Re: [CAD_CAM_EDM_DRO] Re: Re: High Speed Machining Look ahead EMC

Hi Fred

I'll intersperse some comments among yours....

> The real problem is that you have a huge massive assembly that
> cannot physically make a 90 degree turn at 150 ipm. If you slow
> down to 25 ipm just before you get there (JIT-just in time) the
> cornering will be more accurate, and the machine will take the
> corner smoothly, within the limits of the strength of the frame,
> mass of the assy, and acceleration required.
>
> How far in front of the corner is a matter for experimentation, and
> will probably vary with the weight of your tool, depth of cut, material
> type, and desired max feed rate. In short, it is situational, and not
> totally dependent on the controller capabilities. 2 axis cutting will
> be different from 3 D.
>
> Aluminum and wood will yield widely varying sets of capabilities.
>

It's true; I have a huge massive assembly and it can't go around corners
perfectly.
But I also have huge servo power... 60 amps peak! 5000 kVA! In my case that
results in
about a .2" minimum radius at 150 ipm. Dropping to 37 ipm gives a radius of
of about 0.012" so what you are talking about is a good thing I know. Chip
load
can get a little flakey if spindle rpm doesn't drop proportionally as well.
But there
is some lattitude there.

Sometimes I want pretty sharp corners and the machine has the power to do it
at moderate speeds. What I don't want is that machine gun series of pulses
around a smooth curve that doesn't need it. Can the machine do it? Yes.
Is it good for it? Probably not. It is just a shame to do max performance
moves with the resultant extra wear and tear when It really isn't needed.

> That is what Vector HSM option does. It also controls a distance
> past the corner at which the slower feed rate is maintained to assure
> that the controller does not try to reaccelerate too fast on the back

side.

>

That's good. I need that for 3-d lettering (like vcarvz).
But I think EMC really needs a quintic interpolator as well.
It would dramatically improve high speed performance.
Combined with cam features you mention the results could be
truly astounding!

Les

Leslie Watts
L M Watts Furniture
Tiger, Georgia USA
http://www.alltel.net/~leswatts/wattsfurniturewp.html
engineering page:
http://www.alltel.net/~leswatts/shop.html
Surplus cnc for sale:
http://www.alltel.net/~leswatts/forsale.html