My 36" acme screw goes into a bad vibration when the gantry is at one end or the other of the screw.
When the gantry is halfway down my 36" screw, the gantry itself divides the screw in half and it's quiet as a mouse.
As the gantry proceeds towards either end of the screw, the longer screw section at some point it starts vibrating.
I can reach my hand up under the machine and touch the screw and it stops and behaves itself.
I'm not running my X axis motor very fast, it's not whipping from high RPM's.
This is not motor induced vibration, it's more that my screw is not perfectly straight and the Delrin bearings are not as tight as say a ball screw is and so there is some slop.
My gantry is very heavy and the ACME screw is under a bunch of stress.
I really need a nice ball screw, but that's some big bucks.
The best method I can see is to somehow dampen the screw at it's longest sections. I came up with a design that I may try.
These swinging pulley dampners could be placed at the 9" and 27" mark on the 36" screw.
When the gantry contacts one of them, it pushes it over and the pulley eventually rolls under the gantry and then pops back up.
The gantry can push them over in both directions.
The cable at the bottom of each pulley dampner is attached at the ends by two identical springs that keep the dampner balanced when upright.
If you had two of these dampners, you could stagger the cable to one side on one dampner and the other side on the other one and the cables would bypass each other.
The pulley could have some sort of dampning material that contacts the screw.
Have to figure out a way to let the pulley come up slowly so it does not slam up and into the screw making a bit clunk noise.
That would be as annoying as a vibrating screw
All the lengths of the pulley stick, other parts and where to attach the cables would have to be figured out so the pulley dampner can tip over and the cables don't hang up on something.
Just an idea at this point. Any ideas are welcome.
Here's a pic of how my gantry,screw and bearings are set up and a diagram of my dampner idea.