A month after asking, I still haven’t heard back from cloudray on custom bed sizes. I have asked lightobject, but they don’t list custom beds as something they sell. Does anyone know where to buy plain honeycomb mesh? I don’t really need a pre-made bed, just the mesh to fit inside the openbuilds extrusion bed I’m making.
What search terms might find me vendors who would sell the material?
Thanks!
What size piece are you looking for?
I have seen that people make them from hacksaw blades 
I moved away from the bed and use spacers under the LO tables array of holes.
I always thought if I did this again I would use a wire array spot welded.
800mm x 1440mm — rather on the large side. 
Hmmm…You might want to use “Cores” as a search term since the honeycomb mesh is used as cores for aluminium honeycomb panels.
Largest piece I could find off hand was 24"x48" from McMaster-Carr. Not sure what thickness or cell size you want.
Seems that 24"x48" will be a common size since panels sizes are probably scaled relative to to the 4x8’ dimension. Might have to consider making your bed with some cross support trays and have multiple pieces of honeycomb.
This site sells 1270mm x 2540mm (50x100") cores.
https://www.rockwestcomposites.com/aluminum-honeycomb-series
A bit pricey and that’s not even looking at shipping.
Here’s a 32x20" piece listed on Alibaba. You could do a 3 section bed with this.
https://guide.alibaba.com/shop/aluminum-honeycomb-grid-core-1-4-cell-32-x20-x-500_59467113.html
Bingo! Thank you!
Honestly I probably don’t need to fill the whole thing with honeycomb. I don’t expect to usually need the full width, so I could suspend a smaller bed inside when I want honeycomb, and do some other form of support if I need to go larger for a particular job.
https://www.lightobject.com/Laser-CNC-accessories/Hardware/600X900-Honeycomb-for-CO2-Laser-Machine
I note that the beds for sale from lightobject and cloudray are steel honeycomb. That has led me to discover that at least some honeycomb is bonded with adhesives instead of welded. Seems like for laser cutting I would prefer welded.
“aluminum honeycomb cores” led me to thicker options like this from seller honeycommcore who calls it out as appropriate for renewing laser cutter beds and offers to cut arbitrary sizes, and has thicknesses up to 6" available. 
I have one from LO I do not want???
Do you have a lift in Monocle?
Yeah, I’m going to hang the bed from Spectra line rolled up onto pulleys on a torsion rod across the back, turned by a worm gear so it doesn’t unspool when I turn it off. The spectra line will run through v-groove pulleys. X and Y will be fully constrained by openbuilds wheels running in grooves in the corner posts — the only place that I’ll really be using the V-feature of any of the extrusion; everything else could equally be T-slot.
I couldn’t get a closed belt loop long enough to use four lead screws with a timing belt turning them in sync.
(If the spectra idea is a failure, there is room for me to mount lead screws and have a separate motor on each side, and drive them in series so that it’s difficult for them to get out of sync. But I wanted to try something different to start out.)
Be aware that large honeycomb beds are very flexible and will sag in the middle unless fully supported underneath with something like a solid platform, or better, a knife bed that the slats do the supporting of the honeycomb.
We have contacted a company doing honeycomb cladding (as in, buildings) panels. They were happy to help us out and stretched one for us. The 1200x1200mm panel was stretched and shipped (within the Netherlands) for 300 euro, roughly 350USD.
It is a 3/8" honeycomb in 15mm thickness.
And as @funinthefalls points out, we have built a support structure to keep it from sagging. The honeycomb material itself is as stiff as 3mm MDF, it will not hold any shape. A larger aluminium ribbed structure is underneath it, but I have also seen people (in for instance a Lasersaur) use a piece of the galvanized ribbed structures used in scaffolding and stairs. Don’t know the exact english term for it though, like this image below…
@Steven_FF Ah, nice idea. I wasn’t sure what term was used in industry, but it looks like it’s “grating” as in “walkway grating” or “bar grating” — at least, that gets me lots of search hits. 
Here’s an example that is rectangular rather than square:
That might be too heavy for my bed suspension system, though.
What you show there looks like press-locked bar grating:
https://www.steelgratingsupplier.com/steelgrating/press-lock-bar-grating.html
I might use lengths of angle or square tube at a 45⁰ angle underneath instead.
I did this. $79 for the 600x900, plus about $100 in shipping.
The honeycomb bed arrived today. It wasn’t super well packed, and the frame had a small bend in it (cosmetic, I think). It had one layer of bubble wrap for a pretty heavy object, and other than that the box was just filled with packing peanuts. But I think it will be fine.
I didn’t think to test the bed for being square when it arrived. When I set it into the frame, I discovered that the bed was far out of square; it’s trapezoidal with a skew of over 20mm. That’s pretty bad. 
Here you can see how crooked it is, as well as the damage to the frame. The bed it is sitting in is square; the frame is decidedly not square.
I emailed lightobject asking for their suggestion for remediating the problem, but haven’t heard back.
Here it is in context: The top of the black bed frame is aligned with the top of the honeycomb, so I can cut past the edges of the honeycomb when I need to, but most of the time I’ll be operating only over the honeycomb.
Lightobject complained that I hadn’t brought this up soon after it was shipped (when I thought it was just cosmetic and was trying to not be a nuisance) but suggested a soft hammer to knock it back into shape. It’s now close enough, I think.
