Re: [CAD_CAM_EDM_DRO] Look-ahead

Hi Jack,

Yeah, I'm writing a controller, and I'd like to know too! Sorry I can't
help you. You might ask on the TurboCNC list. I'd like to hear more
about your efforts, on the TurboCNC list or off line might be better.

Alan KM6VV


jcc3inc wrote:

>
> Gentlemen:
> I'm sure some of you have experience in the design of CNC controllers
> so I wonder if you could elaborate on just what "look-ahead" means
> and what its benefits are.
>
> I am making a 3 axis CNC controller, DOS based, for my own amusement
> and would like to have smoother operation at high speeds with some of
> these programs which consist exclusively of short, straight line
> approximations. High speeds are defined as 100 IPM and above, with
> the smallest increment of motion being .001". My accel and decel
> cause slowdown between blocks since my cornerspeed is set at about 30
> IPM.
>
> As I see it, the factors effecting the slowdown speed between blocks
> are: 1) the angle between adjacent line segments, 2) the length of
> successive line segments, 3)radius of an arc which follows a str line,
> 4)the length of the arc, and no doubt there are more factors.
>
> As to how to handle the setting of speed between segments, it seems
> to me that one can either 1) pre-process the data setting in the
> calculated minimum speed or 2) do the calculations between reading
> the blocks. The second alternative would seem to slow down things
> too much!
>
> I would appreciate hearing from all of you who have experience and
> ideas along this line. Thank you
>
> Jack C. Cain jccinc@...