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Detail Drawing - section through ribs


Detail Drawing - section through ribs


We need detail drawings of some cast components where section planes run through ribs created by the rib tool. The required drafting standard excludes ribs, shafts, fasteners etc. (based on BS8888). Hence in demo below Section A-A is wrong; it should look like Z-Z even though it is in position A-A (I cheated to make example but cheat will not work in general!). We have BS8888.dtl

Any Config options or techniques to achieve this would be much appreciated


John Prentice

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Hi John,

We have a similar issue with gear teeth - if a part has an odd number of
teeth, then one side of the section will inevitably show as solid.

We extrude a thin cut, say 0.2 symmetrical about the section plane, to
cut away the 'tooth' for the section. We generally leave these in our
models, although obviously suppress them if we're going to run Mechanica
or other FEA.

Not sure how well this will apply to your situation though...



The only things you can do are:

1) Make the section a local section & draw your spline to avoid the rib. I think it will be very difficult to make this look good.

2) Not place the section through the rib. This seems like the logical thing to do. In the case of revolved parts you can use an offset section to avoid ribs on both sides of the axis.

3) Not follow such an antiquated drawing standard.

You might also try to change the spacing for the rib to be so large that it doesn't show any lines.


From: David Gallup [

Instead of a planar section use a sketched "offset" one and avoid the rib. This may look a little funny though. The dwg std isn't antiquated, PTC needs to make the software capable of doing things based on standards that have been in place for many years and still work fine.

We've stopped using offset sections - I can't recall specifics, but we
concluded some time ago that they weren't worth the trouble they can


Thanks to all who replied.

The summary is that there is no general way to avoid hatching the rib.

With circular and symmetrical parts an offset section will allow one to avoid the rib in the section - but not show its presence like the drafting standard allows.

There was some debate about the British Standard - the PTC responder was unaware of its existence. My personal opinion is that it (and the equivalent ISO ones) neatly let you show the cross-section of the bulk of the part and the presence and shape of a rib all in one view. However, whatever one thinks, if the standard calls for a convention, one will be asked to follow it.

Thanks again to this invaluable community.

John Prentice

You should be able to use an offset section to show what you want, you just have to make sure the the section jogs tothe correct side to still show the rib. The only place it looks funny is at the point where it jogs.
23-Emerald II

ASME Y14.3 2003 (US standard) calls for the same practice for the rib sectioning BUT allows also for the rib to be shown with section lines. Of course then you have to provide additional views for dimensions that are not available in that view anymore.

This gives you an out if your CAD software is incapable of doing the job.


-----End Original Message-----

I think that the standard does this because the quick-and-easy fix in
Pro-E is to show hidden lines, but sections aren't supposed to have
hidden lines shown.

The showing of bolt circles in section, ribs in section, tabs in
section, etc... are all holdovers from when you were creating the
designs by hand.

Another annoying thing about sections is the showing of shafts, bolts,
etc in assembly section views. You don't need to section those in
assembly sections. In pro-e you can 'exclude' these items from being
shown in section, but just the section lines are removed, the object
lines for the excluded parts are not shown.

Hopefully, we will get to a model-based definition soon, (I'm hoping for
STEP-NC) and make all these discussions moot.

Christopher Gosnell

FPD Company
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McMurray, PA 15317
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