Arcol blog Just another RepRap weblog

20Feb/10Off

Raftless — My fourth heated bed prototype

Living in the shadow of a giant:-)
It's not easy to be the second all the time. Presenting something, which has been already done.
But maybe I can show you some improvements, or some really nice pictures...

Yes, my fully working heated bed prototype!

There is not much to say here, except I promised you, I would publish the next day my working prototype and almost a week has already passed.

Well, my second prototype had been mirror drawed (the power resistors' holes), and thats why I could not present it to you at Monday.
However the build quality was pretty awesome:

I have found a friendly CNC shop, where they have fabricated the bed for me.

The next one had a bit too small working area (the exact same, what bitsfrombytes is shipping), just the pins were too close to the printing head, so it could not freely move. (because the metal sheet is only 0.3mm thick, while the plexi one, is 3 or 8mm. So the pins was too high)

Also I experimented lot with Neodymium magnets. I ordered from bestofferbuy.com magnet discs, like 6mm diameter and 1mm height, 8x1, 10x1, 12x1. But they were mostly a joke. They could maybe work for wallets;-\

Also I went to a specialized magnet shop here, and bought 20x3mm and 20x5mm neodymium discs.
They are anything but cheap:-(1.8EUR/pieces)
Two days later I went back and bought some more to experiment with, like N48 7x5mm, N48 10x10mm discs, and N35 10x10x15mm cube one.

So I dismounted the power resistors from my steel heated bed, and mounted on the aluminium:

And I made a simple testing setup from some leftover threaded rod (from my Mendel build), and M8 nuts:

And I realized that the bed is huge. No, really, I mean it is a gigantic heatsink: 106W is only enough to heat it to 70C.

Also for the old bed, I used necklaces:

But it is not a requirement. Simply twisting the 1.5mm2 copper is enough, and can withstand high temperature without problem.

So I sat down, and recalculated the needed resistors, and I bought more beefy power supply too.
Here is the new resistors:

And the thoroid transformers with builtin thermal protection, and housing, so I only need to plug in, and play;-)

And from the bottom:

I printed out the motor gear of Wade's new extruder design, with raft for the first time:

Here you can see the old heated bed vs. new heated bed printing quality:

It is more uniform, maybe the old printing bed was set too high temperature, and the plastic was too jelly while it was printing.

After this, I have gone wild, and printed it without raft. (btw, skeinforge bug: writing in the Raft plugin 0-0 for interface and base layers results the extruder go in circles...)

I also printed the big gears too:

If you look at the above picture carefully, you can see the sunset;-) The bottom of the printed plastic is like a mirror. Really beautiful.

I also reprinted my old owl, as it warped too much, so I wanted a new one;-)
Here is it during the printing of the first raftless layer:

Here is a comparison picture between the new and the old owl:

Also for the media-hungry readers here is a video, how I remove the object immediatly after it was printed:

Quick release while it is still hot.

Basically the same idea what Chris uses, just there is a small polyimide "ear" what you can grab (room temperature), and remove the top part of the bed. Wait a little (<1 min), and remove the plastics.

Also after seeing this, you can come to the same conclusion, that strong magnets are essential, because the metal sheet deforms, so pulling down to the table with as many super strong magnets, as possible is highly recommended.

If you are interested buying one, drop me an email to order (at) arcol (dot] hu

Also my aluminium sheet is deformed at one corner about 0.2mm. I could check in the CNC shop, because they have a special flat milled steel table.

I could buy purpose machined aluminium, just the price more then twice what I bought (and I have already bought the hardest aluminium available (AlMgMnSi1)). And the bed is heavy: 2.4kg.

So I dont know in which option are you interested guys?:

  • Heated bed with flat milled (purpose machined) aluminium sheet
  • Heated bed with "normal" aluminium sheet
  • Heated bed with "normal" aluminium sheet without power supply

Im planning to adapt my heated bed to Mendel, as soon as I have one, printing.
Which is some months ahead, because I need to come up with a reliable extruder for it, and
also if everything goes fine, I can assist in a making of a completely new electronics system.

I also assembled Wade's extruder, just this blogpost is long enough already,
I will make a new article presenting it.

Feedbacks are always welcome.

Comments (5) Trackbacks (2)
  1. Hey! :-)

    I wish you good luck with Heated Bed little business! I am sure you have a good one and users need them! I think Makerbot solution that they are selling is “ugly” and should work bad when compared with yours (and mine, and NopHead, etc) :-)

  2. AlMgMnSi1 sounds like it might be the recipe for 6061 ( typically made as 6061-T6 ) which is the same stuff they use for scaffolding, aircraft, etc. really strong.
    http://en.wikipedia.org/wiki/6061_aluminium_alloy

  3. buzz: Im not an expert myself either. But the official standard for this sheet (AlSi1MgMn) is EN AW 6082, EN 485.

    I only knew, that the CNC shop recommended this alluminium alloy, which is the second best after the purpose machined, flat milled one.
    But the flatness cant be guaranteed. (And it do have some error).

    It affects the total printing areay. Maybe I cant use my full bed. I need to test it more. Im printing all the time, since this is working, so I will test it out;-)

    casainho: Thanks, but people are not *that* interested in heated bed;-\
    Maybe there is not enough Rapman machine sold, or whatever. I could redesign for Mendel, but I haven’t seen anybody successfully printing with it.

    Laszlo

  4. is you heated bed suitable for Rapman 3.1?I would be interested to buy one. Could you ship to the uk? I am wondering whether it is too heavy 2.4 Kg for the z motor of my Rapman?How much do you sell them?Is it a complete heated bed kit, I mean transformers, sensors and power supply?
    Cheers

  5. JVCAD: mail sent. Thank you for your interest.