Another contraint problem...

[Stou]

Hi, I'm new to freecad. I did many tutorials and start to be able to do many things. But sometime get stuck on some things I need to do. Right now I'm working on a multiple parts motorcycle air filter case. I'm working on the second part and I'm stuck since this morning on a simple sketch that I can't completely constraint.

Also after I will get those contraint problem, I will need to do the same sketch but with 5mm all around the first object, the one I have contraint problem. What is the best way to do that. Is the a way to do it simply or I need to design it manualy and constraint it correctly after. In the software I use for my 2D design (CorelDraw) I use the CONTOUR command. In FreeCAD CONTOUR is completely different from what I saw.

OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.17.13541 (Git)
Build type: Release
Branch: releases/FreeCAD-0-17
Hash: 9948ee4f1570df9216862a79705afb367b2c6ffb
Python version: 2.7.14
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.2.0
Locale: French/Canada (fr_CA)

Thanks!

[chrisb]

Hi Stou, welcome to the forum.
What is missing is the overall position relative to the origin (see below).

What you have modeled is impossible, with the horizontal lines and the tangencies you have to have the same radius left and right. The problem occurs at the left upper side where the points are not connected. If you use the Slot tool you will get the elements properly connected. In general you should try to avoid explicit dimensions in favour of geometric constraints,in this case equality.

If you want to center the slot, remove one of the horizontal constraints, and add a symmetry and a point on line constraint:

[openBrain]

Also after I will get those contraint problem, I will need to do the same sketch but with 5mm all around the first object, the one I have contraint problem. What is the best way to do that. Is the a way to do it simply or I need to design it manualy and constraint it correctly after. In the software I use for my 2D design (CorelDraw) I use the CONTOUR command. In FreeCAD CONTOUR is completely different from what I saw.

Indeed there is no offset function in FreeCAD (at least I never found it. If one knows about, please tell ).
A simple way to do so may be to use the "Copy the geometry from another sketch" and the "Create an edge linked to an external geometry" functions.
You can use the first in a new sketch and copy the geometry of the 1st one. With the second you can stick constraints and dimensions to the 1st sketch.
After removing the copied dimensions and adjusting the constraints in the new sketch, you will easily obtained an offset shape.

clone.png (7.21 KiB) Viewed 1117 times

For more details about constraints adjusting, I linked to the left arc as an external geometry, I removed the "point on line" constraint and make coincident the 2 centers of the left arcs. I then set the offset dimension.

If you want to center the slot, remove one of the horizontal constraints, and add a symmetry and a point on line constraint:

Chrisb, just saw that your dimension numbers are correctly displayed while mine tends to have their right side cut (especially numbers with several digits, like '240' on the below screenshot). Did you parameter something so it works well ?

dim_cut.png (5.56 KiB) Viewed 1117 times

[Stou]

Thanks Chrisb and OpenBrain, I'll check that tonight and let you know if I understand correctly your advices. There's so much possibilities in FreeCAD, I pass many hours to look at the documentation, the tutorials and try many things. I have a lot of experience in 2D design but 3D is really new for me, but I really like it!

[openBrain]

I have a lot of experience in 2D design but 3D is really new for me, but I really like it!

Actually we're still discussing 2D things. But true that you're switching from the geometrical (conventional) 2D to parametric modeling (we could say from the drawing board to the magic of the digital world ).
And from my experience, people having a long experience with geometrical 2D drawing got by some way a harder learning curve as it's a mindset change.

EDIT : Looks like you have a fellow countryman (https://forum.freecadweb.org/viewtopic.php?f=3&t=33146) and like fully constraining slots is highly trendy in Canada.

[Stou]

You are right openBrain. The problem is more to learn all the differents workbenchs and functions of FreeCAD. It's completely different than the one I use for my 2D work.

After a few try and error, I finally got it. The slot is really simple and a lot more easier than lines and arcs. I had a few problems with the "Copy the geometry from another sketch" in fact more with the TOGGLE to/from construction mode. The first try, I always had the blue lines (construction) and it took me a few research to understand what was the toggle.

I did it on 2 different sketch, I think it will be easier to work with the PAD after.

The first sketch with the outside shape:


The second sketch with the inside shape:

[chrisb]

Indeed there is no offset function in FreeCAD (at least I never found it. If one knows about, please tell ).

You are right as far as PartDesign is concerned. In Part you have 2D offset which works excellent on slots.

[Bance]

Also if one is creating tubular/pipe type objects there is the thickness tool......

[openBrain]

After a few try and error, I finally got it. The slot is really simple and a lot more easier than lines and arcs. I had a few problems with the "Copy the geometry from another sketch" in fact more with the TOGGLE to/from construction mode. The first try, I always had the blue lines (construction) and it took me a few research to understand what was the toggle.

I don't really understand why you may need to use construction items in your current design.

I did it on 2 different sketch, I think it will be easier to work with the PAD after.

The first sketch with the outside shape:

The second sketch with the inside shape:

The difference here with my former proposal is that you don't use external geometry and thus the 2 sketches are not linked. If you update the 1st sketch dimensions, the 2nd one won't be automatically resized accordingly while it will be in the case of my design.

Indeed there is no offset function in FreeCAD (at least I never found it. If one knows about, please tell ).

You are right as far as PartDesign is concerned. In Part you have 2D offset which works excellent on slots.

That was the meaning of it. If I remember well, Draft WB also has an offset tool.

[chrisb]

Stou, you may tell us what you finally want to achieve. Sometimes it is better to follow a reasonable master plan than to start with tiny bits.