different max speed for rapid and feed movement?

Dear all

I understand that I can define a max velocity for each axis in stepconf and that this commands rapid movement (G0).
Question: How can I define another (lower) max velocity limiting the programmed feed movement (G1, G2, ...) for each axis?

(Hints to doc where I could have found this info are appreciated)

Thanks and regards
Volker

Hi

This outlines the velocity settings
linuxcnc.org/docs/2.5/html/config/ini_config.html

You can set max velocity, stepgen max velocity and default velocity.
The former sets your max G0 rate, the second allows stepgens to exceed this to bring off co-ordinated moves within the required feed rate and the latter defines the default slider position and jog rate for axes.

The feed rate for other moves is solely defined by the F value in your G code, to the limit set in max velocity, AFAIK

regards

Why do I think I need to?.

I use a DIY 3-axis mill to cut wood with inexpensive cutters.
I have found that I can do let's say 700mm/min feed when cutting in X or Y direction, but I'm losing steps when cutting more than 200mm/min in Z direction.
Anyhow max Z speed for rapid movement is beyond that.

I want to do a helical G2 movement cutting into wood. XY plane selected with G17.
If I could limit Z speed for G2 (and all non-G0 movements), then I could use F700 for the coordinated G2 movement without bothering about Z because the machine would slow down XY movement accordingly when Z speed limit was reached. Otherwise I have to calculate the speed limit for the F-word in my procedure.

(btw: I've already done the speed-limit calculation - no need to help me with that)

helig wrote:

Why do I think I need to?.

I use a DIY 3-axis mill to cut wood with inexpensive cutters.
I have found that I can do let's say 700mm/min feed when cutting in X or Y direction, but I'm losing steps when cutting more than 200mm/min in Z direction.
Anyhow max Z speed for rapid movement is beyond that.

I want to do a helical G2 movement cutting into wood. XY plane selected with G17.
If I could limit Z speed for G2 (and all non-G0 movements), then I could use F700 for the coordinated G2 movement without bothering about Z because the machine would slow down XY movement accordingly when Z speed limit was reached. Otherwise I have to calculate the speed limit for the F-word in my procedure.

(btw: I've already done the speed-limit calculation - no need to help me with that)

you will probably find this is more a mechanical issue than software , or down to the type of cutters you are using ..
also look at reducing the default velocity in the [traj] section of your z axis in your INI file .

if your loosing steps or missing steps theirs a reason for it . be it stepper performance or mechanical issues
or just plain running the machine outside it's physical capabilities or performance

cncbasher wrote:

you will probably find this is more a mechanical issue than software , or down to the type of cutters you are using ..
also look at reducing the default velocity in the [traj] section of your z axis in your INI file .

if your loosing steps or missing steps theirs a reason for it . be it stepper performance or mechanical issues
or just plain running the machine outside it's physical capabilities or performance

Yes, exactly this was my point - I wanted to tell the software about the limitations of the hardware. Anyhow: the more I think about it I prefer explicitely calculating the optimal speed. Thank you anyway - the statements in the forum were really helpful for me