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14May/10Off

Heated bed improvement


Its always nice to see how others are developing further your design.
This just happened: my previous heated bed buyer thought further the design.
He insulated the bed, and made a control-circuit for it.

It's time to update my version too;-)

Im recently developing some bigger things, like an enclosure case
for Openmoko phone and some circuitry.
Here is a failed print about the first prototype:

The final case will be 200x140x80mm, so it is pretty big. (however, I will redesign it to make a bit
smaller, so only about 160x140x80;-)

All in all, I needed to develop a bit further my heated bed.
I always assumed it is operating a bit too low temperature.

Some days ago I was in Ikea store, and there were some leftover items, what you can buy at a reduced price,
and I found a 100cmx40cm MDF sheet for ~1.2EUR, it was an "instant get";-)

The rest of the story is obvious, I went to home, and three days later,
I had my improved heated bed:

I covered the aluminium bed with MDF sheet even at the top:

I also added one more power resistors at the bottom (6 in total), and borrowed a
wool coat from my mom as an additional insulator. I have seen on Nophead's blog, that wool is perfect insulator:

Im a bit worried though, I think the whole thing will catch fire sooner or later ...

The power resistors are at 170C, and the MDF sheet are smelling like it were burning.
So the machine has a really unpleasant smell right now. I have not really liked the ABS
fume, but burning wood is way stronger smell...

Anyway small price for the final result...
Im thinking of covering the bed with Polyimide tape first, and after with the MDF sheets.

z-switch-holder

When I assembled the whole bed, noticed, that my z_switch_holder are no longer working.
So I designed a new one, along with the "big_foot":

I dont know about you guys, but for me nothing works at the first time. Everything
what I design have at least 4-5 iterations. Just like when I do programming,
which is mainly a trial-and-error process too.

Sunk magnets

With each aluminium plate machining I make a small improvement.
This time I made blind holes for the neodymium magnets:

Final thoughts

This heated bed became some kind of a monster. It is pretty complicated, has an
enormous size, which I dont think the machine will ever use...

I also made recently some test prints with some bigger objects (need to write a
blogpost about it though;-), to push a bit to the limit of this heated bed, and
the result were a bit ...

Comments (3) Trackbacks (2)
  1. Nice work :) .

    With regards to controller, I made a simple one and both schematic and source are available on reprap blog: http://blog.reprap.org/2010/05/quick-hot-bed-temperature-controller.html and it works like a charm for few days. Unfortunately I cannot send I2C from BFB electronics but the reprap motherboard has i2c header and it works. It’s pic rather then atmel based (I have limited supply of atmels at home and a lot of pic’s and ti’s so that’s why) but it is very simple to port to any mcu. It uses same thermistor as bfb hot end does.

  2. Thanks for the hint Bogdan.
    The thing is, Im stilla bit low on temperature, so I dont really think about temperature control, as Im only working with ABS currently.

    However Im a bit scared about this MDF sheets, dunno what temperature they catch fire, but definietly there is an unpleasant burning wood smell.

    So this insulation thing is still not finished…

  3. The MDF won’t actually burn until it gets plenty of air as well. However, you shouldn’t get it hot enough to fume, as it gives off some nasty products (formaldehyde) from the glues and resins used. So make sure you have plenty of ventilation!