Explain This

Discussion created by Chris Kamery on Jul 16, 2008
Latest reply on Jul 28, 2008 by Matt Lombard

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Messing around with swept cuts, i ran into a situation where when the cut intersects itself, it doesnt cut and in my case creates another solid body. yes i do know that it gives me the option of which bodies to keep, i just find the process less intuitive. i would think that a cut would cut everything in its path, and not act as it does when the cut overlaps. What does everyone else think?

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Matt Lombard Jul 16, 2008 2:27 PM
I think what you see is exactly what you should expect. You can't expect the software to read your mind when you give it input like that.

I suggest that you sweep a surface and use the surface to cut the solid. When you make the surface, just draw the lines in the profile that you need to make the cutting face, don't draw all those extra lines that you only draw to enclose a solid. Those extra lines are the ones that are causing this problem you see.

Or better yet, make the surface before the extrude, and extrude up to the surface.
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- Dan Eldred @ Matt Lombard on Jul 22, 2008 10:36 AM
  just an fyi. in my experience extruding up to surface increases rebuild times far more than Cut with Surface. i had some trouble in my last job with a forging assembly taking 5 minutes to rebuild. when i finally got tired of waiting i went through the feature statistics of all the parts and the ones with the greatest rebuild times had Extrudes Up to Surface. so after some experimenting i found out that extruding past the surface and then cutting with it seriously decreased my rebuild times.
  
  in this particular case it doesn't look too bad but, it's something you might consider.
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  - Jerry Steiger @ Dan Eldred on Jul 28, 2008 12:45 AM
    Dan,
    
    That is totally counter-intuitive! Perhaps Matt or some other very knowledgeable person can figure out, and possibly even explain, why that would be. My mind boggles!
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    - Matt Lombard @ Jerry Steiger on Jul 28, 2008 1:27 AM
      Jerry,
      
      I agree, it doesn't seem to make sense. But I don't doubt that it may have actually happened that way in one particular circumstance. There might have been a situation like an S curve where a surface curves back on itself and makes a situation which is difficult to extrude to but a cut would work fine. I think it would be incorrect to say that extruding up to in general takes more time to rebuild than cutting with a surface. I could believe it in one particular situation, but not across the board.
      
      Any single feature that makes that big of a difference definitely has something wrong with it, especially if it is just an extrude. It might have been having problems with a certain merge. It's impossible to say without seeing the actual part, and even then you might not find a definitive answer.
      
      Sometimes a replace face function might be the only way something works, but replace face can take a lot of rebuild time as well.
      
      There is rarely a single answer that is always right in 100% of situations. But a solid swept cut would rarely be my first choice for a feature like what the original poster showed.
      
      To me the real problem here is that SolidWorks is marketed to total novices, and the sales message makes you believe that you can do anything without any special knowledge or training. SW gives you a DVD and a pat on the back. The software is loaded with really powerful functionality, and many users bravely dive right in without much idea of how it works. I have to admit, this is the way I had to learn, without any realy formal training. I learned and continue to learn from a long series of mistakes.
      
      People rip me apart every time I suggest that there is no such thing as a level playing field, but I strongly believe that some people have either natural or developed skills in particular fields, and some people's talent lies elsewhere. I've trained enough SW users to see that some people understand what is happening behind the interface intuitively, and some people would be better off as accountants than CAD operators.
      
      I don't mean to suggest anything personal about anyone involved in this thread or anyone at all. We all had to start learning from ground zero.
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