gettng started

[drmacro]

Can't have open shapes in the sketch.

Close the shape.

Shouldn't attach to generated geometry, Use Attachment offsets to avoid topological naming problem.

edsut.png

Not sure what you mean by an "open shape".

Open the sketch in my file with the arc. There is now a line across the end vertexes of the arc. A shape (profile) in a sketch that is to be used in a Pad/Pocket/Revolve/etc. operation must be closed.

[chrisb]

@chrisb Are you saying that I should create the second sketch (with the arc) on the same plane as the first sketch?

Yes. It will make the same groove, just from the other side.

[NewJoker]

I don't know why your original approach didn't work for you (it was likely a mistake in sketch or an incorrect use of some option) but it's also possible to draw this part like you initially wanted. Still, the way to go for me would be to pad the whole length of the rectangular section and then use pocket to make the semi-circular cut.

Original approach.FCStd

(19.91 KiB) Downloaded 38 times

[drmacro]

I don't know why your original approach didn't work for you (it was likely a mistake in sketch or an incorrect use of some option) but it's also possible to draw this part like you initially wanted. Still, the way to go for me would be to pad the whole length of the rectangular section and then use pocket to make the semi-circular cut.


Original approach.FCStd

I think, if I understood, he was attempting to select the end face of the first pad and attempting to pad the face.

[edsut]

Ok, first of all, this is an excellent forum...
Thanks very much to all for the suggestions.
I stuck with the original suggestion from jmaustpc as I mentioned earlier. The reason that didn't work initially was because I had an "open shape" as mentioned by drmacro. I see now what "open shape" means, and I realize now that I didn't have the top line to "close" the arc. Once I did that things got better. NOTE: It does seem strange to me that an open shape doesn't flag some kind of "you ain't done yet" message.
Anyway, the final trick that got things to work for me was that I had to pad the initial rectangle negatively so that I could set up a second sketch (with the arc) on the same face as the first sketch (instead of the other end of the pad). This gave me what I wanted, but I'm a bit confused as to why I had to do that. I see several comments/text saying that its not good to attach sketches to random faces on your body, but I thought that was the whole "paradigm" of FreeCAD... that I could pad/pocket on any face by just attaching a sketch to that face...
So, I'm over the initial hump; but if anyone can point me to docs/youtube/whatever that would explain this, that would be icing on the cake.
Again, thanks to all...
Have no fear, I will be back with more questions as I progress with this.

[drmacro]

Ok, first of all, this is an excellent forum...
Thanks very much to all for the suggestions.
I stuck with the original suggestion from jmaustpc as I mentioned earlier. The reason that didn't work initially was because I had an "open shape" as mentioned by drmacro. I see now what "open shape" means, and I realize now that I didn't have the top line to "close" the arc. Once I did that things got better. NOTE: It does seem strange to me that an open shape doesn't flag some kind of "you ain't done yet" message.

There are reasons that it doesn't.

If you happen to be using the sketch as source for other sketches, then it may not matter if it's open.

A sketch can be used to Extrude in Part workbench where non-closed shapes will extrude into faces (crossing lines are also allowed here)

There are techniques like using a master sketch where, again, the closed condition is not required.

For Part Design workbench, the rule is, they must be closed. And if you attempt an operation...the operation tells you you have not provided valid data for it to complete the operation...as you found.

Anyway, the final trick that got things to work for me was that I had to pad the initial rectangle negatively so that I could set up a second sketch (with the arc) on the same face as the first sketch (instead of the other end of the pad). This gave me what I wanted, but I'm a bit confused as to why I had to do that. I see several comments/text saying that its not good to attach sketches to random faces on your body, but I thought that was the whole "paradigm" of FreeCAD... that I could pad/pocket on any face by just attaching a sketch to that face...

This would be the case...except for the bug that has been mentioned. So, until that gets fixed...no generated geometry for support. And one must learn how to use attachment correctly. Fortunately, it is a skill that will, when the bug is corrected will still be a useful skill.

https://wiki.freecadweb.org/Basic_Attachment_Tutorial

...
[/quote]

[edsut]

Ok, I worked through that Basic_Attachment_Tutorial.
If I understand it correctly, the difference between this and visually clicking on any face and attaching a sketch to it is that I create a sketch at the origin and then move (or attach) it to the body by moving its X/Y/Z position. Then I can pad/pocket as needed.
Does that make sense?
Assuming yes, then that also implies that the body (similar to the tutorial) should be moved off the orgin just so the additional sketches can use the origin as a point of reference. True?

[drmacro]

No, I think he did it that way to emphasize the sketches were not necessarily on base planes.

[jmaustpc]

Note I didn't use a circle 'cause half of it would be outside the plane that I want to pocket. See attached project.

Can't view files as I am working from my phone.

The others have answered most but I thought I would comment on your circle comment, you are wrong, the extra half would just pocket from emptying space while the other half would create your cut out.

You don't have to use a circle, I was just keeping it simple, and a circle would involve slightly fewer constraints and geometry in the sketch, no problems for something simple but if your model becomes very complex then any simplification will slightly speed up computing your model.

As you found out, you have to think about Pad and pocket direction options. By default a pocket is a hole going into the screen whereas a Pad is a lump coming up out of the screen towards you. The logic of all this will make sense once you get a better understanding of FreeCAD. Also note that as you get more advanced, there are many more options like mid plane or going in both directions at once, also you can define offsets and get more advanced again by using Expressions... but learn the simple stuff first or otherwise you will just be overwhelmed.

By the way guys, I am back at my old farm for a couple of days doing more cleaning up and moving yet another load. I was a bit over tired today so we split up the 7 hour drive by visiting my mate's farm on the way for about 2 hours. We arrived at milking time so I help milk, milked 200 cows. My girls play with the really cute calves, the waiting cows and a bull, they really enjoyed it. They have been missing all our cows and goats. They are greatly hoping we will finally get another farm soon, we have to sell the old one first. The new school has a farm attached so runs a serious agriculture program including running a red charolais cattle herd. My younger two are really looking forward to starting at the new school after the holidays next month. Australian school years follow the calendar year.

Another thing Chris, I love chocolate mousse as well!

Jim

[edsut]

Yea, I see what you mean...
I just tried using the circle instead of the arc and it is simpler 'cause I don't need to "close" the arc with the extra line.
It also makes me realize that it is legal to pocket into empty space.
Thanks,
Ed

PS... never milked a cow! Sounds great.