# Speeding up the heating of the heated bed

Currently I am using a 12 volts, 20 amperes power supply (Model S-240-12)

The stepper motors and the extruder need 5 amp, and the heated bed build plate needs 11 amp.

Technically you only need to use a 12 Volts, 16 amperes power supply, but I understand that you use the one with 20 amp because pulse currents from extruders and stepper motors can be stressful to supplies loaded to the max, so for reliability and performance, it is better to use a supply rated for 25% more than you need

In the place where I buy the spare parts for my 3d printer they also sell 12 V power supplies capable of delivering 25 amp and 30 amp and they told me that if I use those ones you are going to be able to speed up the heating of the heated bed. Is that true? I understand that the heated bed is only going to take the 11 amp that it needs so is not going to make any difference to use power supplies capable of delivering more current

• are you trying to print ABS materials? What temperature is required? – profesor79 May 3 '18 at 8:52
• you could add a 2nd power supply that outputs a higher voltage, and use the old 12v to power a relay or switch a mosfet which controls the higher voltage. – dandavis May 6 '18 at 0:58

Changing the PSU with one with a higher amperage will not make the bed heat up any faster unless the PSU is underrated for the amperage required and the voltage is dropping as a result of the load. This can be checked by measuring the output voltage with a multimeter (when the PSU is loaded e.g. by a heating heat bed). In this case, the PSU has a marginal higher Amperage than the printer consumes (even has some room for the over-voltage; under the assumption that it is a good working PSU). Increasing the voltage will decrease the heat up time. There is a screw next to the 12 V connectors that can change the output voltage of the PSU. Usually it is save to increase the voltage up to 14 V, but that depends on your whole setup (and 14 V is applied to the whole setup, increasing the current for all parts, including your printer controller board, this board must be rated for the 14 V). Please do check the stability of the voltage during load.

Although it can be done, it is not something I used. What is an extra minute on a print of several hours?

You can do the math: say the heat bed has a resistance of 1.2 Ω:

• at 12 V that will draw 10 Amps (12 V / 1.2 Ω) resulting in a 120 Watt (10² A * 1.2 Ω or 12 V * 10 A) bed,
• at 14 V that same bed will draw 11.7 Amps (14 V / 1.2 Ω) resulting in a 163.3 Watt bed.

What you could do to decrease time to heat the bed without changing the PSU or the voltage is to insulate the bottom of the heat bed with heat bed cotton sheets or cork (placemats from IKEA ;) ), put a sheet of cork onto the heat bed before printing and start heating the bed through the LCD panel of the printer or any attached printer controller programs over USB prior to printing.

• Changing the PSU with one with a higher amperage will not make the bed heat up any faster.  - unless the PSU is underrated for the amperage required and the voltage is dropping as a result of that. This can be easily verified with a multimeter (measure the voltage coming out of the PSU with the bed on and with the bed off). Increasing the voltage has a number of other benefits (the hotend heats up faster too, and the stepper will have a higher top speed). – Tom van der Zanden May 3 '18 at 7:29
• Unfortunately, I had to lower back the voltage on that kind of psu, as the voltage was not stable and temperature readings on thermistors were jumping up and down by 4 to 6 degrees. So this is something that you need to take into account. – profesor79 May 3 '18 at 8:38

May I recommend an alternative approach, which does not require any change of hardware? The time required to heat the bed is not huge, so either via USB from your computer or from the front panel, instruct your printer to heat the bed first, while you're setting everything else up (loading gcode files, changing filaments, or whatever). This way tasks are completed in parallel.

• I am using a preheat custom function in marlin which does the job +1 – profesor79 May 3 '18 at 14:39
• Insulation at the bottom works also, also putting a piece of cork on top during pre-heat and remove just before printing – 0scar May 3 '18 at 19:08
• The question at hand is whether getting a higher-rated PSU would speed up heating of the heated bed. This - while helpful - doesn't answer that. – Tom van der Zanden May 4 '18 at 6:10

I glued (high temperature silicone) an isolation (cork 5-8mm) on the bottom side of my heatbed. It avoids loosing heat thru the bottom side. Effect: minimal faster heatup and less energy consuming over the time of use.

• The question at hand is whether getting a higher-rated PSU would speed up heating of the heated bed. This - while helpful - doesn't answer that. – Tom van der Zanden May 4 '18 at 6:10
• this is a correct answer @TomvanderZanden as it focuses not only on the tiny area given by OP, but also provides an alternative way to the solution. – profesor79 May 4 '18 at 8:06
• @profesor79 The question is "Would using a higher amperage power supply result in faster heat up times?". This answer doesn't also provide an alternative solution, it provides only an alternative solution. The question is very specific - the person asking the question wants to know whether upgrading the power supply makes sense - and this does not address this at all. – Tom van der Zanden May 4 '18 at 8:49
• @TomvanderZanden the thing is that we can be closed to what it says, or be open to what it means. – profesor79 May 4 '18 at 9:33
• i did the same think with kapton tape on the bottom. it cut about 15 seconds off the heat up time. – EvilTeach Aug 1 '18 at 22:27

Also a thing that helped to preheat faster: make sure no draft is cooling down bed. It sounds obvious but cold-end fan and window draft, even psu fan draft can contribute significantly to preheat time. Eliminating draft source changed bed preheat time from 10 down to 5 minutes in my case...

• The question at hand is whether getting a higher-rated PSU would speed up heating of the heated bed. This - while helpful - doesn't answer that. – Tom van der Zanden May 4 '18 at 6:10