Measuring a .66mm slot

[Ruda66]

I'm trying to probe a .66mm slot. Switching from a .5mm probe to a .3mm probe helped. But I still get a lot of "no probing within probe limit" and "lower trigger not reached" I have to adjust the prehit and retract distance for each hit for it to run. And then the next part is changed a little so it requires adjusting everything again. Any advice for a newer programmer?

[Matthew D. Hoedeman]

You should NEVER have to adjust the prehit and retract for a small hole. If you have a 10mm prehit and retract, and are trying to measure a tiny hole, Pcdmis will adjust the prehit and retract in the background to the 'radius' (or half the width) of the hole you are trying to measure. Pcdmis will only try to probe past the nominal of the touch it is trying to take by twice the prehit value. So, for that tiny hole, if you put your prehit at 0.1, it will only go 0.2 past where the touch SHOULD take place and may not touch the part. You could put in a check distance to help, but you shouldn't have to lower your prehit/retract values.

You can try using FIND HOLE (but for really small holes it kinda sucks for that) or you could turn on READ POS (you will be prompted to manually position the probe in the 'center' of the hole.

OR, if you have a bigger hole that is close to that hole that is being put in at the same time in the same operation, you could measure the tiny hole RELATIVE TO that bigger hole.

[Ruda66]

It's not a hole, it's a slot, and it opens up near the top. And it's pretty small so it's hard to tell if I'm touching the part or not.

[UKCMM]

If you have another feature you can relate it to that allows for the position change then use that to control the hit positions

[Ruda66]

OK thanks, I will try that if there is anything

[Matthew D. Hoedeman]

hole/slot, same thing for prehit/retract (a slot IS a hole, it's just an elongated hole or a squared elongated hole)

[Ruda66]

I'm running a program that measures the slot as vector points and then creates planes out of it. Still the same? Should I change it to measure as a slot?

[louisd]

You could gain a few thousandths of location error, by taking a couple find-the-slot center points a thousandth or two of an inch below the top of the slot.

IE your 0.3mm tip is 0.012" in diameter. so if you measure a few points 0.004" or 0.005" ABOVE the top plane/surface of your slot, you will be hitting the 0.3mm tip on the breakedge corner of the slot, giving you about 0.005" of extra location variation to robustly find the slot.

Align-locate to the mid of the find-the-slot points, then dig down further to actually take your hits.

[Matthew D. Hoedeman]

I would measure it as a slot, a 'hole' feature will automatically adjust the prehit/retract for the size, a vector point will not.

Any time there is a round slot that is "long", I select it as a round slot from the cad, but then change to square slot because it lets you get a much better width value. IMO, the slot needs to be more than 2.5 times a long as it is wide to switch to the square slot.

[Ruda66]

OK thanks for the info, I will try that.

[Ruda66]

If I measure a slot and it can't take all the points, can't it still calculate the slot based on the points it can take?