Building heated print beds is very popular these days, so I want to publish our 2 months findings. You should first read Look ma, no Warping, Nopheads Hot metal and serendipity, Zaggos Canned Heat and Zaggos Raftless. Now we have Heated Print Bed MK2, first design wasn’t as durable as we wanted (sandwich consist of 2pieces of acrylic) and the heat wasn’t spread evenly. [ad]
Our second design is much more better. First layer is floor tile for strenght and heat insluation, then we’ve put resistive wire on it, taped down with kapton tape. Next layer is glued to this by epoxy glue and its 3mm aluminium. It’s great to spread the heat evenly. I saw that Nophead can print directly on to Alu or Alu with kapton on it, but we are using piece of acrylic as top layer. Because it’s working without any problems.
Detail of insides of print bed.
Detail of sandwich.
Detail of sandwich.
Some informations
Temperature of surface: 70°C
Wattage: 80W
Volatage: 42V – 3.8Amps
Skeinforge
We are using modified Raftless plugin from Zaggo. First layer (whole, not only outline as in original) is printend at half speed but with same extruder RPM so its fattier and the contact with bed is much better, which is important to transfer heat into the object. And this is important to avoid warping.
We’ve had a problem with removing objects from bed that was caused by too much heat on connection so we’ve had to lower the temperature of the first layer downto 215°C instead of 235°C. Bond was just too tight so we had to use hammer and knife to remove objects.
Raftless, warpless
You can do pretty impressive things, you can print pretty fast at 30mm/s with no warping, you don’t have to waste fillament and time on printing rafts.
Plans
MK3 will be even better, I have to recount the resistance of wire to be able to power it from computer power supply, but the are not many things to improve. Next thing will be bowden extruder and heated print chamber.
RepMan things
Since we have RepMan there are some specific problems. Acrylic expands with heat, you have to modifi some more parts. At first you have to make the big piece on which print bed sits from plywood or you will have pretty serious warping and you can’t accurately set extruder Z-axis lift.
And we’ve done even heat shield for extruder. From aluminium foil.
BTW
You can watch our printer online and live here on USTREAM 
Free TV Show from Ustream
A floor tile! What a lovely idea! I’ve got pretty everything else I need to make one.
Hi Josef, looks like a big improvement. I also like the tile, especially for stability reasons (mechanical and thermal robustness).
It seems like quite some of the heat would be transferred downward into the tile. That it spreads the heat, which is useful, but it’s also heat loss a the same time. If the Aluminium spreads the heat enough already, maybe a glass-fiber mat could be placed between the tile and the filament. It also makes sure that the nichrome wire is evenly pushed against the aluminium.
P.s. good luck with the bowden setup
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I´m trying to so a similar design at
http://www.bitsfrombytes.com/fora/user/index.php?topic=398.msg5148#msg5148
but without replaceing the bed-holder and with cheap commercial heating-pads that can be powered by an off-the-shelf universal laptop power-supply (asjustable voltage, temperature controlled manually).
This calls for drilling holes through the floor-tile.
I´ll try coper for the surface and long screw-holes +1 sunk screw in the middle.
If that fails I´ll go with custom clamps like you did.
Co takhle pár detailů celý mašiny?