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30-11-2016 #11
Andy Acceleration can make huge difference to how machine performs, not only in quality of cut but also Cycle times.
Often on Smaller jobs with lots of very short moves ie: V carving engraving setting Accelleration higher and lowering velocity can increase cycle times quite drasticly.
In daves case the cause was being set to constant velocity mode G64. Meaning the control trys to maintain constant feed rate around corners. Obviously the laws of physics come into play at some point and becomes impossible to maintain this rate around tight corners.
Simplisticly put It does this by overlapping Accelleration needed for the new move with De-accelaration of the current move and the point they meet is when corner rounding occurs.
So obviously if acceleration is low then de-acceleration must happen sooner and the point they meet is further up the road. Think of it like car with poor skinny tyres and throttle stuck on.!! You turn sooner to get around corner else you crash.!! . . Having higher acceleration is like Car with brand new wide tyres so can turn later.
If you want to follow the Tool path exactly you'd use G61 Exact stop mode. Which goes exactly from point A to B and repeats for each following move. The down side of this can be very jurky movement and pause at each start/end point. If Cam software creates Arcs with tiny little lines G61 with high feedrate can shake machine to pieces.!
To see this in action Try some G-code which doesn't have G64 at the top or change to G61. If doesn't have in code Type G61 in MDI before running.Last edited by JAZZCNC; 30-11-2016 at 09:55 PM.
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