Reasonable probe speed

This might be a dumb question, but I am setting up a touchoff plate and am curious what a reasonable probe feed rate would be. I know that machine acceleration and deceleration play a part. I plan on touching off twice. I was thinking a feed rate of 25IPM on the first touch, retract .250 inches and then touch again at a feed rate of 5IPM.

Is this reasonable? I will have up to 6 inches of travel on the first probe.

Regards,

Joe

If you have relatively high acceleration and the probe has a decent amount of travel, you can do your first probe as fast as you want.
I think my probe moves are 50 ipm, back off 0.1" and probe again at 2.5 ipm.

Sorry I just read you are using a touch off plate.
I',m guessing there is no travel then.
I would just get in the habit of jogging close, and doing a 5ipm or slower probe move.

Alan,

Thanks for the input.

The six inches of travel, I figured would be if I hit the touch off button from the Z-Axis home position at the very top of the Axis. I agree though that to speed things up it would be better to jog close to the plate then do a touchoff. Let me ask you this, would it be beneficial to do two touchoffs or just one at a slow rate, say 2.5 IPM?

I am putting together a series of tutorials on how to setup and configure a touchoff plate as part of my CNC build. I am trying to break the tutorial into parts that would help someone new to the hobby to get a grip on how things work in LinuxCNC. Here is how I have broken them down.

Part 0 - What is a touchoff plate and how it works
Part 1 - Finding an available input pin, determining its logic level, bringing out the complement to that pin, testing with Hal Meter, and changing the logic if needed from negative to positive logic.
Part 2 - Developing the G-Code to probe, set the offsets and retract the tool
Part 3 - Setting up PyVCP in Axis and adding the button.
Part 4a - Setting up the touchoff using Classic Ladder, building the ladder and adding it to the config, making the connections and testing.
Part 4b - Setting up the touchoff using o codes.

This is still a work in progress and as I develop and go through the material i will refine it. My end goal is to provide a written and equivalent video totorial on how to do it.

I want them to see the process and testing that has to happen to build upon and existing configuration. Up to part three I have demonstrated how to do these things with the Stepconf Wizard and by editing the files by hand. Parts 4a and b have not been worked on yet.

But I digress, I want to give sound values and feeds for people to use, then they can adjust how they think they need to.

Joe

The fastest I'll probe is 600mm/min about 23-5/8" ipm sometime, when I'm really bored, I do it at about half of that.

andypugh wrote:

You can consider doing a fast probe-to-break followed by a probe to make rather than a fixed retract.
Then a very slow probe-to-break won't take long as you are already very close to the material.

Good idea Andy, I will work that direction in my touchoff plate project.

Joe

Are just using the plate for tool length or Z touch off? In which case, jog the machine as fast as you want to near the plate, then probe slowly. The slower the probe the more accurate (and the more time you have to react if something goes wrong).

pippin88,

After some experimentation in MDI with the probe command, I think your spot on. Rapid down till you are close to the plate then use a probe command fairly slow. I run the command about 50 times last night, and the slow feed speeds <=5IPM gave very consistent results.

Thanks,

Joe