Polyline following reference curve?

[[No...]]

Hi,

I have zero experience with the curve option (training scheduled for January), so I thought I just ask:
Is it somehow possible to make a polyline follow a measured reference curve, like this:
I need to scan a plane with a polyline on this narrow rib, but it deviates from the CAD model at least as much as it is wide (plastic part) and that deviation may also change in the future. So what I would need is a polyline that follows a measured reference curve (blue). I think the picture is self-explanatory. Any way to achieve this?

[[Ri...]]

Could you create a Section with a radius slightly larger than the reference curve, then use the section for the curve?

[[Cl...]]

Can't check this in simulation right now to see if it works, but I think that if you create a best-fit alignment from the Reference
curve and pull that alignment into the Polyline. As the reference curve (surface) changes the Polyline should follow.

[[Ma...]]

On newer Calypso you can have this option, but i think this driving curve should be symmetry curve from both sides.
It depends on your Calypso version

If you want real time polyline, then i affraid you can do it with formulas and fixed points.

Let's say you will measure 10 points ( hard way ).

• Measure curve for 10 points
• Create 10 points
• Recall each point
• Make another 10 points
• Modify it's nominals with formula of matching point nominal and vector + needed distance and let it measure
• Recall measured points into new plane

[[No...]]

Maybe I should add that the rib shown above goes around the whole part and makes some turns. The deviation form the CAD is not the same everywhere.

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Problem is that I have to go round the whole part, and different sections have different deviations. So I would need a number of best fits, one for each section. Not impossible, but time-consuming.

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Sounds promising. How would it be done?
Right now I'm still on 7.6, but I can have 7.8 installed if needed.

[[Cl...]]

If you do have to go around the entire part. I wonder if you could scan the curve all the way around the part. Recall the curve points into a single point (to get kind of a center). Create a secondary alignment from that point (XYZ). Pull that secondary alignment into the polyline and as the scanned surface changes the polyline should change with it?

[[Ma...]]

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It should be in that version - i think when you open curve feature window, then like projection on circles there should be option for guiding curve. It should be documented in manual. I am at home until monday.

Edit: In Calypso 2023 manual - 01 curve on page 1-44 and 1-45 is mentioned reference feature and parallel curve.
On page 1-17 is entioned symmetry curve.

[[Je...]]

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Hey Norbert.

There are several ways to use a feature such as a curve as a navigational aid for another feature's strategy.

One method would be to create an alignment from the curve feature and then set the plane feature to this new alignment. This will navigate based on the calculated curve feature but will not assist point-to-point. It's worth a shot unless you need tight point-to-point navigation and expect significant form changes.

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Another option would be to use the "measurement reference" option. For this approach, you will need to collect the points for your plane inside a 3D curve and then recall those points to your plane for evaluation. The tricky part is that the curve you use as your measurement reference has to have exactly the same number of points as the curve you're using to collect the points for your plane:

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And yet another approach, albeit a tedious one, would be to use formulas for each point inside the polyline of your plane and link those formulas to single points on the reference curve:


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You can also use text files and other methods for defining your polyline. There's a lot of ways to do what you're asking.

The "edge curve" function inside the measurement reference window I discussed is also a phenomenal tool, but that is solely for guiding a curve based on a nearby planar feature.

Good luck, and keep us posted on what you figure out.


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[[Da...]]

There’s a function built in to Calypso to take any curve and modify it, so in your case:
[list=1]

Expand the curve parallelly

Translate the curve to a new height

Rotate the curve's vectors 90°

I know that this will work, since I’ve done this before, but it’s been about nine years ago, and I was fiddling around with Calypso and couldn’t believe this worked on the first go. Unfortunately, I don’t have the steps handy. Maybe it’s in the Curve Manual.

[[Ma...]]

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I believe he needs to have this automated, because of small area and imperfections on parts

[[No...]]

A guidance curve sounds like exactly the thing I need. I'll see if I can fumble something together, but I guess without any curve training this'll be hard. So it may take a while (next year) until I can give feedback on how it actually worked out.
Anyway, thanks for all the suggestions!

By the way, this is what the whole plane looks like. Red(dish) is the CAD, green is the actual part. The rib is 1.5 mm wide. The deviation doesn't look that bad actually, but this is only because i did a best-fit of the whole part in GOM. The actual alignment on the CMM will be different and the form error may change in the future (e.g. when somebody decides the molding process needs to be "optimized" 😃), then the measurement needs to adapt automatically.

[[Ma...]]

I don't have that option yet, but in theoretical way it would be like this.
[list=1]

Scan side curve ( should be enough one, just one side )

Set that side curve as reference curve for problematic curve

[[An...]]

_____

[[Da...]]

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There are some info in C:\Program Files (x86)\Zeiss\CALYPSO 7.6\userinfo\manuals\en-US\Calypso_01_curve.pdf

Check for term edge curve.

[[Je...]]

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Hey Norbert. I sent you a pm regarding this.

Also, after viewing your screenshot of the entire feature, I would definitely recommend breaking up the curve into sections of smaller curves for measurement. You can always recall all of the segments into a singular curve feature afterwards, but it will be more manageable to navigate based on sections, perhaps 8 or more. You've probably thought of this already though.

[[Cl...]]

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https://www.bing.com/videos/riverview/r ... ORM=VRDGAR

[[No...]]

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Great video!
I love the speaker's accent. You can clearly hear his swabian origin (mine too) 🤣

[[No...]]

Hmmmm....

I tried to define the curve according to the video, but I run into several issues.
First, I defined an open curve (by clicking curve segments in the model), but somehow Calypso seems to try and "close" the curve by generating an "air" curve from the (randomly placed) starting point (green) to one end of the curve. How can I avoid that?

Second, the vectors of the guidance curve sometimes got flipped 180° somewhere in the middle of the curve where a new segment started. Unfortunately I didn't make a screenshot of the situation. How can I fix that?

Third, the edge I'm measuring has a radius, which makes the points of the guidance curve end up inside the material. Is there an offset option somewhere to handle situations like this?

And fourth, the starting point (?) of the curve (green) seems to get randomly placed. Because I started clicking the segments from left to right in the picture. I want the measurement to start on the left too..

[[Ma...]]

When you open curve feature, click on CAD view and select "Show all nominal points" - this way you will see if any of points have inverted vector - this can be corrected on curve feature by clicking "arrow" button to show list of points. Right clicking bad point and select invert vector.

You can arrange nominals to have continuous line and direction by selecting nominal points and clicking "cut" and then "paste".
Beware there is "paste point" which will allow you to put one point with editable fields.

[[No...]]

In the meantime I was able to resolve my issues with curve definitions and programmed a first draft of my measurement. Calypso sometimes seems to get the order of clicked edges wrong, resulting in erroneous curves like the above.

 

But now now there's a new issue. I defined all of the curves as 3D curves from the edge around the lower end of the radius (in the pics above it's still the upper end), shifted the nominals in +Z by the radius height, rotated the vectors to point to +Z and then defined the guidance curve parameters d1 and d2 so that the actual curve is measured in the middle of the rib. Since I'm not interested in the actual curve results, only in the actual points to recall them to a plane, I didn't care much about the rest of the many curve parameters. I just started the measurement and it seemed to work well for most of the segments. But one of them just won't make it to the end. The stylus slips off the top of the rib at some point as if it would ignore the guidance curve. But its parameters are the same as for the other curves.

Any suggestions as to what might be wrong here?

Edited November 27

[[Ma...]]

Check curve nominals if they are in right order.

Open curve, right click on CAD and select to show all nominal points.
Then in curve window click on "arrow" symbol for unpack nominals, select first from list and hold down arrow key and watch on CAD window if all points are going as they should ( on some cases you can have some thing like this: starting on left, going right, then in middle the next nominal is on right and goind left to middle )
Calypso is making spline from nominals and probe then follows that spline. If you have curvy material and nominals too far from each other, then it can throw collision message.
Or it will do turn around to catch nominals going backwards.

[[No...]]

All curve points are in the correct order. But I am beginning to suspect there may be some kind of software bug in Calypso, because the behavior of the CMM while scanning is odd. I spent the whole day trying to optimize the scanning path on top of the rib, but to no avail.

In certain segements, every now and then after scanning the guidance curve, the stylus seems to completely ignore the d1 offset (half the width of the rib) and therefore misses the rib completely. Instead it touches a surface below the rib and somehow makes it almost to the end of the curve, but then throws a collision. If I immediately repeat the measurement without any changes, it suddenly works again. This behavior is quite unpredictable.

Something is terribly wrong here. 🤯

Edited November 27

[[Ma...]]

Only thing i have in mind would be usage of filter on curve - maybe due to open curve it can do something.

Other than that i don't know how to help more.

[[No...]]

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I think you hit the nail on the head. The problem was indeed the filter. At first I had used no filtering at all. Later I turned it on to see if it had any effect, but left it on the default Gauss filter. My actual problem was that I didn't have enough knowledge about how curves and their results are visualized. The small green dots representing the actual deviations should have told me the whole story, but I ignored them, not knowing what they mean. Now, after switching to spline filtering , the program seems to run stable.

Thanks for all the suggestions!

P.S.: Let me add that defining the curves from the CAD model was one of the weirdest experiences I had with Calypso in years. The amount of sh*tty data generated by the "Creating Features" function was hard to believe. For one of the curves the curve points generated were running back and forth along the selected edges several times at low density instead of once from beginning to end. I have no idea how and why that happened, but it was only one of many odd quirks.

Edited November 28

[[Ma...]]

Use Gauss only on closed curves - on opened loops you should use Spline ( meas. points filter ) - morphological filter is added on newer versions on Calypso and i don't know much about them.