Question about the heated bed.

I have designed a 300mmx300mm (actually 300mmx400mm) 3d printer and I have Mic6 and above the Mic 6 the actual heated bed so how do I keep the heat on the bed and not travel down the scews into the other Mic6 then that will transfer the heat into the actual extruded aluminum frame? The top Mic6 will be using a 300mmx300mm heated pad.

edit: I found these that are all made out of peek and are a bit pricey but is peek a good insulator? I know my real J-Head's peek burns the snot out of me a few times when I was careless. [www.solidspot.com]

My jaw dropped on the prices for these [onlinecatalog.tpa-us.com]- ptfe hardware and 1 M5x10mm bolt is almost $17.00. Great insulator for heat, from what I read, but that makes me wonder about Teflon coated pans used for cooking and if it insulates well then what is it doing in cookware that has to heat up to cook the food?

Edited 3 time(s). Last edit at 09/17/2015 07:29AM by Dark Alchemist.

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.

Just use stainless fasteners (standoffs/spacers). Stainless is a relatively poor conductor of heat (used in hotend heatbreaks) and quite cheap.

If you want complete overkill you can get ceramic spacers very cheaply: [www.mcmaster.com]
A stainless fasterner through a ceramic flange and unthreaded spacer will have no metal on metal contact and only cost a few bucks.

Suitable plastics are really too expensive to be practical here IMO.

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691175002
Just use stainless fasteners (standoffs/spacers). Stainless is a relatively poor conductor of heat (used in hotend heatbreaks) and quite cheap.

If you want complete overkill you can get ceramic spacers very cheaply: [www.mcmaster.com]
A stainless fasterner through a ceramic flange and unthreaded spacer will have no metal on metal contact and only cost a few bucks.

Suitable plastics are really too expensive to be practical here IMO.

I agree but I do have to say on my boat weight of an i3 rework (reasons I designed my own) the heat went down the black oxide screws and even made my smooth rods hot so I switched to SS and that helped a ton but after 3 or 4 hours the heat still gets to the frog plate (unlike the minutes when I first used the black oxide screws) so SS + an insultator would be best bet I think but I am having a hell of a time finding these things in Metric which is all I deal with.

For instance the holes in standard plate and the phenolic MK2B are for using M3 screws AND my t-nuts are M3 as well so how do I insulate those stand off screws?

Edited 1 time(s). Last edit at 09/17/2015 11:07AM by Dark Alchemist.

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.

Unthreaded spacers can be used for imperial or metric screws since a bit of play is acceptable.

Its hard to know how much room there is for improvement once you have stainless. Even with perfectly insulated fasteners, radiation and convection will allow the heat to transfer to the frame.

Insulation will slow down the movement of heat, but it doesn't stop it. Stainless transfers heat about 1/4 the speed of normal steel, and epoxies and plastics about 1 millionth. Google "thermal conduction".

To keep something cool, you need to remove the heat faster than it travels through the insulator(s). Try a heat sink of some kind (e.g. a large metal washer) in contact with the screw to conduct heat away from the screw and radiate it to the air.

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frankvdh
Insulation will slow down the movement of heat, but it doesn't stop it. Stainless transfers heat about 1/4 the speed of normal steel, and epoxies and plastics about 1 millionth. Google "thermal conduction".

To keep something cool, you need to remove the heat faster than it travels through the insulator(s). Try a heat sink of some kind (e.g. a large metal washer) in contact with the screw to conduct heat away from the screw and radiate it to the air.

Agreed but wouldn't a plastic screw, or a ceramic screw, be optimal in this situation or can they not handle it the shear stress? Yeah, people love saying springs are sprung but in this instance the bed doesn't move except up and springs make leveling a lot easier but can the threads of a Peek or a Ceramic screw handle Ultimaker springs?

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.