Cheap, simple and powerful heated bed

I've developed a simple heated bed, based on an aluminum plate with copper heating-wire and a rescue blanket for isolation. You can find it in the Wiki already: Robert's Heated Bed

I'm using the 13A variant (12V DC) at 120°C, driven by Traumflug's SevenSwitch. Heat-up time from 21°C to 110°C is app. 6 minutes (didn't stop the time for 120°C yet, but you'll have to add a few minutes).

What do you think about it?

This kind of heated bed have already be done with cork and wire long time ago. But it's a really good ideato make custum size heated bed.

The knurled nut idea is not bad but it's don't protect the nozzle again crash on the table.

Quote
zelogik
This kind of heated bed have already be done with cork and wire long time ago. But it's a really good ideato make custum size heated bed.

The knurled nut idea is not bad but it's don't protect the nozzle again crash on the table.

Thanks for your thoughts on this.
What was the cork for then? Guessing it was a heat isolation then the rescue blanket is lighter, cheaper, easier attached to the platform and consumes less space. And most of all it's easily replaced in case of damage, because it is only fixed at the platform rim.

The idea with knurled nuts for leveling was not intended to prevent nozzle-crashes. That's the job of endstops, isn't it?

I'm wondering, if someone has experiences with polished aluminum, instead of Kapton. Or maybe not polished aluminum does the job, but a certain "roughness" of the surface? People often print on glass, so I think a polished aluminum surface could do the job too. Anyone here with experience in that?