Originally Posted by
vger
Hey there machinedude, just reading through your build and love the pics. I am just beginning a build on my 4th machine. Your issue with flex in the bridge is something I ran into on my second machine. It’s structure was similar to yours although shorter in length. I at certain feeds and speeds, I had chatter due to flex in the bridge. It was only an issue when the head was near the center of the bridge. My fix was... adding a “torque tube” to the back side of the bridge. I had some 1/4” wall 2 1/2” OD aluminum tubing standing in the corner of the shop. I cut 5 brackets out of some 1/2” aluminum plate about 4” square and bored 2 1/2” holes in the center. Drilled two mount/clamp holes through the 4 inch length of 2 edges of each piece. Lots of drill clear the chips, drill, clear the chips..... then cut the pieces in half making each clamp 2 C shapes so that 4 1/2” bolts would pull them together around the tube and run into the T nuts in the extrusion slots. The tube was about an inch shorter than the bridge extrusion. I put one bracket at each end of the tube, one in the middle, and the other 2 half way in between. Or 5 equally spaced brackets clamping the torque tube. Only way for the extrusion to twist was for the tube to twist. Sort of like trying to twist a drive shaft tube. Hope my explanation was clearer than mud. I’m on an iPad or I would sketch it for you. I don’t have that machine anymore, sold it to a friend a few years back before retiring and moving to Mexico.
Steve
Trapped on a small Caribbean island