Scanning OD with Dent with Passive Head

[[Ni...]]

Good Morning,

We have a 26 inch round part that has a dent on the OD that is probably an inch deep. The contour of the dent should allow the probe to go in and out of the dent without getting stuck and alarming out.
The issue is that it will scan the OD but when it gets to that portion of the dent, it doesn't go inside the dent and out. It just scans above the empty space and keeps going all around.
I believe this is because it is a passive head sensor instead of an active one.

My understanding is the active one keeps pushing inward while scanning while the passive just scans where it should be.

So is there any way to scan this OD and the dent too? or should I just do points on that area and scan the rest of the OD and then combine with recall feature points into a blank circle?


I need to report what the diameter is with the lowest point which i was going to use the 2 point diameter characteristic. And i need to report how deep that dent is as well. Wanted to do all of that with just a simple circle scan strategy but so far it seems like i have to do more.
There is no CAD model so I can't do curve without spending a while on the machine trying to figure it out.

Thank You,
Nixon Uruchima

[[DW...]]

I am assuming for this cylindrical part with a dent that it has a face large enough to make a plane.

There's a few ways to go about this but this is what I came up with.

Create Plane1 on the +Z plane.

Create Circle1 (26 inch OD).

Create Circle2 (Dent).

Create Projection1 (Project Circle1 to Plane1).

Create Projection2 (Project Circle2 to Plane1). Both circles now exist in the same plane.

Create 3d Line1 (Recall Circle1 and Circle2).

Create Intersection1 (3d Line1 and Circle2).

Base alignment should be Plane1 for Spatial in +Z, 3d Line1 for planar rotation in +Y, Circle1 for X, Circle1 for Y, and Plane1 for Z.

Create CaliperDistance1 (Go to Size>Distance>CaliperDistance). The distance is between Circle1 (Maximum) and Intersection1 (Center) in Y.

Might have to tweak this to your specific situation.

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[[Da...]]

Use Circle2 directly as planar rotation.

[[DW...]]

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Absolutely do not do this.

[[Da...]]

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In your example to get the distance, I like the approach with projecting before intersecting.

I understand Gafner as to use circle directly to lock rotation in alignments. (IIRC this wasn't possible until Calypso 5.6)

[[Je...]]

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Hey Nixon. This sounds like a fun task. It's definitely atypical, and perhaps that's why it interests me.


One possible strategy of many: Do you have curve? If so, even with a passive sensor, you can touch-point probe an area in the dent to create an approximated feature in the software, which would be several 3D curves. Essentially, you would map the dented area.

Once this step is done, you now have approximated nominals for the dent. Then, you could leverage the "actual to nominal" option in Calypso, which might be close enough to guide the probe and avoid "air scanning."

If you don't have curve, you could still attempt a similar strategy by using space points, but curve is optimal for the type of situation you explained.

In any case, the process is the same: (1) collect the points into a feature (2) evaluate the diameter character per customer requirements. It's important to ensure that the stylus radius correction is being applied appropriately, which is tougher to do with a passive sensor but not impossible.


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[[Ri...]]

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Calypso is already doing the projections for you, there shouldn't be a need to do these manually, same with the line. In other software, this is not the case, but unless I'm mistaken (which is always possible) Calypso will natively handle this for you.

[[DW...]]

I am fairly positive you are correct that Calypso will handle this without the projections. It is overkill probably but I am used to being asked how I achieved a result. I program with the mindset that I will end up having to show a customer step by step how the measurement was performed. They might be a little skeptical if I say the software handles the projections for me 🤣

[[Ni...]]

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This was my first idea, but I am so used to doing curve in offline station with a cad model that I got stuck when trying to do it without a cad model. I wasn't able to create a path without the model so i tried to find a different way.

[[Ke...]]

To create the curve, you could potentially do an unknown contour measurement. There is a pretty good guide to that function in this post viewtopic.php?p=54761