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joe_c14-Alexandrite
14-Alexandrite
July 30, 2026
Question

Conic arc thru multiple points

  • July 30, 2026
  • 2 replies
  • 27 views

Hello everybody

It seems that the limit to constraint a conic arc is 4 points. I picked the start and end point and lay the arc as close to the 5 sketch points. Then i apply the constraints but it wont let me pick more than 4 unless i start making other dimensions References  like the Rho, etc.

any ideas. i need to keep the Radius (Rh), so a Spline feature will not work and neither a Curve by points. 

i guess i can go back to Manufacturing and delete the rest of the sketcher points. 

thanks

 

2 replies

tbraxton
tbraxton22-Sapphire II
22-Sapphire II
July 30, 2026

PTC documentation implies that you can use 5 points to define a conic arc in sketch mode. This of course would require that the curve would actually contain these points as the conic arc is defined using a mathematical function (equation of the curve).

 

I would first verify that the points are in fact defined by a conic arc (an ellipse for rho=0.4). If the points are not on said curve, then this is not going to be a valid set of sketch constraints. Also note that the end point conditions of the arc (tangent etc.) also serve to constrain the definition of the conic so that can make alignment to points redundant constraints.

Have you attempted to use the following technique? The start and end point are included here I think such that you can have 3 “internal” points used to define a conic arc. 

 

J
joe_c14-AlexandriteAuthor
14-Alexandrite
July 30, 2026

i have attempted different ways. I noticed the tangent constraints and Rho dim count towards the anchor limit.

Here is 3 point constraint + ends (2) = 5

Here is 2 point constraint + ends (2) + Rho = 5

 

 

Here is 1 constraint point + ends (2) + Rho + tangent = 5

 

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