Overshooting Max Velocity

This is a new one on us.

One thing to be aware of is the maximum velocity sets is used by traverse (G0, $_vm) and it reacts differently than a feed (G1, $_fr). A traverse is designed to go as fast as possible for point A to point B. The $_vm sets the maximum velocity *for that axis*, not for the traverse move. In a multi-axis traverse the resulting movement can therefore be faster than any individual axis in the move. For example, if you moved from (x0,y0) to (x100,y100) and had both xvm and yvm set to 1000, the move velocity would be 1414. Neither axis exceeds it’s limit of 1000 (1414 is just the vector sum of the velocities, i.e. 1000 * sqrt(2))

This is as opposed to feeds (G1), which limit the total rate of the move to the F rate specified in the move (e.g. G1 F1000 x100 y100). Alternately, a feed may be limited by the max feed rate for a given axis, and the total feed rate of the move therefore reduced.

So if your move had a minimal Y movement and a long X movement it’s still possible that the move itself will achieve a speed well above the Y limit. This may or not be the situation in your case.

If you think there’s some other problem can you let us know a few things:

– What firmware build you are running? – e.g. $fb 380.08

– What are your X and Y settings (assuming only X and Y are in the move), $x, $y

– What is the starting point of the move? Assuming the end point is X-43.992 Y224.789.

– Just for completeness, what kind of machine are you running? Sounds like a belt driven machine given the high velocities you are using

Interesting.

Can you explain what you mean by “takes away the ability for me to have NC limit switches”? As far as I know nothing has changed in that area and the $st (switch type) parameter is still present and active. If you found otherwise we should fix this.

Thanks for the list of commands you removed from the Gcode file. To my knowledge none of these should prevent the file form running, but there may be a bug. I’ll try them out and see if there’s a problem somewhere.

Is it possible to provide a link to the Gcode file you ran, or short of that posting the first 100 lines or so? I’d like to run this in context if possible.

If your machine won;t do 8000 mm/min you should probably drop the velocity maxes down to what each axis can actually handle. That should prevent the stalling. You may also need to adjust your jerk values. See here for some tuning guidance: https://github.com/synthetos/TinyG/wiki/TinyG-Tuning