Improvement for Plasmabot/Precision Plasma/any using IVTAAG

[I Lean]

I'm using the PBC Linear IVTAAG aluminum extrusion for my gantry, and have been pretty disappointed in how flexible it is, allowing a fair amount of "wobble" visible in the cut. It's worse with higher speeds, hard direction changes (especially transitioning from Y axis movement to X), and higher acceleration rates.

So I modified the extrusion. At first I bolted a piece of 3/8" x 1.5" aluminum to the bottom, using the T slots in the rail. That helped a little, but not very much.

Now I cut some strips of 1/8" aluminum, and had them welded into the T slots on all 4 sides, effectively making more of a "square tube" structure rather than almost an X shape as it is from the factory. The hope was to add rigidity, primarily in torsion. Here's what it looks like now:





And here is a before/after shot. Both of these were cut from the same Gcode file. 2" square with a 1" hole inside, 14ga steel, cut at 250 IPM. On the left, the oscillations are clearly visible, and quite large. On the right (today, after the strips were welded in), they're much smaller and go away more quickly. The first one, the waves are visible all the way across the top. Now, they only exist for the first 1/3 of the top. You can also see the difference in the circle--the original has wobbles from where the lead-in started, the second does not.

Overall, a definite improvement that will allow me to cut faster and/or increase my acceleration. (both of which I've kept artificially low to get better cut accuracy) There are a couple things I still need to do to reduce the effects even more...shorten my Y rails to bring my gantry down closer to the slats, and move them forward so I can mount my torch tighter to the Z axis--both of those won't do anything to the rigidity, but will lessen the amount the tip of the torch moves since it'll be closer to the axis of rotation/wobble)

[travmc1]

I Lean
From looking at how far your Z and torch mounts out away from your gantry I would say that is where all your problems are. When you mount something that far out it has a lot of leverage on your gantry and when you have a fast change in direction it will cause the gantry to flex a lot. If you take a look at my post on my machine and look at the pics with the x axis you will see how close I have the z axis. If you rework it closer you wouldn't need to modify your gantry.

[I Lean]

I Lean
From looking at how far your Z and torch mounts out away from your gantry I would say that is where all your problems are. When you mount something that far out it has a lot of leverage on your gantry and when you have a fast change in direction it will cause the gantry to flex a lot. If you take a look at my post on my machine and look at the pics with the x axis you will see how close I have the z axis. If you rework it closer you wouldn't need to modify your gantry.

Right...which is why I said:

There are a couple things I still need to do to reduce the effects even more...shorten my Y rails to bring my gantry down closer to the slats, and move them forward so I can mount my torch tighter to the Z axis--both of those won't do anything to the rigidity, but will lessen the amount the tip of the torch moves since it'll be closer to the axis of rotation/wobble)