Finding the center of a rotary on the table (probe)

Hi,

I am coming up with my next issue to tackle.

How are you guys finding the center point of rotation on a rotary attached to the table turning around Y axis.

As for programming purposes in cad and cam the coordinate system is set always in the center of rotation.

I would like to be able to probe the chuck to find the center as I think that would be easiest but than I need to find the center based on probing 3 points. Mathematically that is a little far.

Buy maybe you guys have a better solution cause in the end the tooltip need to be set to 0 on the center of rotation and that isn't a flat surface.

Hope someone can help.

Regards,

Stephane

Hi Andy,

I want this to be an automated script to find the center. To touch off the probe shouldn't be the hardest issue I guess.

I was thinking that with 3 points on a circle it should be calculable.

On the other hand what you say is true aswell, knowing the diameter of the chuck holder , I should be able to just center it and substract the radius.

Is there any script around doing exactly that movement. In Y direction. Going left, touch off, going right touch off. Centering it touching off and setting xyz to 0. If than I can touch off the probe as reference height as first tool in a gcode , i could work with my current manual tool change script from the forum that works perfectly.

So did anyone write a script like this already?

Regards,

Stephane

@Hi Stephane,

To find the centerpoint of a chuck with a probe sensor :

Input's :
1.Chuck_diameter
2.Probe_correction (if needed)
3.Probe_sequence ( 2 circle or 3 circle arc centre point's calculation )
4.Probe_trigger_x
5.Probe_trigger_y

Output's :
1.Centerpoint_x
2.Centerpoint_y

If you want to write a scrips to find the center point, that is possible. Script's in linuxcnc are usually written in C language, this language include's all the mathimatical possibilities so far i know. This script's / function's are named component's in linuxcnc. You can write your own. This way of programming is almost unlimited. You can even make multiple component's to achieve your goal.

You could imagine, that number 3 input parameters is handy. Then you can select a formula routine with the chuck diameter input.
In C code, you can make a Case 1 or 2 or 3.
After that the C code will trigger your sensor in 2 or 3 step's while your probe function is executing. It will calculate your centre point exactly.

For 2 poin't circles, you could go negative or positive centre point's. That you can solve to do *-1 to get it to the positive quadrant.

So this can be your solution. If i needed it, i would write this solution.

Hi Andy,

Last there was a academic guy in other topic who could not solve circle crossing point's in linuxcnc.
You solved that in matlab.
But maybe the solution is to add a minus/max implementation in linuxcnc too. Then the restart function at arc's can also be solved.

(and, in fact, it is very difficult to start a probe move, or any axis move at all from a HAL component).

For the most user's i agree.
If you use external offset's, you can imagine your right or left hand is moving in the air. Your hand is moving in all kind of position's.
In the external offset branche the robot will follow your hand exactly. Offset's are not difficult. Probing is easy.

Also adaptive feed. Negative g-code speed. Where is it?
I have it all in one version merged myself.

The linuxcnc boss has work to do.