topic Re: Inverted Chamfer in Inventor Forum

Inverted Chamfer

andrewdroth — Wed, 05 Feb 2020 21:38:13 GMT

I know better than to try and add a chamfer to a fully constrained sketch (or to sketch at all), but sometimes I like to play fast and loose.

Bad modeling practices aside, what's going on when applying this chamfer? Obviously the constraints I've applied confuse the feature.

Re: Inverted Chamfer

Curtis_W — Wed, 05 Feb 2020 22:06:13 GMT

Hi @andrewdroth ,

This has come up before... it has to do with the sketch constraint (often on a midpoint) trying to maintain itself.

if you open the attached 2020 file and place a 2 mm chamfer on the circled corner you will see that the constraint on the midpoint of the 1 cm line attempts to hold it's position, and does so by lengthening the line. If you undo and then chamfer the other end of that line it guesses correct and shortens the line.

I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com

Re: Inverted Chamfer

johnsonshiue — Thu, 06 Feb 2020 00:36:06 GMT

Hi Curtis and Andrew,

This is new to me. I took a quick look at the part Curtis shared. Indeed, I do think it is about the mid point constraint. This symmetric-like constraint can force the sketch to behave unintuitively when there is topological change. I think it is a combination of the mid point constraint and the vertical dimension causing the problem. The wacky solution is still mathematically correct but violating design intent. I can follow up with the project team but I don't anticipate a quick fix. It looks like a limitation for now.

Many thanks!

Re: Inverted Chamfer

karthur1 — Thu, 06 Feb 2020 12:47:36 GMT

@andrewdroth wrote:

I know better than to try and add a chamfer to a fully constrained sketch (or to sketch at all), but sometimes I like to play fast and loose.

Bad modeling practices aside, what's going on when applying this chamfer? Obviously the constraints I've applied confuse the feature.

I get what you are trying to do.... but the next guy that comes along would want it flipped that way instead of a chamfering the corner. Best practice would be to model it square and then add the chamfer as a feature. Makes dimensioning easier downstream as well.

Re: Inverted Chamfer

JDMather — Thu, 06 Feb 2020 13:01:17 GMT

Not sure if this is 100% reproducible.

I got behavior that was the opposite of what I expected.

Re: Inverted Chamfer

andrewdroth — Thu, 06 Feb 2020 14:59:34 GMT

@JDMather That's exactly how I had it dimensioned. Edge to Edge rather than the line itself.