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Need help stylii & speed selection, prehit/ retract & probe modules selection.

Hello everyone again!
This community is so awesome, I just wanna say thank you everyone. :-) I've already had so many questions answered by y'all just from reading here and learning. So, over the weekend, after taking y'alls advice and retweaking even more of my program, I ran into a little bit of a snafu. Basically, what happened is that some parts that were consistently checking good all of a sudden started checking bad. I traced the problem down to a portion of the program where I had re-tooled it to use a different size probe to take points on a smaller hole. (I went from probing the hole with a 1mm to a 4mm ruby) . The hole sizes are .290 inches and .286. I am also using the 1mm ruby to measure a hole that is .100 inches in diameter. The .100 inch hole has always measured really well on this part, even though the 1mm ruby barely fits in the hole. I only have 2 probe modules right now (we are currently in the process of buying more modules and looking at a tool changer). I have an SF probe module and an MF probe module. The 1mm ruby is in the green/MF module, and the 4 mm ruby is in the yellow/SF module. I am fairly confused here too. I thought that since the 4mm ruby was in the Standard force module, that it would actually be more sensitive in this case than the 1mm ruby because the 1mm ruby was in the MF module...??? Also, the data when using the 4mm ruby is so bad, it scared everyone in production. Some of the values were 6 or 7 thousandths off, but whenever we checked it with the 1mm ruby that error went down to the tenths, like .0002 off and such. I just don't understand, because I thought that CMM operators generally tried to use the biggest ruby within reason to cut down on time wasted (the ruby having to travel a big distance). I was having trouble with the 1mm ruby when I had the touch speed jacked up to 3mm/sec in the small .100 holes. When I changed that touch speed to 1mm/sec, the ghost and double hits in the hole went away. Which really confused me because you think I would have many, many more problems with the 1mm probe exploring a .100 hole. Nope! For some reason the 4mm ruby just does not like the .286 holes.

In general, I just need more experience with the ins and outs of CMM operation. I just really don't have enough experience here and am humbly asking anybody for more information for all these nuances/ if any of y'all have a really down and dirty guide for the behind-the-scenes data that doesn't seem to be talked about very much. i don't really understand the difference between the probe modules either (LF/SF/MF/, and EF). I don't really understand the relationships between accuracy and prehit distance and retraction either. I get that the slower the touch speed is the more inherent accuracy the operator will get. I'm just really stumped by the 1mm ruby outperforming the 4mm one. Especially since I was told from the beginning that the smaller probes can be finicky and unreliable, yet in this instance it is quite the opposite, and the smaller probes have been great. Selecting the right stylii and all the little accessories was not something that was explained to me very well. We used generic stuff at the Hexagon training labs, and it seems that every QC lab I've toured just has their own preferences, and when I've queried about different stuff in their operations, they just respond "it's what works/what we do and we just haven't changed it). I've found that a lot of the settings/preferences/data seems many times to be set by someone before the current operator/they just use what they always do and don't have an explanation.
Parents
  • You need to make sure your probes are calibrated correctly. I know you're new so lets go over some things. You HAVE to designate a master probe.
    1. if you are using a tp20 (touch trigger), use a large diameter ruby with a short stem like 4x10 or 5x10. If you don't have something these size just use what you have but just make that probe the master probe.
    2. If you are suing a LSP scanning head, you can use a 5x20. That is only size that is supposed to be used for the lower matrix calibration so might as well make it the master probe for the probe calibrations.
    3. I don't use my master probe for any measurements, I only use it for locating the sphere and calibration. Some people have to use their master probe for measurements and that fine. Some people have multiple angles with their master probe and that fine too. You gotta do what you gotta do sometimes.
    4. ONLY the master probe is yes_man or yes_dcc. All other probes and angles MUST be set to NO.
    5 On some of my machines, the cal sphere might not physically move from the granite. You still have to use YES for the master probe. If you move your sphere in and out of your machine, you have to calibrate your master probe first by saying YES and then your other probes by saying NO.

    If you use parameter sets to calibrate, make sure your master probe is set to YES and your other probes set to NO.

    All this keeps all your probes and tip angles in relation with the master probe. Calibrate touch speed has to be the same as your program touch speed. If you calibrate you 1mm probe with 1mm touch speed, change that in your program. Say you are using your 4mm probe with 2mm touch speed and you switch to your 1mm ball. Before your probe that feature, type touchspeed and 1. Then your touchspeeds will be 1mm per sec throughout the rest of the program. Then when you switch back to you 4mm probe, type touchspeed and 2.​
Reply
  • You need to make sure your probes are calibrated correctly. I know you're new so lets go over some things. You HAVE to designate a master probe.
    1. if you are using a tp20 (touch trigger), use a large diameter ruby with a short stem like 4x10 or 5x10. If you don't have something these size just use what you have but just make that probe the master probe.
    2. If you are suing a LSP scanning head, you can use a 5x20. That is only size that is supposed to be used for the lower matrix calibration so might as well make it the master probe for the probe calibrations.
    3. I don't use my master probe for any measurements, I only use it for locating the sphere and calibration. Some people have to use their master probe for measurements and that fine. Some people have multiple angles with their master probe and that fine too. You gotta do what you gotta do sometimes.
    4. ONLY the master probe is yes_man or yes_dcc. All other probes and angles MUST be set to NO.
    5 On some of my machines, the cal sphere might not physically move from the granite. You still have to use YES for the master probe. If you move your sphere in and out of your machine, you have to calibrate your master probe first by saying YES and then your other probes by saying NO.

    If you use parameter sets to calibrate, make sure your master probe is set to YES and your other probes set to NO.

    All this keeps all your probes and tip angles in relation with the master probe. Calibrate touch speed has to be the same as your program touch speed. If you calibrate you 1mm probe with 1mm touch speed, change that in your program. Say you are using your 4mm probe with 2mm touch speed and you switch to your 1mm ball. Before your probe that feature, type touchspeed and 1. Then your touchspeeds will be 1mm per sec throughout the rest of the program. Then when you switch back to you 4mm probe, type touchspeed and 2.​
Children
  • Ok, this is going to get some re-reading and time to digest and understand...this "master probe" theory is something new to me. I think I may have heard it mentioned in passing in the PC-DMIS forum? I'm not sure. I mean, I know a lot of times whenever I boot up the program that "MAIN" will come up, but I always just thought that was a default setting or name or whatever. So, if I understand what I'm reading correctly, you are kinda saying that all the other measurements of other probes and angles are driven off the Master/MAIN probe?? It sounds awfully similar to our lathes where the first tool (generally the turning tool) will be designated the first tool and all the Z lengths are driven off that? So if we crash a tool on a lathe all we have to do is reset it, and then measure it off of the turning tool. Is that somewhat similar to what this is? Will the Master probe being lacking in a probe file do really bad things? Because the data that I'm getting back seems believable, I just don't understand the function of the master. Will the lack of a master probe give me really funky readings later that I won't be able to track down/weird runoffs? Either way, I really need to get more probe modules/probechanger. I have as many stylii as I want really, I just have the 2 modules and I would probably have to tear one down or keep one as the Master probe and retool some programs.