bad probe hits

[MikeF]

I get these random bad hits the prehit distance above the part, if I have a .100 prehit the point will measure .100 above. I am using 2015.1 and a Leitz LSPX1H_T.
I have fast probe mode turned on just wondering if I turn that off will my problem go away.

[BKulpa]

I've had some strange issues with fastprobe, I'd try turning it off.
Are you sure you haven't exceeded the max weight the probing system can carry?

[Paul Sarrach]

What is your probe set up? Are you using TP20"s?

[RIDER]

I have the same Leitz probe and have had the same problem when I push the probe to the max weight as BKulpa said. I have one program that uses an 8x75x150 tip and had to turn the move speed down to 200 mm/sec to avoid the false "air" triggers.

[Paul Sarrach]

That is one big set up

[MikeF]

do you use fast probe mode? and yes I am using a 100mm long with a 5mm dia. ball, I was just wondering if I turn off fast probe mode would the false triggering stop.

[RIDER]

No. I am not using fast probe mode. 95% of the program is scans. I don't think turning off the fast probe would help because it's designed to speed up the motion as the probe moves away from the hit. What is your move speed set to MikeF?

[AndersI]

It could be that acceleration/deceleration is too aggressive...

[KIRBSTER269]

maybe you're to aggressive

[Mike Ruff]

I've had the same issue with our Leitz LSPX1H_T also in 2015.1. It's not due to weight because I was only using a 10X1.5X30. I also had FASTPROBEMODE/ON. I would have to rerun a bunch of points once the program ran thru to get actual dimensions. And it happened with different points every time it ran- it seemed totally random. My acceleration is set very high on that CMM and it may have had something to do with it- I didn't try changing it when we ran those parts. I ran the parts at only 40-50% speed though, so I'm not sure that the acceleration is the issue

[MikeF]

I have slowed it down from 400 to 200 now so far so good, but it is slow.

[N8VES]

I had false triggering too until I figured out the speed settings. I have a Global FX with a DEA controller. Specs for the max speed and acceleration is 300 and 1000 respectively. I set the max speed in the Part/Machine tab of the Setup (F5) menu. I left the Display Relative speed box unchecked because I frequently inspect parts in English and Metric. That lets me think of the Movespeed command as a percentage of the max speed instead of having to know the setting in in/sec when I'm measuring in English. With everything at max (300 / 1000 & Movespeed 100) my machine jerks badly. Enough that I can not only feel it with my hand on the table but see it as well. Of course I get false triggers, even with a relatively short stylus. I used to think acceleration and speed were kinda the same thing. But then it hit me. Acceleration is how hard I'm stomping on the gas and brake pedals when I tell it to move from point A to point B. On my machine, Movespeed affects not only the speed but acceleration as well. So i don't even touch the max settings. I just don't run anything faster than 70%. At that Movespeed setting I've reached the point of diminishing returns on time saved. I've tried using Movespeed 100 and lowering the acceleration values to smooth out the jerks but I wound up with the run time being within a second of just using Movespeed 70.

I guess it depends on what you want to accomplish with speeds. If you have a big machine and big part to inspect, lowering the acceleration values might shave off more time than lowering the Movespeed percentage. Most of the parts I measure fit within a square box no bigger than 250 mm³. At 70% most of the moves in that box never make it to the max speed before it starts to decelerate and stop.