Heated bed improvements ?

Hi all,

Ormerod heated bed, in my opinion after 1 month of usage, is perfectible. Some ideas:

1) plywood (or mdf ?) is not very rigid and stable, I would prefer something like aluminium and/or plexyglas for bed insulator
2) to isolate lower layer (aluminium and/or plexyglas) from heated bed why don't use a sheet of corkboard instead of cardboard ? Much more insulating, compact and stable in my opinion.
3) why don't use a mirror instead of glass for upper layer ? Perhaphs it would also possible to choose a suitable proximity sensor, that can sense the reflecting layer of the mirror, avoiding that cheap stripes of aluminium. We could then zero the Z axis at any point we need.
4) In general, I would like to pull away the central Smooth rod 12x350mm by some 10cm in order to better handle the bed. I would add another bearing to that axle, 4 in total, then fix the bed to the clamps (2 per rod) and design a better transport system (3 pulleys ?) for it. As now, bed is quite instable, every two or three prints I need to recalibrate all...
Regards,
Paolo

I think the biggest problem is that the mdf is not stable enough and the back rib is too far away from the back corners. This causes the back corners to sag a variable amount. There are a number of solutions:

- use an aluminium bed support in place of mdf, as I and several others have done
- reinforce the mdf (someone used carbon fibre square tube)
- Turn the bearing supports over so that the back rib is behind the bearings, hence closer to the back corners

I'm not sure that two bearings are needed at the front. The bed only needs to be supported at 3 places. I'm using a triangular aluminium bed support that doesn't support the front corners.

The mirror is an interesting idea, especially as I print PLA direct on glass, so there is no Kapton to get in the way.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42
The mirror is an interesting idea, especially as I print PLA direct on glass, so there is no Kapton to get in the way.

I see plenty of people that swear by this. If nothing else it seems to ensure a better surface uniformity as the glass is chosen for minimal distortion.

Ambient IR would be my only concern as it would ping around from all over the place, but your relative measurement scheme ought to handle it OK

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RS Components Reprap Ormerod No. 481