topic Unable to draw rectangles when using geometry to constrain in Fusion Support Forum

Unable to draw rectangles when using geometry to constrain

alex_biggsPZU7J — Wed, 17 Sep 2025 19:26:26 GMT

I am trying to draw rectangles on a part in fusion where I use the edge of the part as the edge of the rectangle, however, every time I try and draw it the rectangle dissapears when I hover over the edge and I am not able to place it. This is not only on this face but every face on this design. I have tried restarting but it has not helped.

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Re: Unable to draw rectangles when using geometry to constrain

TheCADWhisperer — Wed, 17 Sep 2025 19:31:50 GMT

@alex_biggsPZU7J

Can you File>Export your *.f3d file to your local drive and then Attach it here to a Reply?

I noticed several beginner mistakes in your technique.

One of the experts here will create a video on robust/predictable techniques using your actual design.

Re: Unable to draw rectangles when using geometry to constrain

jeff_strater — Wed, 17 Sep 2025 20:44:58 GMT

I've seen a handful of these over the years - essentially something in the constraint set is causing the rectangle to collapse, and become degenerate. As @TheCADWhisperer said, having your design is the only way to really provide an answer. But, one thing to try: If you create the rectangle so that it is not coincident, then later add a coincident constraint between these two points, does it still collapse?

Re: Unable to draw rectangles when using geometry to constrain

alex_biggsPZU7J — Thu, 18 Sep 2025 12:05:19 GMT

I cant attach the file, but to get around this I have been using the coincident constraint to size the rectangle to the proper size. It does not collapse if I draw a line and then make the rectangle coincident.

Re: Unable to draw rectangles when using geometry to constrain

alex_biggsPZU7J — Thu, 18 Sep 2025 12:05:53 GMT

I cannot attach my file as a fusion file here, but I am curious what sort of beginner mistakes in my technique am I making?

Re: Unable to draw rectangles when using geometry to constrain

TheCADWhisperer — Thu, 18 Sep 2025 16:21:25 GMT

@alex_biggsPZU7J

If you cannot attach this particular file here because of proprietary data - attach any file that does not include proprietary data.

Any file you create will demonstrate your modeling techniques and one of the experts here can demonstrate how to improve your techniques.

I refer to your current techniques as "building a house of cards on a foundation of quicksand". Not robust and the only thing predictable is you will experience unexpected behavior. You want totally robust and predictable behavior in Fusion.

Re: Unable to draw rectangles when using geometry to constrain

alex_biggsPZU7J — Thu, 18 Sep 2025 17:15:15 GMT

The way I am using fusion is very proprietary. I am not building model in fusion, instead I am taking pre-existing step files from different software, importing them and making minor geometry changes to the file to then be used in an analysis. Thank you for the feedback on the technique, I am not sure how I would change much of the modelling methods, as for the most part is involved drawing and then extruding and or lofting rectangles on various surfaces. I was able to solve this issue by just creating an offset plane and doing my drawing and sketches on the plane instead of directly on the surface.

Re: Unable to draw rectangles when using geometry to constrain

TheCADWhisperer — Thu, 18 Sep 2025 17:29:43 GMT

@alex_biggsPZU7J

I would not mark as solved as you haven't solved your issue.

I am very familiar with using STEP file and imported geometry from any source.

You are not using the geometry correctly.