Dishwasher Panel and Warpage

[John T.]

Hi everyone, could use some quick advice. I'm making a dishwasher panel to match existing shaker style cabinet doors. The rail and stiles are poplar. The handle will be attached to the inset panel, so I'm using 1/2" baltic birch for rigidity (also need to meet the panel weight range).

The issue is the panel, which I haven't cut the rabbets on yet, has some warpage, about 1/8" or 3/16". I had it clamped down to the MFT in the hopes that moisture will even out. I clamped it to my table saw today after I realized the MFT isn't very flat and I'll double check the flatness tomorrow. This is my first time making a shaker cabinet door, but I'd assume normally when you're using 1/4" inset panels they conform to the flatness of the groove in the frame.

I need to call Bosch tomorrow and ask them if they have an actual spec for warpage for the panel, the instructions just says no warpage. Maybe some moisture-resistant marine grade MDF would have been a better material to use.

Edit: clarified inset panel is 1/2" baltic birch ply

 

[tjbnwi]

MRMDF is the answer, it finishes well and will stay stable. Change the rails and stiles to hard maple.

Do not exceed the maximum height, wont be able to open the door is you do.

The warpage is zero as the specs state.

We also apply clear bra to the back of the dishwasher panels to help protect them from moisture.

Tom

 

[John T.]

Thanks Tom, I'll look to see where I can source that MDF from. Why do you say maple instead of poplar for the rails and stiles, is it for more strength or stability?

By clear bra do you mean 3M automotive protective film? And you use that even when the panel is going to be primed and painted?

 

[tjbnwi]

We use hard maple for all of our face frame and radio and stile pieces. It is more stabile and finishes better than poplar.

Yes, the 3M protective film. If the directions for drying are followed once the wash cycle is over the door is to be partially opened, this runs a lot of moisture across the upper edge of the door.

Tom

 

[smorgasbord]

Clamping sheet goods to something flat isn't going to make those sheet goods flat. That said, as @tjbnwi says, the moisture coming out of the dishwasher when opened is considerable (and very warm if not actually hot), so you're going to have some short-term moisture content imbalance. My Fisker-Paykel dishwasher came with a piece of film to be applied to the back side of a wood front panel. They recommend doing that no matter how the wood panel is finished, but I suspect they're partially/mostly covering their bases/arses.

Note the moisture is short-lived, so I believe that the film or even a really good protective finish can slow down moisture absorption by the panel enough that actual wood movement due to that moisture can be minimized. Still, I wouldn't want to start with a warped panel. The only way I know to flatten a panel is to change the balance of moisture on each side of the panel. A sheet good panel may cup away from the wet side - use that info to try to change the panel flatness. Maybe.

 

[John T.]

Right, I wasn't too confident clamping it would help, but I was hoping it was warped due to moisture imbalance and keeping it clamped while it equalized would help.

I found some some outdoor MR MDF (Armorite) available locally so I'm going to pick that up for the inset panel and will report back on how it turns out.