Hi Gary and others with this sort of gantry - I have downloaded the 80x160mm section and created a model 2m long. How long is the Gantry Gary? I have run a modal analysis which determines the vibration modes of the gantry by itself. Structures have global and local vibrations. Global is when the entire element or part moves, local is when a small part of a part moves. Here they are with comments:
122htz global banana thru thin direction
218htz global up and down
261htz local at hole end
327htz second order banana back and fwds
362htz torsion global
428 local at hole in end
430 local at hole in end
446htz local at hole in end
450 local at hole in end
Gary if the holes in the ends are threaded screw a bolt into them to stop the small local vibs. There are literally hundreds of them associated with these holes. They are what's called a "free edge" and they are prone to vibration. Now I know the rpm vs speed I'll try to figure the possible driving frequencies. Peter your motors are 200step/rev?
We are not in mid-band resonance territory Gecko say this is 60-120rpm area. So the motor is doing 5.09rpm. This means that the mechanical steps are tapping the structure at 5.09*200/60= 16.97htz and the usteps are tapping at 5.09*2000/60= 170htz so it would seem we are in the territory. (EDIT corrected the maths)
if you disengage the rack and run at the 5ipm and the structure vibrates then the vibration path is thru the pivot. This would be a good clue. Can you check the 5.09rpm please...
https://www.geckodrive.com/support/s...stability.html
One thing I'll investigate was there were a few "rigid body motions" This means the whole part is shaking vs vibrating. A small technical difference. In this case have to neglect these as the gantry is connected to the structure so shaking depends on the entire structure not just the part as I have modelled. But rigid body motion (or shaking) may have something to do with your machine.
Gary what is distance between your columns and the full length of the gantry? Do you have a CAD model of the gantry and mounts? STEP export?