Touching Probe stylus

[Ajesh George]

Can anyone pls tell me , how to check our probe stylus is touching or not the samples instead of ruby ball , while taking features ?

It seems even if ,i'm taking features with stylus touched , it showing very less form error. ( say 4 microns )

is there any way to find this out ?

[DAN_M]

I am sorry, I don't understand your question. Can you please try to re-phrase?

[Ajesh George]

While taking features with 0.5 mm or 1 mm probe , its extremely difficult to check the ruby ball is actually touching our samples. Because for drafted surface or wrapage surface , probe stylus ( probe stem ) is touching the samples. Thus we will not get repeatability for measurement,
So at this moment , is there any way to check our probe ( ruby ball ) is actually touching the surface or not ?

[Schlag]

" ASSUMING" here you are referring to " shanking out " ? The shank of the probe is making contact and not the RUBY ? How can you tell ? Measure size / location by other methods and compare ? I 100% program off line and its something that is constantly looked at / considered when I choose tip angles and create features. It doesn't come up that frequently but when it does you had better pay attention or your numbers will be garbage. Good RUBY contact is mandatory. The programmers I took over from at this job didn't care about checking a hole with a shank probe being off a few degrees from the probe...... If you are in a tight spot and using extremely small probes ON-LINE, I have no clue how you would really address this.

[Ajesh George]

yes , for 0.5 mm and 1 mm probes , its extremely difficult to check good ruby contact , instead of probe stem. So that's why i'm asking , is there any way to check this out ?

There isn't much difference in form error , if we take features with ruby contact or stem contact. So while programming drafted surfaces, it become difficult to check. Please let me know is there any way for this.

[ThePudds]

If possible, watch the probe through the whole program? Make sure its touching by visually looking at it? Other than what Schlag said above, i cant think of anything else.

[UKCMM]

The only sure ways to reduce/prevent shanking out is to physically orientate the part to the probing system, increase the ball size used, angle the head to give side clearance take individual points and construct the features you want, very slow as multiple head orientations would be needed but may be the only option.

[DAN_M]

Ajesh George

Thank you, now I understand.

Do you write your programs offline using a cad model?
If you do, what I would recommend you try doing is set your
prehit and retract distance to 0.0001 inches while you are programming. This will give
you the ability to put your probe on the model and zoom in really good and
physically see by eye if you will be shanking out or not. Once you're done programming,
remember to set these back to normal parameters. You might also try utilizing PCD's
collision detection feature.

If you write your programs at the machine without a model, the only way to know
whether or not you will be shanking if out is to run the program nice and slow with your fingers crossed lol.

[Ajesh George]

Thank you Dan, unfortunately i don't have CAD model, and its very tight area to check also. Anyway, thanks for the info, it might help me to try with other samples.