Size of bed

If you want much more go with a larger power supply. External P/S and you could go huge, internal ones that replace the stock one are available to a somewhat higher wattage (I have seen 350w). Not sure how high.

 

On the bigger one, 200 or 250 watts won't make a difference towards reliability. The determining factor being just how big your power supply is. The Meanwell 12v - 360W PS is about the same physical size as the one in the Robo, most Chinese power supplies are clones of the Meanwell (with varying degrees of precision). 360 watts is plenty to drive anything below a 300 watt heater. I thought the Robo used a Chinese clone at 300 watts but I could be wrong. If it's only 300 watts then the a 200 watt heater may be easier on the power supply. The only compromise within the power consumption restraint will be speed of heating, and only heating up. Maintaining a temp requires minimal power and cooling afterward requires none.

 

If you really want prompt heaters.. go to a 24v supply. You need a minor 12v adapter for the RAMPS/Arduino but the heaters (most of them) can deal with 24v and will work a lot better/faster. Check the specs.

 

Unfortunately, for US suppliers, no one can beat what AliRubber is doing, each and every one is custom and they are cheaper than anyone in the US.

As far as wattage goes, I don't even think the Default Robo heater is 200 watts. I believe @Mike Kelly mentioned that it is only a 110 watt heater, so it will be faster to heat up.

 

@Nathanfish If breaking glass plates is going to be an ongoing issue for you, I might suggest an alternative bed material. I am not going to say Aluminum either, although that would be a good choice, but there are better solutions. If you have your own table saw, or someone who does, then a large sheet of G-11 Epoxy Glass Laminate Board is the answer. In large sheets you will have many beds so you can be as impatient as you want, break as many as you want.. They are stronger than the glass beds, distribute heat better than glass, are perfectly flat and are very rigid. With G-11 you don't need to add something like PEI to the bed as it has superior adhesion properties than glass. Remember to use the smooth surface as you build surface. Of course you can find suppliers that will custom cut, but 4' x 8' sheets would yield a butt load of beds (I don't want to actually do the math here).

You must make sure it is G-11 not G-10, You can also substitute FR5 as it is a fire retardant version of G-11.

What Is G-11 Material?
G-11 FR-5 is a thermosetting industrial fibre glass composite laminate consisting of a continuous filament glass cloth material with an epoxy resin binder. This product, first introduced in the 1950's, has characteristics of high strength, low moisture absorption, excellent electrical properties and chemical resistance. These properties are maintained not only at room temperature but also under humid or moist conditions. NEMA G11 was the designation given to Glass Epoxy sheet composite by the National Electrical Manufacture Association (NEMA) to specify a consistent product between manufactures.

 

@Nathanfish As I am building my second printer I went with MIC-6 but I will use glass plate on the top. If Glass is the only bed material, I don't think standard cheap (buy it from Lowes) float glass is a good choice. Borosilicate glass would be better, but it ain't $11! A piece of float glass on top of your MIC-6 plate may be the final answer as you can then have removeable build plates. Float glass even as thin as 0.125" would work great since it's fully supported by the Aluminum. My bed has a supported area of 15" x 15" so I went with 0.250", but with the Robo I would think that even 0.125" Mic-6 would be plenty stiff, or something in-between. Don't forget to buy a bunch of neodymium magnets* to epoxy at each corner.

For everyone else, MIC-6 is the correct choice as it is cast and milled flat, other aluminum is made in rolls and flattened after the fact (no guarantee of flatness).

*Links:
For screwing in something like these: http://www.banggood.com/50pcs-N50-D-103mm-Strong-Ring-Magnet-3mm-Countersunk-Hole-p-940059.html
For epoxying on: http://www.banggood.com/20pcs-N52-S...mm-Rare-Earth-Neodymium-Magnets-p-998141.html

Where did you eventually order the heaters from?

 

I should also mention, do not make the bed too heavy as you are then relying on the electronics and motor torque to stop the inertia of fast moves of the bed. Increased mass means more inertia, means more current may be needed to stop the darn thing.

 

I believe Sivia is a she.

0.250" will make a pretty stout bed. I am still going to do the glass on top as it gives me easily removeable build plates without disconnecting the heater. In the RC world we use Anderson PowerPoles or Amass XT60 connectors. More than sufficient for carrying the heated bed load.

 

@Nathanfish I ordered mine from:

Phil Phillips

Midwest Steel & Aluminum
9151 International Parkway
New Hope Mn 55428

Direct # 763-582-1927
Main # 763-582-1925
Fax # 763-746-8918
www.midweststeelsupply.com
ephillips@midweststeelsupply.com

Cheapest place I could find on the web. But I only spent about 30 minutes looking. Took exactly 10 days from order to my door in NC.

 

@Nathanfish I think I paid $42 for a single 15 x 15 ATP-5 (Vista Metals trade name of Alcoa's trade name for MIC-6), That included shipping. So that seems reasonable.