First Build 5 x 12 Steel Frame CNC router

[Clive S]

Scott Damman

Did you remember you needed longer cables !! that listing say 3mtrs

[Ger21]

Most industrial servo driven routers use 25-32mm pitch screws, which virtually eliminates whipping. With steppers, you don't want to go that high because you lose resolution, but with 10,000 steps/rev with servos, resolution isn't an issue.

Imo, on a machine that large, you want at least 1000ipm, preferable closer to 1500ipm. With a 10HP spindle, you should have no trouble cutting sheet goods at 1000ipm if you want.

[Scott Damman]

Did you remember you needed longer cables !! that listing say 3mtrs

Email to Fred before I ordered and he confimed he can make the longer cables for me.

[Scott Damman]

OK, maybe I am missing something here, but the more I read about proper servo motor design the more I see that the load inertia to motor inertia should be as close to 1:1 as possible. So although the rule of thumb is to be under 10 what I am seeing is for the ratio to be closer to 1. From what I am reading (and it is very possible I am mis-understanding this) the system should be better tuned and more responsive the closer to 1:1 ratio that can be achieved. This can be achieved with gearing or with sizing the motor to the load. I have included a 2:3 ratio in my calculations.

http://www.motion-designs.com/images...s_Dec_2008.pdf

http://www.diequa.com/download/articles/inertia.pdf

Am I mis understanding this? To me this would tell me that my inertia ratio of 1.75 --> 2.06 that was calculated for the system would be pretty good.

So as long as the inertia ratio doesnt go the other way...i.e. the motor inertia is larger than the equivalent load inertia... it is better to have the load to motor inertia as close to 1:1 as possible.

Of course from there one has to consider continuous torque and peak torque for the motor etc etc...