Padding issues

[FreeEngineer523]

Question that someone can probably answer pretty quick, even though I can't find it probably because I don't know how to word it properly in search.

So the problem is I can't understand a certain problem with my workflow in sketching, then padding. If I sketch a shape and a circle in the middle then pad it, I get the following:



Of course, this is what I expected, but when I increase the circle size, there is a point when it pads out like this:



So my question is what is going on here, because I am trying to pad it out so I just have the outside shape. I guess I could always just make a pocket with a through all command, but that adds history into the tree, and I'm trying to avoid that, any ideas?

[drei]

Hello FreeEngineer523 and welcome to the forums,
We (the community) will gladly help you within our possibilities, but we're gonna need to things:

1. Your detailed FreeCAD information
2. The file you are working with

Check this link for detailed instructions for how to do both. Since FreeCAD runs on many different configurations, we need this information to diagnose what's going on on your end.

[jmaustpc]

the problem is most likely that you have the wrong feature or features "not" hidden.

In PartDesign wb, after each operation the last step is set to "hidden" when the next step is created. When you go back and edit a previous stage of the model, you often set view on, hence you are showing two stages of your model at once. This is where accidentally forking the model history becomes more likely.

If we had you version data and the file I could test for the above and tell you if and how it may be possible for you to test it yourself.

[FreeEngineer523]

No problem! Here is the about info page:

OS: Windows 7
Word size: 64-bit
Version: 0.14.3700 (Git)
Branch: releases/FreeCAD-0-14
Hash: 32f5aae0a64333ec8d5d160dbc46e690510c8fe1
Python version: 2.7.6
Qt version: 4.8.5
Coin version: 4.0.0a
SoQt version: 1.6.0a
OCC version: 6.6.0

And I've attached the file with the part padded, I've just been learning that FreeCad has some not so obvious rules you have to follow in order to achieve a proper workflow.

[sgrogan]

Hello FreeEngineer523 and welcome to FreeCAD. Thanks for posting your about FreeCAD information.

In your posted file I noticed that your sketch was not fully constrained so I thought that might be causing you some problems. I fully constrained the sketch but when the center radius is 35.2 mm or greater the model fails. I get self intersects with Check Geometry. My version of FreeCAD has extended BOP checks that yours doesn't so I don't know if Check Geometry (found in the Part WB) would have found this. The strange thing is I don't think there are any self intersects.

Padding_Issues1.FCStd

(9.22 KiB) Downloaded 33 times

I then deleted your circle. Mapped a new sketch to the remaining pad, drew a circle, and pocketed through all. It works as expected with no limit on the diameter of the circle.

Padding_Issues2.FCStd

(13.33 KiB) Downloaded 30 times

I believe the two methods should be identical. So you may have found a bug in the OCC kernel that FreeCAD depends upon.

Maybe someone else has another idea. Anyways the second method works as a work around

OS: Windows 7
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.15.4435 (Git)
Branch: master
Hash: f24e216db4fb923b2571ad9d856f934e81bec797
Python version: 2.7.8
Qt version: 4.8.6
Coin version: 4.0.0a
OCC version: 6.7.1

[bejant]

Greetings FreeEngineer523, For some reason the original circle has 3 degrees of freedom, but yet I can't drag it away from the origin. The Pocket fails for me too when the edge of the original circle is close to the edge of the solid.

I then deleted your circle. Mapped a new sketch to the remaining pad, drew a circle, and pocketed through all. It works as expected with no limit on the diameter of the circle.

This works for me too. There's something odd about the original circle but I don't know exactly what.

FreeEngineer523, just a tip here. To constrain the endpoints of two segments onto one another you should apply the "Fix a Point Onto a Point" Constraint:

and not the "Fix a Point Onto an Object" Constraint:


When the "Fix a Point Onto an Object" Constraint is applied to a point and a line segment, the point can lie anywhere in line with that segment, as though the segment is a ray. That's not what you want in that model.


OS: Ubuntu 14.04.1 LTS
Word size of OS: 32-bit
Word size of FreeCAD: 32-bit
Version: 0.15.4437 (Git)
Branch: master
Hash: c5b2609974dd754fc91151d0e8ee3d5697f72d89
Python version: 2.7.6
Qt version: 4.8.6
Coin version: 4.0.0a
OCC version: 6.7.1

[sgrogan]

The problem is not due to the original circle (at least not totally)

1. sketch a 76.2 mm square
2. add a circle to the sketch inside the square (it doesn't need to be exactly centered)
3. when the circle's radius exceeds 35.199mm a subsequent pad will fail with self intersect errors

pad.JPG (28.73 KiB) Viewed 2690 times

Padding_Issues3.FCStd

(5.93 KiB) Downloaded 33 times

[FreeEngineer523]

All right then, thanks for your input. The methods described work, so I'll have to just go ahead and manage with that. Just have to get used to this specific ways I need to work things in order to get a proper sketch. The constraining idea is still a little new to me as far as FreeCad goes, I've constrained models in solidworks but freecad does it differently and I will try to learn how to constrain my sketches better. Thanks for your time and effort!

[quick61]

Another way about it would be to make the solid from one sketch and Pocket the Circle in the next operation.

This is strange - I can confirm that when one makes a 72.6 mm square with a 33.6 mm radius (67.2 mm diameter) Circle it fails. Change the radius by -0.1 (33.5 mm) and it works. Actually, on my install it fails at 33.5369 mm - 33.5368 works.

Looks to be a bug in there somewhere - maybe OCE, maybe something in FreeCAD???

Mark

OS: Kubuntu 14.04.1 LTS
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.15.4437 (Git)
Branch: master
Hash: c5b2609974dd754fc91151d0e8ee3d5697f72d89
Python version: 2.7.6
Qt version: 4.8.6
Coin version: 4.0.0a
OCC version: 6.8.0.oce-0.17-dev