Stuck on how to start a particular drawing?

Post here for help on using FreeCAD's graphical user interface (GUI).
Forum rules
and Helpful information
IMPORTANT: Please click here and read this first, before asking for help

Also, be nice to others! Read the FreeCAD code of conduct!
Lazlow
Posts: 23
Joined: Tue Mar 10, 2020 4:52 pm

Re: Stuck on how to start a particular drawing?

Postby Lazlow » Sat Apr 04, 2020 5:16 pm

Guys, just to cut off any misunderstanding. I KNOW the way I have done things is not optimal. I tend to get in a hurry and then get frustrated when I cannot find the last unconstrained element. Then I just start nailing down everything I can. Prior to this exercise, I had always built with starting off point of 10,10. That way i could move the entire drawing, allowing the unconstrained element to surface.


Still experimenting with common (or at least what I think is common). I can get it to apply to parts within the same drawing (say revolution and pad) but I still cannot get it to work between to files. When I do compare things the output I am getting (bottom box opens up) is:

"Part::MultiCommon / Common001: Links go out of the allowed scope"
Bance
Posts: 2030
Joined: Wed Feb 11, 2015 3:00 pm
Location: London

Re: Stuck on how to start a particular drawing?

Postby Bance » Sat Apr 04, 2020 5:28 pm

Lazlow wrote: Sat Apr 04, 2020 4:21 pm Is that to do with this being two different files?
Yes, you can copy and paste one body into the file of the other. You'll also have to revolve the body so it has the correct orientation.
When mating two parts in this fashion, it makes sense to have them in the same file, the sketches of one can then be used as reference for the other.
Intersection is the right tool, it provides the logical common operation.
chrisb
Posts: 35949
Joined: Tue Mar 17, 2015 9:14 am

Re: Stuck on how to start a particular drawing?

Postby chrisb » Sat Apr 04, 2020 5:54 pm

To find a last missing constraint the solver can give some help. Click on the blue part of the solver message will select a geometric element which is not yet fully constrained. Please note, that there may be better ways to constrain your model than to blindly follow the solver's guesses, it's no mind reader.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
Lazlow
Posts: 23
Joined: Tue Mar 10, 2020 4:52 pm

Re: Stuck on how to start a particular drawing?

Postby Lazlow » Sat Apr 04, 2020 10:54 pm

So common did not like me rotating the cap drawing to match the nozzle drawing. So I redrew the cap. I TRIED to reduce the number of distance constraints. I did find (through the transparency) that I had a couple of errors (forgot to include the fin length in the overall upper diameter of nozzle). But I still seem to be having a problem with common. I suspect that I just do not know what I am doing. Could one of you have a look and see what I am missing?

Thanks
Attachments
Combined parts.FCStd
(282.82 KiB) Downloaded 3 times
Bance
Posts: 2030
Joined: Wed Feb 11, 2015 3:00 pm
Location: London

Re: Stuck on how to start a particular drawing?

Postby Bance » Sun Apr 05, 2020 8:56 am

I was able to use common on your model and the outcome was nothing, which is what I would expect, given the tolerance fit modeled.
I also modified your model slightly to try to get something more exact, I used a shape-binder of SketchFins to adjust the internal surface of Cone Shell. This does improve the fit, but there is now interference at the edges of the fins, as is shown in the result of Part Intersection. Square peg Round hole :D. Measuring this shows it to be 13um, maybe it could be improved by making a partial revolve of Sketch fins instead of a pad, But I suspect that there would still be some issues at the top of the fin.
Your sketching has improved, but repetitive dimensions also smells fishy...(nit picking :twisted: )
CommonFins.jpeg
CommonFins.jpeg (56.7 KiB) Viewed 224 times
SquarePeg.jpeg
SquarePeg.jpeg (30.64 KiB) Viewed 224 times
Attachments
Combined partsBance.FCStd
(353.29 KiB) Downloaded 5 times
Bance
Posts: 2030
Joined: Wed Feb 11, 2015 3:00 pm
Location: London

Re: Stuck on how to start a particular drawing?

Postby Bance » Sun Apr 05, 2020 9:15 am

A model using revolution for the fins.
No problems with Part common.
I assume you are using CTRL to select both parts for Part Intersection?
Steve.
Attachments
CurvedFins.FCStd
(212.89 KiB) Downloaded 7 times
Lazlow
Posts: 23
Joined: Tue Mar 10, 2020 4:52 pm

Re: Stuck on how to start a particular drawing?

Postby Lazlow » Sun Apr 05, 2020 2:56 pm

I worked on this a littler before bed last night. Hopefully cleaned up the constraints. Still need to go read that page.
The open space near the inlet between the two parts is a compression chamber. Supposedly necessary for all this to work.
This will be 3d printed so the .1 mm gap between the two is intentional. Not sure how precise 3d printers are.
Using revolution instead of polar pattern was very nice. I had to zoom in a long way to even see the arc.

My intent all along was to clean up some of this with fillets(radius in every shop I ever worked in). Inside of the bell(outer shell), outside of the bell, and the corners of the mount plate. On the cap it would allow me to put them on, but it will not show all three of them at the same time. One the nozzle I was going to fillet the two hard corners of the fin and again the corners of the mount plate. It would not let me even apply them. Why let me put the fillet on the mount on the cap but not the nozzle? Why not all three at the same time?

Thanks again. This has progressed MUCH faster than I had suspect. Due entirely to the help I have received in this thread.
Attachments
Combined parts.FCStd
(268.01 KiB) Downloaded 6 times
Bance
Posts: 2030
Joined: Wed Feb 11, 2015 3:00 pm
Location: London

Re: Stuck on how to start a particular drawing?

Postby Bance » Sun Apr 05, 2020 5:33 pm

Fillet and chamfer are weak points in the underlying geometric kernel that facilitates Freecad, so they are notoriously fragile, this is not exclusive to FC, professional packages suffer similarly I'm led to believe.
Anyhow, I was able to apply the fillets as per your stated need.
It is important to realise that each feature builds upon the last feature created, the last created feature should be the visible feature before adding the next one (the tip, in FC terms.)
When initially adding a fillet or chamfer, it's possible the model will disappear, this can be caused by a number of things, but adjusting the size of the dressup often cures the issue.

I should add that due to the shear number of edges that require dress-ups it would make a better workflow to add them in the sketches.

Steve.
Chamfer.jpeg
Chamfer.jpeg (64.4 KiB) Viewed 197 times
Combined parts-1Bance.FCStd
(619.69 KiB) Downloaded 6 times
Lazlow
Posts: 23
Joined: Tue Mar 10, 2020 4:52 pm

Re: Stuck on how to start a particular drawing?

Postby Lazlow » Tue Apr 07, 2020 5:59 pm

Ok, the 40mm-noozle-assembly is what I have been working on up to this point and I consider it complete (at least I renamed it so I would quit screwing with it).

The second file is my work in progress. With only one diameter of hole ring I suspected that there would be a hot spot in the centre. So I added a second smaller hole ring. I also scrapped the central cone core. Going with a more spoke type design. It has worked pretty well. I added a V-trough to one of the spokes with the intent of the hole coming directly through it. Not working for some reason. The gaps you see between spokes is temporary as it makes it easier to see the non penetrating holes. When completed, the Revolution Inner Fins will be widened to close the gap. Any idea how to get that holes to come through?

I did run into a FreeCAD issue in that it was not updating the drawing after I changed the attachment angle. IF I edit and close the sketch (changing nothing) it then updates the drawing. Bit me in the butt numerous times. Is that just a FreeCAD thing, a .19 development not cleaned up yet thing, or other?

Thanks
Attachments
TopViewZooom.png
TopViewZooom.png (155.5 KiB) Viewed 174 times
TopView.png
TopView.png (157.15 KiB) Viewed 174 times
Combined parts.FCStd
(670.11 KiB) Downloaded 8 times
40mm-Nozzle-Assembly-30-Hole.FCStd
(265.61 KiB) Downloaded 6 times
Bance
Posts: 2030
Joined: Wed Feb 11, 2015 3:00 pm
Location: London

Re: Stuck on how to start a particular drawing?

Postby Bance » Tue Apr 07, 2020 7:05 pm

This caused by the feature on feature, I last spoke about. Inner holes appears too early in the tree. I tried moving the polar feature and the pocket to the end of the tree but no joy!
You just have to delete them, but not the sketch, that can be moved and the features should then be re-built.
This model feels overly complicated the way it is, I'm sure it could be simplified.

Steve.
Attachments
Combined parts-3Bance.FCStd
(1012.99 KiB) Downloaded 4 times