Material doesn't disappear after it is cut.

[Hop]

Hello,

I originally dismissed FreeCAD as shareware due to the Free prefix. I would expect open- or libre-. Free- has unfortunately negative connontations associated with it. However I feel your dedication will show through in the end and I'm certain FreeCad will be a household name in the near future.

CAD has been an interest of mine for some time now. In the past I've been discouraged, due to the lack of a suitable libre software alternative. I can't express the joy of stumbling here from /r/cad on reddit, other then to say that my journey learning FreeCAD has begun!

I've enjoyed watching numerous video tutorials and am very impressed with the format. It's very intuitive and easy to follow and absorb the information. It's a great way to promote FreeCAD. The content really does speak for itself!

I've run into my first snag doing this tutorial:

https://www.youtube.com/watch?v=pLgSuu_ ... AY&index=6

On the last step I cut some material away from the top of the spring using a cube, however I can still see the material afterwards. An outline of the cut is visible.

I expect there is a beginner mistake to be learned here. I'd appreciate some insight.

Cheers!

OS: Linux
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.15.3986 (Git)
Branch: master
Hash: 93e01c16b67e48c4954568033940a4b2732c99f0
Python version: 2.7.8
Qt version: 4.8.6
Coin version: 3.1.3
SoQt version: 1.5.0
OCC version: 6.7.1

[ulrich1a]

Hello,

welcome to FreeCAD. It seems you are already managing not so easy parts.

I expect there is a beginner mistake to be learned here. I'd appreciate some insight.

There is no beginners mistake. The cut does work as expected by just moving the cube to 59.99 mm instead of 60 mm.

The point is: the helix function does produce notoriously fragile parts. Boolean operations with helix parts with a higher number of turns are failing often. This is a known weakness, which is probably caused by the underlying CAD-kernel. At working with the helix function, I often needed to try more than one approach, in order to get something to work.

Ulrich

[jmaustpc]

Ulrich has a very good answer but I thought I would add a more general comment as well.

Whenever you get a strange result from a Boolean operation, most of the time, it will be due to an invalid solid being used in the Boolean. The invalid solid will often not appear to have a problem until you try the Boolean operation.

So when this happens, go to the Part Workbench...Part Menu...Check geometry.. and see if you find any errors also expand the bottom window and confirm that you have the component expected (mostly, only one solid with optionally one compound and a whole assortment of edges and vertices etc.). Run this on all your solids in your history until you find where the error starts.

Your libs are up to date, so it should work quite well for you...but be warned that 'no errors" just means that no errors were found, which does not always mean there are no errors. There is an option to extend the check, under tools menu edit parameters you can find an option to turn on BOP check. This will make testing very much slower, particularly on complex models, but will sometimes find extra errors. By default it is turned off.

As Ulrich said, helix does seem to be pretty fragile at this time.

Jim

[ickby]

Hello,

I found that this is actually a freecad issue and not a occ one. issue #1739

[jmaustpc]

Hello,

I found that this is actually a freecad issue and not a occ one. issue #1739

Hi ickby

That's really interesting, well done working it out.

Just from memory, I have not tested, but it seemed to me that these sort of helix issues were rising since after more recent OCE updates.

Is there any chance that the issue of the helix going crazy after a certain number of turns might also be something adding up somewhere until it reaches a difference greater than the precision value somewhere?


Jim

[Hop]

Greeting everyone,

I see now that the problem is common here in the forums. Thanks Ulrich for the tip; this has helped me on the model attached. I now understand to try multiple approaches to arrive at a solution. Would there be a benefit to compiling FreeCad against the latest source of OCC (I can't seem to find the source) ?

EDIT::: [Ignore]

So being inspired by a tutorial covering the modelling of a hex nut, I decided to try and model my own after DIN 932 and ISO 68-1. This was last evening. Eight man hours and countless attempts later, I've managed to model all the hard parts, overcoming hurdles at every step to reach this point: I can't fuse the bottom revolution to the middle, even though I suceeded in fusing the top revolution.


My goal is to acheive a 1:1 copy of a real world DIN 932 Hex Nut. I'm having trouble pinpointing where the problem is. Perhaps it lies in my workflow and there is a better approach.

EDIT:::: [/Ignore]

Jim, I appreciate your tips on troubleshooting, however using Check Geometry I haven't managed to discover anything as of yet.

Ickby, I'm glad my post is of use! Thanks for doing the hard work!

Cheers

P.S. It appears the maximum allowed attachment size is 512Kb. Can anyone recommend where to upload fcstd? Would prefer a service where no registration is required.

In the mean time: https://mega.co.nz/#!bp0ynZwa!alXazuLu1 ... HZjuOuyoPU

EDIT::: Back to square one, I must figure out how to create sweep with helix that produces a valid shape.

[jmaustpc]

Jim, I appreciate your tips on troubleshooting, however using Check Geometry I haven't managed to discover anything as of yet.

I find errors when I check it, but then I have BOP check enabled.

OS: Ubuntu 14.04.1 LTS
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.15.3987 (Git)
Branch: master
Hash: d1fb7fa8396eacc7568f91157e4282e858630fd0
Python version: 2.7.6
Qt version: 4.8.6
Coin version: 4.0.0a
SoQt version: 1.6.0a
OCC version: 6.7.1

[jmaustpc]

My goal is to acheive a 1:1 copy of a real world DIN 932 Hex Nut. I'm having trouble pinpointing where the problem is. Perhaps it lies in my workflow and there is a better approach.

Run tools menu ...dependency graph and have a look ....your model history is all over the place. If dependency graph does not work for you the make sure you have Graphviz installed.

[Hop]

Ah! A restart was required. So many errors I can't count!

Should I just start again? Or is this still worth saving.

[jmaustpc]

Ah! A restart was required. So many errors I can't count!

Should I just start again? Or is this still worth saving.

for now I would suggest you practice modelling on things that don't use a helix. I think its going to give you heaps of difficulties. Unless of course you need to model something with a helix for some reason.