Re: [CAD_CAM_EDM_DRO] Re: I'm curious

Ted Gregorius wrote:

>The should be titled : I'm Ignorant
>
>Really, I don't know nearly as much as most of you. The amount of experience here is amazing.
>
>I do know that my home built mill / router is running on steppers, diven by Gecko's, and told what to do by Mach3. I NEVER lose steps unless I try to do somthing beyong the capabiliities of the machine. When used withing it's capabilities it is flawless. No it does not move at 400ipm (100 is it's normal rate) and it will not handle deep cuts in much of anything, but it does whit I designed it to do perfectly.
>
>I have a question about the error corection of the closed loop system. In the closed loop system I understand that when the expected position and the actual postion do not aggree, the system will attempt to correct or catch up.
>
>Now, I'm making a 3D cut (X, Y, and Z all moving) and my Y axis begins to lose position won't the loss of this position and any correction applied ruin the work?
>
>

It depends. Will .001" of position error ruin your work? That could be
the extent of the servo following
error on some arbitrary system. On the mini-mills I'm working on, the
following error is usually held to
.0003" or so, even up to 100 IPM. These machines are set up with higher
resolution, but possibly lower
speedsm, than a router.

>Seems to me that a systems design should NOT expect to have to deal with lost position. Isn't the the real point. Build the machine for it's intended purpose.
>
>

The ultimate in this regard is "feedrate compensation" where the CNC
control slows down ALL
axes in a coordinated manner when one axis begins to lag. I don't know
any hobby-level systems
that have this feature right now. Mariss of Gecko has been talking
about it on the G100.

>
>

Jon