The following referencing objects might break, Why?

[baiyuxiong]

Dear all, I am realy confused about objects reference. Please help.

The following part, two pad over a square pad , as follow:


Pad002 is created over bottom pad, has nothing to do with Pad001. But if i right click over pad001 and delete it . The following message alerted:


How to explain this ? thanks.

This is the info of freecad I am using:

Code: Select all

OS: macOS 10.16
Word size of FreeCAD: 64-bit
Version: 0.20.29177 (Git)
Build type: Release
Branch: (HEAD detached at 0.20)
Hash: 68e337670e227889217652ddac593c93b5e8dc94
Python 3.9.13, Qt 5.12.9, Coin 4.0.0, Vtk 9.1.0, OCC 7.5.3
Locale: C/Default (C)
Installed mods: 
  * Render 2022.2.0
  * pcb
  * A2plus 0.4.56a
  * POV-Ray-Rendering

[edwilliams16]

A file would have helped. Is Sketch002 attached to the top face? If so, if you remove Pad001, the face numbering might change and break the model.
OTOH if you have the sketches attached to primary planes - offset if required - then the problem is something else.

[baiyuxiong]

A file would have helped. Is Sketch002 attached to the top face? If so, if you remove Pad001, the face numbering might change and break the model.
OTOH if you have the sketches attached to primary planes - offset if required - then the problem is something else.

Thank you.

Sketch001 and Sketch002 are both attached to the top face.
Can you give me some info about What is face numbering and why it might change. Is there any doc about this?

[edwilliams16]

https://wiki.freecadweb.org/Topological_naming_problem
https://wiki.freecadweb.org/Feature_edi ... ble_models

It isn't that difficult to work around. The developers are hard at work incorporating the work of realthunder on this, which should make it harder to trigger.

[Shalmeneser]

If you delete a feature, following features in the construction tree 'might' break.
If they are independant from the deleted feature, no problem, otherwise a problem 'might' occur.

If Sketch001 and Sketch002 are supported by the top face of Pad(000), they are independant.
If Sketch002 is supported by the top face of Pad001, they are dependant and a problem will occur.

You should not sketch upon faces for this reason.

[GeneFC]

I think all the replies above have missed the correct answer.

Even if there is no TNP the warning will come up. (I just tried it to make sure.) The reason is that Pad001is NOT just the cylinder that was added, but rather it is the entire body at that point.

If good practices were followed and the sketchs/pads were not linked to faces of the original base pad there will be no harm from deleting Pad001, in spite of the warning.

However, there can be problems if the secondary sketches are attached in a manner that invites TNP.

The warning is a bit overcautious, but if good practices are followed it is harmless.

Gene

[papyblaise]

if the sketches are not linked to faces of the object, but to general XYZ planes or Datumplans not linked to the object, there is no problem deleting a Pad or Pocket, the warning is a warning not the harbinger of an announced catastrophe.
it is therefore advisable to use the general planes rather than the attachment to the existing faces of the object, but it is not always possible
it is often possible to move the sketch to the right place using the "Attachment" and "Placement" functions