Extracting a point from the plane

[[Ja...]]

Need to measure the distance between two planes, is it possible to create an average point from a plane. If there is no such option then is there any alternative.

[[Lu...]]

Hello Jakub,

there are several options, here are two examples: 

Option 1: if these planes are two opposite, parallel planes, then you can simply use a linear feature of size, via GD&T Quick Creation -> Dimension (Independence Principle)

Option 2: select the points of your plane, then Construct -> Point -> Fitting Point. This point is the "centre of gravity" of the surface. Do this for each plane, so you can then simply determine the distance between these two points.

I hope this helps to get you started.

Lukas

[[Ja...]]

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Thank you for your help

[[Br...]]

Hi Lukas, could you please expound upon the above suggestions? Attempting "Option 1" above, I get stuck at the process below, which seems to be sort of an incomplete step, with no dimension to possible select, the i inspect wheel just seems to be locked at this point.

In attempting "option 2" , I get no point, unless I pull up CAD, and "select all", then my point ends up in the middle of part, which is indicative of simply mid-point of the part, independent of the plane altogether. 

[[Lu...]]

Hi Brian,

to option 1:

You need to create a symmetric plane between plane 1 and plane 2, via Construct -> Plane -> Symmetric Plane. You can then check this plane for a linear size using the I-Inspect in the GD&T area.

to option 2:

You select a plane, with RMB you select Restore Point Selection, then you construct the fitting point. The measurement principle of the fitting point must be Referenced construction. Then you get an Actual Fitting Point on your Actual plane. Do the same for the other plane. You can then determine the distance in a specific coordinate direction. 

Option 3:

You take one of the two fitting points and create a perpendicular (Construct -> Distance -> Projected Point Distance) on the other plane. Then you have evaluated a perpendicular distance.

Best regards,

Lukas

[[Ja...]]

In the end measuring between two planes as suggested in option 2 and 3 is highly ambiguous and doesnt really make sense in my opinion.  Planes are infinite they cannot by definition be described by a point.  Doing a fitting point as suggested will create some kind of weighted point in space , but nowhere actually related to a contact on a surface .

Beyond the unambigous gd and t approach at a basic level this looks like you are trying to evaluate a caliper max distance between these faces?

You might need to be smart how you do that on the bottom face but i think it is would be plausible.

One method i like for understanding is to construct a plane on one side then do a deviation to geometry on the other side , allows you to see the deviation to the reference plane as colours .

I hope this helps in some way

[[Br...]]

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Thank you Lukas, very helpful!

[[Br...]]

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Thanks for the reply James, I do agree that a "fitted point" approach to a plane may not always be best case, this is still an option that can be useful in some applications. I did end up utilizing a caliper measurement on this project, worked out fine. This thread was helpful to my persistence toward figuring out steps that I know are possible, and just cant seem to find a workable resolution. A 'more tools in the toolbox" kind of thing. Appreciate the response and insight! 

[[Ja...]]

No problem brian,  i am very curious as to the application example where this would give valuble and reliable output.  If you are allowed to discuss im interested in your thought process.

In the end measuring between 2 planes looks easy when you do it on nominal models but there are many many ways to perform the evaluation in the real world.

[[Ti...]]

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  I'm not arguing with you on the fitted point from plane strategy. On large planes I'd be cautious for sure.

PCDMIS CMM software utilizes the centroid of a plane as the basis of a plane to plane measurement. The 1st plane you click will be the centroid of the hits and the 2nd plane you click would be a plane. I was tasked with doing some correlation to the CMM so I used this strategy for the correlation. If the plane is small enough, I don't mind this approach.

Edited February 25

[[Br...]]

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The most recent application provides an example of what I was attempting, which I ultimately ended up utilizing a GOM caliper function for. The thought was that making an attempt to simply go with a plane-plane would reflect much the same as a CMM would see this cap, which I thought would be a normalized point from each plane, and a height in the resulting perpendicular axis. It is great that Tim would have brought PCDMIS into the discussion, as that's exactly what I'm often tasked to match up with in any correlative studies. The CMM's plane-plane may not match up with the GOM mesh / caliper measurement, and having alternative methods of approach often goes a long way in helping to explain any variance between the two measurement systems.  ALWAYS appreciate all responses and insights, a ton to learn on this platform, this forum is a great place to gather these viewpoints, great resource, thanks for taking the time to reply! To add: I was always the kid that would take apart a lamp or radio when I was a kid, just to see how it worked (my poor mother), so I usually like to know the "why" I cannot get something to work 🙂 

Edited February 26

[[Ja...]]

No problem Brian . Thanks for the explanation and thanks Tim too.  Correlating to cmms is a fun game and my interest is many years of apps experience at gom!   by whatever means there is usually a way to replicate to understand differences .   So in this use case id be careful to not selecting hundreds of points on the plane by selecting on the mesh.

id use the same cmm target points , apply appropriate meas principles , most likely intersection with mesh,  then select these specific points to create a plane or create a weighted point from . 

[[Ti...]]

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I use the disc calipers from time to time. Long story short, I don't like using anything tied to the CAD model. I actually have to wash my hands after using two of these random white points b/c they are just a starting point, but I'm so use to making sure I program proper, I feel a little dirty using these suggested points in space that are tied to the CAD 0,0,0. 

 

We generate good quality meshes so I use my part features to direct all my measurement directions. Therefore, all my caliper checks I use a feature to orient the check, not the XYZ of the CAD. It may not make a difference with .020" tolerance, but for the tight tolerances you need to orient your measurement correctly. Just my 2 cents.

 

 

Edited February 27