AC Bed SSR Box

I designed and printed this AC Bed SSR box. I have 3 printers converted to use AC power using this box for a much faster warm-up time on my 300mm sized beds. Many 3D printers rely on low cost Power Supply Units with limited lifetime at the top of their power rating. Switching to AC power for your heating bed greatly reduces the demands on your PSU and will likely greatly increase its life expectancy.

You will need the following items to complete your own:

• SSR
• Silicon AC heat pad
• AC inlet with rocker switch
• 40x40mm fan
• 4x M4 screws for the lid
• 2x M4 or M5 to fix the heatsink to the bottom of the box
• 4x M3 screws for the cooling an
• Wire of sufficient gauge
• Soldering iron and screw drivers

The SSR sends the AC current direct from your wall outlet to the heated pad. It is controlled on and off by a small DC current, coming from your existing heated bed port on your 3D printer.

The common 40x40mm fan is made to draw heat out of the box and is fed by the heated bed port from your 3D Printer controller board, at the same time that same signal is driving the SSR, so the DC side of the SSR and the cooling fan are connected in parallel. Whenever the chip on your controller board activates the Heated Bed port, the SSR will turn on as well as the fan. I use old and beat up fans and the noise they make let me know whenever the heated bed is on.

There are several sources for these parts. Here are some I used.

SSR:

SSR-25DA, SSR-40DA and Heat Sink
https://www.ebay.ca/itm/25A-40A-100A-SSR-25DA-SSR-40DA-SSR-100DA-250V-Solid-State-Relay-Module-Heat-Sink/122855145065?ssPageName=STRK%3AMEBIDX%3AIT&var=423306029021&_trksid=p2057872.m2749.l2649

.

Silicone bed:

Lower cost 300mm Round AC bed (20$us)
https://www.robotdigg.com/product/562/300mm-Round-Silicone-Rubber-Heater-Pad

Lower cost 300x300mm AC bed (20.50$us)
https://www.robotdigg.com/product/115/300-or-310mm-CR-10-Silicone-Rubber-Heater-Pad

Keenovo has a large selection of high quality heating pads – https://www.keenovo.com/info/shop.html

More expensive at 69$ for a Keenovo 300 x 300mm –
https://www.amazon.com/gp/product/B00V81ZI70/ref=as_li_tl?ie=UTF8&tag=3dkc-20&camp=1789&creative=9325&linkCode=as2&creativeASIN=B00V81ZI70&linkId=89d8faa054e270e3c94849262c00dce4

AC Inlet with rocker switch:

This diamond shaped inlet is fused and available widely.
http://amzn.to/2hejnXb

40x40mm 12v fan:
https://www.amazon.ca/Extra-Quiet-Brushless-Cooling-AV-F4010MB/dp/B01KX0U8HG/ref=sr_1_7?crid=1O15PBNKHHIV4&keywords=40mm+fan&qid=1577297763&sprefix=40mm%2Caps%2C163&sr=8-7

There is a similar version without the ears and using springy grips to hold the AC inlet in place. I prefer the ears and screws for a more positive attachment.

A 350 watts AC heating bed only draws 3 amps at

Jterranella has a similar design but it is not using the heat sink for the SSR. Check here for his Thingy: https://www.thingiverse.com/thing:1844330

For more information on how to convert your 3D printer to an AC Heated Bed using a silicone hot pad and SSR, check this tutorial – 120VAC Silicon Bed controlled by SSR – 3D Printing
https://www.youtube.com/watch?v=rjmCIzG2v5g