4 hits inside a circle before a scan

[[Me...]]

In some programs that existed before I got here, sometimes hole features will be measured with 4 hits inside the circle before it is then scanned. What controls this and why would you use it?

[[SH...]]

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Get into the strategy window,check whether it has four point in addition to the scanning strategy. If it is additional four point Delete that four point. I hope that you don't have any condition to the circle.

[[Ma...]]

Is it possible that someone created the circle using 4 points and then added a scan path to the strategy forgetting to remove the 4 points? Other than that, I can't see a reason why it makes sense.

[[SH...]]

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Yes possible I made that mistake while l learning scanning...

[[De...]]

Either as stated it was not done intentionally, or the other likely reason for this that I can think of is to perform a rough alignment to the hole using 4 points, then perform a scan based on the actual location of the hole.

If the tolerance for the position of the actual feature allows the feature to be significantly out of position then this method can help insure that the data collected from the scan will be as accurate as possible.

In my experience this is not necessary all that often.

In order to do this, the circle / cylinder is likely programmed two separate times.

The first instance would use a 4 point strategy to "find" the hole, and would be used to create a secondary alignment which could be assigned to the second version of the feature.

The second version of the feature would then use the alignment created using the first (four point) feature in order to insure that the scan was performed as close to the actual location as possible.

[[Me...]]

The strategy only has Circle Path (1 Section). There are no points in the strategy. As I said, I've looked all through the strategy and there is nothing there out of the ordinary that I can find.

This feature is used in the base alignment and if I run it manually, it makes me pick up the circle twice.If I run it in CNC mode it still picks up the circle first with 4 points and then scans it.

This is a single feature, not two separate features.

[[Th...]]

Is this what the "own geometry" measurement reference option is used for? Under the projection settings for the feature, and on the meas. ref. tab. It's not a function I use, but if it's selected, I think it does a 4-point rough feature check to adjust its location before running the actual strategy.

[[Ow...]]

I haven't used it in a very long time so, not sure on the specifics but,
In the feature, click on "none" under projection. On the 1st working plane tab you can choose the three point method to find the hole at the right location, I think you can set it to take as many points as you want.
Under the 2nd tab "measurement reference", you can choose another previously made feature for locating the hole.

[[De...]]

Another possibility would be if the nominal values for the feature are using a formula that references another feature like getActual("Some Other Feature Name").x this would force Calypso to run that other feature prior to running the feature in question.

If this was the case the nominal values in question would show up as a yellow background in the feature window.

You would also be able to see this if you right click the feature while it is selected and choose 'References for selected feature'.

[[Me...]]

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Projection is set to none, but the meas ref is set to "own geometry". I don't have this part set up any longer, but as soon as I do I'll try setting "own geometry" to none.

Thank you

[[Me...]]

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There are no formulas associated with this feature. No Yellow.

This is why it's such a head scratcher.

[[SH...]]

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Do you have start alignment?? what type alignment you are using, ordinary base alignment or something else.

[[Me...]]

Standard feature based base alignment.

[[Me...]]

This is exactly what OWN GEOMETRY does. It will locate a feature that wanders and then set the measurement to that location then measure there. When I switched to NONE here it stopped the 4 extra hits.

Thank you for all of the assistance.

[[Cl...]]

Not related, but I worked on the F-4(G) at Seymour Johnson AFB. Easy job for an environmental guy.

[[No...]]

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"Own Geometry" is kind of a last resort if you need a reference measurement but have absolutely no ref. geometry other than the feature itself available to do it. Of course it only works reliably if the probe is at least able to dive safely into the feature at the nominal position. If even that can not be guaranteed, you're doomed. But if it's possible, own geometry is a nice way to get a clean scan at a reasonable speed. Sometimes very useful for certain plastic parts.

[[Me...]]

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Cs, Ds, Es, and Recce Cs at Eglin AFB. We were always busy with the old war horse. Radar, Inertial Nav, and Weapons Delivery and some of the best times of my life to be honest.