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They don't have a picture up yet but i presume that they are the same as their other ones, just round.

The Solidoodle people seem to like their square ones.

http://store.qu-bd.com/product.php?id_product=59

I have one due to be delivered today. However, I did the surface area calculations and the round one is not the one to get based on area (it also only comes in a 24V model).

The round one: 8" diameter is 50.3 sq in surface area

I then determined the largest square that will fit in a 12" diameter circle (easy trigonometry): turns out to be an 8.4" square. They offer an 8" square mat (12 volts) that gives 64 sq in of surface area.

With my aluminum heat dissipation plate on top, I would expect to get very even heating all the way to the edge. If this thing is as efficient as they claim (120°C in one minute with 15amps at 12V) then I should be golden with the 30Amp 12 volt supply I have.

I'll report back when I have tested it out.

Yeah, I was trying to decide on this or the Onyx, ended up getting the Onyx because of the mismatched dimensions, but with that aluminum spreader it's less of an issue.

Would be great to see some numbers of one vs. the other. Doubt it would be that much better to justify the cost at this point, but you never know.

I was going to ask you about that spreader - does it help retain some of the heat? I noticed that once the heat is turned off the surface temp drops pretty fast. Would be nice to have a slower cool down, but I guess if I upgrade my power supply the wait time for heat up is less of an issue.

Also, do you use any thermal agents between the three parts to even out the heat more? Like maybe thermal paste between the Al and Onyx? I haven't tested big prints yet, but I'm a little worried the Onyx is not evenly heating the glass, especially with the large fan I currently have blowing across the print area.

No, I do not use a thermal grease or anything. That stuff is messy and didn't provide any noticeable change when I tried it.

The spreader does help retain heat - it's mass. The glass above provides some insulation to slow down the cool off. I actually like that because it allows me to get back up to temperature quicker. I guarantee the Onyx is not heating the glass evenly. I have seen a 24°C temperature difference from the center the the edge when the center was at 80°C.

You're trying to sell me one of your heat spreaders, arencha?

I'd be happy to but you could make your own too. I posted the plans on my blog for folks to download. But, I do get materials in bulk and have the fixtures to make these pretty cost effectively.

Cheers,
Michael

Buy one it's cheaper than getting 1 piece of stock even if you don't count your labor it's still cheaper.

Yah I know, the price is extremely reasonable. I was just ribbing him.