out by large shops.  It's hard to compete with that level of industrialized precision, but with attention to detail one can get pretty close.  And the next time around you'll know better what sorts of problems to anticipate.

I sometimes stack and sticker sheet goods panels to let the air circulate when I'm not working on them.  As soon as is reasonable after cutting out the parts I like to assemble because assembled structures reduce movement.  It's particularly important when making solid wood furniture.

 

[Kodi Crescent]

I'm not making any inset door cabinets yet.  A bit beyond my skill level at the moment.  Overlay doors for now.

I have some carcasses that are off by about 2 or 3 mm on the diagonals, but they won't get doors.  I get upset at myself for that, but I'm learning to recognize and calm my neuroses when they appear and to stop beating myself up.