you can see on the picture shadow/pencil like lines and outside outlining of the blanket
MDF and heat
Moderators: Head Monkey, kelvin, bigKam, skidesmond, chrismp
-
MadRussian
- Posts: 712
- Joined: Thu Sep 30, 2010 12:32 pm
- Location: USA
MDF and heat
yesterday heat up my blanket first time. One cycle only for 10 min. total brought it up to 180°F no pressure . When this morning went to move the blanket over and what I discovered MDF tabletop practically melted under the blanket not a lot maybe quarter of millimeter or less, little deeper on the outside edge and under wires. Right below resistance wire MDF went dark gray. It was like imprint of resistance wires. I read people have problems with MDF under heat but didn't expect this much damage in 10 min. I had to use sender to smooth out MDF because I could feel the wave
you can see on the picture shadow/pencil like lines and outside outlining of the blanket
you can see on the picture shadow/pencil like lines and outside outlining of the blanket
I have not failed. I've just found 10,000 ways that won't work.
Thomas A. Edison
Thomas A. Edison
-
MontuckyMadman
- Posts: 2395
- Joined: Fri Jun 20, 2008 9:41 pm
-
MadRussian
- Posts: 712
- Joined: Thu Sep 30, 2010 12:32 pm
- Location: USA
yes humidity high past couple days. In the summer we get 80 to 90% humidity all the time here in New England.MontuckyMadman wrote:you must be in a very humid climate i would assume.
what to do now? why humidity affecting MDF that much?
I have not failed. I've just found 10,000 ways that won't work.
Thomas A. Edison
Thomas A. Edison
-
MontuckyMadman
- Posts: 2395
- Joined: Fri Jun 20, 2008 9:41 pm
-
MadRussian
- Posts: 712
- Joined: Thu Sep 30, 2010 12:32 pm
- Location: USA
the humidifier is good idea but not practical for now in my shop.MontuckyMadman wrote:because mdf is pretty much a wood pulp sponge.
Dehumidifier?
Or move west.
I wouldn't worry about it under pressure.
would be nice. Unfortunately not happening.
I'm not worried because minimal amount of MDF in my press.
To me damage looks like adhesive, MDF made with, got soften up.
Why not to worry about under pressure? To my understanding with heat under pressure MDF might deformed even more maybe evenly or unpredictable but more.
I have not failed. I've just found 10,000 ways that won't work.
Thomas A. Edison
Thomas A. Edison
MDF is most tolerant of heat and pressure when it is cut into strips and vertically laminated. This approach minimises the amount of direct contact between the adhesive and the heat blanket. I'm guessing the inner sections of the boards must act like a heat sink ... to a certain degree. This method appears stable upto 80oC ... here in the UK, where humity is not such a factor. Obviously not all MDF is made to the same quality ... so local conditions rule.
If you want to push past that temp ... face laminated MDF with a thin piece of plywood - 3mm or if you are feeling brave, hardboard. I believe hardboard is subject to a great deal of pressure during manufacture. I use hardboard within my press, I've seen no issues and it has outlasted the original MDF mold.
If you want to push past that temp ... face laminated MDF with a thin piece of plywood - 3mm or if you are feeling brave, hardboard. I believe hardboard is subject to a great deal of pressure during manufacture. I use hardboard within my press, I've seen no issues and it has outlasted the original MDF mold.
-
MadRussian
- Posts: 712
- Joined: Thu Sep 30, 2010 12:32 pm
- Location: USA
whatever local Home Depot have that's what I got for MDF. I'm sure MDF in Home Depot is low quality.Richuk wrote:MDF is most tolerant of heat and pressure when it is cut into strips and vertically laminated. This approach minimises the amount of direct contact between the adhesive and the heat blanket. I'm guessing the inner sections of the boards must act like a heat sink ... to a certain degree. This method appears stable upto 80oC ... here in the UK, where humity is not such a factor. Obviously not all MDF is made to the same quality ... so local conditions rule.
If you want to push past that temp ... face laminated MDF with a thin piece of plywood - 3mm or if you are feeling brave, hardboard. I believe hardboard is subject to a great deal of pressure during manufacture. I use hardboard within my press, I've seen no issues and it has outlasted the original MDF mold.
In my mold, only tips and tales part made of MDF rest metal. Plus I going to use some insulation to minimize heat loss and heat effect to MDF.
In the future I'm planning not to use MDF at all to make mold or any wood products for that matter for exactly the reasons discussed here
I have not failed. I've just found 10,000 ways that won't work.
Thomas A. Edison
Thomas A. Edison
The body of the ski heats up more quickly than the tips, so you may find that the different materials provide you with a even temperature range/accurate cure.
Last edited by Richuk on Fri Jul 05, 2013 1:36 pm, edited 1 time in total.
-
twizzstyle
- Posts: 2204
- Joined: Tue Mar 07, 2006 8:25 pm
- Location: Kenmore, Wa USA
If you look at a cross section of an MDF board, the outer "skins" look much denser than the core. By having a bunch of vertically oriented boards laminated together, you get the benefit of the denser outer bits acting as ribs. I've never had any deformation with molds like that, however when I've had a center camber section that was a single board of MDF laying flat that I had machined the camber into (thus exposing the less dense core) it deformed like crazy.
