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Heated Bed insullation

Posted by Anthrochick 
Heated Bed insullation
August 27, 2012 12:44PM
I know a lot of people use wood or MDF to insulate their heated bed. Has anyone used one of those silicon pads you put under hot pots (I can't remember what they are called)? What about cork or would that dry out and crumble?

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Re: Heated Bed insullation
August 27, 2012 04:30PM
silpad baking sheet by any chance? Not a bad idea I suppose. it's rated for far higher temperatures that the heated bed will ever reach under normal circumstances.

I've seen cork suggested in various posts elsewhere and possibly in this forum as well.
Re: Heated Bed insullation
August 27, 2012 04:43PM
Yep, those. Maybe it was the lack of sleep and the infomercials that made me think of it. I was just wondering if anyone had used something like that since, for me, it's easier to get than very thin MDF without having to order it.

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Re: Heated Bed insullation
August 28, 2012 11:02AM
what about engine heat blocker sheets? i found some on amazon, was thinking to try some, i even got some heat shield tape to try out on the hotend ... instead of the usual kapton
Re: Heated Bed insullation
August 28, 2012 12:26PM
redreprap, not a bad idea. that's more inline with what I figured out after briefly considering expanded foam solutions (the pink and blue r-13 stuff from home improvement stores)

Personally, I'll be using standard fiberglas insulation, cut into 1/2"-1" wide strips and peeled back so it just fits in the space between the MK-1 and the support panel below it. My plan includes providing a small flap at the front and back that I can *easily open following a print, to force-purge the space's hot air and reduce bed cooling time.

I suppose it wouldn't be the sort of material I'd use were I selling machines or using them around little kids, but it's safe enough in an adult-minded situation and won't offgas or contribute to any bending stresses when in contact with the bed and the carrier plate. In any case, the main thing (wrt specifically to the heated bed itself) is to stop the convective flow pattern so the bed temp stays more uniform across its profile.

I'd like to again thank Anthrochick for suggesting silpad as a raw material, since that might just make a very nice flap material. I was planning on 080 or 0125 aluminum sheet, but the silpad will, I think, have far better insulating properties.
Re: Heated Bed insullation
August 30, 2012 01:41PM
Another material to consider is what is often referred to as rigid fiberglass insulation. As I understand it, it is basically fiberglass insulation (what is used in batt form in attics and walls) but with an added binder to make it semi-rigid. You commonly see it sold in tube form for insulating iron steam pipes. The binder is the limiting factor in its temperature range and will in essence, burn off at something like 600 degrees F leaving a still viable, but binder less, fiberglass mat. The other place you find it is fiberglass ceiling tiles (2 feet by 4 feet) with an outer "skin" layer of some sort of paper/plastic film that has a aesthetic pebble finish (white and paintable). Very easy to peel off the "skin", leaving a panel of rigid fiberglass, about 5/8 inch thick and, while resilent, is easily compressible. Just bought sheet for my hot bed for about $7 at the local Home Depot.
Re: Heated Bed insullation
August 30, 2012 01:57PM
I'd recommend that you don't use a full sheet under the bed unless you're using an open carriage.

For those who have a carrier comprised of a solid plane (aluminum, wood, or similar plate), the critical areas seem to be around the periphery, between the carrier and the heated bed, since most of the heat is lost to convection, and most of the problems in the heated bed are in the same areas...the edges. For me, that means using strips of material placed inside each edge

If you are one of the latter group, using strips rather than a full sheet allows you to open a gap to either literally "blow into it" or use a fan to purge the space following print, thereby speeding up the cool down process.
Re: Heated Bed insullation
August 31, 2012 09:14PM
hmmm wait a minute ... silpads ? arnt they for heat transfer? you wanted heat insulation ? (or its a different kind of pad?)
Re: Heated Bed insullation
September 01, 2012 02:00AM
Hmm...now that I actually read up on them yeah, maybe not such a good choice. I've never used them but thought they were supposed to make a cookie that baked from the air instead of the sheet. Guess I made a wrong assumption. 'Tweren't the first, won't be the last. winking smiley Thanks for making me do my homework.
Re: Heated Bed insullation
September 01, 2012 02:13PM
well i just thought silpads sounds familiar cos i use them in transistor backings esp the TO3s grinning smiley

the foam tubing used in air conditioner piping looks like a very nice insulator but im not sure what is the heating limit. i hear there is a sheet version of it that some air con shops have, it may even come with a adhesive back.

i am interested to find this, [www.tradekorea.com] , in mylocality
but no luck for me

Edited 1 time(s). Last edit at 09/01/2012 02:17PM by redreprap.
Re: Heated Bed insullation
September 01, 2012 02:45PM
Yeah, sorry for that misdirect on my part. I don't know how I got it into my head that they'd be an insulator...doh!

Anyway, my choice is still good old fashioned fibergals wall insulation. Cheap, effective, and easy to use. It's spun glas, so it's not going to be melting at ANY of our heated bed temps, from PLA well beyond what's needed for nylon and Polycarbonate when they become more common place... afaik.

I still need to come up with a flap material though. Maybe some high temp mat like the compressed stuff for auto hoods, or just a piece of FR-4 with fiberglas glued on as a crude gate-valve that can be flipped or slid open with a small solenoid after print.
Re: Heated Bed insullation
September 01, 2012 10:19PM
ok...still slightly puzzled. I was directed by a female freidn to an article at a baking site after she siad "silpad? Oh...you mean silpat"

read this redreprap

what is silpat? and note what it says about insulating characteristics. Silpad heat-sink gaskets are a different beast. They're meant to have a high coefficient of thermal conductivity.
Re: Heated Bed insullation
September 02, 2012 10:26AM
o my, thats interesting ...

i think if i am to make a flippable heat cover, i think the car heat shield would be my choice, unless i can find some of those air con insulation foam sheets.
Re: Heated Bed insullation
September 02, 2012 12:44PM
yep. something like that. wall insulation is my choice simply because it's handy and as close as my attic, where I have a few extra rolls leftover from some work and waiting for rebuild of a window on the east side of the attic. it'll never miss a few feet.
Re: Heated Bed insullation
September 04, 2012 12:13PM
My only concern with the fibreglass insulation has to do with loose fibres and health risks. Am I just being paranoid (my mother is a risk manager so I'm often treated to horror stories)? Isn't there a sort of foam rubber-y insulation that you put around hot pipes or use for washer/driers? I'm trying the cork around the edges on my mendel so I'll post my results with that onceI'm satisfied with my set up.

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Re: Heated Bed insullation
September 04, 2012 01:20PM
If cork works for your purposes, use cork. If you're using PLA exclusively, your bed temp will only reach ~60C max during normal operation anyway, so my guess would be that expanded foam might work out for you, although it's proper to vett the materials by doing a bit of googling for safety related info, including their max temp range, and if the material's plastic can be identified, doing MSDS searches to see what they produce when they offgas at elevate temp.

I personally think there's a bit too much 'oragano-gaian' hype regarding fibeglas insulation, transferring data from workers exposed to large quantities on a daily basis back to a consumer whose exposure would be very very tiny. And if you're using ABS, then Acetone (often used for prepping the glass platen and/or for welding and finishing of printed items) and decomposition hydrocarbons from the ABS if/when it's accidentally overtemped are far more dangerous in opinion. For me, it's an acceptable risk and safer than attempting to use expanded foam. I do not propose to speak for anyone else though.
Re: Heated Bed insullation
September 04, 2012 02:08PM
ABS decomposes at the temperatures we extrude it at. That is why you can smell it. I don't know what the products are but on my machines that have a heatsink close to the extruder they condense into gooey brown stuff.

Re: Heated Bed insullation
September 04, 2012 02:27PM
Ah... thanks nophead. I kinda thought so but was reluctant to suggest it for fear that I'd be flamed for fear-mongering. I punted and read up on the technical decomposition temp, which is a bit higher than the ~220-230C melt temp.
Re: Heated Bed insullation
September 06, 2012 01:46PM
The rigid fiberglass insulation sheet (ceiling tile variety) (see my posts a few up this chain), while certainly not fiber free, has far fewer loose fibers than the batt stuff used in walls. I guess if you really were worried you could smear some silicone/rtv on the edges to bind and further immobilize the fibers. I personally don't worry about the fibers, particularly in the environment and quantity a reprap would use and the fact that it is not subject to being routinely disturbed/abraded/shredded in normal use. If I did worry, I would worry alot considering the hours I have spent in various houses putting in fiberglass insulation and almost literally, swimming in the stuff.

As far as the foam pipe insulation, I believe some (all?) is some form of foamed either polyolefin or may be polyurethane. I don't think they really are up to the job for temperatures (like 120 to 140 degrees C bed temps) that I have heard used for ABS printing. PLA printing at something like 60C bed temps may be fine for that kind of insulation. I guess one could even consider something funky like vermiculite if there was a practical way to contain it and keep it from pouring out. Cork would seem a reasonable choice in terms of temperature rating (my guess it would burn at about the same temperature as paper?) but my guess is that it is a not-so-great insulator in terms of R value...but it is safe... (unless you get hit in eye harvesting it from a champage bottle).
Re: Heated Bed insullation
September 06, 2012 03:25PM
I agree with Mars. (except for the vermiculite suggestion...what a mess! winking smiley )

And some of this depends on how your bed mounts of course.

Mine will be a 0.125" aluminum sheet to which the slide bearings and belts are applied, with a ~1/2-3/4" gap, followed by the MK1 and topped with double-strength glass sheet. So for me, four small pieces of fiberglass situated around the periphery are perfectly suited to sealing off the interior space underneath the MK-1 (considering that I have yards of the stuff available). the space also gives me somewhere to direct a stream of cool air following the print to speed up cooldown.

If I were using a printed beam carriage (big plastic "X"), or a quasi-laminated approach - substrate mated to MK1 mated to glass - then I'd probably consider a woven, mat, or slurry-extruded insulator like has been described above by Mars in at least two posts.

I think Anthrochick makes a good point regarding use of contentious materials in an educational setting (presumably k-12?), since some parents are liable to go ballistic for the most innocuous of reasons. Safer than sorry for that, and my apologies for rambling on about a material that might not suit the requirements of a an K-12 scholastic setting. (I would note again that you should make a hood to evacuate the fumes anthrochick. cheap 4" ducted fans from Homedepot/Lowes/similar-over-the-pond-big-box-hardware OR online for ~$30 US ( ?15 pound) and some flex dryer vent tube, plus a simple 1/8" Luan hood to rise over the machine itself.)
Re: Heated Bed insullation
September 07, 2012 04:59PM
I'm using self-adhesive pipe insulation strips under the bed. Works really well. High-temperature variants are rated up to 150C, here's one example.

As for the heating, since the corners lose more heat than the middle, mounting 25W power resistors near the bed corners gives quite even heat all over the bed. I think I measured +-2 C at 110 C with this kind of design.
Re: Heated Bed insullation
September 28, 2012 05:32PM
I'm just using cardboard wrapped in Heat Tape, simple and effective.
Re: Heated Bed insullation
September 28, 2012 11:41PM
fwooo very nice DIY implementation. i recently did a thermal reflector, rather large scale and i did not want to spend alot. i bought cheap plastic corrugated sheets (about 4mm thick) and stuck 1 side with cooking ALU foil. i ended up making about 4-5 sq metres of it, under $70 bucks i think. and up it went to most of my windows and odd what not ports.

> I'm just using cardboard wrapped in Heat Tape,
> simple and effective.
Re: Heated Bed insullation
September 30, 2012 09:48AM
I've been using oil filters for cooking hoods to insulate the bottom of the heated bed for a while now. They are to be used above the cooker, so should be able to handle a bit of heat. The filters I got indicate they might be used as padding on the ironboard too.

I did some very basic testing on it. When putting a soldering iron to it (~230?) the fibers will melt and a a big hole will appear. When heating it with a lighter for several seconds, it will burn though. It seems to handle temperatures below 150 C very well, but I did not accurately test that. (The iron might actually be a good way to test this, now that I think of it writing this.) Don't think it's unsafer that cork, but it's a pretty good insulator.

I am using the romcraj.com durbee heated bed, and am running it at 110 C (measured between the pcb and the insulation.)
The pcb is mounted with the resistive side up, and a slab of 3mm mirror on top
Underneath I have 2 layers of this filter material, with a layer of thermal blanket sandwiched in between (I had it laying around anyway, and figured that any infrared radiation it might reflect might aid insulation, not sure if its any good.)

I just have to include a picture of the oil filter packaging too: link
(look for the slogan above the illustration smiling smiley)

I also use some of it to cover the bed while heating up before printing, it helps cutting the warm up time.

I think they are a really good alternative to the materials mentioned above. Not dangerous, can take quite a bit of heat, lightweight and a good insulator (lots of air inside). You might want to give it a try.

Edited 1 time(s). Last edit at 09/30/2012 09:50AM by Wauter.
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