Constraing a sketch line to a cylinders edge
Constraing a sketch line to a cylinders edge
(OP)
New to UG NX. Took the online course and the Design course. How do you constrain a sketch line to be colinear with a cylinders edge (Silhouette edge) in a sketch. After entering the constraints mode to add the constraint I cannot pick the edge of the model. Do I need to convert the edge?
Guy
Guy Edkins
Managing Partner
Delta Group Ltd
www.deltagl.com
Guy
Guy Edkins
Managing Partner
Delta Group Ltd
www.deltagl.com





RE: Constraing a sketch line to a cylinders edge
In my limited experience with the sketcher, I would create a datum plane tangent to the side of the cylinder and use that for the sketch plane. I don't know exactly what your end goal is, so my method may not be applicable for you. Hopefully a sketcher guru will come along and educate both of us.
RE: Constraing a sketch line to a cylinders edge
Using a 20mm diameter cylinder, I created a datum through the center of the cylinder then created an offset datum plane. Taking it a step further, I used the expression that controls the cylinder diameter (p0=20)to control the offset distance of the datum (p0/2). That way, if the cylinder changes shape or location, the datums should move with it.
A simpler method would be to create a line through the center of the cylinder's end faces & associatively project the line onto the cylinder's surface. I didn't know if more geometry would be tagged to the line once it is projected.
Hope this makes some sense.
Tim Flater
Senior Designer
Enkei America, Inc.
www.enkei.com
RE: Constraing a sketch line to a cylinders edge
Guy
Guy Edkins
Managing Partner
Delta Group Ltd
www.deltagl.com
RE: Constraing a sketch line to a cylinders edge
1. Select PROJECT GEOMETRY command in sketcher.
2. Make sure the ASSOCIATIVE link is depressed.
3. Select the desired edge of cylinder to reference (Note: More than one edge can be selected).
4. Select OK to create the lines.
5. Turn the projected lines into reference lines using the CONVERT TO/FROM REFERENCE command.
6. Now constrain the sketch object to the referenced
object(s) using the colinear constraint.
By having the associativity turn on when projecting the cylinders edge, it will resize itself if the cylinders diameter changes. Also, other constraint types or new lines can be used with the referenced/projected line(s).
RE: Constraing a sketch line to a cylinders edge
you can create a datum plane tangent to the cyl face by:
create a first datum pl (DP1) thru the cylinder center by clicking the cyl face. then create the tangent datum pl (DP2) by clicking the cyl face, then DP1. use the alternate soln (1-2-3) button to go to quad pt u want. if you need a DP tangent at a non-90 deg angle, create a third plane by clicking on a datum axis thru the center, then DP2, then input an angle.
create the "silhouette" line by using insert - curve op - Intersect. turn on asoociative output. pick the datum plane as "fist set" and then the cyl face as the 'second set".
you can now create a sketch and add geo constraints back to the associative intersection curve.
-rich
RE: Constraing a sketch line to a cylinders edge
Using the datum or face you are positioning your sketch on, create an associative section curve of the cylinder face using the "section curve" function. Use this to create a "colinear" constraint in the sketch.
Mark Benson
CAD Support Engineer