Replaced print bed with custom design
PET Tape
12V 30A Power Supply
E3D Extruder
OctoPrint
PowerTail
Never going to buy another Solidoodle, but she is a lot more useful now in making quality prints.
]]>First test, 60C in ~60 seconds. Not bad! Now I just want to beef up the traces on the printrboard for the 11.5 amp heater by scratching off the solder mask with a fibreglass pen and laying down some solder. I also think I could of gotten away with 6 or 7 mm stand offs to help reduce my platform height... but that is my next project. Another option may be using a build plate PCB that is 6x6 and screwing it to my bottom plate. (as it lets me use whatever mounts I want)
Right now the M3 screws are going through 8mm stand-offs... I think that is a little more complex then it should be. Going to replace the female-female standoff with a male-female and screw the standoff into the top plate. Surface is pretty flat and level... gonna have to turn the extended z-stop way out though :-)
]]>Things working out really well... under $50 and almost done!
Now I just need to find some good (heatsink?) tape to stick the heater to the bottom of the top plate. Surface is a *lot* flatter than SD's stock bed... there is a slight bow but it is miles better.
Some pictures attached. Used springs on the junction of the top and bottom bed to help with waping when heated.
Tapping M3 (gotta be M3
) half way into the top sheet may be a better option... worst case if I screw up the tap I can drill through.
Just drill and tap through, I assume you'd be glassing the top anyway, and the far corners are the least useful bit of the build area...
I was considering some screw tight holes to prevent wobble, but maybe replacing the stand offs with some bolts with springs? (that might prove too much wobble though) maybe I should rigidly fix the bottom plate to the Z-axis and then redo the spring system between the two plates.
There is kind of a redundant layer here, I suppose.
If it was me, I'd keep doing exactly what you're doing, it's a tidy design: but make sure there was a tiny bit of slip in 3 out of 4 of the mounting holes to allow for expansion. The 4th one can clamp right down and prevent it from being knocked around more than absolutely necessary. I suggest the nylon washers as they'll slip a bit even when snug (i.e. tighten just to the point there's no axial movement in the joint), and the loctite/superglue in the thread will prevent a not-fully-tightened bolt from coming loose due to vibration.
There's wobble inherent in the cantilever design of the bed (it bends those 3/8" rods) as well as the bed springs, so introducing the possibility of a touch more is not a huge deal, and might just be a price of a warp-averse arrangement. I think you could easily arrange it such that the other wobbles were much easier to actuate than the slip allowed in the bolts in your bed sandwich, so you'd never see any adverse effects.
]]>Looks like a good plan - the thicker the top plate the better, within mass/height/cost constraints to your liking!
My 2c:
* I would personally drill and tap the mounting points into the top plate, use a collar as a standoff and bolt it on from underneath, making sure the screws were 1mm or so short to leave the top surface flush for glass etc.
Yeah, that was one side effect of the wider build plate... no dump area on the back right. (and a potential screw head to interfere)
Tapping M3 (gotta be M3 ) half way into the top sheet may be a better option... worst case if I screw up the tap I can drill through.
* Note that one of the functions of the spring-mounting is to allow for thermal expansion in the plate without causing warping. If you have a hot alu top plate rigidly bolted to a cold bottom one, it's possible the whole assembly will warp. Based on CTE for 7075 from here I'd calculate a distance movement between 185mm (guesstimated) centers of ~ 0.5mm (for 100C TD). With the plate distance from your diagram, assuming the two plates were perfectly 'bonded' (like a bimetallic strip; very much worst case!), looks like up to 1mm of height diff from bolt hole to plate center. In reality it would be much much less as it would just push around or bend the standoffs (much less stiff than the plates...): knowing they're going to move whatever you do, consider allowing for some slip in the lower plate mounting holes (e.g. ~0.5mm oversized bottom plate holes, nylon or fiber washers both sides of the bottom plate, loctite on the thread into the top plate and only tighten the bolts snug).
Great thought on the warp. I was considering some screw tight holes to prevent wobble, but maybe replacing the stand offs with some bolts with springs? (that might prove too much wobble though) maybe I should rigidly fix the bottom plate to the Z-axis and then redo the spring system between the two plates.
]]>My 2c:
* I would personally drill and tap the mounting points into the top plate, use a collar as a standoff and bolt it on from underneath, making sure the screws were 1mm or so short to leave the top surface flush for glass etc.
* Note that one of the functions of the spring-mounting is to allow for thermal expansion in the plate without causing warping. If you have a hot alu top plate rigidly bolted to a cold bottom one, it's possible the whole assembly will warp. Based on CTE for 7075 from here I'd calculate a distance movement between 185mm (guesstimated) centers of ~ 0.5mm (for 100C TD). With the plate distance from your diagram, assuming the two plates were perfectly 'bonded' (like a bimetallic strip; very much worst case!), looks like up to 1mm of height diff from bolt hole to plate center. In reality it would be much much less as it would just push around or bend the standoffs (much less stiff than the plates...): knowing they're going to move whatever you do, consider allowing for some slip in the lower plate mounting holes (e.g. ~0.5mm oversized bottom plate holes, nylon or fiber washers both sides of the bottom plate, loctite on the thread into the top plate and only tighten the bolts snug).
* Insulation in the sandwich will be handy for quick bed heating - adhesive auto stuff is fine. But note that any heat lost from the bottom of the bed just goes to heating your chamber (which is the best way to keep your warping down), so it's not really wasted - just the time!
]]>Looks good but IMHO a piece of fiberglass mat in between will keep the bottom plate from cooling the system .
Tin
Hm. Maybe Nylon stand offs? The melting point of Nylon is 190 C (well above what the bed would be run at, although I wonder at which temperature nylon gets soft.)
Insulation was also a thought with this design, pretty easy to slip some glass matt between the top and bottom layers. The goal is an air gap between the top of the QU-BD pad and the bottom, but might as well do some fibreglass while i'm at it.
]]>Tin
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]]>That plus a 6x6 $19 heated bed... I think we might have a winner.
http://store.quintessentialuniversalbui … product=36
Two plates of Aluminum...
top: 7075 Aluminum 6.35" x 6.00"
bottom: some cheap Aluminum 6.35" x 6.00"
Hold both plates together via 4 standoff nuts and screws in the extra 5.mm on each side.
Drill the 3 mounting holes on the bottom plate, and stick the heater to the bottom of the top plate.