Real time feed rate change



  • Hello,

    I am considering a duet for my homebuilt cnc. I'm currently using marlin firmware but frustrated with the fact that I cannot real time change the feed rate during the cut. Does anyone know if duet/reprap has this same limitation?



  • i dont have a cnc, but would changing the speed factor not change the feed rate?

    this is possible on marlin and on the duet.



  • Do you mean during a single line of g-code?

    I know cnc controls can often adjust their speed during a line, but I don't think that's something reprap type firmware in general has implemented... for multiple reasons.



  • The web interface (called DWC) has slider adjustments for both printing speed and extrusion rate which I am guess is what you are calling "feed rate".

    But I have never used the CNC mode so I cannot be sure.

    Frederick


  • administrators

    Once a move has been planned it will be executed using the planned acceleration, constant speed, deceleration profile. If you want to change speed during a single move that is currently not possible, feedrate changes will be applied to subsequent moves.

    The way to get around this if you make long moves with a single gcode line is to split those moves up into lots of short moves. If the velocity stays the same then they will execute as one long straight move, but the feedrate changes will be applied much quicker (they still won't be instant, how long will depend on how short the moves are and how fast you are going).



  • @tealfixie said in Real time feed rate change:

    Hello,

    I am considering a duet for my homebuilt cnc. I'm currently using marlin firmware but frustrated with the fact that I cannot real time change the feed rate during the cut. Does anyone know if duet/reprap has this same limitation?

    You can't do real time feed rate changes but you get close (unless things have changed). It always used to be the case (and I think it still is) that a small number of gcode moves are held in a queue. So any change to feed rate (via issuing an M220 speed factor override percentage command or using the slider in DWC) will affect moves that happen after those that are in the queue are completed. So point at which the change takes effect, rather depends on the type of cut. If it's a segmented arc, then the change will appear to happen very quickly. But if the machine is doing very long moves, then there might be a noticeable delay.

    Edit. Started typing the above before @T3P3Tony's post


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