Humble Beginnings - For Alu

[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.