Why is this not fully constrained?

[Hilmi]

Hi,

I am trying to get my head around CAD and I know it is good practice to have everything fully constrained. I created a rectangle by center referenced to the origin, defined height and width and it is orange not black. What am I missing here?

 

[Stu3d]

It probably needs a horizontal or vertical constraint on one of the lines.

 

[Hilmi]

Thanks, that works straight away. Sometimes it's confusing for a beginner to identify why their sketch isn't constrained, especially when self taught.

 

[HaroldL]

When using the Rectangle by Center there are no Horizontal or Vertical constraints applied. That sketch figure only has Perpendicular constraints so you need to apply a Vertical or Horizontal manually. That should be fixed but Development must have had a reason for leaving it this way.

 

[BigKahunaFL]

When using the Rectangle by Center there are no Horizontal or Vertical constraints applied. That sketch figure only has Perpendicular constraints so you need to apply a Vertical or Horizontal manually. That should be fixed but Development must have had a reason for leaving it this way.

I've used "Rectangle bt Center" to create pseudo-diamond-shaped figures:
1. Iinsert the square, dimension it.
2. Insert a reference line corner-to-corner.
3. Apply a vertical/horizontal constraint on the reference line (or an appropriate angle).
Viola!

 

[WillB]

Usually the best way to see what's wrong is to grab a node and try to drag it.

 

[simonb65]

That should be fixed but Development must have had a reason for leaving it this way.

Because not every rectangle or square sits parallel to an axis. You might want to rotate it, so this gives you the option by either adding a horizontal/vertical constraint OR add an angular dimension to an axis. It would be a pain if you had to remove an 'inferred' 'developer assumed' constraint every time you added a sketch figure like this!

 

[HaroldL]

You know there are is another option, Rectangle by Three Corners. Like the rectangle by center it only has Perpendicular constraints applied and can be rotated and an angle dimension applied if needed or add a vertical or horizontal constraint.

It would be a pain if you had to remove an 'inferred' 'developer assumed' constraint every time you added a sketch figure like this!

No more a pain than having to Add a horizontal or vertical constraint every time the feature is used, to me that is more a PITA. When I used CAD programs I don't recall them not constraining the Rectangle by Center with a vertical or horizontal constraint and didn't have you interrupt your workflow to add a constraint. For those times I need a rectangle that is not horizontal or vertical I use the 3-point tool. Seems to me that's why it's available.

 

[DavidJ]

But rectangle by 3 point doesn't have that nice centre point to position it by...

 

[HaroldL]

The center point is a real bonus to position the rectangle. However, since it always gets created horizontal or vertical depending on how you draw it out, I don't recall ever using it at an angle other than horizontal or vertical so I always need to apply a constraint. The majority of sketches that I use the rectangle by center is to locate it on the origin for the initial/base feature or for slots that are centered on a plane and for those there is @Ex Machina's Midpoint constraint method to constrain a regular rectangle. And if a center point is really needed one can be added and constrained using @Ex Machina's method.
Point is that there are many different ways to use the sketch tools in Alibre and I doubt there is only one correct way. It would be nice to hear from Dev on why they opted to create it as they did.

 

[DavidJ]

Point is that there are many different ways to use the sketch tools in Alibre and I doubt there is only one correct way. It would be nice to hear from Dev on why they opted to create it as they did.

Exactly - none of us have a monopoly on being 'correct'. Preferring the rectangle by centre to not be initially fixed horizontal/vertical is just as valid as preferring that it is so fixed. There are pros and cons to both.

 

[stepalibre]

I often use "Rectangle By Center" with an axis line and an angle. For geometry based on a centerline it is essential. There is no other efficient way to rotate a rectangle or square on a point with lines perpendicular or parallel to a centerline axis.

 

[stepalibre]

I often use "Rectangle By Center" with an axis line and an angle. For geometry based on a centerline it is essential. There is no other efficient way to rotate a rectangle or square on a point with lines perpendicular or parallel to a centerline axis.

Adding or deleting a horizontal or vertical constraint is easier than drawing a rec or square by center point from scratch.