Feature request: Different acceleration for rapid and feed moves

I would like to be able to set different acceleration values in the ini for rapids and feeds.

Right now I use a custom m code to execute something likeright before G0 lines. With a custom CAM postprocessor. And after the last G0 movement another custom m code to set it back to the default. This works well and shaves of a lot of time while keeping the finish quality high. The particular machine has more than 3000mm of travel and can move with 82000 mm/min (3200 in/m) thus it makes a huge difference for G0 moves what acceleration the config has. On the other hand, acceleration needs to be set low during cuts to have a high surface finish.

I'm wondering if there are cases where this hack is not going well. E.g. with G64 active and switching acceleration between two G0 or G1 codes that will be affected by path blending. I have not checked if the halcmd does bust the queue.

I think you should look for analog output and change it for G-code using M68 E<Out_numb> Q<acceleration>
in hal you should use input to your acceleration from motion.analog−out−NN.
For example:
Inhal
And from G-code you should write:
M68 E0 Q9800

Yes that might be cleaner than using halcmd. But how to ditch m codes to change acceleration before and after every g0 entirely?

Currently it's not question for linuxcnc program. I tried to tell you what to do to operate your accelaration from g-code.

1) The simplest way to write G0 with M68 command is to use "Replace" statment in your text editor, for example "G0 raplace with M68 E0Q100 G0".
2) Configure your post for generating G-code that you need.
3) Remap G0

1.) is a bad idea as it will break blending between two subsequent G0 lines. A custom m code that checks a flag if the acceleration needs to be altered is better. Any M68 will bust the queue.
2.) Is the current state. As I explained, I have a custom m code and the post processor handles it, only inserts it once, not for every G0 line. I would like to ditch this and have separate acceleration values for rapid and feed moves.
3.) Can you give advice on how to do that without recompiling? AFAIK G0 can't be remapped.

Try to read Remap G-code linuxcnc

andypugh wrote:

Note that the ini.pins are not sampled in realtime or when G-code is running.
forum.linuxcnc.org/24-hal-components/331...running-a-file#97437

Thanks Andy, that's good to know.

andypugh wrote:

What is the purpose of having different accel in G0 ?

Saves of a lot of time while keeping the finish quality high. The particular machine has more than 3000mm of travel and can move with 82000 mm/min (3200 in/m) thus it makes a huge difference for G0 moves what acceleration is used. On the other hand, acceleration needs to be set low during cuts (G1 etc) to yield a good surface finish.

Running a high acceleration makes the whole head of the machine nod a bit (everything's a spring), this little mechanical overshoot might be acceptable with scanning (probing many points) and rapids, but not while cutting.

aleksamc wrote:

Try to read Remap G-code linuxcnc

I G0 can't be remapped.