Sunday, 28 March 2010

Recycled Heated Bed

I finally put together an idea that I've had floating around for a while.
My wife had an old heated pad where the fabric had worn through. I took out the plug and element, and saved it, because I though it probably had some nichrome wire in the element.
Fast forward several months, to all this recent talk of headed beds.
I uncovered the element from my 'parts' box, and inspected it - the insulation is all intact, all well covered, no damage and safe. A careful test showed it still warmed up when plugged in.
I grabbed a couple of steel baking trays from Wilkinsons (£1 each) and my kapton tape.
From HeatedBed
I punched a hole in one of the trays, carefully bending the edges and masking them with tape so there were no sharp edges. I could then feed the element through and taped it to the back of the tray in a rough spiral with the kapton tape.
From HeatedBed
The other tray, I covered the base with strips of kapton tape, and placed over the element tray. VERY IMPORTANT: I added an earth wire grounding both of the trays to mains earth (the PSU case).
From HeatedBed
Hey presto, heated bed.

Firing it up, it reached 80C+ in a couple of minutes on 'full'. I haven't run it further than that without mounting it properly first.

Potential problems:
  • Using Mains electricity - you need to be *very* careful and earth the case. Check your safety three times.
  • I don't know what temperature it will reach: it needs to be mounted properly and tested. Temperature control is provided by the original power box - I can have 1, 2, or 3 and it will automatically switch off after 90 mins. (probably not a problem unless I'm doing a long print).
  • The surfaces of the tins are relatively thin pressed steel. I suspect they're flat enough for 'small' prints (up to makerbot size) - I'll have to see if they're flat/rigid enough for larger objects.
Potential improvements:
  • I could fill the thin gap between the element and the two plates with fire cement: it might improve heat conduction and possible help with stiffness/flatness.


paul said...

Some slightly more expensive baking sheets should do fine if this is too thin.

dissidence said...

kiudos good idea, may still need to be a tad thicker but more money can solve that one and baking pans even good ones that are thick are not much money.

caution though dont take the ones from the oven, the mrs might think its a good idea