Probably somebody has already thought of this, but just in case they haven't...
On larger bores, Find Hole is way too slow, even with the touch speed jacked up. We normally have our touch speed set to 2%. So 10% seems reasonable.
So what I ended up doing was to do two auto circles (this is done without a CAD model... We don't have CAD models for a lot of our stuff, but I normally program with autofeatures rather than teaching the software where stuff is. In the instance where I used this, it was a round part with a 99mm bore in the center. My CMM is misbehaving and won't let me take manual hits, but autofeatures work just fine. My original program used manual hits for the alignment, but doing those would lock up the machine. I had to "retrofit" the program with a Readpoint Alignment.
Set prehit and check high. In my case I did 10mm. Jack up the touch speed to 10%.
Park the probe approximately 1/4 inch out from the center of the bore. Create a Readpoint and do an alignment with that as the origin.
Do an autocircle and lie to the software and tell it the diameter smaller than the actual size. The bore I was measuring was 99mm, I told the software it was 93mm. I set the number of hits to 4. I normally don't use the depth setting on the autofeature, but set the origin value for depth to where I want the hits to happen.
With the undersized circle and the prehit/check distance being so high, the CMM has enough wiggle room to deal with the initial readpoint being off center. It also doesn't have to travel so far at touch speed to reach a surface it can take a hit on.
Once you have this circle, make a new alignment off it and use that to do another autocircle at the normal touch speed with prehit set to whatever you usually use.
Yeah, it's kind of clunky. But it works.
On larger bores, Find Hole is way too slow, even with the touch speed jacked up. We normally have our touch speed set to 2%. So 10% seems reasonable.
So what I ended up doing was to do two auto circles (this is done without a CAD model... We don't have CAD models for a lot of our stuff, but I normally program with autofeatures rather than teaching the software where stuff is. In the instance where I used this, it was a round part with a 99mm bore in the center. My CMM is misbehaving and won't let me take manual hits, but autofeatures work just fine. My original program used manual hits for the alignment, but doing those would lock up the machine. I had to "retrofit" the program with a Readpoint Alignment.
Set prehit and check high. In my case I did 10mm. Jack up the touch speed to 10%.
Park the probe approximately 1/4 inch out from the center of the bore. Create a Readpoint and do an alignment with that as the origin.
Do an autocircle and lie to the software and tell it the diameter smaller than the actual size. The bore I was measuring was 99mm, I told the software it was 93mm. I set the number of hits to 4. I normally don't use the depth setting on the autofeature, but set the origin value for depth to where I want the hits to happen.
With the undersized circle and the prehit/check distance being so high, the CMM has enough wiggle room to deal with the initial readpoint being off center. It also doesn't have to travel so far at touch speed to reach a surface it can take a hit on.
Once you have this circle, make a new alignment off it and use that to do another autocircle at the normal touch speed with prehit set to whatever you usually use.
Yeah, it's kind of clunky. But it works.