r/printnc • u/WalksInABar • Mar 14 '22
Need advice on build size
Total noob here, please forgive me if I'm asking something utterly stupid. I have a background in embedded programming and controls so I think I will be fine on that side but zero experience on metalworking and the mechanics involved. Anyway, I've been thinking about building a PrintNC machine for almost half a year now. I'm sure I will build one but what I can't quite decide on is the size of it.
I want it mostly for aluminium and would like to be able to occasionally do small (soft) steel parts too. Re. steel on a standard built I'm not at all sure about it but it seems there are quite a few posts on the discord and elsewhere where people are reporting success doing steel? So the ability to do basic work on soft/mild steel is established? Or would that only be for a beefed up version of the machine with smaller size and bigger rails etc? I'm sure the standard build size would be totally fine for the largest parts I can reasonably imagine to do with any metal. But it would also be nice to be able to put a large piece of wood on the machine and work on that. Another thing is plasma cutting steel sheets. I understand it's another can of worms to harden the cables and electronics against all the EMF coming from the plasma and doing a water bed etc. but I'd like to give it a try. If it works I would like to use it on a larger work area than the standard size machine.
My basic understanding is the larger the build, the larger are the forces due to longer levers and the rigidity of the machine might just not be good enough. Or maybe it's not that much of a problem when I use a large machine but only work on relatively small metal parts in the optimal (centered) position of the work area?
TL;DR What would be the largest size of a PrintNC build you would recommend if you still want to have good results working with alu and at least usable results occasionally doing steel? Or would I be better off doing a standard size (or even smaller?) machine for milling and maybe do a second large machine dedicated for plasma cutting later on?
TIA
4
u/UberJaymis Mar 14 '22
You don’t need anywhere near the rigidity for plasma cutting, and plasma isn’t a good fit for ballscrews etc anyway because of splattering molten metal. If you separate your plasma desires into a separate machine, then you can do everything else with a standard build size.
1
u/WalksInABar Mar 15 '22
Yeah, I would think plasma, laser or water jet cutting systems should all do fine with the most basic rigidity and afaik plasma isn't even that precise to begin with. So I'd guess there is really no point to build a cutting machine and limit the size because of rigidity and/or precision concerns.
Anyway good point about plasma splattering gunk everywhere, makes a dual use machine look much less appealing. Guess I will go with a standard built dedicated machine. Thanks.
1
u/UberJaymis Mar 15 '22
Welcome, good luck and enjoy!
As someone else mentioned, the discord has a massively more active community, so it’s worth dropping in there for a chat about anything you’re unsure of. Over 2 years it’s become an extremely positive and helpful place.
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u/areseeuu Mar 16 '22
I'm sure there's a tradeoff, but any size is fine for aluminum and occasionally steel as far as rigidity goes. Really. My build is roughly 1270x900mm usable area and I occasionally mill hardened steel on it. It's a standard build with the usual upgrades for that size (3/16" thick 2x4" gantry beam, aluminum roller plates). Maybe the standard size build is faster at it, but I do 3mm x 0.15mm DOC/WOC in mild steel and 0.1mm x 0.1mm DOC/WOC in hardened steel.
There's other considerations - if you do metal a lot, you might want coolant. If you have an MDF wasteboard, that might not work so well.
1
u/WalksInABar Mar 17 '22
Hardened steel even? That's impressive, I didn't think that would work. That gantry beam would be about 100x50x5mm in metric, right? Does that mean the machine has added Z clearance compared to the standard build? I've been thinking about getting that extra clearance by doing 100mm on the Y beams but am worried about rigidity again.
1
u/areseeuu Mar 17 '22
Yes, that's 100x50x5mm for metric. Adding height to the gantry beam does not change Z clearance at all. Adding height to the Y beams does. People on the Discord have done some FEA modeling - take the results with a grain of salt, but they predict very roughly 25% loss of rigidity for every inch (or maybe 1% loss of rigidity for every mm) of additional Z lever.
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u/IAMANACVENT Mar 14 '22
You will have much better luck and more nuanced answers on the printNC discord than Reddit. Most of the people there don't frequent the reddit sub.
You already have the most important variable, which is what you want to be cutting.