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I don't understand why I can't use the tangent constraint in Sketch 2 in the attached part file.

voxelman

voxelman

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2026-01-05_140519.jpg

In sketch2 shown above I am unable to use the tangent constraint to connect disconnected straight line to the adjacent circular curves. I don't see any constraints on the straight line but I get the following error.

1767644004601.png
 
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Are you clicking on the curve first then the line. The message you see is probably because you did it the other way around and it's trying to move the circle to the line rather than what you actually want!
 
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Simon ,
Thank you for your speedy reply.
No, I am aware of the selection precedence. After leaving this post, being desperate, I used the sketch Move function and copied the sketch to an adjacent position.
This removed all of the constraints from the drawing. I deleted the original and moved the copy back to the original location. I reapplied the locks to the curved lines and then the tangent constraint worked as I expected. I don't know if this is a bug or feature but it seemed that Alibre thought that the straight line segment was constrained in some way.
 
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I've noticed that when using the select tool to move a newly drawn line segment the movement is constrained to positions parallel to the line segment. This seems strange. Why is a newly drawn line segment (in a new part) constrained in this way? Shouldn't it be possible to move the line segment freely in any direction while it retains its orientation?
 
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As far as I know the only snap setting that I have turned on is snap to working plane. It isn't clear to me which of the constraint inferencing settings would control this behaviour. I've turned them all off and this behaviour remains the same so it must be a design decision that determines how the select tool works with line segments.
 
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I duplicated your sketch as close as possible and found that If I deleted the Lock constraint on the circle I am then able to apply a tangent constraint on the line to both the upper circle and the arc of the slot sketch.

Give that a try and see if it helps you. You should be able to apply a dimension to the circle sketches instead of the Lock and still be able apply tangents to the slanted line figure.

I think the Lock may be doing something to the constrain solver that precludes applying any other constraints.
 
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Thank you for taking the time to look into this and the suggestion Harold. I've solved the problem for now but I will keep your suggestion in mind for the next time I run into quirky Alibre behaviour. Sometimes it just seems to have a mind of its own.;)
 
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I've noticed that trimming the middle of a line away (leaving 2 separate lines) can result in invisible constraints existing between the remaining line sections. There may be something similar that happens in another workflow.
 
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