HEATED BED UPGRADE – DIY power supply / relay

Do you have to wait a very long time before the 3D printer starts printing? I’ll explain how to improve your 3D printing start-up times. Coming up!

See the video about it on YouTube!

On my original Velleman K8200 3D printer the power supply is only 15V 6.67A which gives roughly 100W. As the nozzle heating block is very small, it gets to the desired temperature very quickly. The major problem here is heating up the bed. This applies to all printers. Mine is size of 20 by 20cm. With its resistance of around 6 ohms, it means it consumes 37.5W of power. So, as you have figured out, the heated bed is the bottleneck of fast starting up the prints. Let’s dive into the solution.

INTRO (& some math)
So we want our heated beds to consume more power to heat up faster. In short, we have to install a more powerful supply. Higher voltage, higher current.
For the enthusiats I prepared short calculations. You can skip them directly to the connection part.
As you know voltage multiplied by current gives us power (P=U*I). If you want to increase the power, you have to deliver more voltage or current. Analogy: we cannot force the water to flow faster through the canyon, if there is not enough additional force to push it through. That is what Ohm’s law tells us about electricity. You know that at certain voltage, the current is limited by the resistance. (U = R * I. So the I = U / R.)
So we will have to increase the voltage.
Let’s see the original situation and upcoming one.
15V in my case / 6ohms gives us 2.5A. So the power will be 15*2.5=37.5Watts. Or you can calculate the power from equation 4 on the screen.
If we use 24V power supply the case is: 24V / 6ohms gives 4A. So 24*4=96W. This would give us roughly 2.5 times gain. Nice.
If you use several layers of different material above the heated bed (i.e. thick aluminum, glass plate etc.) and do not use 3D printer enclosure, the start up time will be longer. The stated times above are true for using only glass plate above the bed and using the enclosure.

Almost all 3D printer electronics use MOSFETS to drive the heating. If we want to connect higher voltage power supply, and do not want to interfere with original electronics, I suggest you use a DC/DC solid state relay between the printer electronics and heated bed. Find the links below for the needed parts.
We will connect printer electronics to SSR via a small resistor of about 12k ohms. At 15V on the original PCB this gives us 15mW of power loss on the 3D printers’ side which is negligible. Then we connect our 24V power supply on the other side and to the bed. Simple steps and no intervention into printers’ electronics. I chose an AC/DC converter from Geekcreit which is very small and fits nicely alongside the solid state relay. See the link below for more. I fitted them in a small printed enclosure and fastened it to the printer.

With a stock power supply when I wanted to print with ABS filament, which requires 110°C hot bed, I had to wait 3/4 of an hour to 1 hour to start the print. Not to mention, if I opened the window to get rid of the ABS smell, the bed temperature dropped and it caused my prints to get ruined. By upgrading the bed power supply with a 24V-one prints start in about 10-15 minutes. Estimated cost with custom printed ABS box were around 20€. An investment worthwhile.
Don’t forget to hit LIKE below, COMMENT what you think of this upgrade or have better ideas, SHARE this video with your friends and consider SUBSCRIBING to my channel and watch my other videos on 3D printing. Thank you for sticking by, see you next time.

A 3D printer heated bed power supply upgrade – a very simple and cheap 3D printer heated bed DIY.

See the links under the LINKS menu…

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