newbie how to handle curves in OS

daniel_weseman

I am struggling with "curves" or splines in OS. If i import a DXF or sketch a spline the shape is not correct, and has flats spots in it. also if you zoom into the line the nodes and the lines do not match. Also the highlight to select the solid does not match the line or nodes? I've been told by OS support that OS converts to poly line (segments) and only exports polylines. I am trying to understand how to design parts like Airfoil with internal structure when the representation accurate. This also bring up the question of how these parts will machine (CNC) . This may be a very basic question, but im lost here?
here is the link to a example. 
https://cad.onshape.com/documents/a7b5c96033382327853c8107/w/0716637c26914015e43324d8/e/46978352192e81c5e83e0155
Daniel

mahir

I'm not sure I understand your question. What do you mean by "representation accurate"? Accurate relative to what? I don't have much experience importing DXF files, but I have a decent understanding of splines. Splines are simply polynomial curves that are fit through control points (solid dots). So if you fit a spline to some preexisting reference points, you should get a single curve, not segments like you're saying.

You can also adjust the endpoints of splines using tangent control handles (white dots). There are FeatureScripts out there than can fit spline to existing points. There is even an aerofoil FS that may be able to generate the exact curve you're looking for. I also wrote another FS that generates a curve based on equations. What I'm trying to say is you have options.

daniel_weseman

If you look at the link ,and zoom in you will see the line has flat spots, the line does not actually touch the  "control points" ,and if you highlight the shaded area it does not have the same profile as the line ,or the points. I Think i understand that some of this is simply "display" but how can i design parts to fit if do not "look" correct? Also how can I export curved profiles (parts designed in OS) and machine them if they are faceted?
Dan

MBartlett21

the spine is not meant to go through the control points