Jumping probe

[[Mi...]]

Hello at all,

we have a problem on our Prismo Navigator with Vast Gold.
Sometimes the probe is "jumping" up and down while trying to measure a self-centered point in a gearing. That process will only stop if we hold down the probe in the gearing or we turn down the machine speed to almost 0.
Does anyone have any suggestion?

Greetings, Michael

SHVF1470.GIF

[[Ow...]]

Interesting.
Is this a new program that's never been run before?
If it has been run successfully before, I'd try restarting the CMM and the CMM computer and doing a new manual alignment.
You might try going to the measurement plan editor , select probing and select distance before probing and set it to the same as your retract distance. This will allow the probe to search for the nominal probing point in a slower fashion and if it's in a different spot than it is supposed to be, it will take the point.

[[Mi...]]

Hello Owen,

it´s a new programm, but we have the same problem at different programms.
Distance before probing has no effect, we tried several times. It´s a litte strange that the problem is not at every run, sometimes we check 10 parts without any problem.
It has nothing to do with the alignment, we don´t have an planar rotation for the gearing but have to check the runout of the pitch to axis A-B.
I try to explain our strategie. To find the gap in the gearing, i check two self-centered points, one at Y=0 and another one at Y=1.
Then i create a Minimum Feature, select the two self-centered points. This Minimum Feature ist used to build a new alignment.
Now the probe falls in the gap at the first point. At the second point the probe hits the tip and is sliding slowly into the gap and starts jumping up and down.
We tried to change the Y-distance between the two points, higher and lower retract distance, higher and lower travel speed, higher and lower measuring force, but the problem still exists.

[[De...]]

I have seen the probe bounce like that before, I was able to stop it by raising the probing force and lowering the probe dynamic at calibration, that made it feed in slower and use more force when it did take the point so that didn't happen anymore.

An easier solution however might be to go into features setting editor and make that feature be manual for the self-centering point.

Now you manually probe a tooth space, and use that manually probed point in an alignment that is used to probe the rest of the teeth.

This gets around the need to 'find' the tooth space with self centering the way your currently going about it.

[[Ow...]]

I used to (10 years ago) do something like this before we had gear pro and I remember it being kind of cumbersome.
The type and how you evaluate the self center point was critical to repeatability and, like I said it's been a while but, I remember the type of point was mysteriously changing on occasion.
Maybe of no help but, I'm attaching a nice instruction acquired from Ryan Stuaffer, hope it helps.

Spline_Gear_Self_Center_Points_Min_Max.pdf

[[Mi...]]

We use exacty the same solution of your pdf, Owen 🙂
I will try the calibration method posted by Derek.
Manual probing of the tooth space ist not an option, we have to check up to 100parts.

Another way for pre-orientation would be to use ja very large probe-Ø. Measure a circle with 30° very slowly, no filter and no outlier elimination and then use this circle in a Minimum-Coordinate feature for planar rotation. Unfortunatly we can´t use big balls in this inspection 🤣

[[Re...]]

I would try to change the settings of self center probing to manual. (See attachment)

SCP.JPG

[[Mi...]]

Grüß dich Reiner,
Y-Axis clamping is already active.

I thought Derek´s solution was to use the joysticks for the self-centering point. Maybe i misunderstood his suggestion.
Ususally i use english only to order a beer in holiday 🤣

[[Re...]]

Hi Michael,
you understood Derek's solution the right way. 😉

Not only the clamping is important. Try the measuring force with "own selection" and give the force only in Z-direction.

[[Mi...]]

We tried Fz-100; 200; 400, Problem still exists 🙂

[[Mi...]]

Now we got a workin solution, we set up the mearuing force to Fz-1000mN. The probe fits in the tooth space very hard, but the jumping of the probe has immediately stopped.

[[Ow...]]

Just thinking out-loud and it may not matter but, do you have the clearance distance set to zero?
I don't know how long your extension on that probe is but, have you tried taking the point with a straight down probe?
I've seen a few times where probes built unbalanced (twice as long on one side as the other) and it causes issues like this but, that was with 500mm length extensions.

[[Mi...]]

The value of clearance distance has no effect, we tried different values.
Probe #1 (Z-) isn´t possible due to clamping situation.
Probe #3 and #5 (X+ and X-) extention is nearly the same with about 130mm.

Setting the measuring force higher seems to be a good method to avoid the jumping, working now for about 20 parts without any problem.

[[No...]]

Have you considered a hardware problem of the head? Active VAST heads have an internal damping mechanism, reducing vibrations during movement or probing (just like in a car). This mechanism is subject to wear, especially if there were many collisions over time. I rarely use self-centering, but maybe a worn damping can lead to the probe jumping.

[[Mi...]]

Hallo Norbert,

We have 4 Prismo, all with Vast Gold, service and maintenance said the machine is ok in March 18, no collision since then.
Probe jumping only appears on the machine with Navigator option, we made several tests, so i thinks it´s a result of Navigator option in combination with suboptimal probing situation.

[[An...]]

Ein mir durchaus bekanntes Problem am Vast Gold Kopf.
Ein Taster mit Kugeldurchmesser 3mm und Schaftlänge 55mm lässt sich
ganz normal kalibrieren. (Tensor)
Verwendest du aber einen Taster mit Kugeldurchmesser 4mm und einer
Schaftlänge von 100mm,dann entsteht dieses "Hüpfen" und zwar immer
wenn in negativer Z-Richtung angetastet werden soll.
Ich meine mich erinnern zu können,dass in den Katalogen für
ZEISS-CMM-Taster auch immer beschrieben wurde,für welchen Typ
Tastsystem dieser oder jener Taster verwendet werden darf.
Der Taster,der in deinem Video zu sehen ist,scheint mir keiner mit
Standard-Maßen zu sein.

[[Th...]]

Hi ihr,
hat sich zu diesem Thema noch etwas ergeben?
Wir haben im Moment das selbe Problem auf einer Fläche wenn wir diese in Richtung -Z antasten.

[[An...]]

See attached.

Contribution_25_02_2019_a.pdf

[[Th...]]

Ok das Leuchtet ein. Habe aber an etwas größere Tastersysteme gedacht (siehe Bild) da wird es warscheinlich ähnlich sein.
Gibt es da eventuell änderung in der Steuerung oder im Tastkopf da wir dieses Problem früher nicht hatten (ca. 2015).

Der Taster ist eine Hohlhalbkugel DK15 und die Verlängerungen sind aus ThermoFit.

1.jpg

[[Ri...]]

Ah.... I'm glad that I'm not the only one who has seen this. I was at a customer who had a VAST Gold, and when we were qualifying a long skinny probe it would do this when trying to probe TDC. I think our solution was turning down both the probing dynamics, and probing force.

[[Th...]]

We had this problem in every axis. Prismo Navigator with VAST Gold XT.
Open the Self Centering Probing, check "Probe Self Centering", check the clamps and define the force. Touch OK and make your points. Finally, to turn it safely off, you have first to uncheck the clamps, then the "Probe Self Centering" and after that close the window.
Now it should work correctly.
To be safe, try it in another fresh program in other axises to be sure it works, ehm, to be sure it does not work - you know what I mean. 🤣

The first time this behaviour showed up, we used Calypso 4. Since doing this, we met it never again.