Introduction: 3D Printer Heated Bed

I've tried several kinds of heated beds over the last months. But I
was wondering, if there wasn't a far simpler, more efficient and even cheaper way to build one. So I've developed a heated bed, based on an aluminum plate, heated by isolated copper-wire. No etching is required, no exotic machinery and only materials any RepRapper should easily be able to buy.

In its 13 A-Version at 12 V the bed heats up from 21° C to 110° C within 6 minutes. You can drive the bed with 18A (e.g. with SevenSwitch; 216 Watt), which gets you to 110° C in app. 2 minutes.

The list of materials needed for this heated bed is quite short:

  • Bed of nails, made form wood and 64 nails with 2.2mm diameter
  • Aluminum plate, 220 mm x 220 mm x 3 mm
  • Kapton adhesive tape, slim (e.g. 20 mm)
  • Rescue-blanket (gold on one side, silver on the other)
  • Thermistor (e.g. EPCOS B5781S104F40)
  • Copper wire, isolated, 0.56 mm diameter (0.6 mm with isolation)
  • 1.5 mm² wire (has to withstand the heating current)
  • Wire to connect the thermistor

Step 1: Form the Heating Wire With a Bed of Nails.

Make a bed of nails and place 32 nails in equal distances on two sides. You may add nails in the middle of the first and the last row too.

Cut off the heads of the nails.

Stretch the copper wire using the nails like shown in the picture to form a regular pattern. The less windings you make, the more powerful the heated bed will become, consuming more power though. Using only every second nail on each side will result in an 18A heated bed (I love it!).

Remember that you need a powerful electronic to drive an 18A bed (e.g. SevenSwitch). RAMPS1.4 only drives up to 11A and you shouldn't push it to it's maximum abilities. A cheap SevenSwitch is a good replacement and works with 18A beds like charm.

Step 2: Fix the Wire Distances

Use some Kapton tape to fix the wire in its actual form. The tape should only adhere to the wire, not to the bed of nails below, because you'll have to lift the wire up in the next step.

Step 3: Lift the Wirefrom the Bed of Nails

Because you've cutted the heads off the nails earlier you can now lift the wire from the bed of nails. The Kapton tape keeps the form you gave to the wire.

Step 4: Place Wire Below the Platform

For my builds I drill 3 3.5mm holes into the aluminum (two on egdes on one side and one on the opposite side in the middle, because I use three points for leveling the bed). Prepare your platform in your own purposes and requirements.

3mm Aluminum are just enough to give a plain and stable building platform. And you don't need anything else for printing on it. Just spray some hairspray on the platform before you print. That's all. And after printing let the platform cool down and your print will come right off the platform by itself (because aluminum has a very different thermal expansion coefficient to plastic). And printing at 110° C and above prevents warping just perfectly. So forget about glass, clamps and expensive coatings.

Fix the wire to the bottom side of the aluminum platform, using the Kapton tape on the wire. You can add some tape if you seem to need it. Most if the isolated copper wire should touch the aluminum.

You don't have to be very accurate here, because the aluminum will spread the heat from the wire to the surface very evenly.

Step 5: Uninsulate the Wire-ends

The isolated wire needs to get uninsulated so you can connect it to the supply cable.

Step 6: Place Thermistor Under the Platform

Place thermistor in the center of the platform between the wiring. You should use a thermal conductive adhesive or Kapton tape and thermal conductive paste for that.

Step 7: Check Resistance

You should measure the resistance of the heating wire, to ensure you didn't short-circuit it.

Be aware that standard meters are not very accurate at low resistances like we use it. Well, it's not that important know the exact resistance, as long as you didn't left out more than one nail per row to form the wiring.

SevenSwitch can drive far more than 18A at 12V, but you need an adequate power supply!

Step 8: Add Thermal Cover

After connecting the power-cables to the heating wire (don't solder, but crimp it!) you can cover the bottom side of your new heated bed with a rescue blanket.#

The silver side should face to the aluminum, the gold side off the platform. The silver side is electrical insulating, in case some of the wire insulation fails in operation (remember, we're operating at over 110° C).

The silver side reflects the heat of the wire and from the platform back to the aluminum, resulting in less power consumption, faster heating up and, more important, leaving anything below the heated bed cool without additional thermal isolation!

Tipp:

Some of the rescue-blanket may melt on your first attempts. That's no problem at all. You can leave the resulting holes as they are, except the construction underneath become too warm. Then you can just place a patch of rescue blanket with some Kapton tape to fix the holes or just replace the whole blanket.

I love this solution. It's very inexpensive and easy to make. Even the Thermistor is a very cheap one (only has to work slightly above 110°C though).

And it's a lightweight solution, so if your printer moves the bed, this solution is good to your bearings and motors on the long run.

Comments

author
fewtheG (author)2015-02-08

Would using screws instead of nails work? this may seem like a dumb question.
however I find screws easier to place evenly and they make for a nice Grove for the copper wire to "sit" in..

author
RobertKuhlmann (author)fewtheG2015-02-09

Hi fewtheG,

screws instead of nails will not work, because you'll not get the heating wire lifted up from the bed of nails. It will stuck on the thread if the screws.

So, please, use nails and cut their heads of after hammering them into the bed of nails. To get even spaces between the nails you may print a mask for the nail-positions and drill a small hole for every nail.

But you don't have to be 100% accurate with that, because little differences in the spaces between the nails don't matter, because the aluminum delivers the heat very evenly from the heating wire to its surface. As long as there are no short-circuits between loops of the wire, anything will work just fine.

The better the contact of the wire to the aluminum, the more effective the heating bed will operate.

author
lathe_makeatio (author)2015-01-26

Nice and simple solution!
The only thing I wonder if the coating of the wire will stand a long time good at 110 C and doesn't become hard an peels apart. I just remembered overloaded transformers which coils where overheating. ;-)
My solution for power supply wires are those soft measuring wires that sold for laboratory power supplies or measure units.

author

Over the years you might have to replace the wire - maybe. So don't through your bed of nails away and you can replace the wiring anytime. (making the bed of nails costs the most time here, but it will let you make many heated beds though)

The materials are so inexpensive, that you can e.g. make two beds, so if one fails (what I didn't observe until today, printing often at 130°C) you have a replacement.

And you're right. Good power supply cables are important, as 18A are a heavy load for the cables.

author

Whuaaahhh. It should read "don't THROW your bed of nails away", of course.

author
RobertKuhlmann (author)2015-01-28

Just one comment on wire-temperatures, isolation-failure and short-circuits:

The
risk of short-circuits because of isolation failure is very low,
because the wire only becomes hot where not in direct contact to the
aluminum (where it gets cooled, because its heat is conducted into the
aluminum). So the isolation of the heating wire will, if ever, most
likely fail where it doesn't matter.

author
RonC70 (author)2016-07-01

I am building a 3-d printer based on visious1 CNC. I printer I am building is 12 x 12 by 24. Big build volume. Would this build scale up?
RC

author
RobertKuhlmann (author)RonC702016-07-05

It may scale up. You should use several heating fields under the platform and supply them in parallel (the aluminum spreads the heat very evenly). Of course you need a sufficient power supply for that, or several supplies in parallel and, more important, you should use several switches (e.g. SevenSwitch) in parallel, because their abilities are limited too. But if you scale up everything in parallel it should work like charme.

author
Phoenix17 (author)2016-01-16

Maybe look into fiberglass insulation as a bottom cover. It won't reflect, but will conserve the convection heat. I would expect that to work pretty well.

author
RobertKuhlmann (author)Phoenix172016-01-16

Hello Phoenix,

the reflecting property of the rescue blanket is essential. It protects the printer-parts below the building-platform against the heat and reflects this heat to th bed, which therefore need less power to hold its temperature.

So there's no problem with the rescue blanket that fiberglass would solve and would be more expensive.

But thank you very much for giving your thoughts and ideas to my project. New and further ideas are welcome.

Yours

Robert

author
richfiddler11 (author)2015-07-10

In theory, you could power a heater like this this with AC line voltage. You'd need a power resistor to limit the current (and/or a different type of wire with higher resistance) and some type of thermostat. Electric blankets/heating pads do this with very little circuitry. Naturally, insulation would be come a much bigger concern!

Here's a link to an electric blanket circuit from a US patent: https://patentimages.storage.googleapis.com/pages/...

author
printrbot932 (author)2015-01-26

Is there a way to make this work on a 100 mm by 100 mm bed?

author

It may work for 100mm x 100mm as well. You need a smaller bed of nails and should use the same length of wire, as for the 200mm variant.

Lets calculate it:

32 nails on each side give 32 rows in maximum, each app. 195mm in length, plus app. 4mm for the way around the nails of a row and 6mm for the way between the rows. For 18A I use every second row. That makes

16 x 195mm
+ 16 x 4mm
+ 16 x 12mm
= 3376mm

For a 100mm bed each row would be app. 95mm in length. You'll have to place the 32 nails on each side more narrow to place them on the 100mm distance. Then you can form the wiring, using all 32 rows. That should result in a wire length, similar to the 200mm variant with 18A.

The alternative, using thiner wire with less number of rows/nails is not recommended. Thinner wire gets too hot and you'll burn the insulation of the wire. Well, you could insulate the aluminum with Kapton instead, but the thermal transfer between wire an aluminum, and more important the heat-reflection from the rescue-blanket to the aluminum would suffer from that.

I hope this helped.

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