When should fillets and chamfers be applied: early or late?

[chrisb]

There seems to a wide consensus among professionals and other power users that fillets and chamfers (for the rest of this post I will talk only about fillets, but every argument holds for chamfers as well) should be applied as late as possible in the modeling process. this holds not only for FreeCAD, but also for other parametric modeling approaches, e.g. https://community.plm.automation.siemen ... ba-p/25914. I have learned it here myself e.g. from professional NormandC and spread the word whenever such question is asked.

This workflow is very sensible if all necessary changes to the model are made before applying the fillets.

However, if changes to earlier steps are necessary, then very often the underlying edges of fillets change and the fillets have to be reworked.

If a model is built following the paragraph about creating stable models we can build very stable models where toponaming issues can be reduced to a minimum.

I want to discuss here if a model would not become even more stable if fillets are applied as soon as possible in the modeling process, because all subsequent modeling steps cannot affect the fillets. The sketch based features are not affected by toponaming issues (yes there are exceptions) so the number if steps where the model can break is reduced.

It boils down to:

• Apply fillets late:
  - Sketch based features are not affected by changes to earlier steps
  - Fillets can be affected by changes to all non fillet modeling steps
• Apply fillets early:
  - Sketch based features are not affected by changes to earlier steps, especially not by fillets
  - Fillets are affected only by the modeling steps before them and not by later steps

I would like to learn if and why why it is sensible to apply the fillets nevertheless as late as possible.

[ppemawm]

if a model would not become even more stable if fillets are applied as soon as possible in the modeling process, because all subsequent modeling steps cannot affect the fillets.

Since V0.17 I have been applying as many fillets as early as possible in the model tree for the very reason you mention. Sometimes I even go back into the tree via "set tip" and add a fillet rather than add it at the end. Ideally I like to have one fillet at the end of the tree, if possible. The other practice that is helpful is to include the fillets and chamfers in the sketches when possible.

[Hartwig]

Hello,
I design complex plastic parts for 19 years. If we are talking about Catia or Siemens NX I definitely recommend applying fillets as soon as possible. Sometimes there is no other way to achieve the desired geometry. And in general it leads to the more robust cad model.

I would like to do so in FreeCad as well. But unfortunately I did'nt find a way yet to make the sketches and planes in the subbodies visible to edit them. The attached sample file shows my prefered way to structure a feature tree.

Hartwig

OS: Windows 7
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.17505 (Git)
Build type: Release
Branch: master
Hash: 755536e9df94d2d39da1468420f1fd333c35da7a
Python version: 3.6.6
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: German/Germany (de_DE)

[TheMarkster]

Hello,
I design complex plastic parts for 19 years. If we are talking about Catia or Siemens NX I definitely recommend applying fillets as soon as possible. Sometimes there is no other way to achieve the desired geometry. And in general it leads to the more robust cad model.

I would like to do so in FreeCad as well. But unfortunately I did'nt find a way yet to make the sketches and planes in the subbodies visible to edit them. The attached sample file shows my prefered way to structure a feature tree.

Hartwig

OS: Windows 7
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.17505 (Git)
Build type: Release
Branch: master
Hash: 755536e9df94d2d39da1468420f1fd333c35da7a
Python version: 3.6.6
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: German/Germany (de_DE)

In the view tab of the booleans there is Display property that can be either Tools or Result. Also, for a sketch to be visible the body containing it must also be visible (but its features can be hidden).