Renishaw Probe Calibration Problem

colton_m · Jun 12, 2018

Hello,

I have a 2015 VF3 (not the NGC control) with the Renishaw WIPS system.

I have run the probe calibration cycles and the disk on my tool probe is dialed in flat within .0002"

After probing a machined surface I have observed that the machine always cuts .0018" deeper than expected. Does anyone know what parameter I need to change to make up for this error? I believe the Spindle probe Z calibration off the OTS is causing the issue.

Thanks!

DMF_TomB · Jun 12, 2018

colton_m said:
Hello,

I have a 2015 VF3 (not the NGC control) with the Renishaw WIPS system.

I have run the probe calibration cycles and the disk on my tool probe is dialed in flat within .0002"

After probing a machined surface I have observed that the machine always cuts .0018" deeper than expected. Does anyone know what parameter I need to change to make up for this error? I believe the Spindle probe Z calibration off the OTS is causing the issue.

Thanks!

.
does probe use tool length comp ?? i have adjusted probe tool calibration before by adjusting tool comp. some machines change height as they warm up and cool. difficult to get stable <.0005"

Larry Dickman · Jun 12, 2018

what are you calibrating the probe with?

colton_m · Jun 12, 2018

Larry Dickman said:
what are you calibrating the probe with?

I have a 2" Mitutoyo setting ring and a 3" tool probe calibrator from Maritool

Setting Ring Series 177-Accessories for Inside Micrometers,Holtest and Dial Bore Gages
CAT4 Tool Probe Calibrator - Made in USA MariTool

I believe my problem occurs when the Spindle probe touches off on the tool probe during the calibration cycle. I'm just not sure where any of the results from this calibration are recorded so I can adjust them to remove the .0018" error I am observing.

Larry Dickman · Jun 12, 2018

If you set the TLO of the calibrator, does it come out exactly 3.0000?

Booze Daily · Jun 12, 2018

How big is the tool that’s cutting too deep? Endmills ain’t flat on the bottom.
If it’s bigger than the tool presenter disc that could explain it.
Otherwise, I think I just might adjust the probe length. It should be a tool length offset.

LockNut · Jun 12, 2018

You cannot calibrate the spindle probe off of the tool setter, if I am reading this correctly. You will nor calibrate to the trigger point but to the dead length of the probe. Set a work offset to a good surface with a known length tool, like a tool setter calibration standard. Call up that work offset and calibrate the spindle probe off the same surface you set the work offset to.

Paul

Larry Dickman · Jun 12, 2018

LockNut said:
You cannot calibrate the spindle probe off of the tool setter, if I am reading this correctly. You will nor calibrate to the trigger point but to the dead length of the probe. Set a work offset to a good surface with a known length tool, like a tool setter calibration standard. Call up that work offset and calibrate the spindle probe off the same surface you set the work offset to.

Paul

Sorry, but this is complete nonsense.

LockNut · Jun 12, 2018

Larry Dickman said:
Sorry, but this is complete nonsense.

That's it? Just complete nonsense? Would you like to explain? I have had this happen numerous times. There is always a .001-.002 deflection in the Z axis when calibrating. I proved this by measuring my probes in an offline tool setter before calibrating in the machine. Always a difference. Look on the side of a Renishaw probe. There is a trigger point adjustment screw.

Larry Dickman · Jun 12, 2018

LockNut said:
That's it? Just complete nonsense? Would you like to explain? I have had this happen numerous times. There is always a .001-.002 deflection in the Z axis when calibrating. I proved this by measuring my probes in an offline tool setter before calibrating in the machine. Always a difference. Look on the side of a Renishaw probe. There is a trigger point adjustment screw.

I don't know. Maybe the probe you're using is busted.

LockNut · Jun 12, 2018

Larry Dickman said:
I don't know. Maybe the probe you're using is busted.

Sorry, but this is complete nonsense.

pmack · Jun 12, 2018

You should be able to change the probe length offset in your tool table to correct it.

guypb · Jun 13, 2018

LockNut said:
That's it? Just complete nonsense? Would you like to explain? I have had this happen numerous times. There is always a .001-.002 deflection in the Z axis when calibrating. I proved this by measuring my probes in an offline tool setter before calibrating in the machine. Always a difference. Look on the side of a Renishaw probe. There is a trigger point adjustment screw.

I have to agree with this - the trigger point for a Spindle Probe is always different to the actual physical length of the probe dependent on the trigger force of the probe, the speed at which the probe is calibrated, the stylus choice and the skip signal of the machine - I believe the WIPS cycles do use the tool setter (TS27R) to calibrate the length of the Spindle Probe (OMP40) however as you correctly point out, dependent on the trigger force of the Spindle Probe compared to the trigger force of the tool probe there may be some difference between triggering off the Tool Probe when compared to triggering off a work piece or machined surface. The best way to calibrate the spindle probe length offset is off a gauged surface or from a machined surface created by a master tool. Failing that you could adjust the trigger force but unless you have reason to do so then leave it alone. Lastly if the deviation is repeatable across all tools then adjust in the Tool Length Offset for the Spindle Probe itself.

thesidetalker · Jun 13, 2018

LockNut said:
That's it? Just complete nonsense? Would you like to explain? I have had this happen numerous times. There is always a .001-.002 deflection in the Z axis when calibrating. I proved this by measuring my probes in an offline tool setter before calibrating in the machine. Always a difference. Look on the side of a Renishaw probe. There is a trigger point adjustment screw.

FYI on the NGC (at least on UMC) the spindle probe calibration cycle uses the tool setter. No more touching off on your ring gage. However, maybe the newer program is setup to accomodate some error. That I don't know.

On the other hand, it isn't a big deal to just adjust your probe TLO to eliminate any error.

Larry Dickman · Jun 13, 2018

thesidetalker said:
FYI on the NGC (at least on UMC) the spindle probe calibration cycle uses the tool setter. No more touching off on your ring gage. However, maybe the newer program is setup to accomodate some error. That I don't know.

On the other hand, it isn't a big deal to just adjust your probe TLO to eliminate any error.

That's true. Every machine I've ever used a probe on, it's been a non-issue. So, I ask myself, Renishaw is the world leader in probes and they've sold hundreds of thousands of them all over the world. But they say to themselves, lets let all these probes be a few thousandths off, because we're either too stupid or short sighted to solve a simple problem. I doubt it. But then we have our crew of armchair engineers who mindlessly develop a half baked hypothesis to explain away a non existent problem. Think is through, guys, if you can.

DMF_TomB · Jun 13, 2018

there is adjustment by adjust tool length comp of probe and also there is grid shift adjustment. grid shift is how you fine adjust from the zero return position to a known spot say table top.
.
basically i run a program and if its off more than .001 i adjust grid shift parameters, restart machine and remeasure. if i probe a surface i want to only mill a .001 off and the mill tool length comp not in sync to probe length comp i can also adjust probe length comp so it is in sync with rest of tools.
.
grid shift parameter adjustment requires turning PWE or parameter write enable on on many machines. you need to read your maintenance manuals. i once adjusted grid shift value it was suppose to be -.0127 and i put in .0127 and machine would not tool change cause it was too far off. need to be careful and write the before and after changes. i use a standard worksheet made for my machines to help.
.
tool setter might have parameter adjustment too. i saw once a tool unlocked accidentally and fall on a tool setter. obviously that would make the calibration go off. usually that stuff not in operator manuals but in the maintenance manuals

LockNut · Jun 13, 2018

Larry Dickman said:
That's true. Every machine I've ever used a probe on, it's been a non-issue. So, I ask myself, Renishaw is the world leader in probes and they've sold hundreds of thousands of them all over the world. But they say to themselves, lets let all these probes be a few thousandths off, because we're either too stupid or short sighted to solve a simple problem. I doubt it. But then we have our crew of armchair engineers who mindlessly develop a half baked hypothesis to explain away a non existent problem. Think is through, guys, if you can.

Larry, Larry, Larry, who's the armchair engineer? I work for a MTB and have developed my method with Renishaw standing by my side. They know about this and it is not a flaw. This happens with a Renishaw, Blum, Marposs and Heidenhain. You can't have the inside end of the probe constantly sitting on the trigger. It is a machanical switch after all. False triggers will be the least of your worries. Sure, you can just "adjust" the tool length offset to fix it but why not just do it right to begin with? That is a half-baked method. and tell that to guys who measure a 5 axis machines' kinematics parameters and you want them measured to a half thou. Nobody said you can't touch the probe off of the tool setter but why would you if you want the utmost accuracy? To each his own I guess.

Paul

DMF_TomB · Jun 13, 2018

LockNut said:
Larry, Larry, Larry, who's the armchair engineer? I work for a MTB and have developed my method with Renishaw standing by my side. They know about this and it is not a flaw. This happens with a Renishaw, Blum, Marposs and Heidenhain. You can't have the inside end of the probe constantly sitting on the trigger. It is a machanical switch after all. False triggers will be the least of your worries. Sure, you can just "adjust" the tool length offset to fix it but why not just do it right to begin with? That is a half-baked method. and tell that to guys who measure a 5 axis machines' kinematics parameters and you want them measured to a half thou. Nobody said you can't touch the probe off of the tool setter but why would you if you want the utmost accuracy? To each his own I guess.

Paul

.
i have seen probes repeat to .0002" and have seen probes that were sticking or some sort of internal problem that were not repeating to .001"
.
i just put in maintenance request and they change the probe and they send it out for repair. some coolants can cause rubber orings to swell bigger and cause probe to stick
.
not for nothing but most machines change .001" from cold to warmed up. that alone can cause repeatability problems. i run grid shift 3 or 4 times in a row. it always changes the most from the 1st to the 2nd test as machine warms up
.
dropping a tool on a tool setter will almost always knock it out of calibration. it happens and often person who did it might not say anything. obviously got to be recalibrated

Chris59 · Jun 13, 2018

DMF_TomB said:
.
dropping a tool on a tool setter will almost always knock it out of calibration. it happens and often person who did it might not say anything. obviously got to be recalibrated

The tool setter or the person? Fun times.

colton_m · Jun 13, 2018

guypb said:
I have to agree with this - the trigger point for a Spindle Probe is always different to the actual physical length of the probe dependent on the trigger force of the probe, the speed at which the probe is calibrated, the stylus choice and the skip signal of the machine - I believe the WIPS cycles do use the tool setter (TS27R) to calibrate the length of the Spindle Probe (OMP40) however as you correctly point out, dependent on the trigger force of the Spindle Probe compared to the trigger force of the tool probe there may be some difference between triggering off the Tool Probe when compared to triggering off a work piece or machined surface. The best way to calibrate the spindle probe length offset is off a gauged surface or from a machined surface created by a master tool. Failing that you could adjust the trigger force but unless you have reason to do so then leave it alone. Lastly if the deviation is repeatable across all tools then adjust in the Tool Length Offset for the Spindle Probe itself.

The deviation was the same across all tools like you mention.

I adjusted the probes TLO by the same amount as my deviation and that solved my issue.

Just have to remember to do this every time after running a probe Z calibration, for whatever reason.

Thanks for the replies.

Renishaw Probe Calibration Problem

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