@@TheRainHarvester thanks for your feedback. I haven't checked for a while because I do my designs using the techniques I mentioned in my video. They aren't ideal but they help to avoid the problem.
@@GlassonDesignStudio i used openScad for perfect modeling. Easily changeable. No topo bug because you always have the "program" to know what you're modifying. Then i export csg . then import into freecad to generate cnc paths.
@@TheRainHarvester you've found the most important thing - something that works for you. I know that FreeCAD has its limitations but it suits what I do and so I persevere with it.
Interesting video. I am very new to this but it seems to me that whilst what you describe gets around errors, it doesn't get around the fundamental flaw. I thought one key feature of a parametric editor like this was the ability to go back to an earlier design stage, make changes, and have them propagate through. For instance, I haven't tried this, but I am assuming that if the datum plane is disconnected from the face, and that face was padded by 15mm from the original sketch, then if one went back and changed the pad to - say - 20mm, the cutout would now start 5mm under the original face - because the link to the face has been broken? So, the design file is not broken, but the intent of the design is. Clearly there must be limitations - even with no TNP if the face no longer existed after an earlier stage change, or maybe a design line or vertex made visible no longer exists, some sort of error would have to occur, but it needs to fail gracefully. Maybe therefore, there is no answer to TNP at the moment. Do editors like Fusion 360 have the same issue, or is it specific to FreeCAD?
Hi Nick, you're correct in your assessment and example are correct. I understand that this is a fundamental flaw with the current versions of FreeCAD but that there is an experimental fix for it that has not been merged into the main development stream yet. This means that we'll have to work around the problem for the time being. I can't say whether this is a problem in other CAD packages such as Fusion 360 because I haven't used them,
I find that if I draw on datum planes, I can detach and re-attach to faces, axes, etc at a later stage to fix up the effects of this problem. I'm tending to create datum planes on axes, then positioning them (offset, angle), rather than attaching to faces in order to avoid the naming problem.
Thanks for sharing your experiences Chris. I think that we are achieving the same result even though our methods differ. I select a face and then detach it because I'm lazy
I try to repeat these workarounds with 0.19 version of FreeCAD and always get mistakes on last step (with second sketch) but these workarounds are working fine with 0.18 version
Thanks for your feedback. I have replicated the problem on 0.19 (git version 24291 ) and 0.20 (git version 25429). The rules around referencing external geometry seem to have changed between version 0.18 and 0.19. In versions 0.19 and 0.20, the result referencing external geometry in a sketch works in the same way that sketching directly onto a face, and so the topological naming problem is triggered. The solution (from my limited testing) is to remove the references to external geometry in the sketch that defines the cutout for the foot, and use dimensional constraints to constrain the sketch. There is no connection to the base sketch once you've done this and the topological naming problem is not triggered. I hope this helps.
So glad I found your channel Sir. I'm new to FreeCad and have found the lack of detail and background explanation of most of the content available to be a real frustration. I'm a person who needs to understand the 'why' of how something works and your explanation as to what causes this problem is perfect. Well done. Subscribed.
@@GlassonDesignStudio another alternative is to use the main FreeCAD but avoid attaching sketches to edges/ faces (see forum.freecadweb.org/viewtopic.php?f=8&t=47671#p408943), in other words make every sketch a separate entity. It makes your design robust, however it takes more time to rebuild an object since you need to manually change all features when you update one of them. The advantage of realthunder's FreeCAD version is that you can sketch on top of faces/ edges like in Solidworks.
hi .. I'm always using datum planes. I bind the datum plane to one of the xy/xz/yz planes and then move the datum plane to the right place. so i have never ever a binding to a face. best regards an thank you for the video Michael
Another problem with using the datum plane approach is that if you change the thickness of your plank (from 15 mm to 25 mm for example), the change does not propagate to subsequent elements, so you have to reposition the datum plane. Luckily, this does not completely break the model, and can still be managed.
I didn't think about it in the first instance but I have tried it and have reproduced the error I was trying to demonstrate. I may be missing something and not fully understanding how your question would solve the problem, but I didn't get a workable solution when I tried it. I'd be keen to look at a working model if you've got one.
So this stupid problem still exists? Are they serious there at FreeCAD, this error stops many users that come from fusion-360. Disappointed.
Yes it does unfortunately. Apparently there is a fix that will probably be rolled into the 0.20 release but we’ll just have to wait and see.
@@GlassonDesignStudioi waited and saw. Still there!
@@TheRainHarvester thanks for your feedback. I haven't checked for a while because I do my designs using the techniques I mentioned in my video. They aren't ideal but they help to avoid the problem.
@@GlassonDesignStudio i used openScad for perfect modeling. Easily changeable. No topo bug because you always have the "program" to know what you're modifying. Then i export csg . then import into freecad to generate cnc paths.
@@TheRainHarvester you've found the most important thing - something that works for you. I know that FreeCAD has its limitations but it suits what I do and so I persevere with it.
Large-scale design work cannot be done because of this problem. only one-piece models can be drawn.
Interesting video. I am very new to this but it seems to me that whilst what you describe gets around errors, it doesn't get around the fundamental flaw. I thought one key feature of a parametric editor like this was the ability to go back to an earlier design stage, make changes, and have them propagate through.
For instance, I haven't tried this, but I am assuming that if the datum plane is disconnected from the face, and that face was padded by 15mm from the original sketch, then if one went back and changed the pad to - say - 20mm, the cutout would now start 5mm under the original face - because the link to the face has been broken? So, the design file is not broken, but the intent of the design is.
Clearly there must be limitations - even with no TNP if the face no longer existed after an earlier stage change, or maybe a design line or vertex made visible no longer exists, some sort of error would have to occur, but it needs to fail gracefully.
Maybe therefore, there is no answer to TNP at the moment.
Do editors like Fusion 360 have the same issue, or is it specific to FreeCAD?
Hi Nick, you're correct in your assessment and example are correct. I understand that this is a fundamental flaw with the current versions of FreeCAD but that there is an experimental fix for it that has not been merged into the main development stream yet. This means that we'll have to work around the problem for the time being.
I can't say whether this is a problem in other CAD packages such as Fusion 360 because I haven't used them,
Absolutely wonderful explanation. I wish more people were as thorough with their dialogue as you are. Thanks for the help.
Thanks for your kind words. Please let me know if there’s anything specific you’d like to see and I’ll see what I can do
Glasson Design Studio Ha, I could go on for days with video requests. A video on simple part assembly would be great.
Thanks for explaining. This is such a silly problem and is the Achilles heel of Freecad…
Thanks for your feedback. It's an interesting problem. All software has its ideosyncracies but at least you can work around this one.
I find that if I draw on datum planes, I can detach and re-attach to faces, axes, etc at a later stage to fix up the effects of this problem.
I'm tending to create datum planes on axes, then positioning them (offset, angle), rather than attaching to faces in order to avoid the naming problem.
Thanks for sharing your experiences Chris. I think that we are achieving the same result even though our methods differ. I select a face and then detach it because I'm lazy
I try to repeat these workarounds with 0.19 version of FreeCAD and always get mistakes on last step (with second sketch) but these workarounds are working fine with 0.18 version
Thanks for your feedback. I have replicated the problem on 0.19 (git version 24291 ) and 0.20 (git version 25429). The rules around referencing external geometry seem to have changed between version 0.18 and 0.19. In versions 0.19 and 0.20, the result referencing external geometry in a sketch works in the same way that sketching directly onto a face, and so the topological naming problem is triggered.
The solution (from my limited testing) is to remove the references to external geometry in the sketch that defines the cutout for the foot, and use dimensional constraints to constrain the sketch. There is no connection to the base sketch once you've done this and the topological naming problem is not triggered. I hope this helps.
So glad I found your channel Sir. I'm new to FreeCad and have found the lack of detail and background explanation of most of the content available to be a real frustration. I'm a person who needs to understand the 'why' of how something works and your explanation as to what causes this problem is perfect. Well done. Subscribed.
Thanks for your kind words Aidan, and thank you for subscribing
Download realthunder FreeCad Assembly 3 which is FreeCad with that problem solved
Hi Carlos, thanks for the advice. I'll have a look into it.
@@GlassonDesignStudio another alternative is to use the main FreeCAD but avoid attaching sketches to edges/ faces (see forum.freecadweb.org/viewtopic.php?f=8&t=47671#p408943), in other words make every sketch a separate entity. It makes your design robust, however it takes more time to rebuild an object since you need to manually change all features when you update one of them. The advantage of realthunder's FreeCAD version is that you can sketch on top of faces/ edges like in Solidworks.
Just saw your additional comment. Thanks for the additional information Carlos. I'll check it out
hi .. I'm always using datum planes. I bind the datum plane to one of the xy/xz/yz planes and then move the datum plane to the right place.
so i have never ever a binding to a face.
best regards an thank you for the video
Michael
Hi Michael, thanks for the information. I'll have to look into trying the same thing.
Once again an excellent video, well explained, showing how we could make a mistake and how to add a plane the correct way, thank you
You're welcome. Thanks for your kind words
Another problem with using the datum plane approach is that if you change the thickness of your plank (from 15 mm to 25 mm for example), the change does not propagate to subsequent elements, so you have to reposition the datum plane. Luckily, this does not completely break the model, and can still be managed.
Yes you’re right about that
You can work around that by making the thickness a reference variable and making the plane offset equal that thickness.
Indeed, that works.
Great explanation!
Also good to hear another Aussie doing this too.
Thanks for your feedback mate. It’s just my way of giving something back and I just hope that people find it useful
Why didn't you pad reversed, then you could've put your pocket on a std plane?
I didn't think about it in the first instance but I have tried it and have reproduced the error I was trying to demonstrate. I may be missing something and not fully understanding how your question would solve the problem, but I didn't get a workable solution when I tried it. I'd be keen to look at a working model if you've got one.