I have a 200mm x 200mm MK3 / MK2b Aluminum Heatbed and resistance measures a high 1.9-2ohms ( this is after subtracting the resistance in my cheapo meter ) Is this normal for the aluminum beds or is it possible mine is defective? https://reprap.org/forum/read.php?1,506452,506452#msg-506452 Sun, 16 Aug 2026 00:20:38 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?1,506452,507907#msg-507907 https://reprap.org/forum/read.php?1,506452,507907#msg-507907
I have PCB type heatbed on order, and I already have the glass, so I'm going to see how that goes next. I may try another aluminum bed in the future, but only if the dealer can assure me of a proper resistance. I'm not sure if the seller will give me any sort of refund on this high-resistance unit. Might be too late for that, but I will definitely let them know.

dave3d, I have a voltage buck module / converter to limit the power going into my Mega and I've disabled the D1 diode on the Ramps board, so there is no way I'll damage it. I have been looking at the 24v power supplies, and I may get one. But I really do not want to run dual power supplies. Since I altered the Ramps, I could almost run 24v now, although I may need to change some fuses ( maybe something else? ) and I would have to replace the heater cartridge on the hotend for 24v.]]> ML3D General Mon, 11 May 2015 19:30:53 -0400 https://reprap.org/forum/read.php?1,506452,507751#msg-507751 https://reprap.org/forum/read.php?1,506452,507751#msg-507751 My aluminium bed now heats up to 110 deg C in about 2 mins.]]> dave3d General Mon, 11 May 2015 12:46:54 -0400 https://reprap.org/forum/read.php?1,506452,507748#msg-507748 https://reprap.org/forum/read.php?1,506452,507748#msg-507748
How much power is drawn by your board can be theoretically computed based on it's resistance and voltage. This eliminates your RAMPS board, mosfets, fuses, and your power supply. If you had measured your board with a resistance of 1.4 ohms but were still having heating problems or you measured only 6.5 amps of current being drawn with a resistance of 1.4 ohms, then you would want to look more into all those things. But you measured your resistance, voltage, and actual current being used, and everything matches up like how Ohm's Law says it would.

You're bed's resistance is the problem. You can't force it to draw more current than it does. You have the choice of sticking with the bed you have, but never being able to get high temperatures and having longer heating up times. Or you can get a replacement board. Whether you get a refund/replacement from your original source, or you go with a different site is up to you.]]> cdru General Mon, 11 May 2015 12:29:20 -0400 https://reprap.org/forum/read.php?1,506452,506792#msg-506792 https://reprap.org/forum/read.php?1,506452,506792#msg-506792
It should be pulling 10 Amps, correct? Although with the voltage higher, that would affect the Amps, I think.

I imagine this could be the high resistance, ramps board ( mosfet? ) limiting amps, or perhaps the power supply itself.]]> ML3D General Fri, 08 May 2015 15:25:40 -0400 https://reprap.org/forum/read.php?1,506452,506762#msg-506762 https://reprap.org/forum/read.php?1,506452,506762#msg-506762
cdru, thanks for confirming what I thought may be the case.

I really like the aluminum, but honestly, now I'm worried that if I fork out for another, it will have the same issue.]]> ML3D General Fri, 08 May 2015 14:08:02 -0400 https://reprap.org/forum/read.php?1,506452,506667#msg-506667 https://reprap.org/forum/read.php?1,506452,506667#msg-506667 cdru General Fri, 08 May 2015 09:29:23 -0400 https://reprap.org/forum/read.php?1,506452,506580#msg-506580 https://reprap.org/forum/read.php?1,506452,506580#msg-506580 atunguyd General Fri, 08 May 2015 04:17:30 -0400 https://reprap.org/forum/read.php?1,506452,506521#msg-506521 https://reprap.org/forum/read.php?1,506452,506521#msg-506521
The problem is the common one of limited temperature and speed of heat up.

Details are:

200mm x 200mm MK3 / MK2b Aluminum Heatbed, wired to Ramps 1.4 with 14awg wire to board and to power supply.
Power Supply is the standard 12v 30A switching type, commonly called an LED power supply.
Ramps has a heatsink on the Mosfet. It's being powered with 14.7 volts. The D1 diode has been removed and the Mega 2560 is powered via a buck module, voltage converter. Othewise, the Ramps board is a stock, cheap one.
Approximately 13.9+ volts are moving from the ramps 1.4 into the bed.
The bed is insulated on the bottom, which did improve temperature and heat up time a bit.

I can achieve only about 90 degrees at full power, and this takes a good 20+ minutes. With a magazine on top, I have achieved 110 degrees. ( but drops quickly when I remove it )
I can get it up to PLA temps in about 6 to 7 minutes, and it can hold there fine. I can print with PLA. I'm just trying to get it up to higher temps comfortably, and so far, it's not working well.

So, I'm trying to determine my next course of action and also figure out if this is normal for these aluminum heat beds.

I am thinking about:
Replacing the aluminum bed with a PCB type and using glass on top.
Replacing the power supply.
Replacing the ramps board or perhaps using a relay.

Any thoughts or advice is greatly appreciated.

-Marc]]> ML3D General Thu, 07 May 2015 22:55:16 -0400 https://reprap.org/forum/read.php?1,506452,506502#msg-506502 https://reprap.org/forum/read.php?1,506452,506502#msg-506502
- Tim]]> tadawson General Thu, 07 May 2015 21:23:48 -0400 https://reprap.org/forum/read.php?1,506452,506452#msg-506452 https://reprap.org/forum/read.php?1,506452,506452#msg-506452
Is this normal for the aluminum beds or is it possible mine is defective?]]> ML3D General Thu, 07 May 2015 17:34:30 -0400