Master probe

[Smallsvillanova]

How do you guys go about your master probe set ups? do you have a separate program that you bring in to locate the ball? I was told that a short robust stack up is ideal for a master probe however all of our stack ups that we use are usuall longer with extensions. would I just create a "find qual ball" program and then use that everytime my ball moves or how do you guys usually go about it. Our qual sphere moves all the time and is not tied down to the table due to availability of space if that matters.

[mb0258]

One master probe; short, bigger dia, with this one, and ONLY this one, you answer yes to question if calib. ball has moved, all other probes you answer NO.

[Disal]

We have Auto Calibration set up. And like the previous person said-you just say Yes on the first one and No on the rest

[CODE]
AUTOCALIBRATE/PROBE, PARAMETER_SET=ALL-TIPS-WITH-DEFAULTS, QUALTOOL_MOVED=YES_MANUAL,
SHOW_SUMMARY=YES, OVERWRITE_RESULTSFILE=YES

[Smallsvillanova]

Thank you for the replies.

I do understand the concept of the master probe. I am curious as to how you go about actually utilize it though. Do you have a separate program that you use to locate the qual sphere with your master probe and then just open the program you wish to run and change the stack up and qualify those angles?

Like say my master probe is the short robust stack up like you describe, but then my program calls for a stack up with a long extension. do you locate the sphere in a separate program with your master? Then change to the program you want to run and change your stack up and tip accordingly and calibrate those?

Sorry if im not being clear I am having a hard time trying to describe what I mean.

[Smallsvillanova]

BTW how did you tag me in that comment? I tried "@ing" you and it didn't give me the clickable result like yours did

[acgarcia]

Create a calibration program that automatically calibrates your probes for you. That should be the only program you would need to load the master probe.

You can also put that into every part program you have and calibrate your probes before every part. You can use flow control to give operators the choice to skip the calibration or not.

It’s all about what you want to accomplish.

[HxSwartwood]

acgarcia i agree. We don't run calibrations before every program, so I forgot about that.

[Schrocknroll]

BTW how did you tag me in that comment? I tried "@ing" you and it didn't give me the clickable result like yours did

You misspelled HxSwartwood

[Smallsvillanova]

lol and I'm supposed to be an inspector. thanks Schrocknroll

[Smallsvillanova]

HxSwartwood does everyone misspell it that way? Is it like some weird mental trick that causes people to flip the W? Because just glancing at it I that it was an M again and had to do a double-take lol

[HxSwartwood]

Smallsvillanova Literally EVERYONE spells it that way lol. My name induces dyslexia for some reason

[A-machine-insp]

I run calibration before every program because we do first articles and don't typically run production inspections. I just add a LOADPROBE line to the beginning of the program, calibrate the "reference probe", delete the added LOADPROBE line, calibrate the probes to be used, then go about my merry day. My CMM is small enough/parts big enough that I can't leave the cal sphere on the table so I relocate it every time. That being said, I always mount the sphere in the same location so I use "yes, sphere has moved, dcc hits to locate" since it is close enough for the machine to find.

[DAN_M]

I give my operators the option to calibrate at the beginning of every program. See below.

In order to make autocalibrations work, you'll have to familiarize yourself with setting up "parameter sets" for calibration.

If you need anything here further explained, don't hesitate to ask.

GROUP_PROBEQUAL_FLOWCOMMANDS=GROUP/SHOWALLPARAMS=YES
QUAL_QUESTION   =COMMENT/YESNO,NO,FULL SCREEN=NO,AUTO-CONTINUE=NO,
              Has the CMM been calibrated??
              IF_GOTO/QUAL_QUESTION.INPUT=="YES",GOTO = LABEL_END_CALGROUP
QUAL_ACTION   =COMMENT/INPUT,NO,FULL SCREEN=NO,
              1--> Let's calibrate the CMM now.

              2--> Just run the program. I
              don't need to calibrate.

              3--> I need help.

              IF_GOTO/LEN(QUAL_ACTION.INPUT)<>1,GOTO = QUAL_ACTION
              ASSIGN/VAR_1=ARRAY(1,2,3)
              ASSIGN/VAR_2=MIN(ABS(VAR_1-QUAL_ACTION.INPUT))
              IF_GOTO/VAR_2<>0,GOTO = QUAL_ACTION
              SELECT/QUAL_ACTION.INPUT
                CASE/1
                  DISPLAYPRECISION/7
                  COMMENT/OPER,NO,FULL SCREEN=NO,AUTO-CONTINUE=NO,
                  Screw sphere into calibration hole. Ball facing CMM's Y+ (if applicable). Press okay when complete.
                  AUTOCALIBRATE/PROBE, PARAMETER_SET=T1A0B0_MASTER, QUALTOOL_MOVED=YES_DCC,
                                CHECK COLLISION=NO, SHOW_SUMMARY=NO, OVERWRITE_RESULTSFILE=NO
                  LOADPROBE/7107_B_FRONTTIP_2
                  TIP/T1A0B0, SHANKIJK=0, -1, 0, ANGLE=0
                  AUTOCALIBRATE/PROBE, PARAMETER_SET=4594_FINAL_01_SLVS, QUALTOOL_MOVED=NO,
                                CHECK COLLISION=NO, SHOW_SUMMARY=NO, OVERWRITE_RESULTSFILE=NO
                  LOADPROBE/7107_G_4X20
                  TIP/T1A0B0, SHANKIJK=0, 0, 1, ANGLE=0
                  COMMENT/OPER,NO,FULL SCREEN=NO,AUTO-CONTINUE=NO,
                  MOVE PROBE FAR OUT OF THE WAY.

                  Once probe is out of the way, remove
                  the sphere & put in safe place.
                  DISPLAYPRECISION/4
                  GOTO/ENDPRG
                END_CASE/
                CASE/2
                  GOTO/LABEL_END_CALGROUP
                END_CASE/
                CASE/3
                  GOTO/ENDPRG
                END_CASE/
              END_SELECT/
LABEL_END_CALGROUP  =LABEL/
            ENDGROUP/ID=GROUP_PROBEQUAL_FLOWCOMMANDS

[DAN_M]

This is how I calibrate for production jobs.

When its just me driving the machine, I "F9" the loadprobe commands and tell them when to do from there

[Smallsvillanova]

Well I would need a lot further explained. Ive only done level one so I really have no understanding of the expressions and variables and whatnot but that is definitely one thing I am really excited about learning. Trying to get my company to send me back for level 2 right now so I can make my way to level 3 because I feel like that's where all the fun stuff happens lol. I can understand what you are accomplishing by reading your code I just don't have an in depth understanding about the syntax PC-DMIS uses and how I would go about getting what I want. That is a facet of programming that is really exciting to me so hopefully I can make my way there soon! Also what do you mean by "parameter sets"?

[Kp61dude!]

Smallsvillanova go to town in offline mode while you can! Don't wait to go to 'training' or 'school' to make things happen. Google everything and ask questions here (after you've searched high and low for an existing post).

[kingsld1]

A parameter set is all the information necessary to qualify a particular probe setup. It has the move and touch speeds, all the tips you want to qualify in that set, calibration sphere information etc. The parameter set saves all that information into one container that you can access thru a program.

All of my measurement routines have a calibration parameter set that was created for that routine. I then have a little menu routine that I use where "Calibrate Probes" is one of the options. Removes an excuse for other people to get into the part program.

[acgarcia]

Smallsvillanova this person had the same question

hope this helps

https://www.pcdmisforum.com/forum/pc-dmis-enterprise-metrology-software/pc-dmis-for-cmms/460978-auto-calibration

[Kp61dude!]

"Who needs class...."- Smallsvillanova
That's the spirit!!!!!

[Smallsvillanova]

Kp61dude! That book learnin is for rich folk, which my company has made explicitly clear...we are not. lol

[Kp61dude!]

Amen brother!!! Though if you keep insisting (not tantrums) they'll, eventually, send you to all them classes.

[NinjaBadger]

I just want to make one thing clear here - you only need to employ a masterprobe when you're using multiple probes which are on separate modules.

If you're literally taking probes (styli) apart and rebuilding them then this doesn't help.

If (as is the case in a place I'm doing some work for) you only have two modules you can still use a masterprobe.

[Smallsvillanova]

I only have a few modules. not enough to dedicate one to every tip that I use. But if I need to get more modules that isn't a problem. I am only concerned with making my set up and programs as repeatable and reliable is possible. I would like to eliminate as much room for potential error as possible.

[NinjaBadger]

Anytime you unscrew any component of a probe you MUST re-calibrate it.

If you have a few modules I'd pick a useful tip that you use a lot and use that as the master probe (ideally with a master probe you don't use it for anything else, but that's not always feasible), in theory you want a short tip with a reasonable diameter, but again it might not be practicable, I'd try stay away from anything less than Ø2 and over 40mm long.

Now you can take apart and rebuild probe builds on the other modules as you require, but always define the Ref sphere position (answer Yes - Sphere has moved) with the Master probe, and answer 'No' with all other probes. This will give you the best way of ensuring measurements taken with one probe relate to measurements taken with another.

If you can get more modules then do so, then you can have 3 or 4 main 'weapons' and build up others as required.

[Smallsvillanova]

Gotchya. I do have a 4mm ball that has never been used I was going to dedicate that as my master. Also I have a 1mm barrel, a 3mm ball, a 2mm ball, and a 2mm barrel that get used. I will have to get each of them their own module. Also lets say I get them all their own set ups and they don't ever need to be taken apart, how long would you say calibration of those tips is valid for?

[AndersI]

how long would you say calibration of those tips is valid for?

The calibration is valid until it isn't... It doesn't degrade by time, only by physical events - different speeds, different temperature, different form (after a collision), different seating in the magnet coupler (dirt on the connecting surfaces), different size of the tip (scanning all day long may be quite abrasive), damage to the tip (not spherical any more) or the stem (micro fractures in carbon stems).

The only way to know if the calibration is still valid is to validate the tips on a certified artifact, for example the datum sphere.

And remember, the datum chain is broken when you answer "YES, the sphere has moved" - tips calibrated after this do not relate to tips calibrated before (unless you follow the Master Tip procedure (to the letter)).

And the datum sphere may have 'moved' even if you haven't touched it, but powered off, or just re-homed, the CMM. It has definitely moved if you unscrew it, even if you put it back in the same hole.

And so on...

[Smallsvillanova]

So I am constantly taking down my cal sqhere between jobs due to space, therefore if I need to cal tips after I have moved the sphere it will now be unrelated to anything I previously calibrated? So in order to relate them all again I would have to re located with the master probe and then continue to calibrate them all again together?

Sorry if this is repetitive I am just trying to be clear

[AndersI]

No, by locating the sphere with the Master Tip (assuming it is always reset to nominal) you restore the relation, and only need to calibrate tips that need to be calibrated (new tips, new angles, etc.). There are many long posts on this forum about the Master Tip process - read carefully.

[Smallsvillanova]

Thank you that's what I thought. I have read through several of the posts about the master tip process and believe I have a pretty good understanding now, however i will admit that everyone has there own little nuances in which they explain things specific to their situation so it gets a bit confusing.

Thank you again for taking the time to explain.

[AndersI]

everyone has there own little nuances in which they explain things specific to their situation so it gets a bit confusing

Yes, I understand. Maybe the following makes it even fuzzier, but I like to explain the Master Probe like this:

If you just locate the datum sphere with *any* tip (in *any* state), you never know where the sphere is now in relation to where it was the last time you calibrated. This also reflects in the tips you calibrate - previously calibrated tips do not relate to tips calibrated after the locating of the sphere.

By *always* locating the sphere with the Master Tip *and* keeping that tip at nominal values (Reset to nominal), you have a fixed point which the sphere relates to, and consequently, all the tips will also relate.

We have moved the start of the datum chain *from* the sphere (which moves around), *to* the Master Tip (which stays fixed).

[Smallsvillanova]

Had to re-read it a few times to un-fuzzy it but you make perfect sense, I take snippets out of some of these posts to save for later for a manual I am working on for training, this will be going in there. I think its a very understandable way of explaining the master probe. Thank you.

[NinjaBadger]

Yes, I understand. Maybe the following makes it even fuzzier, but I like to explain the Master Probe like this:

If you just locate the datum sphere with *any* tip (in *any* state), you never know where the sphere is now in relation to where it was the last time you calibrated. This also reflects in the tips you calibrate - previously calibrated tips do not relate to tips calibrated after the locating of the sphere.

By *always* locating the sphere with the Master Tip *and* keeping that tip at nominal values (Reset to nominal), you have a fixed point which the sphere relates to, and consequently, all the tips will also relate.

We have moved the start of the datum chain *from* the sphere (which moves around), *to* the Master Tip (which stays fixed).

That's the thing right there!

If it's being done properly by everyone who uses it, this step isn't necessary, as the measured xyz offsets for the Master probe-tip will always be the same as the nominal values.

The number of times I've been places where they're supposedly using Master probe procedure and these values don't match (i.e. someone has calibrated the Master probe saying 'No sphere hasn't moved').

I also always set my systems up to append calibration results. That way a quick search of all the results files will tell you if someone has defined the sphere location with any other tip.


Probe file=MASTER_4BY20 Date=16/08/2019 Time=20:16:48

CalSphere CENT X 245.687 Y 327.331 Z -452.647 D 25.000 <<<<<< See this anywhere other than right before your Master Probe-Tip and something's gone wrong!!!!
T1A0B0 THEO X 0.000 Y 0.000 Z 161.520 D 4.000
T1A0B0 MEAS X 0.000 Y 0.000 Z 161.520 D 4.989 StdDev 0.001

If MEAS X Y and Z values above aren't the same as the THEO X Y and Z then something's gone wrong!!!!!

[AndersI]

My take is "never trust anyone else to do it right, give them an auto calibration program that resets the Master Tip..."
+100 on appending the calibration results, that cuts debugging time considerably!

[Smallsvillanova]

That's the thing right there!

If it's being done properly by everyone who uses it, this step isn't necessary, as the measured xyz offsets for the Master probe-tip will always be the same as the nominal values.

The number of times I've been places where they're supposedly using Master probe procedure and these values don't match (i.e. someone has calibrated the Master probe saying 'No sphere hasn't moved').

I also always set my systems up to append calibration results. That way a quick search of all the results files will tell you if someone has defined the sphere location with any other tip.

This is a very good point. Not something i have been doing but will definitely be doing this moving forward. Thank you!