Ramps 1.4 current for 2 heated bed

Hi

I'm on final stages (I hope...) of designing a 3d printer.
I was looking at the RAMPS 1.4 current supply and it seems that it can deliver 11A which is probably enough for 1 heatbed.
What can be done if I need 2 heated beds?

thanks

If you want to run two standard pcb heated beds you could either run them using a DC ssr triggered by the heated bed output.
Your better option would be to get a 120v silicone heater. You can get them custom made on allies press for not to much money and have the bed heat up quicker.

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Prusa i3 Rework - Ramps 1.4 - E3d Lite6 - Full Graphic LCD Controller

silicone heater is a bit expensive so the MK2B will have to do.
will use ssr
thanks!

Make sure to get a dc version with heatsink.

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Prusa i3 Rework - Ramps 1.4 - E3d Lite6 - Full Graphic LCD Controller

Why not use sevenswitches to power the heatbeds?

Yeah, I found it wasn't easy (what's the deal with all of them VAC?)
finally found this
[www.ebay.com]
and this
[www.ebay.com]

thanks for the tip

For a large printer needing more than 280W of bed heating power, my advice is to use a mains voltage silicone bed heater controlled by a DC-AC SSR. These heaters are not as expensive as you seem to think. For a heater of more than 120W but not more than 280W, my advice is not to use RAMPS but to choose 24V-capable electronics that can drive a 24V heater at up to 12A directly.

If you use two PSUs (24V for the bed, and 12V for everything else) then you can use RAMPS. But using two PSUs is over complicated IMO.

Do not use a DC-DC SSR. The cheap ones are useless, they have a voltage drop of 1.5 to 2V which greatly reduces heating power and makes them get very hot - which means they fail unless you use a big heatsink and fan to cool them. The ones that are adequate cost more than a modern 32-bit controller board that can use a 24V supply.

The SevenSwitch is good to about 15A AFAIR, so it won't drive two standard 120W bed heaters. I guess you could use two of them, one for each heater.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I guess that two sevenswitches (or relays) are needed anyway since you probably need to control the temperature of each bed individally. The resistance of the MK2s may vary quite a bit, so I don't think that controlling both with a single thermistor will work well.

First of all thanks for the info.
Every now and then I encounter a big issue I haven't though of and I'm glad I find it now and not after I bought all the parts.

I was looking for silicone heaters. 200X400 are hard to find and if I do, they cost more than $50.
That might not be a lot, but I rather spend this money in other parts. 2 MK2B cost less than $20

I wasn't aware of the sevenswitches. Glad I know it now.

As I see it, the best option (money taken in account):
- a big 12v PSU. let's say 400w. (Any advantage in using 2? 12V+24V?)
- 2 MK2B
- 2 sevenswitches
still using Ramps 1.4....

What do you think about that?

These people [www.aliexpress.com] will make a silicone heater to your size, voltage and power specifications for relatively little money. I advise against using 12V for a heater of that size because it would need 20A or more current. If you go for 24V 10A or perhaps 12A, then any 24V-capable electronics should be able to drive it directly.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I rather use the MK for many reason.
Going to silicone heater will require big changes in the design, which I don't really want to do right now.

Is there any major advantage for the silicone heater that worth the effort? other than faster heating time

With two mk2b heaters, as has already been mentioned if they don't have closely matched resistances then you will get uneven heating. Whereas a silicone heater under an aluminium bed will heat evenly. Also with a silicone heater you get to choose the heater power you want. Printed circuit heaters often struggle to reach 100C or more for printing ABS unless you increase the supply voltage.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

"if you want something done right - just do it yourself"

I found the robert's heated bed
[www.reprap.org]

Seems pretty easy and gives me all the flexibility I want for my design.
I'll use it with 400X200 aluminum plate, 3mm thick
I'll calculate the wire for about 300w.

Is there a problem to use 24v?
He said he wouldn't use more than 12v, but I think it was because he couldn't change the resistance after the assembly