Peltier heated bed

Re: Peltier heated bed

D.Goncz — Sun, 13 Oct 2024 00:29:33 -0400

Yeah

My signature ranges from null to very long and it is rather odd habit

I have an IQ of like 166 and severe brain damage

I hope the method did not trouble anyone

Dgoncz

Re: Peltier heated bed

MKSA — Sat, 27 Jan 2018 12:21:34 -0500

He just woke up from a 6 years old coma, like this thread :)

Re: Peltier heated bed

o_lampe — Sat, 27 Jan 2018 12:13:42 -0500

The signature is a pretty uncommon place to put your resumé. Are you applying for a job here? ;)

Quote

D. Goncz
See Also KSRM p.40 footnote
ORCID (r) is 0000-0001-5483-448X

1979 Thesis at MIT in XXV: Self-Replicating Shelter

Coined "Replikon" in 1984 to include machine tool building shelter

Built S/R 4 Axis Mill in 1997, Sold $300, 1 of 2, enough to build 2 more

Now working on RepStrap Bateson, from Unimat One to X Axis for $50 or so;
From 1 X Axis to 12 X Axes in a Cube for < $600
Groups of 4 make XYZ Inside WLO Generality
Diagonal Axis is Vertical
Arrays to Billions
Wraps in Octets
Adds/Subtracts
Also Foundry!

Re: Peltier heated bed

D.Goncz — Sat, 27 Jan 2018 09:55:14 -0500

I mention Peltier heated cooled bed in multi development page Quad
Doug

Re: Peltier heated bed

Emmanuel — Tue, 09 Oct 2012 17:35:06 -0400

Quote

Question: how are you holding them on?

Kapton + thermal grease :)

The kapton is definitely held in place by the wood insulation: [reprap.org]

200px-Foldaslot_peltier-heatbed_step4.jpg

I couldn't resist to add this pic :

www.flickr.com

My prints were never such at the edge of the plate x)

www.flickr.com

Got a little curling this time :P

Re: Peltier heated bed

mars bonfire — Tue, 09 Oct 2012 11:55:46 -0400

GIven you have what I called the hot side on the bed and cold side up against insulation, my guess is that the Peltier is working like a resistor i.e. the amount of heat you are getting into the bed equals the power you are putting in...virtually no efficiency gains due to "pumping" action...not unlike running an air conditioner inside a closed room (knew someone who did this and couldn't figure out why the room was heating up...). So if you have a source of cheap peltiers, why not...they certainly have a nice form factor in terms of thermal contact with the bed. Question: how are you holding them on? Typically, they are mounted with a controlled force using thermal grease so that any difference is thermal expansion between the peltier and what is being heated or cooled won't crack the ceramic on the peltier while still getting good thermal transfer. I believe using a hard adhesive like epoxy could be trouble.

Re: Peltier heated bed

redreprap — Tue, 09 Oct 2012 08:06:18 -0400

this is definately interesting ... i have about 30-40 peltiers lying around ...

Re: Peltier heated bed

Emmanuel — Tue, 09 Oct 2012 05:15:56 -0400

@N314
I think I already linked it somewhere, but I'm using this one : [cgi.ebay.com]

For the peltier effect, I see it more like a pump than a "cold/hot sides", so in my setup I keep the cold side warm by having some insulation, thus, I guess, the heat is just circulating (using the heat from the bed rather than looking to pump the normal ambient heat) and you only need to compensate for the dissipation of the bed (which at 4-5mm thick have a good inertia, it take quite a long time to cool down from 53°C to 20°C)

Re: Peltier heated bed

mars bonfire — Mon, 08 Oct 2012 11:39:45 -0400

A couple of comments. My guess is that in order to enjoy the increased efficiency of heating using the peltier, you need the "cold" side to be in good thermal contact with the room ambient (a heat sink on the cold side and a fan would be good). Otherwise, the heat available to be pumped across the Peltier would be limited but what can be moved into the bare Peltier side.

If you have a source of cheap Peltiers (cheaper than power resistors) and you need to heat and you are concerned about power efficiency, it could make senses to use Peltiers. It would seem to me to make a lot of sense if you wanted to both heat and cool (very tight temp control or active cooling post print). My experience with Peltiers is that they can be fussy to use in terms of mounting them and achieving high reliabilty. They are easy to crack if torqued down too hard and they are subject to failures due to repeated thermal cycling weakening the internal solder joints. If you plan to use them, I would recommend studying the applications literature at one of the major Peltier manufacturers.

Also, per the question of stacking them to get better heating, they can be purchased that way, typically with the goal of getting the very coldest temperatures. These stacked arrangements have something like 1/3 the area peltier on each successive layer...say for example, a 1 square inch device on the bottom, next a 1/3 square inch device, next a 1/9 square inch device. Not more than three stacked usually. The 1/3 ratio relates directly to their efficiency and the need to more the heat out.

So, whatever works for you, well...works. But it is, in my experience, rare to find a heat only application (save for where *very tight* temperature regulation is needed) that doesn't use simple resistive heating.

Re: Peltier heated bed

yngndrw — Mon, 08 Oct 2012 08:11:01 -0400

In this use, both sides are kept at approx the same temperature meaning that it acts just like a resistor.

If you was to attach a heatsink / fan to the "cold" side, it would also operate as a form of heat pump, meaning that it would be more efficient in terms of the electrical energy used versus the heat produced on the "hot" side.

Re: Peltier heated bed

NewPerfection — Mon, 08 Oct 2012 00:32:38 -0400

N314 Wrote:
-------------------------------------------------------
> @Emmanuel
> What about price. How much did the peltier you are
> using cost?
>
> -Nick

He already said. $5-6. I've seen them for about $3 in quantity on eBay.

Mogal Wrote:
-------------------------------------------------------
> How about condesation on the cold side?

The "cold" side doesn't really get cold in this type of setup. In fact, it shouldn't get below room temperature at all.

Re: Peltier heated bed

N314 — Sun, 07 Oct 2012 19:03:37 -0400

@Emmanuel
What about price. How much did the peltier you are using cost?

-Nick

Re: Peltier heated bed

Mogal — Sun, 07 Oct 2012 18:26:38 -0400

How about condesation on the cold side?

Re: Peltier heated bed

jzatopa — Sun, 07 Oct 2012 18:18:34 -0400

Even if there are other ways of achieving the same results, that doesn't mean having options is a bad idea. Considering the ease of using a peltier, it looks to be a viable option. It is also quite easy to use 2 of them to spread the heat more evenly over the print table without much extra work.

Re: Peltier heated bed

NewPerfection — Sun, 07 Oct 2012 18:10:37 -0400

xiando Wrote:
-------------------------------------------------------
> Peltiers are an impractical solution for the
> purpose described here (aside from cooling for the
> motors). Seeing that one of the goals of rerap is
> to reduce expense and system complexity, this
> seems a specious discussion.

Cheaper than using power resistors, easier than using nichrome wire, and far simpler than a PCB heater. How is it impractical? They are basically being used as thin power resistors, and do a better job of transferring heat to the build plate than power resistors because of the increased contact area.

Re: Peltier heated bed

Emmanuel — Sun, 07 Oct 2012 17:16:03 -0400

Impratical ? stick it to the alu plate with kapton tape and that's it

Complex ? two wires (one +, one -) add a thermistor to drive it like any other resistor heater (Cdnreprap even use it without control if I remember)

Expensive ? at only 5-6$ it's the easiest/cheapest solution I found :P

Re: Peltier heated bed

xiando — Sun, 07 Oct 2012 16:38:19 -0400

Peltiers are an impractical solution for the purpose described here (aside from cooling for the motors). Seeing that one of the goals of rerap is to reduce expense and system complexity, this seems a specious discussion.

Re: Peltier heated bed

Emmanuel — Sun, 07 Oct 2012 13:06:04 -0400

A little report on the peltier bed, it's still working fine !

I rarely use the full print surface, but recently I made some prints that can show that with a 4-5mm alu plate (140x140mm) the heat distribution is good even if the peltier is only 40x40mm : no curling.

A spool roller which is ~100x100mm

www.flickr.com

Or this 135mm wide part (foldarap-y-idler)

www.flickr.com

Re: Peltier heated bed

Emmanuel — Wed, 16 May 2012 08:37:22 -0400

nothing special, but I added insulation to keep the under of the bed and the peltier warm (just like if it was a big flat resistor)

Re: Peltier heated bed

yngndrw — Mon, 14 May 2012 18:05:22 -0400

What did you have on the "cold" side ? Nothing or did you put a heatsink on it ?

Re: Peltier heated bed

Emmanuel — Mon, 14 May 2012 16:50:54 -0400

Today I could test my peltier heated bed in normal use condition (i.e properly mounted, direct on a 6mm alu plate with heatsink compound, with insulation : [reprap.org], [reprap.org] and driven by the mainboard, that was my main concern because I failed to make it work previously due to an inadequate firmware)

And it seems to went from 20°C to 50-60°C in maybe 5 seconds... ! (:D
(I didn't measured the temp rise, but it quickly became too hot to keep touching the print surface)

yngndrw Wrote:
-------------------------------------------------------
> That's a fair point while it's at its final
> temperature, but when it starts heating from cold
> the temperature difference is going to be less.
> Therefore you should get a faster warm-up time and
> use less energy getting it up to temperature.

Re: Peltier heated bed

yngndrw — Mon, 30 Apr 2012 16:08:27 -0400

That's a fair point while it's at its final temperature, but when it starts heating from cold the temperature difference is going to be less. Therefore you should get a faster warm-up time and use less energy getting it up to temperature.

Re: Peltier heated bed

ttsalo — Mon, 30 Apr 2012 12:16:36 -0400

Well, here's a performance graph from one manufacturer. (The ratio of pumped heat to input power)

We were talking about 60+ degree temperature differentials, in those conditions you only get at most 10% bonus from the Peltier effect compared to a power resistor. At a differential of 30 degrees or less, you can get a lot of useful work out of a Peltier, but not at 60.

Re: Peltier heated bed

yngndrw — Fri, 27 Apr 2012 19:19:01 -0400

ttsalo Wrote:
-------------------------------------------------------
> At 60C temperature differential the peltier
> element does pretty much no more useful work than
> a power resistor would. And this applies both to
> heating and cooling applications!

I disagree, for heating they are ideal.

Using either a reasonable size heatsink with fan on the cold side, (Or water-heating it to allow for a larger heatsink and less moving mass.) you not only have the pumped heat going into the heat-bed but you also have all of the electrical energy put into the peltier going towards the heating of the heat-bed.

Re: Peltier heated bed

ttsalo — Fri, 27 Apr 2012 17:52:54 -0400

At 60C temperature differential the peltier element does pretty much no more useful work than a power resistor would. And this applies both to heating and cooling applications!

Stacking peltiers is a pretty esoteric configuration. Because the basic efficiency is pretty low, the second (and further) peltiers have to transfer the heat dumped by the first one and have their heat dumped forwards so efficiently that their performance doesn't go down the toilet.

Even in a single 50W element fridge setup, you have to dump the total heat (80W or so) with no more than 10C difference between the hot side and the ambient to avoid the efficiency plummeting. That's really hard to do with air cooling. (Which explains why the cheap and cheerful peltier travel fridges have afwul performance).

Re: Peltier heated bed

lutjanus — Fri, 27 Apr 2012 11:46:15 -0400

Has somebody tried to pile up two peltier elements to get a higher output temperature. As fas as I know the difference between the plates of an element is max. 60°C. With two elements "in line" that could make 100° to 120°C difference?!
Have a great weekend!
Lutjanus

Re: Peltier heated bed

ttsalo — Sun, 22 Apr 2012 06:55:21 -0400

I'd love a Peltier-heated platform, I could print plastic and chocolate without swapping the build platform.

The heat sinks are a problem, though. Peltier element's CoP (coefficient of performance, which is the amount of transferred heat divided by the input power) drops dramatically as the temperature difference between the sides increases. In practice this means that the heat sink must be significantly better than 1 K/W, or the Peltier won't be doing almost any actual work except converting input power to heat. And heat sink like that, if air-cooled, is pretty big. I have built a couple of Peltier fridge projects and even for a 50-80 W Peltier, water cooling on the hot side is almost mandatory for getting good performance.

But here's an idea I just had: print a thin plastic piece containing water channels and sandwich that under the top build plate. Then pipe cold or hot water through it. I think I'll try that for the chocolate printing.

Re: Peltier heated bed

CdnReprap — Sat, 21 Apr 2012 21:14:42 -0400

You could have it cool at a slower rate by PWM if your circuit can handle it or simply using a simple "ON", "OFF" cycle.

I think the major disadvantage is the weight of the heat sink on the Y axis.

Re: Peltier heated bed

theodleif — Sat, 21 Apr 2012 18:36:44 -0400

Wouldn't such a fast cool-down have an effect on warping, either instantly or on the long run, as more tension remains?

Re: Peltier heated bed

Emmanuel — Sat, 21 Apr 2012 17:24:53 -0400

I hadn't thought of using the x-axis to wipe the bed !

If reliable (being sure that the parts is ready to be wiped, and with a big heatsink on the cold side of the peltier cell as said before) that could make a sort of automatic-build-plateform at no-cost :)