"One line lookahead" is a little misleading.  The limitation that Steve 
describes comes from the calculation of the suggested velocity for each line 
segment.  The algorithm has the effect of clamping the machine velocity to a 
value from which the machine could decelerate to a controlled stop in each 
particular line segment.  It's nicely described here: 
http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Simple_Tp_Notes

Rogge



On Sat, 22 Sep 2012 02:13:44 +0100, you wrote:

>
>
>On 21 Sep 2012, at 12:32, "aaron moore" <[email protected]> wrote:
>
>> curves and circles are often slow and tend to burn the wood. Can anyone 
>> explain how I can improve this.
>
>This may be because your CAM program is making arcs out of very very short 
>segments. You might get better results by reducing the CAM "precision"  
>LinuxCNC ought to blend the lines anyway, so the result may be identical. 

Ought to, but doesn't very well.

It's been discussed before but Linuxcnc is very choppy on same code that
works perfectly on other controllers. I'm still convinced the trajectory
planner is not optimal and is limited by the one line look ahead.

The code I tested on does NOT contain multiple short segments, only
curves and lines. It's worse with slow acceleration settings and doesn't
seem to calculate what is the "best" velocity very well.

>The full explanation and solution is rather involved. The manual section on 
>G64 might illuminate. (I am on my phone so pasting links is hard)

The only way I can get it to perform fast is forego accuracy :(


Steve Blackmore
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