Humble Beginnings - For Alu

[JAZZCNC]

I'll shoot first. .Lol

Don't need Nema 34's 23's will be more than enough.

Don't need 2x rails per side they won't add much to the machine other than expense. Linear rails can handle massive loads so one rail with 2 bearings will be fine.

The Single piece Box on Gantry is NO where near strong enough for cutting Aluminium and will need massively beefing up.

The 20mm Plate for Bed is Good but will still need a Decent frame building under it and 1 cross piece won't be enough.
Don't under estimate the forces for cutting Aluminium.! . . To achieve decent quality of finish the machine needs to be very very ridged.

What you have drawn so far won't cut Aluminium overly well and full fill your criteria.!! . . . . . More beef required, Esp on the gantry and don't be afraid of the weight for cutting hard materials it helps.

[Husky]

Good thing I haven't drawn the gantry yet I'm still scratching my head on that one, the bar was kind of a place holder, don't panic haha.

Ok, I was worried as I have never used the runners before, I shall go forth and delete the outside ones! Lets me get rid of those angles too, that would have been a pain to line up right in the build.

Yeah I'm going back down to the 23's. I drew those before I really read into it and got some advice. They still look rather pretty though, so I put them up anyway.

On the subject of the bed... Yeah, I'm not sure why this happened with only a 20kg load, but...



I pressed a wrong button somewhere I think But still, I'll put more bars in as you say!


I'll do a fixed gantry version next, I just can't get past the fact it'll be double the size of the cutting bed, minimum.


Thanks guys!

[GEOFFREY]

I,m sure you pressed a wrong button. Not quite double the frame (not bed) length, but much easier to build a really strong machine IMHO. G.

[Husky]

Too many Desperado's me thinks!

[GEOFFREY]

I admit to being biased!!! G

[JAZZCNC]

I admit to being biased!!! G

I agree 100% Geoff fixed gantry is Much Much better option for cutting hard materials if you have the space.

[Husky]

OK, talked to a mate at work regarding my results shown above. Basically he said to look at the results like a scaled graph, it's scaled up so you can see it more easily but the actual numbers are the important thing. So, it could be that it's only deflecting a tiny bit, but scaled up it looks horrific. Also, I used a distributed load rather than a point load, I kind of knew this at the time but couldn't find the correct option, just wanted to see some results :P

Looking forward to chopping it apart tonight for the next version.

[Jonathan]

You've set it to display stress, which is useful when determining if the material will fail, but that's clearly not the case here as the maximum stress is small. Also, you need to be careful at corners or near bolts as the stress outputted by the simulation at these boundaries can be a lot higher than reality, due to some of the assumptions in the calculation. We're interested in the deflection so set the display to displacement and find the maximum points. The results you get will depend greatly on the boundary conditions, so how you attach the bed to the frame in the simulation is important. The mesh quality on the simulation is very poor too, but there's not much you can do about that. If you're going to try and use FEA, then at least start with applying forces to the gantry as the gantry is going to be far less stiff than the machine bed even without additional supports. For the current simulation you needn't include the gantry and X-rails, so you might as well remove them as a significant number of the nodes in the mesh are consumed in these parts.

The extra two rails wont make much difference because the vast majority of the force will be apparent on the other rail, with two blocks, since the structure in between is not particularly stiff. Just use one rail on each side and space the blocks out as far as you can, since the stiffness is proportional to the block spacing which means the deflection is inversely proportional to the bearing spacing squared, so increasing the spacing a little can make a big difference. That's assuming the structure they're mounted to is very stiff, which currently it isn't.