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Tangent to a spline

Question asked by Pet Peever on Aug 14, 2012
Latest reply on Aug 21, 2012 by Roland Schwarz

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Hi,

In this file, I have a given spline, which is fixed and the tangent at the origin.

(Btw, I am wondering why I can fix the tangent at origin : if the spline is fixed, the tangent at any point too, but it's not the matter of my post)

I want to define a segment, being tangent at the origin.

So, I draw a segment, one point at origin, the other free, and I define a tangent property.

And I get what is on my screen.

How can I build this totally elementary construction ?

OK, I can declare some colinearity with the tangent of the spline.

But this kind of behaviour is surely totally normal ?

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tangent to a spline.SLDPRT.zip21.2 KB

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Alin Vargatu Aug 14, 2012 9:51 PM
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What do you mean by "I have a given spline, which is fixed and the tangent at the origin"? Do you want the spline to be tangent to a line that passes through the origin and is vertical?

If that is the case, see attached file.
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- jav - tangent to a spline.SLDPRT.zip19.2 KB
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- Pet Peever @ Alin Vargatu on Aug 15, 2012 12:38 PM
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  No,
  I don't want that the line was vertical.
  I just want that the line was tangent to the spline.
  
  For that, I just have to declare a tangent relation between 2 entities.
  
  And I get was is in my attached file.
  And SW seems to have very odd behaviours in this case. Just one more bugged behaviour, added to an already impressive list.
  
  .
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  - Alin Vargatu @ Pet Peever on Aug 15, 2012 12:47 PM
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    Thanks, I understand now. See attached file. I created the tangent relation first and merged the 2 endpoints later.
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    jav - tangent to a spline.SLDPRT.zip22.6 KB
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  - Alin Vargatu @ Pet Peever on Aug 15, 2012 12:50 PM
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    You can also make the line colinear to the spline handle (select the diamond for that).
    
    See attached.
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    colinear instead of tangent to a spline.SLDPRT.zip22.5 KB
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Roland Schwarz Aug 15, 2012 2:08 PM
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As near as I can tell, it's just a malfunction of sorts. When I erase the line and draw a new one, tangency works no problem.
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- Pet Peever @ Roland Schwarz on Aug 19, 2012 6:45 AM
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  Sorry, but I don't understand how some sort could modify the definition of a tangent !!!!
  
  If one spline and one line generates a problem of sorting, I am really curious about how SW manages assemblies with thousands of components !!!
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  - Roland Schwarz @ Pet Peever on Aug 21, 2012 11:06 AM
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    "sort" = "variety" or "type"
    
    Sounds like English not your primary language. Duì bu qǐ.
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Bjorn Hulman Aug 19, 2012 11:40 AM
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Pet, you seem to be having a lot of user based issues. Are you new to SolidWorks? Why are you fixing all the points on your spline? Use construction geometry, define you sketch with dimensions. Spline handles can be dimensioned with length and angle. Each point can be dimensioned also. Fixing a point is a great way to stop something from moving while you dimension the rest. Perhaps start asking about what you could be doing better rather than elluding to software shortfalls. I was going to tidy up your sketch, but it'd be best to start again, there is no inherent intent, again the use of construction geomtry would help.
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- Pet Peever @ Bjorn Hulman on Aug 19, 2012 12:18 PM
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  Hi,
  I am fixing the whole spline, after a drawing from scratch (the freeform feature, with a spline).
  
  I am fixing it to stop something from moving, as you say too.
  
  Perhaps this drawing isn't in the accademic SW touch, but it's in the general academic purpose, about one curve and one tangent line.
  
  It's really odd that, when I fix the spline, its tangent stays in blue, and if I declare another line as tangent, this behaviour happens.
  
  Sorry, but there are some bugs somewhere in the code. And the word "bugs" is here in the plurial form.
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  - Bjorn Hulman @ Pet Peever on Aug 19, 2012 12:41 PM
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    Pet, how long have you been using SolidWorks for?
    
    Every problem has a solution.
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    tangent to a spline.SLDPRT.zip52.0 KB
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    - Pet Peever @ Bjorn Hulman on Aug 21, 2012 10:38 AM
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      HI,
      
      I am using SW for perhaps 3 years, but only some weeks per year, for my holidays.
      And mecchanic isn't my field, btw .
      
      Here, it's the Summer Edition which makes me come back here : I want to check some simulations, about the assemblies and composite ones, particularly, which seem very powerful, and aren't in the student version,
      
      What makes me sometimes grumbling is about the math rigour of the program : if I can give my 2 cents, I also tried tflex, which is less comfortable, to draw from scratch with the mouse (to grab points and curves are less powerful), but the math of the basic constructions are much more pleasant : the program asks me about what I am expecting the program has to ask something, to go further.
      
      If SW has such option about choices, hidden somewhere, I wish i knew it, really.
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Rick McWilliams Aug 19, 2012 1:29 PM
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Fixing a spline does not necessarily fix the end points. Make spline proportional and set end points may stabilize your sketch. I get best results from the spline shape on one sketch, and a second sketch on that plane that copies the spline as convert entity and has tangent features and appropriate trims. The tangent relation can get stuck off tangent. I delete the relation and redo it. One of the many really silly SW bugs that have been around since 2007.
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