Questions on rail covers, dual servo hunting,and rail preload

[Plugger]

Hi,
If you have some experience, could you please give me your thoughts on any of the questions below?

This machine is going to be used mostly on 6061-T6 Aluminum. It will occasionally be used to route Delrin, Trespa and Teflon. Machine is all aluminum except for the steel plate behind the router. Gantry weighs 190 lbs, bed is 294lbs.

1. Do I need to cover the linear rails to protect them from swarf? They have blocks with ball bearings that have front and side covers. Will the bearing block covers push the swarf and and metal filings away or do I need to sheild them more? I don't know how snug the protective covers will be. (Also, the rail bolt holes will be plugged and I am making plastic "Slinky"/Lycra covers for the ballscrews as discussed in another forum.)

2. Will I have hunting problems since the long axis has two servos running simultaneously to drive the gantry? One will be slaved in Mach3. So, do I just set the following error to something a little larger on the slave to prevent this?

3. Is a light preload in the rails/bearing blocks enough? They are well oversized in terms of stress and moment loads.

4. I am also concerned about chatter and profile finish. Thoughts? Should I add 25 lbs of steel plate to the side of the router to help keep vibration down?

[Zach_G]

If you take very light passes on aluminum youll essentially be making aluminum oxide - the same ingredient used in sand paper, and throwing it all over your rails. This dust will both absorb the grease on the rails, as well as get in them and start abrading their surface so yes it would be a very wise idea to cover them.

Your rails should be fine and ive heard of people succesfully slaving an axis in mach, that's the best way to do it other than a mechanical connection between both such as a timing belt.

Steel isnt really a good damping material. It has high stiffness to reduce deflection so Id say go for it if you use it structurally, otherwise might want to look into some homebrewed epoxy granite mix which has fantastic damping properties. Not hard to mix up some sand gravel epoxy and fill your sub structure.