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Minimum radius of curvature vs. Thicken/Shell/Offset

Question asked by Daniel Sevier on Jan 6, 2021
Latest reply on Jan 7, 2021 by Jason Edelman

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I have some confusion over the relationship between the Minimum radius of curvature vs. the potential values for thicken, shell, and offset. My understanding is that if the thicken distance is greater than the minimum radius of curvature, the thicken will fail.

I've attached a simple model of a pan with 10 mm corner fillets. It would be great if some could explain to me this relationship in simple terms. When I checked, it did say the minimum radius was 10 mm. The current shell has a thickness of1 mm. When I tried a thickness over 10 mm, it failed. I guess my main confusion is why this is called a "Minimum Radius of Curvature," and not a "MAXIMUM radius of curvature." Any help is much appreciated! Thanks!

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Jason Edelman Jan 6, 2021 3:27 PM

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Minimum radius = radius after the shell..... so 10mm (external) - 1mm (thickness) = 9mm (internal R.)

But 10mm - 10mm (thickness) = 0 (zero radius face left)

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Jason Edelman Jan 6, 2021 3:27 PM
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Minimum radius = radius after the shell..... so 10mm (external) - 1mm (thickness) = 9mm (internal R.)

But 10mm - 10mm (thickness) = 0 (zero radius face left)
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- Daniel Sevier @ Jason Edelman on Jan 6, 2021 5:58 PM
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  Thanks all! Jason, the equation was very helpful.
  
  So, any idea why if the "minimum radius" is just the interior radius (after shelling or thickening), why it is called the "minimum? "
  
  I ask because if I have a 10 mm exterior radius and thicken 2 mm, then the interior radius would be 8 mm, but we know that if I max out the thicken to 10 mm, we could get the interior radius down to 0 mm, and we'll just have sharp corners internally (below).
  
  So, I guess I am just hung up on the terminology. Even before I shelled out the pan model, it said the Min Rad = 10 mm, but doesn't that seem like a "maximum" for shelling and thickening, not "minimum?"
  
  Like if I was shelling out a very organic form that could have some problematic areas for shelling because of very tightly curved areas, I would think the like a radius check would inform me of what is the Maximum thickness of the shelled/thickened wall that I can use without having issues. Hope my question makes sense.
  
  Thanks!
  -Dan
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  - Matt Lombard @ Daniel Sevier on Jan 6, 2021 6:17 PM
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    Daniel Sevier wrote:
    
    Thanks all! Jason, the equation was very helpful.
    
    So, any idea why if the "minimum radius" is just the interior radius (after shelling or thickening), why it is called the "minimum? "
    It's just telling you what the smallest radius on the model is. From that you have to make your own decisions about if the feature you want goes to the inside or outside. The minimum is the one that is most likely to fail, under certain circumstances. You never want to know the biggest radius on the part, you're only ever interested in the smallest/tightest radius.
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    - Krzysztof Szpakowski @ Matt Lombard on Jan 6, 2021 6:55 PM
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      Matt Lombard wrote:
      
      Daniel Sevier wrote:
      
      Thanks all! Jason, the equation was very helpful.
      
      So, any idea why if the "minimum radius" is just the interior radius (after shelling or thickening), why it is called the "minimum? "
      It's just telling you what the smallest radius on the model is. From that you have to make your own decisions about if the feature you want goes to the inside or outside. The minimum is the one that is most likely to fail, under certain circumstances. You never want to know the biggest radius on the part, you're only ever interested in the smallest/tightest radius.
      Much times I try explain (here too) that this parameter not allways determines success. But... Even official SW materials are misleading.
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    - Daniel Sevier @ Matt Lombard on Jan 6, 2021 6:58 PM
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      Thanks Matt!
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    - Daniel Sevier @ Matt Lombard on Jan 6, 2021 6:58 PM
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      Thanks Matt!
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- Krzysztof Szpakowski @ Jason Edelman on Jan 6, 2021 7:08 PM
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  Jason Edelman wrote:
  
  Minimum radius = radius after the shell..... so 10mm (external) - 1mm (thickness) = 9mm (internal R.)
  
  But 10mm - 10mm (thickness) = 0 (zero radius face left)
  What???
  Minimum radius is input geometry parameter!!!! Shell is output.
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  - Jason Edelman @ Krzysztof Szpakowski on Jan 7, 2021 2:10 PM
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    sorry for not completely explaining with paragraphs of detail for your complete understanding of my statements. I was trying to be general to the original question and my experience of SW failure... "relationship between the Minimum radius of curvature vs. the potential values for thicken, shell, and offset... the thicken will fail."
    
    Minimum radius is of the existing geometry, but minimum radius error is of the new 'offset' faces that fail. If the offset is to large and creates a degenerate face, the feature command MAY fail.
    
    If newer SW versions or a specific workflow is necessary that is beyond the general question and understanding I was trying to convey.
    
    2016 SOLIDWORKS Help - Error Message - Shell Errors
    The shell operation failed to complete. One of the faces may offset into an adjacent face, a small face may need to be eliminated, or one of the faces may have a radius of curvature which is smaller than the shell thickness
    
    The Thickness value is greater than the Minimum radius of Curvature. The shell may succeed, but could cause undesirable results, such as bad geometry
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Krzysztof Szpakowski Jan 6, 2021 3:41 PM
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Sorry Daniel but... bad workflow.
Min. radius curvature not allways limits the thicken, shell, and offset value. In your case - if you make prism as Boss-Extrude with Draft option, after add round and Shell all works!
In simples cases this limits don\t work
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- Jason Edelman @ Krzysztof Szpakowski on Jan 6, 2021 5:55 PM
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  Good modeling solution suggestion Krzysztof, but I think he is asking the existential question why do these 'tools' fail? and how is Minimum being defined.
  
  These features fail, because when a surface is translated/ offset (dependent on said shape) if the offset causes the 'face' to no longer exist, SolidWorks does not know how to 'calculate' (besides SW2020 surface offset and PowerShell addin features)
  
  Minimum (IMO) is being defined as dont 'break' SWs, and not know what to do with a translated face...
  
  happy modeling. cheers. J
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  - Krzysztof Szpakowski @ Jason Edelman on Jan 6, 2021 7:00 PM
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    Jason Edelman wrote:
    
    Good modeling solution suggestion Krzysztof, but I think he is asking the existential question why do these 'tools' fail? and how is Minimum being defined.
    
    These features fail, because when a surface is translated/ offset (dependent on said shape) if the offset causes the 'face' to no longer exist, SolidWorks does not know how to 'calculate' (besides SW2020 surface offset and PowerShell addin features)
    
    Minimum (IMO) is being defined as dont 'break' SWs, and not know what to do with a translated face...
    
    happy modeling. cheers. J
    Its no true. In my sample the corner rounded faces after Shell command no longer exist, but SW know what do....
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Paul Salvador Jan 6, 2021 4:21 PM
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..yes, the shell will give you a R8...(image)... so, I'm not sure what you are saying?
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Minimum radius of curvature vs. Thicken/Shell/Offset

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