Classic Gantry Side vs. Extended Profile rigidity

[Blazedazer]

I currently have a classic Gantry and i was wondering if a extended profile would be as rigid, when and needed supported by braces
A benefit would be that the whole table surface would be machinable, currently i have a rim i can not reach at the sides.

i attached 2 images to clarify the design difference

For any input i am gratefull

Cheers
Alex

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[NIC 77]

The problem with your two designs, is that in the 2nd design you still don't have more movement of your Y-Z axis assembly as the Z axis is lower than the gantry tube and will still contact the plate.

That is a slim profile for anything but a small length gantry intended only for wood at low accelerations. Of course if that's what you're doing, and you're sure it will meet your expectations, then forget I mentioned it. It is possible to bolt some square steel tube to the unused face to make it stiffer. That's a cheap and easy stiffening technique for T slot, but perhaps not the best.

Many designs that use more than one spindle have extended length tubes for more movement because the the wider Y-Z axis assembly from using two spindles. Perhaps look at some of those designs.

My personal preference for a moving gantry is to have the front bearing at least as far forward as the cutting bit. For a fixed gantry, the angled support can go in the other direction because you don't care as much about the weight and you can make everything stiffer, but those are just my opinions. Like I said you can do some searches to see what multiple spindle designs typically do and that might help you. I believe you would have a cut out where the spindle can pass the uprights, and the front bearing is still forward, but the uprights are typically made of a box type structure for this to be more rigid, not a single flat plate with more of a cut out in it.

The two things you have drawn will probably perform about equally. If you are dedicated to using flat plate for your gantry risers, then you could also bolt on some Heavy duty steel angle iron to the sides, that would stiffen them up.

[Blazedazer]

Hi,

the pictures are just for the difference in mounting the Profile to the sides.
The profile i use is a 80x160 heavy, plated with 15mm aluminium on the front and top, the sides are 25mm ST355 steel reinforced with diagonally screwed on t beam, the gap between sides is 700mm.

was just wondering if a extended profile would be as rigid as the wedged in version, setting up a correct FEM for this is quite tricky

cheers
Alex

[ger21]

The rigidity of the mounting method will dictate which is stronger. The beam itself doesn't change. You really shouldn't see any difference. Even though the one beam is longer, it's supported in the same place, so you have the same unsupported span.

[Blazedazer]

so if i proper brace the beam to the sides with some steel angles it should be fine, the mounting surface would be much higher as well on the braces then the direct contact with the sides.
the beam itself would stay the same, so the unsupported length would shrink a bit, it is just a measure to reach the full table area, and i feared that the new way of mounting would allow more flex

cheers
Alex