Distance(depth) between 2 parallel planes with same direction

[[Ge...]]

Hello colleagues, I want to check distance between 2 planes(the depth between them), but when I make them, GOM said that the planes must be opposite each other. When the planes are opposite the function (independency principle) works, but when they are with same direction(example +Z) not. I want to know if there is a way to check those distances the minimum and maximum between two planes? See the pictures.

Thank you in advance colleagues!

[[Ch...]]

Hello,

 

an evaluate size evaluation is only possible if the inspected distance is a linear size according to ISO 14405-1. This is not the case if the used planes do not lie opposite to each other. To make things worse it is complete unclear what the distance you like to inspect in such a case. Therefore we can not provide a out of the box solution for such a case. Instead you have to define your own measuring strategy.

More explanation can be found in our software direct help (The document is named "General Information on Size and Distance Dimensions") starting with GOM software 2020. This document also explained the GD&T based approach to solve this problem; as well as the classic two point distance approach. Of course, if these solutions do not fulfill you needs you can define your own strategy (e.g. using deviation to primitive).

Hope this helps

Christoph Schult

 

[[Ge...]]

Please sign in to view this quote.

Hello Mr. Schult,

thank you very much for the reply, but unfortunately I could not find a solution in the manual guide, I have searched in it before write at the forum. I will be more specific - I have two parallel planes, which directions are in (+Z) see picture 1 above. The distance in drawing between them is 1,20mm. I want to check the minimal two point distance and the maximal two point distance between these parallel planes(picture 2 and picture 3 above), not middle surface points.

I think this is very standard situation to check the depth between 2 parallel planes with same direction(see  Example.png), and the software could calculate 3 values - LP min(minimal two point size), LP max(maximal two point size) and middle size between two planes, but I do not know how?

 

[[Ch...]]

Hello,

as I mentioned before this distance check is not unambiguous. Obviously you cannot project all points from the lower mesh area on the higher mesh area. Therefore you have to define what you want instead. Some possible approaches that are possible:

a) Project all points from the upper area to a fitting plane estimated from the lower area (then the question is what fitting algorithm you will using to estimate the primitive plane) using the plane normal as projection direction

b) Project all points from the lower area to fitting plane estimated from the upper area using the plane normal as projection direction (the question of the fitting algorithm is the same as in (a)

c) Estimate two parallel planes with variable distance from the current selection (Question again: What is the correct fitting approach). Project each point from both area on the opposite plane.

d) ...

Some of this approaches are possible in the software using fitting elements and the function "deviation to geometry". Afterwards you could evaluate this deviation plot to find the minimum or maximum point. But nevertheless the ISO does not recommend such approach (see ISO 14405-2), instead you should use a clear inspection task using GD&T language, i.e. surface profiles or positioning tolerancing.

 

In case of further question please contact your local GOM partner to get further support.

 

Hope this helps

Christoph Schult

[[Ch...]]

Here is a FAQ article showing different options to create distances between planes and its unambiguousity: https://connect.gom.com/x/jJ7VAg

[[Jo...]]

During the basic starter tutorial on GOM website, they share the 'independency principle' method to get a min/max distance between two planes.

As we, know planes can be weird to get proper distances from, but in their tutorial it is quite simple.

It also works for me 80% of the time, but for some reason 20% of the time I get ????? or no scalar data or the planes are parallel errors.

Anyone else notice this?  I think it happens when a surface area isn't very large to make a nice plane. I'd like to share the file but cannot in this case.

[[Ch...]]

Please check if the requirements at mentioned in the techquide are fullfilled

Please sign in to view this quote.

see here: https://techguide.gom.com/en/gom-software-2021/article/general_project_guide_length_information.html

Of course the error message can also appears for very small planes but in general the problem lies in not fullfilled requirements as mentioned in the techguide article.

[[Da...]]

I have very often problems with this restrictions. This logic is hardcore for me - many times constructed features cannot be used for characteristic evaluation becouse not enouf points, some scalar data and other weird problems witch on CMM does not exist. 

20% of job sometimes takes 80% of time because of finding solution, or using another machine for work. 

Often have to to do what Georgi wrote: check minimum and maximum distance between two planes. And its not any super logic - its very simple. 

I can measure this distances on old CMM - so why i cannot do it on super 3D SCAN  ?? 🤪 Its newer so it should not be worst in some cases but much better! 

You let us do alignments not based on ISO / ASME but based on " Geometry"  and its not fantastic - its basic option, do same here. 

You can do " plausibility check" according do ISO, or ASME like checks in point measurement by disc. Its simple. Just write some more code to GOM Suite. 

But you making us to must use old CMM to measure something, what was measured for 10 years in this company, but new software in GOM simply cannot do it. 

So what i have to tell my boss, engineers who produced it for many years ? i have to measure this, and nobody cares about ISO witch they not used maybe for all their live,  and probably will never know it. 

If you listen to me you will many make people happy, many companies save money, and more. 

Many many things on GOM are too restrictive. ISO and ASME are fine but this norms are not oracles, wee need freedom in constructions, and tolerancing...

Please give us more freedom in software. 

Edited September 6, 2022

[[Ad...]]

I agree that more options should be added to the software for easily checking the distance between unopposed parallel planes.

[[Be...]]

Hi,

we recorded your wish to ease up the creation of different distance types for planes (as we already described it in our tech article). Please keep in mind: We won't violate existing norms with any (hidden) flags. GD&T has exactly these "laws" that everybody can rely what was measured and how the computed/measured value can be interpreted.

I can't tell you if or when we will realize such a convenience function for distances between planes.

Regards,

Bernd

[[Ju...]]

Hallo Bernd,

gibt es zu diesem Thema schon Neuigkeiten? Mir würden diese Funktionen ebenfalls sehr weiterhelfen, da ich die gleichen Probleme habe wie oben beschrieben.

[[Be...]]

Hallo,

es gibt bisher keine implementierten Convenience-Methoden (aber als Wunsch wie beschrieben aufgenommen), aber weiterhin kannst du dir das Abstandsmaß konstruieren wie du es benötigst (siehe den Link zum Tech-Artikel).

MfG,

Bernd

[[Ti...]]

Please sign in to view this username.

Many times I'll use a disc caliper or edge caliper for plane to plane. Using calipers can be tricky with tight tolerances because your orientation is very important.

A trick I used sometimes, when I'm confident that both surfaces are cut with precision or the planes are small is to make one of the planes a single centroid point and then use the projected point distance from the point to the plane. To do this you highlight one of the Blue nominal planes > right click > restore point selection, then go to Construct > Point > Fitting points. This will create a centroid point of all the surface data and it is parametric. Then I simply do a projected point distance from this fitting point to the other plane. I wouldn't do this on larger surfaces or surfaces that could have a decent amount of form variation.

Edited July 13, 2023

[[Ju...]]

Please sign in to view this username.

Mit dem Messschieber habe ich sowol gute als auch schlechte Erfahrungen gemacht. Deshalb wollte ich diesen nicht so oft benutzen aber manchmal gibt es keine ander Möglichkeit. Am liebsten benutze ich mitlerweile Einzelpunkte woraus ich eine Elementgruppe erstelle oder halt die Symmetrieebene. Dies funktioniert aber auch nicht immer für alle Abstandsmaße weshalb ich bei großen Flächen den Messschieber oder bei kleinen Flächen den 2-Punkt-Abstand benutze. 

In Calypso war dies nicht so umständlich wie in Gom. Ich hoffe, dass es irgendwann ein neue Funktion geben wird, damit man den Abstand von Flächen mit min/max einfacher auswerten kann.

[[An...]]

Please sign in to view this quote.

Hallo Julian, ich komme da auch nicht weiter... selbst mein junger Kollege hat darauf keine Antwort. :-(