Heated bed setup help.

[shadedurza]

[RetireeJay]

[shadedurza]

[Mooselake]

I haven't use a 120V bed heater, but it's been done before and I've seen a few posts in other places about them. Besides what RJ said I'd add an insulator (Kapton sheet should work) between the heater and the aluminum bed just for some extra protection, and maybe put a piece of glass over it as a print surface. The SSR input essentially drives an LED, which then triggers an optical switch, so as long as you're supplying the correct type of input the bed should work. I'd test it first before connecting up the Printrboard, use a 12V DC source to trigger the SSR and see if the heater works. Be quick, since you're not controlling the input; the Printrboard will turn it off and on as needed, you're manually pretending to be that controller. Before that I'd take an ohmmeter (like the one in your handy digital meter) and make sure there's no connection between the heater and any other conductive surface, like the aluminum bed. You don't want to have a short to the bed and light up your eyeballs, not to mention all that heart stoppage fibrillation stuff, from the shock if you touch it.

Also, with that aluminum wire get some anti-oxidation grease (like Noalox, Ox-Gard, or similar. Tell your local hardware store you're doing some aluminum electrical wire and they should be able to direct you to the right product). Otherwise the connections will develop an oxide layer and start heating up. Burned down a lot of houses when they first started using aluminum house wiring. I have a 100A circuit out to my barn that uses aluminum wire and the proper oxidation guard that's been working well for nearly 40 years.

With that kind of power you should have a very fast heating bed. Just keep an eye on it - it the driver MOSFET fails on or the thermistor fails the wrong way it'll get mighty hot. This has happened with hot ends on many brands of 3D printers, and in a few cases started fires. As always you shouldn't leave your printer (of any brand) unattended while printing. The types of protection (like thermal fuses) in virtually every household appliance haven't made their way into the 3D printer world so you need to give them more attention than your coffee maker. A smoke detector and nearby fire extinguisher are a good idea.

Kirk

[RetireeJay]

[Mooselake]

No Simples here, so I don't know what the underside of the bed looks like or how a heated bed's wiring is routed...
Your diagram shows a barrier strip connecting the heated bed to the SSR wiring. Assuming you can mount a barrier strip (like randomly picked one)on or near the heated bed, and safely insulate it (inside a small plastic enclosure, for example) you could shorten the aluminum wires and then connect them to something much more flexible (another , this is rated for 600V). With some proper wire routing, and the aforementioned anti-oxidant, the flexibility issue is gone.

I have a meter of 12ga silicon coated wire in the Printrbot upgrade box waiting for the next teardown/mod cycle.

I like the idea of a higher wattage heated bed, assuming proper safety measures are added and/or used, but you're definitely into experimenter territory where there be dragons. Iirc the larger print bed machines often use mains voltages, presumably since their bed heaters would require car jumper cables to carry enough current at 12 or even 24 volts. That's the good cables, not the lightweight single use vaporize after one jump cheap ones from Sam Walton's Emporium.

Kirk

[shadedurza]

Nice. I've read to be wary of wiring with dissimilar metals. Since the wire from the pad is aluminum and the new wire I would use would be copper (or tinned copper like in your link) does the barrier strip / anti-oxidant negate that issue? Assuming you suggested this because just soldering the two together would be even worse.

[RetireeJay]

You can't even solder to aluminum (at least not without some very special equipment and materials). Mechanical connections to aluminum are the way to go. But that leads to the question of how the aluminum wires are attached to your heated bed. If it's a mechanical connection that can be un-done and re-done, then throw those aluminum wires away and use copper from end to end.

[shadedurza]

I've sent the ebay seller a message. I'll post the reply here. For now here's the link to the one I have:
h t t p://w w w.ebay.c o m/itm/281275441183?euid=acc14f3d2dc04c8491aabf7928ce4605

[RetireeJay]

Umm... are you sure the wires are aluminum? The eBay web site doesn't say. It's common for some copper wires to be "tinned" so that their color is silvery instead of copper-colored. Tinned copper wires will be shiny; aluminum ones will be dull, duller even than the matte side of aluminum foil. If you scrape a tinned wire with a knife, you'll see the copper under the thin plating.
Frankly, it would be very unusual for them to ship the heater with aluminum wires. I don't think the cost difference between the two metals is very great, and copper is so standard for this kind of use that they would almost have to tell you that they used aluminum.

[shadedurza]

Sooo I learned something today. I'll take a closer look at the wires when I get home. The ebay seller will probably be able to confirm or not too.

[shadedurza]

Yup they're totally tinned copper. Apologies for wasting everyone's time!