Sketch Inversion Problem
I need some ideas on how to make this sketch robust so that it will not invert on me.
I know this has been a long-time problem since the beginning of ProE.
I would have thought this would have been solved by now.
I’m working on creating a UDF for an arc slot.
I also have a different UDF I’m working on for a pattern of these on a bolt circle pattern
On the pattern I had a similar problem if I tried to use the start angle dim as the pattern angle. When I switched to an axis angle, the issue went away.
Here is how my sketch is constructed.
I’m having an issue with the sketch inverting when I exceed a certain dimension on the start angle.
I know this is a bit extreme for the start angle, but I’m trying to exercise the sketch to make sure it works in all cases.
At 126 degrees for the start angle the rounds on the end of the slot invert.
However, if the slot angle is increased at some point, it fixes itself and I can increase the start angle up to 140 degrees, but then it inverts again at 141 degrees.
Any ideas on how to make this work in all cases would be much appreciated.
I've opened a case with PTC....
Dave Haigh
Special Projects for CAD
Office 925-424-3931
Defense Technologies Engineering Division
Working from Home – Part Time ~8-12 hour per week
ACCEPTED SOLUTION
Accepted Solutions
Thanks to all that had suggestion to solve this problem.
Based on the responses, I think I finally have a handle on what is going on.
First, Martin’s solution does work, the only downside is the angle dimensions are not part of the sketch.
Braxton’s sketch also works. I downloaded the sketch and used it in a Creo 10 part.
After re-dimensioning it to give me the dimension I want it worked also.
I went back to my Creo 4 part and redefined the sketch. I removed the two construction lines that define the angles and recreated them.
My initial sketch only had these lines extending to the center of the slot.
See the highlighted comment below. The blue line I added shows where the construction line ends
The modified sketch now looks like this:
The slot now works without inverting.
I prefer this because all the dimensions required for the slot are part of the sketch.
Bottom Line
Here is what I think is happening.
Both solutions presented, controlled both ends of the rounds on the end of the arc.
By extending my construction line to the outside of the slot, I’m now controlling both ends of the rounds.
My initial sketch was only controlling one end of the rounds, leading to inversion of the sketch.
Dave Haigh
Special Projects for CAD
Office 925-424-3931
Defense Technologies Engineering Division
Working from Home – Part Time ~8-12 hour per week
My guess is that not using tangency for the ends allows for the flip that you are seeing. The below sketch behaves well at all angles.
In Creo 9.0.8 I am able to get the inversion even with the tangency explicitly constrained in the sketch. Do not see exactly why it is happening. I am dragging the sketch using the mouse and the inversion occurs. In my sketch above I was not able to induce the inversion using the same method.
Thanks to all that had suggestion to solve this problem.
Based on the responses, I think I finally have a handle on what is going on.
First, Martin’s solution does work, the only downside is the angle dimensions are not part of the sketch.
Braxton’s sketch also works. I downloaded the sketch and used it in a Creo 10 part.
After re-dimensioning it to give me the dimension I want it worked also.
I went back to my Creo 4 part and redefined the sketch. I removed the two construction lines that define the angles and recreated them.
My initial sketch only had these lines extending to the center of the slot.
See the highlighted comment below. The blue line I added shows where the construction line ends
The modified sketch now looks like this:
The slot now works without inverting.
I prefer this because all the dimensions required for the slot are part of the sketch.
Bottom Line
Here is what I think is happening.
Both solutions presented, controlled both ends of the rounds on the end of the arc.
By extending my construction line to the outside of the slot, I’m now controlling both ends of the rounds.
My initial sketch was only controlling one end of the rounds, leading to inversion of the sketch.
Dave Haigh
Special Projects for CAD
Office 925-424-3931
Defense Technologies Engineering Division
Working from Home – Part Time ~8-12 hour per week
