Unexpected result from simple cut extrude

[barnam]

I have a part, it was very easy to model. I wanted to makea longer part, so I did a "save as copy", edited the length and everything went awry. I have this extrude cut, up to surface that no not only no longer stops at the next surface, it's like it ignores the material in between the sketch plane and the next surface, and then decides to do the cutting...


Pictures are worht a 1000 words...


The good part:

The sketch plane:

The feature dashboard:

The resulting feature:

Any thoughts? Rememer all I did was edit the part's length. Nothing else, and these cut extude decided to do its own thing...


Thanks - BM

 

[barnam]

Update: I tried it as a blind extrusion, giving it a depth that should have given me the result I wanted but failed. It told me that my feature did not intersect the part.


Figure that one out. If I set it to a mid plane extrude, it will cut through likea through all cut. BTW, selecting through all give the same result as the up to next option.


BM

 

[charleskim]

Couple of suggestions,


1. Cut upto surface and select the surface.


2. Move the sketch plane down and cut the other way (thru all).


Charles

 

[mcgowanp]

It aint always possible but when avoidable try note to create features on previos surfaces, can cause problems, datums on the fly can keep it all tidy.


Paddy

 

[gkbeer]

Extending the part longer could change the accuracy with which the features are computed to change.

The default accuracy (.0012) can be thought of as the ratio of the parts longest edge to the smallest edge. Making the part longer could make the difference.

Try adjusting the part accuracy to .00012.

Edit: Yep tried it. I couldn't reproduce the error at the standard .0012 accuracy, but by dropping the accuracy to .002 I saw the same error. So it stands to reason that if you increase the accuracy, your problem will go away.

Edited by: gkbeer

 

[ihtsham]

i tried it as you said, first with a length & cut, then same cut but with increased length. same cut result...

I dont think there should be any problem in doing that, extrude the cut upto next surface, n then select the top down surface.

cheers.

 

[barnam]

Slecting up to surface and picking that bottom surface is a no go:

I don't want cuts down in tha bottom of that fillet. That's aslo why making my sketch plane on that surface is a no go. Now, setting the model precision was the hot ticket. Thanks!

I still don't understand the purpose of model precision. I once had a part that it would not let me put a 1/32" round on a corner because of it, but when I increased the precision, my model failed. Go figure.

Thanks!
BM

 

[dgs]

EDIT: I see we were typing at the same time. Glad you fixed it, here's a brief explination of accuracy.


Did you try Glenn's suggestion of changing accuracy?


Standard Pro|E accuracy is relative, meaning it's a ratio of the longest edge to the shortest allowed edge. Because your part is ling ans thin, your longest edge is very long relative to the part size, so your shortest allowed edge ill be fairly long too. Changing the part length means that it will no longer allow an edge small enough for your feature to work.


Increasing your relative accuracy should fix it.


You can also change to absolute accuracy which is the actual shortest edge allowed.
Edited by: dgs