Mdf that has warped. How to make it straight?

Suhagg · 4 Oct 2012 at 7:41 AM

Bought a couple of 32mm MDF boards. Straight and nice directly from the lumberyard. Took them home and brought them into the house right away. Now when I stand them up, I see they've warped about 1-2 cm in the middle. 1200x2400. Will I be able to fix this? I'm planning to use them as sliding doors indoors.

MB77 · 4 Oct 2012 at 8:41 AM

I think it will be difficult to get them in order. They might be quite okay if they hang for a while, but they probably won't be completely flat.
All sheet material should always lie flat or hang.

Suhagg · 4 Oct 2012 at 9:07 AM

MB77 said:
I think it will be difficult to get them in order. It might be that they become quite good if they hang for a while, but they will probably not be completely flat.
All sheet material should always lie flat or hang.

They lay flat in a bundle of 8. Dry and good at the builder's merchant, then directly home to me.
Cut and hung up and immediately it was visible that they had warped.

vagabondo · 4 Oct 2012 at 2:25 PM

when you paint them, it will probably get better, try painting one side (the convex) and you'll see if it straightens out. discovered this when I put wallpaper on a cabinet door about 2m*60cm in mdf - it was unbelievable how much the door bent towards the side where the wallpaper was. had to put wallpaper on the other side too and it became completely flat.

Suhagg · 4 Oct 2012 at 2:54 PM

vagabondo said:
when you paint them it will probably get better, try painting one side (the convex one) and see if it straightens out. I discovered this when I put wallpaper on a roughly 2m*60cm cabinet door made of mdf - it was absolutely insane how much the door bent towards the side where the wallpaper was. I had to put wallpaper on the other side too and it became completely flat.

It sounds fun but I will try. I know how things can warp when they dry or get wet.

MB77 · 4 Oct 2012 at 3:52 PM

The problem with painting slightly larger MDF boards is that they need to be painted on both sides simultaneously, which is not entirely easy.
How big will your sliding doors be? To avoid warping in the future, a frame all around is preferable.

Suhagg · 4 Oct 2012 at 4:26 PM

MB77 said:
The problem with painting slightly larger MDF boards is that they need to be painted on both sides at the same time, which is not entirely easy.
How large will your sliding doors be? To avoid warping in the future, a frame around is preferable.

They are about 950x2300cm
The question is how would a frame around look?
Flat iron around the edges?

MB77 · 4 Oct 2012 at 6:02 PM

Suhagg said:
They are about 950x2300cm
The question is what a frame around would look like?
Flat iron around the edges?

Yes, that might work, the question is just whether it will look nice. Otherwise, wood is probably preferable, I know I've seen someone here on the forum who made sliding doors for a wardrobe, I believe.

MB77 · 4 Oct 2012 at 6:04 PM

Edit: here is the link to the ones I meant.

http://www.byggahus.se/forum/mobels...era-fardiga-verk-till-allman-beskadan-20.html

Alfredo · 4 Oct 2012 at 6:06 PM

Suhagg said:
Flat bar around the edges?

Some form of aluminum profile maybe?

Suhagg · 4 Nov 2012 at 5:13 PM

Any more tips or should it be to paint the side that bulges out first?
A profile around the door would be difficult to achieve unfortunately.

So the side where the number 3 is

Suhagg · 14 Jan 2013 at 8:22 AM

The test with flat iron makes it a little better but not completely good.
I have tried laying the MDF flat on the floor. They then become almost completely straight.
I then screw on 8mm thick flat iron on the long sides. The MDF lifts up and then it's about 5mm crooked in the middle again

It actually bends 8mm thick flat iron.
Now the next test is 10mm thick flat iron and then "over-bend" the door a little. That is, have it on a flat floor but let it be bent a little extra in the opposite direction it wants to bend when I stand the door up.

MB77 · 14 Jan 2013 at 8:41 AM

I don't think it helps to go with 10mm, unfortunately. For it to work, a T-profile that reinforces it is necessary, but if the profile is removed, there's a big risk it will revert.

An L-profile might work as well.

prototypen · 14 Jan 2013 at 9:02 AM

Wipe the disc on the convex side, place it facing up or against a radiator.
If it has been in a stack, the outer side becomes more humid or drier and it inevitably warps.

When it is straight, let it stand upright and paint while it is straight.

Protte

Suhagg · 14 Jan 2013 at 12:14 PM

MB77
Unfortunately, I can't use an L-profile as it will then be thicker than 30mm.

prototypen
The strange thing is that at this point they should be dry.
Hung indoors in a house for 2 months in the warmth.

I don't believe in painting either because how will the paint know exactly where I want the door to bend, so to speak?
Is it always striving for the panel to be completely straight?