Sketch flipping when going more than 180 degrees

[mslosar]

Here's the situation:

I have a tube, approximately 16" O.D., 14" high, and 1/8" thick. This is all a single part.

I'm trying to cut 3.5" wide and 4" tall slots around the top. The number of slots can be 1-6.

I'm driving the size and slots from a spreadsheet.

The orientation of the slots can have the first slot anywhere from 0 to 360 degrees. (FWIW, the spreadsheet redefines 0 and .0001 and 360 and 359.99).

Anyhow, as long as the first slot is between 0-180, it works just great. Once you pass 180, however, the verticals of the sketch flip so it's barely cutting the notch at all.

To make the cuts i've created a sketch off the top of the cylinder and drawn a construction line at 0 and another and put a driven dimension between them to set the correct position of the angle. I think create a workplane off that line tanget it to it's end point. At that point, draw sketch, extrude, etc.

I've also create a workplan off one of the origin planes and the origin Y axis that's perpendicular to the notch (angle driven by spreadsheet and equation in workplanes angle offset). Offset a 2nd plane tangent to the O.D. of the tube, created a sketch, extrude etc.

In both instances, when the angle crosses 180 degrees, the sketch flips on me.

What can I do to keep the sketch from flipping?

[mslosar]

This is odd...

Turns out, it's not so much when it crosses 180 as I thought. It's ONLY at 210 degrees. Now, i haven't tried the other 359 degrees, but i've tried about 30 of them and it works everywhere but there.

I can't figure out why 210 though.

My original tube had a rip in it at 30 degrees. 180 from there is 210 is all I can come up with.

As I said i drew a sketch off the top of the tube to get my movable axis. I drew a circle around the tip and and projected the tube's OD. The did an offset dimension of like 1" between the two.

I've since changed the rip point and it worked everywhere i tried - except 210 still.

30, 120, 300, 209, 211, 350, 35, and numerous other angles work just fine.

I'd have thought that if this was a 0-180 thing where it doesn't really see it as an angle, i'd have the same problem at 30 degrees. Nope. Works fine at 30 and wherever I set the start point to. The sketch flips, though, at 210 degrees and seemingly 210 only.

Now, i've gotten around this in excel using a formula like If(ang=210, 210.0001,ang) so if it occurs it tags a ten thousandth of an inch.

I'd still like to know what exactly is causing this.

[salariua]

Found anything on this yet?

It's dirving me crazy that the sketch entities flip when I drive the orientation of the sketch via parameters.

How can I force the sketch entities in one direction? Can't use vertical horizontal because I I change the position with driving angle?

[Anonymous]

Have you found any solutions?

I have somewhat the same problem. My sketch flips 180 degrees, when the work plane it is defined on is rotated near 0 degrees. If the WP is rotated at any other angle i experience no problems at all.

Sad fact is that the angle defines how open the cabinet I'm drawing is, and i need to be able to close it (0 degrees)