<p>Since 50% of the bed is uninsulated, you're definately into diminishing returns as soon as you start adding any insulation.<br>
With that area, I think you are looking at 1.2W per kelvin for a 2mm thickness. </p>

<p>I'm guessing a bit with these powers, but roughly, maybe from 100 W un-insulated, 75 with 2mm, 60W with 4mm. You can get a reasonably accurate measure of the power by looking at the duty cycle of the heating element.</p>

<p>Actually, its not clear if your primary goal is to reduce energy/maintain a very high temperature, or speed the initial heating. You can place a temporary sheet of cork on top of the bed (preferably extending over the edges to prevent convection) and this will significantly improve heat-up times.</p>

CC BY-SA 3.0
2016-12-03T23:06:13.760Z
Many thanks for the answer. I think that I see what you mean, but just to clarify a few points: By _diminishing returns_, you mean that each increase in insulation thickness gives a correspondingly reduced _increase in actual insulation_ (which, I guess, would make sense)? Are the figures of 100/75/60 W relating to the power used to maintain the heatbed at the same temperature (i.e. 70°C)? Without (necessarily) wishing to get into the mathematics too much, are those figures for the power, _guesstimates_ based on experience or did you arrive at those figures using a formula?
Greenonline
CC BY-SA 3.0
2016-12-04T00:07:37.597Z
Yes, doubling the insulation doesn't double the power saving. The numbers are guesses, I need to work more on the maths for a real answer.
Sean Houlihane
CC BY-SA 3.0
2017-01-06T21:48:13.587Z
Also consider cork on top of the bed during heating.
Sean Houlihane
CC BY-SA 3.0
2017-01-06T22:37:13.823Z
Yes, that is a good idea... I remember reading somewhere that someone suggested even corrugated cardboard helps.
Greenonline
CC BY-SA 3.0
2016-12-03T15:13:00.377Z
2017-01-06T21:47:53.503Z
2017-01-06T21:47:53.503Z
Sean Houlihane
<p>I have been looking at cork sheet insulation for my 200 mm x 300 mm aluminium PCB heatbed, by I am not entirely sure how thick it should be. There seems to be a trade off between losing a few millimeters of print height, and providing adequate installation.</p>

<p>I have seen 10 mm thick table mats, and then 5/3/2 mm thick cork insulation tiles. On some forums people say they use two 2 mm sheets beneath the aluminium heater and then another 1.5 mm aluminium plate under those, to hold it altogether (source: <a href="http://forums.reprap.org/read.php?4,584582,587506#msg-587506" rel="noreferrer">Re: Is a cork board necessary under the heated bed?</a>).</p>

<p>Hopefully this does not come across as a <em>how-long-is-a-piece-of-string</em> type question. I am just trying to get the right amount in the first place whilst spending as little as possible, and keeping the mass/volume and height down. If someone else has already gone through the empirical adjustments themselves, then it might save me the time and expense of having to test various configurations. </p>

<ul>
<li>Would just 2 mm thick cork backing be sufficient?</li>
<li>Is 10 mm overkill?</li>
<li>Does silver foil backing help considerably, thereby enabling one to reduce the thickness of the cork?</li>
</ul>

CC BY-SA 4.0
2019-06-06T12:28:54.600Z
Burning cork is difficult even when you WANT it to burn... Cork is the outer layer of trunks and has specifically the goal of protecting the plant from fires. I would say almost no flame risk.
FarO
CC BY-SA 3.0
2016-12-01T15:24:24.977Z
Cork is bloody cheap. Why worry  -- other than the fact that it's flammable. All that's needed to start a fire is having the thermistor fail or come loose. I'd use a flameproof material if you're going to insulate.
Carl Witthoft
CC BY-SA 3.0
2016-12-01T16:21:11.193Z
@CarlWitthoft - OK, thanks, this is the first time that I have really given thought to the flammability issues, although I had read that cork is preferable to silicon/rubbery insulation, due to less noxious fumes being given off.
Greenonline
CC BY-SA 3.0
2016-12-01T16:29:37.317Z
If you really want to go all out for insulation, buy some [aerogel](http://www.aerogel.org/)!
tbm0115
CC BY-SA 3.0
2016-12-01T16:35:13.507Z
@tbm0115  - :-) That really does look top notch, but is, unfortunately, a bit pricey.
Greenonline
CC BY-SA 3.0
2016-12-01T16:56:24.193Z
@Greenonline I have to admit that you'd have the coolest looking 3D printer with some of that Classic Silica Aerogel insulating your machine!
tbm0115
CC BY-SA 3.0
2016-12-02T11:08:20.493Z
@CarlWitthoft - As the ignition temperature of cork is 300°C, I wonder if there really is a fire risk. Do you know of any examples of burning, or scorching, of cork, when used as a heatbed insulator? Please see my question [Has anyone experienced scorching or burning of cork heatbed insulation?](http://3dprinting.stackexchange.com/questions/3122/has-anyone-experienced-scorching-or-burning-of-cork-heatbed-insulation)
Greenonline
<heated-bed><heat-management>
How much insulation do I really need?
Greenonline
# How much insulation do I really need?

(Asked by: username_0 on 2016-12-01)

I have been looking at cork sheet insulation for my 200 mm x 300 mm aluminium PCB heatbed, by I am not entirely sure how thick it should be. There seems to be a trade off between losing a few millimeters of print height, and providing adequate installation.

I have seen 10 mm thick table mats, and then 5/3/2 mm thick cork insulation tiles. On some forums people say they use two 2 mm sheets beneath the aluminium heater and then another 1.5 mm aluminium plate under those, to hold it altogether (source: [Re: Is a cork board necessary under the heated bed?](http://forums.reprap.org/read.php?4,584582,587506#msg-587506)).

Hopefully this does not come across as a *how-long-is-a-piece-of-string* type question. I am just trying to get the right amount in the first place whilst spending as little as possible, and keeping the mass/volume and height down. If someone else has already gone through the empirical adjustments themselves, then it might save me the time and expense of having to test various configurations.

* Would just 2 mm thick cork backing be sufficient?
* Is 10 mm overkill?
* Does silver foil backing help considerably, thereby enabling one to reduce the thickness of the cork?

**Tags:** heated-bed, heat-management
> **Comments:**
> **username_2**: Cork is bloody cheap. Why worry  -- other than the fact that it's flammable. All that's needed to start a fire is having the thermistor fail or come loose. I'd use a flameproof material if you're going to insulate.  
> **username_0**: @CarlWitthoft - OK, thanks, this is the first time that I have really given thought to the flammability issues, although I had read that cork is preferable to silicon/rubbery insulation, due to less noxious fumes being given off.  
> **username_3**: If you really want to go all out for insulation, buy some [aerogel](http://www.aerogel.org/)!  
> **username_0**: @tbm0115  - :-) That really does look top notch, but is, unfortunately, a bit pricey.  
> **username_3**: @Greenonline I have to admit that you'd have the coolest looking 3D printer with some of that Classic Silica Aerogel insulating your machine!  
> **username_0**: @CarlWitthoft - As the ignition temperature of cork is 300°C, I wonder if there really is a fire risk. Do you know of any examples of burning, or scorching, of cork, when used as a heatbed insulator? Please see my question [Has anyone experienced scorching or burning of cork heatbed insulation?](http://3dprinting.stackexchange.com/questions/3122/has-anyone-experienced-scorching-or-burning-of-cork-heatbed-insulation)  
> **username_1**: Burning cork is difficult even when you WANT it to burn... Cork is the outer layer of trunks and has specifically the goal of protecting the plant from fires. I would say almost no flame risk.  

---

## 1 answers

### Answer by username_4 on 2016-12-03. Score: 2 | Accepted answer

Since 50% of the bed is uninsulated, you're definately into diminishing returns as soon as you start adding any insulation.  
With that area, I think you are looking at 1.2W per kelvin for a 2mm thickness.

I'm guessing a bit with these powers, but roughly, maybe from 100 W un-insulated, 75 with 2mm, 60W with 4mm. You can get a reasonably accurate measure of the power by looking at the duty cycle of the heating element.

Actually, its not clear if your primary goal is to reduce energy/maintain a very high temperature, or speed the initial heating. You can place a temporary sheet of cork on top of the bed (preferably extending over the edges to prevent convection) and this will significantly improve heat-up times.

> **Comments:**
> **username_0**: Many thanks for the answer. I think that I see what you mean, but just to clarify a few points: By _diminishing returns_, you mean that each increase in insulation thickness gives a correspondingly reduced _increase in actual insulation_ (which, I guess, would make sense)? Are the figures of 100/75/60 W relating to the power used to maintain the heatbed at the same temperature (i.e. 70°C)? Without (necessarily) wishing to get into the mathematics too much, are those figures for the power, _guesstimates_ based on experience or did you arrive at those figures using a formula?  
> **username_4**: Yes, doubling the insulation doesn't double the power saving. The numbers are guesses, I need to work more on the maths for a real answer.  
> **username_4**: Also consider cork on top of the bed during heating.  
> **username_0**: Yes, that is a good idea... I remember reading somewhere that someone suggested even corrugated cardboard helps.  

---

