# MDF Warping



## ThePackagerRouterMan (Nov 29, 2016)

I am currently cutting some small furniture out of .750 thick, 4 X 8 sheets of MDF for a new customer. He has requested some detailed scroll engraving work that i am cutting with a 90 DEG V bit, which in itself isnt a problem. What i am having a problem with though is once i get a good portion of the engraving done the MDF board seems to start to warp in the corners. My vacuum table normally doesnt have a problem with holding down full sheets so I am thinking i am releasing some natural tension on the sheet itself. I am wondering if anyone else has had this problem before or do i have a bad sheet? Projects like this I have done in the past have never given me this problem before.


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## ThePackagerRouterMan (Nov 29, 2016)

as you can see they are curling up almost .375 off the table


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## 4DThinker (Feb 16, 2014)

Yes, you are releasing some skin tension, but more importantly you are exposing the core to higher or lower humidity which can swell or shrink respectively making the panel buckle or warp. 

I question the use of MDF for any kind of furniture frankly. Even the vinyl/paper wrapped crud sold at discount stores generally lives only a short life then ends up in a landfill. 

4D


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## ThePackagerRouterMan (Nov 29, 2016)

Unfortunately the use of MDF is per request of the customer so for now I am limited in other options, I have done very similar pieces to what I am cutting now they just didn't have near the amount of engraving.


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## Stick486 (Jan 4, 2013)

the engraving changed the surface tension of the MDF..
the curling is inevitable...


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## AndyL (Jun 3, 2011)

I wonder if the green MR-MDF, the moisture resistant type, would be any better. Supposedly it's more consistent through the thickness of the sheet, not so porous in the middle like regular MDF.


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## honesttjohn (Feb 17, 2015)

This is where corafoam would work fantastic - - if the customer was willing to pay the cost!


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## MEBCWD (Jan 14, 2012)

I agree that humidity probably played a big part in the panel warping along with released surface tension. The surface of MDF is burnished to the slick surface and humidity is usually absorbed and lost equally over the entire sheet. Some times the edges will show some swelling because of the raw edge. When you carved the surface you opened the interior core of the sheet and the new raw surfaces could absorb or loose moisture faster than the uncut surface.

Humidity around here has been a big problem this year, it could be 15% for 4 days and you sticker the wood for a project and everything is nice and flat. Then you start the job and while you are carving the job the humidity rises to around 94% and all the new cuts absorb the moisture and the board rises up in the center. Then starting the next day you have that 94% humidity and start cutting and the humidity drops back to around that 15% and your board starts curling up at the edges. After cutting everything is re stickered and it all flattens out again. The big problem with the boards warping while cutting is the depth of cuts over the board are not consistent. Most times this is not a great problem but depending on what you are carving and how prone it is to warping it could be a major problem. I do a lot of custom inlays in end grained cutting boards and that end grain absorbs and sheds moisture very quickly before it is oiled.


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## Quillman (Aug 16, 2010)

You're sucking out the moisture on the down side.
That is vac-hold down, right?
Do your carving on stickers; clamp the panel to the stickers.


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## subtleaccents (Nov 5, 2011)

I use quite a bit of MDF for signs used indoors. I clamp the MDF to the table. I prefer to use the Ultra Light MDF. It seems to stay flat even when we don't get to seal it right away. Sherwin Williams has a great sealer that I use before painting. Sher-Wood Vinyl Sealer 24% solids Clear Prod # T67 F3 520-3997

We use to use the green MDF under the solid surface counter tops. It is nasty stuff to cut so we try to stay away from it when ever possible.


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## ChiefRunningBull (Jul 29, 2021)

ThePackagerRouterMan said:


> I am currently cutting some small furniture out of .750 thick, 4 X 8 sheets of MDF for a new customer. He has requested some detailed scroll engraving work that i am cutting with a 90 DEG V bit, which in itself isnt a problem. What i am having a problem with though is once i get a good portion of the engraving done the MDF board seems to start to warp in the corners. My vacuum table normally doesnt have a problem with holding down full sheets so I am thinking i am releasing some natural tension on the sheet itself. I am wondering if anyone else has had this problem before or do i have a bad sheet? Projects like this I have done in the past have never given me this problem before.


MDF has a clear coat on each side. When you cut into one side it will curl that side as the clear coate underneath isn't penetrated, that will be stronger and the side you cut into will warp. To stop this there is a number of things to do. First, skim both sides of the MDF by 0.3mm this will take away the coating and stop it from wanting to curl. Second thing, keep a fan blowing on the MDF to keep it ventilated. 3rd thing you can do is put masking tape around the edge of the sheet, this will help, when it wants to lift it will help the vaccum by sealing the edges and keeping it held down to the bed. When the job is finished it will want to pop up though, but it will help to keep the MDF flat while routing to keep consistent depth.
Cheers


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## jw2170 (Jan 24, 2008)

WElcome to the forum @ChiefRunningBull


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## Cocowboy (Aug 16, 2021)

The MDF manufacturing process compresses the little particles with higher density and hardness near the surface. Relax one of these and you get warp. One solution is to laminate thinner MDF sheets. I have used this approach successfully for molds and pattern makiing.


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## Cocowboy (Aug 16, 2021)

Really, all materials suffer from movement. Wood and wood products maybe more so. This fact was recognized centuries ago and many approaches have been used to help minimize the consequences.

You could experiment with a wood breadboard and an MDF breadboard, for example. An MDF "breadboard" might be glued to the moving part while clamping them to a flat reference surface like a flattened workbench.


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## old55 (Aug 11, 2013)

Welcome to the forum @ChiefRunningBull


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