Like many others on the forum I have been completely frustrated by the on going warping of my MDF bed and I am now considering re-fabricating it in laser cut aluminium...the basic question now popping into my head before I proceed is that given that the MDF bed is actually called "MDF insulating bed" in the parts list, is it dangerous for the hot bed to be in direct contact with an aluminium replacement version and should it therefore be insulated from it? Also would an aluminium replacement bed dissipate too much heat "in the wrong direction" and therefore give me problems in heating/holding temperature? Ant advice gratefully received

Hi Crispi, I'm not sure I'd go down the road of using Ally for the frame work. There's a few things come to mind.
1) your going to be drawing heat away from the Bed where you want it.... As you've already thought of. Even thou it's the Cardboard
that does most of the insulating.
2) If you do go down that road, then do watch out for those Hot Bed electrical connections, as a few guys have already killed Duets with
the heat spreader. I've cut some clear plastic packaging to make thin covers for my connections that are superglued in place.
3) I thought about replacing the Bed with Ally, then decided against it because of the added Mass of the table. It's going to be allot of extra load
on the belt, and in my case it was getting some Ally that is spot on flat...... But then I do tend to over engineer things..

I'm going a different route (I think).... I ordered some extra Laser cut MDF Cross frames and an extra bearing. I intend to add a cross frame at each end
of the Main Y axis frame, and then have these two frames resting on the bearings to stiffen up the table, and 'maybe' add another longitudinal at the front
of the table for good measure. So it'll look like an H sideways on with the arms and legs joined. (Did I describe that ok.... I'm Sleepy here).
Now I've had the bits about 2 weeks now, but haven't had the time to progress the idea. Hopefully soon I'll get some time and crack on.
Another thing that's stopped me is that My printer never gets sat in one place for very long (it's clocked up 1200 miles traveling with me, and for two weeks of the month sits for most of the time on my cabin desk, getting bounced about), and yet when I re-calibrated the table it was very nearly perfectly flat (one spot was +0.1 and another -0.1) and the little it is out I can straighten by lifting or pressing down on the glass slightly while doing up the clips.

With all the traveling, changes in atmosphere (dry/damp but never wet), and the heavy vibration it gets from my engines here at work, the only thing that's moved or given way has been the Z axis rear roller has slacked off. I've replaced the nut with a Nyloc nut, and it's great now...
I did have binding on my Z axis lead screw, even with my longer nut that I've fitted, but a dab with my WD40 pen has fixed that. I have noticed that the Z axis gear is worn out now on the motor, as the motor moves and the nut stays still slightly, so the gears will be replaced with Herring Bone gears tomorrow.

Kim

Really good input Kim; thanks very much. I am lucky enough to have access to a set of race car engineers, so high quality materials (including carbon fibre, titanium etc.) and the equipment to work them is possible so I might try a few experiments and let you know how I get on. I am basically looking to mod as little of the machine as possible in this area while stiffening up the bed. I would also be very interested in seeing your final solution as/if it develops as it sounds like you are on to a great mod

Quote
MrCrispi
Really good input Kim; thanks very much. I am lucky enough to have access to a set of race car engineers, so high quality materials (including carbon fibre, titanium etc.) and the equipment to work them is possible so I might try a few experiments and let you know how I get on. I am basically looking to mod as little of the machine as possible in this area while stiffening up the bed. I would also be very interested in seeing your final solution as/if it develops as it sounds like you are on to a great mod

Oh with those guys on board you must make a triaxial carbon uni / nomex honeycomb sandwich bed

regards
Andy

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Ormerod #318
www.zoomworks.org - Free and Open Source Stuff

Several of us have replaced or reinforced the mdf bed. My solution is here [forums.reprap.org]. The cardboard insulation prevents too much heat from escaping via the aluminium bed support. Also see the following post in that thread for am easier solution for those without machine tools.

Edited 1 time(s). Last edit at 02/15/2014 04:44AM by dc42.

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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].

@DC42 do you happen to have a dimensioned picture of your design I could have? - it looks like a great compromise between weight and ease of replacing the standard part

I didn't do a design, I just used the mdf as a template and cut the corners off. There should be a dxf file for the mdf bed on the Ormerod parts repository on github.

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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].

Thanks - I'll check it out...

You might also want to take a look at [forums.reprap.org].

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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].