Context wise - I’m in regional Australia, so we tend to get the raw end of the deal on both postage and anything laser cut - so typically I try to avoid both.
I thought to still get away with mostly printing the XZ plate I could ‘core’ it with 3mm mild steel.
Everything went how I imagined it would. I did apply some gluestick to the ‘print surface’ of the steel and preheated it on the bed while the rest printed.
I think the issue that you’ll have here is that there’s really nothing adhering the steel to the plastic so you won’t get any value out of the steel.
As a mental exercise, if you were to make the steel even thicker such that the plastic was maybe a single printed layer on top of it, the plastic would be super flexible and would just pull away from the steel easily. Any forces that were directly pushing into the steel might be ok but anything pulling on the plastic or applying a torque to something sticking out of the surface of the plastic would move.
This is why laminated structures tend to only have as much performance as the adhesive used to create them. Once the strength of the adhesive is exceeded, you end up with a bunch of thin flexible layers that then start to fail individually.
Understood - so the fact that the core isn’t a true lamination means that the performance can’t be expected to either meet the level of a true lamination, or is limited to the level of performance of any one individual component of the stack?
Realistically I can just use the DRO on my mill to drill the holes accurately and beyond that it isn’t really an issue what the plates look like so long as they fit within the bounds of the machine.
I think it comes down to how the forces are transmitted through the structure. It’s kinda like if you try to bend a ream of paper it bends pretty easily because there’s nothing connecting the sheets together, so the forces that are applied lead to all the sheets just sliding past one another. If you took a bunch of wood glue and cast it in the shape of a ream of paper it’d also be pretty weird and flexible because it’s not a very strong material by itself. If you glue all the sheets of paper together, though, you’d end up with something that would be a bit of a brick. That would be because 90% of the block would be paper which is actually surprisingly strong and then 10% would be the less strong glue that’s just there to transfer the forces between sheets.
Same idea behind plywood. If you take a single ply of plywood then it’s incredibly bendy, if you take 10 sheets they’re still pretty bendy. If you take a 10mm thick sheet of plywood that’s all glued up then it’s remarkably stiffer than the constituent parts.
So yeah, I think you’d need to bond the outside to the core. If you were to make the core able to be slotted in afterwards and were to epoxy it into place then you might be able to do it that way? You’d have the thin flexible skin of plastic epoxied to the stiff steel which would give it structure. As long as the bond between both parts held it should be reasonably good.
I think in reality you’re almost certainly going to be better off making the piece with holes in it directly.
You could always print an XZ piece out as an alignment guide, too, and just glue it to the surface or something. I’d still use the DRO but I find it’s always nicer to use markings or a template to make the big moves and then with the DRO you’re just lining it up to within the last mm or 2.
I tend to do an “XY” chart when I use the DRO and just hit each number pair in turn - drill then move to the next on the list. Ends up working pretty well.
I’ve just ordered a 6mm 200x300 offcut on ebay that was reasonably priced ($35aud so low enough that its not worth my time to print and still have to reasonably accurately cut the steel plate.) edit I thought I had ordered but hadn’t hit buy yet and saw a 380x300 piece for $51 so bought that instead. Enough for 2x plates if I mess up, or other bracketry in the future.
Lacking a DRO, I wonder if 3d printing the xz plate, then carefully use it as a drill guide with a drill press, to drill the metal plate. Clamped to the plate, or tape+CA glue trick.Then a cutoff tool to “shape” the rest
