Whats the difference between the 12v head bed and 24V heat bed?
 
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Whats the difference between the 12v head bed and 24V heat bed?  

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Randall Ward
(@randall-ward)
New Member
Whats the difference between the 12v head bed and 24V heat bed?

Now after reading that title I'm sure 99% of the the people are thinking "you answered your own question ya clown!"  Yes I know the voltages are different but is there any reason I can't put 24v to a heat bed marked for 12v?  I'm looking to swap out my Mk2.5S+ mobo with a Fly RRF board and in doing do I was wondering why can't I just upgrade the PSU to a 24v as well? The replacement thermistor is rated to work on all the heat bed regardless of the voltage, is it something to do with the magnets in the bed? I can't think of any other reasons why it wouldn't work. 

Posted : 25/01/2022 5:57 am
JoanTabb
(@joantabb)
Moderator
RE: Whats the difference between the 12v head bed and 24V heat bed?

the Mk52 12 volt Heatbed shares two mounting points with the mk52 24 volt  heatbed, 

all of the rest of the mounting points are in different places. 

the Mk2 Y carriage  is the same depth on the Y axis as the Mk3 Y axis Carriage. 
BUT... The Mk2 Y carriage width is approximately 1cm narrower than the Mk3 Y carriage Platform

it is possible that he Y axis mounting slots for the linear bearings are just a tiny bit further apart on one printer compared to the other... 
Or it may be a tiny difference in the machining between my original Prusa Mk2 Y axis Platform and My Chinesium Mk3 Y axis Platform

The XYZ Calibration points are different between the Mk52 12volt heatbed and the mk52 24 volt heatbed. so, the mk2.5 firmware will not calibrate a 24 volt mk52 heatbed, using Prusa Firmware.
I believe the Magnet positions also differ between the 24 volt and 12 volt variants. 

If you try to put 24 volts on a 12volt heatbed, your printer will try to use 4 times the power that it is designed for. which may well overload your power supply, cause over heating, and possibly damage the weakest link,   I don't know what would be the weakest link. 
the Heatbed wires are rated at about 20 amps which is twice what the Prusa 24 volt 240 watt power supply can supply, so that is likely to be ok, at least for a while.... The PSU is supposed to have Short Circuit protection, so theoretically is should be ok... the heat bed is literally a printed circuit board with thin copper tracks... whether these can stand the short circuit current limmited power from the power supply, is questionable. 

You are planning to us a non prusa motherboard/controller, so it is likely that you will not have an XYZ calibration option that needs the calibration points.  so that may be a Null point. 
I suspect that the new mother board may have dual power supply capability in which case you may opt to run the heatbed off 12 volts, and the X, Y, Z, E motors and stepper drivers off a smaller 24 volt power supply, in which case the differences are pretty much unimportant. simply retain the 12 volt PSU and add a small 24 volt PSU... 

you need to ensure that this is a realistic option before progressing. 

I believe this page in the Git Hub Repository, holds links to both the 12 volt and 24 volt heat bed design information
https://github.com/prusa3d/Heatbed_MK52_magnetic

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Posted : 25/01/2022 8:23 pm
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