@vistalert said in Requirements to have a 1000x1000 aluminium build plate:
Could anybody please tell me the required thickness of an aluminium plate sized at 1000x1000 which would have the smallest possible "reasonable deflection" due to it's own weight, support at three point like a triple Z kinematic bed support.
And, does anybody have any experiences of building a printer with this build area. Were any alternatives such as a glass build plate (minus any aluminium plate beneath) considered?
Thanks!
Chris
@slimshader said in Requirements to have a 1000x1000 aluminium build plate:
@vistalert I've built several large format machines although not quite as large as 1m square.
My experience has shown that getting large, perfectly flat sheets of aluminium for this purpose is not as straightforward as it sounds. For one, most sheet metal suppliers...
Sheet =/= plate.
@vistalert
You need to contact a local aluminium supplier and ask about sourcing some MIC6 plate. That is cast aluminium that will be reasonably flat.
Typically 1/4" is the minimum thickness that will stay 'flat' at around 12" square. If you want to go to 1000mm, you'll either need to be able to adjust the bed with many many supports to take out any curve (there are a couple of commercial printers with beds like that) just from sag, or you'll probably need something like 3/4 to 1 inch thickness. Maybe both.
Taking to a local supplier is a very effective way to find out who can supply something suitable. The first people you call might not be able to help, but they will usually be able to suggest the right people to call.
There are plenty of companies out there that supply large pieces of MIC6 for things like injection molding tools, its just expensive.
Glass is not a reasonable alternative, a piece that large is going to be either very thick or very fragile. Either way people expect glass to be much much flatter that it actually is (float glass is smooth, not especially flat or of consistent thickness, at least compared to other things, like MIC6).
If you want properly flat aluminium, you'll want at least 1 inch thick and then get it surface ground. Although that will be expensive given the size.
The old joke in engineering: How do you make 8mm expensive? 8.0, 8.00, 8.000...
Getting MIC6 in stock form will probably be just fine, getting it ground to be really flat could be quite expensive (and the company doing the grinding might want a really really thick piece to start from).
@jens55 said in Requirements to have a 1000x1000 aluminium build plate:
@vistalert, If you look at the build plate in isolation I am sure that this is possible but maybe not in a conventional 'just increase thickness' approach.
One could for example drastically reduce the weight of that build plate by milling out a support structure that is part of the bed but with all unnecessary parts milled away. IE a drastic reduction in weight with very little reduction in strength.
Doing so is well beyond my capabilities but someone good at FEA could sort this out without too much effort.
That would greatly increase the cost and adds the risk of deforming the plate. If you really really really wanted to do something like this (which also complicates heating the bed) you would use a custom casting and then just grind the top surface flat.
It would be insanely expensive though.
Thermal expansion also needs to taken into account. A piece that large will expand by ~2mm when heated to 100C. If the bed is rigidly mounted you'll get quite a bow in the surface at that point.
You could also just make the bed from a granite surface plate. Granite works really well as a build surface. Takes FOREVER to heat up, but I never had PET chip it the way it does to glass. And its thermal expansion is so low that 100C is nothing.
Kinda heavy.
I seem to remember that you can get granite surface plates fairly cheaply these days though.
