I'm probably missing something simple but I cant see why its being done like this. Could anyone please explain?
Thanks, Matt

The original 3 hole mounting setup of the 'doodles means that if you use a 200cmx200cm bed, it fouls the mounting/adjusting bolts.  To use the existing bolts, you can only use the 150 (? or 100.. havent looked for ages) pad. The same issue existis with the circular pads due to the closeness of the two front mount bolts relative to the arc and their setback from the edge.

So to use the most appropriate sized heater, you either need to replace the plate as a whole (as per mloebl) or mount it above.

would you be able to send a link to the heated bed on ebay? Also, did you put any insulation on the bottom?

Here's the newer version of what I have:
http://www.ebay.com/itm/NEW-Solidoodle- … 2c9260998f

I did not insulate it...  Probably wasted heat, but goes into heating the enclosure anyways so no big deal.  You will need an aux relay for that heater as usually the stock relays/traces on the different control boards can't take it.   Here's the one I got as it was convenient, but doesn't have to be this one:

http://www.ebay.com/itm/30-Amp-Relay-Bo … 3cea59a775

Thanks, at looks great!
Ill add it to my list of things to do once I get a new power supply. It seems like you cant really do any modifications to the solidoodle that change power consumption without it!

Probably overkill, but I have a dedicated p/s for the heater, then another p/s for everything else.  Could do that with the stock power for the SD board and extruder/etc, then with an aux relay use a dedicated supply (though again could be overkill )

It looks here like the new heaters are going on top of the aluminium plate rather than below it, Hence requiring the metal to be ground down to fit the bumpy underside of the QU-BD heat bed. Why not do it like the original solidoodle bed and put the heater between the insulation and the metal plate?

That's how I did it... I got a piece of MIC6 from McMaster, took off the old plate so I could use it as a template, and drilled out the new plate on a drill press (cheap one I got from HD awhile back.)  I countersunk the holes so the screws would be flush with a larger drill bit.  I then got one of the 200w silicone heat pads that stick on the bottom that another member on here sells on eBay (I think he sells 300w models now.)  Used an external relay as too much draw for my Rumba board.  Works great; heats up in about 10mins, and the thicker aluminum plate holds a steady temperature quite well.

It looks here like the new heaters are going on top of the aluminium plate rather than below it, Hence requiring the metal to be ground down to fit the bumpy underside of the QU-BD heat bed. Why not do it like the original solidoodle bed and put the heater between the insulation and the metal plate?

I'm probably missing something simple but I cant see why its being done like this. Could anyone please explain?
Thanks, Matt

Let me know if this works!