[DiveN4Gold]

I've gotten to the part of my machine build where I just finished the Z-axis and am working on the gantry. I would like to hear ideas about adding rigidity to the 80x160mm extrusion that's used for the gantry. I've thought about adding either a large piece of horizontal steel angle (6" x 3" x 65") or plate (6"x 65") to the back, attached with bolts, putting 1" steel rods in the two large cavities of the extrusion along with epoxy granite in the remaining space surrounding the rods, ONLY using epoxy granite (which I understand won't add stiffness only damping), and that's about it.

The machine frame itself, with all of the sand-filled aluminum is currently around 1700 lbs, so I'm not too concerned about the additional weight throwing it around, and I'm using Clearpath 3421 servos, which according to Teknic, should handle the weight, although gantry weight is certainly a concern.

I'd love to hear thoughts about these or other approaches. I've read through every thread I could find on the subject. Short of remaking the gantry in steel, are there things I could to to add stiffness?

[peteeng]

Hi Dive - Anything you add to the inside will add little stiffness. You have to add geometry to the outside. Steel is the cheapest stiffest material to do this. Although its heavy you don't seem to mind that. Angles aren't much good in torsion. I'd add the biggest SHS or RHS I could to the back of the gantry... Can you flick the extrusion and start with a fresh large section? Peter

maybe double up the 80x160 extrusion?

[adam_m]

Pictures are always useful...