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Why does my sketch go from constrained to over-defined when removing a sketch component?

jacob_sheffieldjacob_sheffield Member Posts: 9 EDU
edited April 9 in Using Onshape
Why does my sketch become go from a constrained state to over-defined (or unsolvable) when removing a sketch entity such as a line or removing a certain constraint? Unlike adding more constraints which will over-define it, we would removing a line or constraint produce an error? I've also found that adding a line (even a driven construction line) will sometimes create an error despite not adding any constraints to my knowledge. I've found that I run into this more when the sketch becomes messy with mirrored vertices and lines, but not sure if this is correlated.It seems like I'm getting an over-defined sketch when I shouldn't. I'm can't see how these changes should have any effect on making the sketch over-defined.

This example shows how my sketch goes from constrained to over-defined when all I do is remove a coincident constraint


This example shows how it produces an error when all i do is add an arced line (without adding a tangent constraint or anything)


Another simpler example adding a simple straight line causing an error


This error is produced when I delete an arced line.


In addition, when the sketch becomes overdefined for whatever reason, everything becomes red and you no longer distinguish between the a referenced constraint (blue) and normal (white). Is there anyway to help determine which constraint needs to be deleted or fixed besides your own intuition?   

Answers

  • mlaflecheCADmlaflecheCAD Onshape Employees, Developers Posts: 106
    @jacob_sheffield thanks for raising this.  The only funny thing I see is the arc length dimension of the slot which is not used as often as other constraints in my experience, which lends credence to the deletion of the arc fixing everything.  The best thing to do would be to open a proper support ticket in the help menu so we can look at the conditions causing the error more closely and provide more advice.  
    Regards,
    Mike LaFleche   @mlaflecheCAD
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