Which would you trust more?

[Marshal]

I'm playing with the probing system on our mill, trying to learn the ins and outs of it, and I noticed a discrepancy today. Basically, when we put something in the mill we usually indicate about a hole in the center to give us our part center. Pretty basic, and we haven't had any problem with it. But I would assume the probe can do the same thing and be just as accurate, if not more accurate. So I tried it, and noticed that the center of the hole using the probed center is 0.0147" different in the X, and 0.0022" different in the Y. Which would you trust to be more accurate, the indicator or the probe?

[Guest]

recalibrate your probe tip, you should NOT be getting anywhere near that much difference

[Guest CNC Apps Guy 1]

I indicate my probe tips to within .0002 TIR.

 

YouI should calibrate the probe also. I use 2" or larger gage rings.

 

John's right though, you should not be getting anywhere near that much difference. I would venture to guess, you should see less than .0005" difference between indicator and probe.

[Marshal]

alright, I'll give it a shot--if I can figure out how to calibrate it lol. Only way to learn is to do it

[K2csq7]

I have an old Starret indicator, ya know what it says on the face?

LAST WORD!!!!

[Guest]

I'll see your Last Word and raise you 3 Interapids (1) .0005 & (2) .0001

[Guest CNC Apps Guy 1]

Macro O9801 This is used to establish the probe length in its toolshank.

Macro O9802 This is used to establish the stylus off-centre values.

Macro O9803 This is used to establish the stylus ball radius values. It is suitable for all measuring cycles except O9821, O9822 and O9823.

Macro O9804 This is used to establish the vector stylus ball radiusvalues. It is suitable for all measuring cycles, including O9821, O9822 and O9823.

 

For complete calibration of a probe system, you must use macros O9801, O9802, and either O9803 or O9804.

The Renishaw calibration cycles are split into separate cycles for flexibility. If, however, the calibration feature is accurately known for both size and position, e.g. a ring gauge where the size is known, and the position is accurately found using a Dial Test Indicator, it is then possible for you to write a program which completes the full calibration procedure in one operation by calling all of the above macros.

 

Example: G65P9803D50.005Z50.S1.

COMPULSORY INPUTS Dd d = Reference ring gauge size

OPTIONAL INPUTS Zz z = The absolute Z axis measuring position when calibrating on an external feature. If this is omitted a Ring Gauge cycle is assumed.

Ss s = The work offset number which will be set. The work offset number will be updated.

S1 to S6 (G54 to G59)

S0 (External Work Offset).

S101 to S148 (G54.1 P1 to G54.1 P48) additional offsets option.

New work offset = active work offset + error.

New External offset = External offset + error.

[Marshal]

Hmm, I'm getting an error saying "part probe readings exceed maximum deviation as defined by the max spread parameter". How do I fix that?

[Müřlıń®]

You got to be kidding me.

 

A interappid in the final say.....

 

As long as the bearings are in there square.

 

I have seen times when sweeping a hole in resulted in error but only if the bearings were in at an angle.

 

Starett last word is the worst indicator on the planet if not in the universe.....

[Joe788]

Marshal, what kind of machine, control, and probe is it?

[Marshal]

Marshal, what kind of machine, control, and probe is it?

 

It's a Hurco VM-1, I believe with the WinMax control, and an OMP-40 probe.

[Guest CNC Apps Guy 1]

I'm out... I know ZILCH about Hurco.

[Scott Lundin Shopware Inc.]

The probe is quick and handy but you just never know if the last guy on the machine bumped it hard and threw it out of calibration.

[Guyinthedesert]

alright, I'll give it a shot--if I can figure out how to calibrate it lol. Only way to learn is to do it

 

One thing to keep in mind. If you remove the probe from the machine, you need to replace it in the same orientation as when it was calibrated.

 

(if your prboe tip is indicated in dead zero, it shouldn't mattet. My guess is your tip is a few thou off, and if you pull the probe out and turn it around, it will be twice that amount off)

[Marshal]

The probe is quick and handy but you just never know if the last guy on the machine bumped it hard and threw it out of calibration.

 

Well, there's only 2 people in the company that know how to use the machine, and the other guy only uses the probe for setting the Z, so there won't be much bumping lol.

 

 

One thing to keep in mind. If you remove the probe from the machine, you need to replace it in the same orientation as when it was calibrated.(if your prboe tip is indicated in dead zero, it shouldn't mattet. My guess is your tip is a few thou off, and if you pull the probe out and turn it around, it will be twice that amount off)

 

The probe is never taken out of the machine, it's in the ATC, so it always goes in the same way, so that's not likely the issue. I just can't get the darn thing calibrated, and it's entirely possible it was never calibrated in the X and Y, since it's never been used for anything other than for setting the Z.

[robk]

Contact Renishaw @ 847-286-9953 for a .pdf copy of their manuals for your machine/control combo. The copies should be free of charge.

FYI, if possible our operators calibrate the touch probes as well as calibrate/align the non-contact lasers on the daily basis. A lot of our operations are 30+ hours per part with probing cycles within the program so it's critical that the probes are always calibrated. But that being said, I would trust an indicator (+1 to Interapid) over a touch probe any day.

[Marshal]

I'm still getting the "part probe readings exceed maximum deviation as defined by the max spread parameter" error, even after adjusting the max spread. I wonder if the probe itself is off center? I know there's some adjustments in the probe head, but I don't want to mess with those if I can help it.

 

I honestly have no idea if this probe was ever calibrated in the first place, certainly not within the last year or two. The Z values have always worked excellent in coordination with the tool setting probe, so I think that value is accurate, but X and Y certainly aren't.

[McLaren]

Mechanical FTW.

I'd stick an edge finder in there. Get the center of your hole. Zero out your relative, then stick the probe in and check center.

[Mr. Wizzard]

Use a .0001 indicator on the tip of the probe and spin it. Your runnout should not be more than .0002, typically. If you want it calibrated properly, you'll have to use the adjustment screw in the head. It's a tedious process, but well worth it and really pays off in the end. If your probe isn't properly calibrated, it's not much use other than getting you "close".

[Guest CNC Apps Guy 1]

Did yu ever indicate the probe tip? How much runout did you get?

[Marshal]

Mechanical FTW.

I'd stick an edge finder in there. Get the center of your hole. Zero out your relative, then stick the probe in and check center.

 

And that's more or less what I've been trying to do. I've got the center of a 2" ring gauge set using an indicator, and have been trying to calibrate the probe from that. When I measure the ring gauge with the probe, I'm getting a centerpoint difference of 0.0050" in the X, and 0.0026" in the Y, and it tells me the diameter of the ring gauge is 1.98992", when it's actually 2". Seems like an awfully big error to me.

[Marshal]

Did yu ever indicate the probe tip? How much runout did you get?

 

Nope, but that was going to be my next step before I got sidetracked on a couple other projects

[Guest CNC Apps Guy 1]

That shoudl always be first... even before you try to run the calibration cycle since you are not certain it was ever calibrated in the first place.

[McLaren]

It seems like 2 different issues if you have a position AND size difference.

[Mr. Wizzard]

Position and size difference are related to the probe tip being off-center. It's calculating from the centerline of the spindle, but that's not where the probe tip is. You'll need to adjust the tip until it's centered, then calibrate it.