G38.x and acceleration (not stopping)

Suppose you had a switch that triggers at exactly .5"
You could set the switch on top of your workpiece and probe with the drill. Down at med speed, back up then slow probe down. (the switch has some overt travel to protect the drill)
The point that the switch triggers would then be .5" above the work. So you have found the top of the work without gouging the work piece.

Rick G

so I make the optical barrier with a hole, let dril go in, measure the distance between the "breakage and work" use that as offset.. should work, not nearly as simple but should work.. thanks!

btw just to confirm, me not finding a way to "override" acceleration for axis is correct, there's no way to do it with linuxcnc?

I ask because in "my cnc world" (3d printing) we use M201 (max acceleration during "work move"), M202 (max acceleration during "idle move"), M204 (default acceleration), GRBL also support "$120, $121, $122" for setting acceleration, never used it so not sure how that works and is is run-time or only configuration..

btw just to confirm, me not finding a way to "override" acceleration for axis is correct, there's no way to do it with linuxcnc?

It has come up before, but i know of no easy solution. I believe the best bet is to set up the machine for the best reliable acceleration and control the probe speed with the F command. The reason for a fast probe then a slow probe is to reduce the time of the probe if it has a long distance to go. If you get the probe close 1st then a slow probe which will stop faster than a fast probe is fine.

Rick G

Rick G wrote: It has come up before, but i know of no easy solution.

well if the M201/202/204 are not supported by the linuxCNC there's definitely no easy way to do it ... I'll figure something out in hw, just wanted to check if there are sw solutions first

arhi wrote: Yes, exactly what I want to stop "faster then set limit" ... is that possible?

No, because the whole point of the limit is to be, well, a limit.

You could look at changing the limit "on the fly" look for HAL pins called "ini.***". You could pass different values to those prior to a probe move.