Refence lines between sketches

[davidmrosner]

I have a sketch that has construction lines defined that i want to reference in another sketch. I have been trying to use project to copy the line from one sketch to another and have done this before successfully. For some reason in this situation when I select the target sketch and edit it the other sketches in my model go away so I can't select the line i'm looking to project (i.e. copy to the second sketch).

In the picture you can see the construction line i'm looking to "copy" or project from Sketch2 to Sketch 1. When I edit Sketch1 then Sketch2 will disappear so I can't select this line. I did a similar operation in my model from Sketch1(1) to Sketch2 and it worked so what is different about this operation? The line in question was projected from Sketch1(1) is that the problem?

 

[TheCADWhisperer]

@davidmrosner 

Would you like simple step-by-step instructions on how to do this correctly?

[davidmrosner]

Sure!

But at the same time i'm interested in why I can do from one sketch but not another which will probably uncover some feature or behavior of Fusion i haven't picked up yet....

[TheCADWhisperer]

Fusion is a history-based modeler.

You can easily use this as a "time-machine" to your advantage once you master a few rules.

Think of this as the classical Hollywood movie on issues encountered when going back in time.

Logically you cannot exist before your parents existed, but with a time-machine this might be possible and powerful, but you have to be careful when exercising great power.

My instructions will follow - and I must warn you will be very basic and start over from the beginning step-by-step.

[TheCADWhisperer]

Start a new design.

Create a new component in the design.

Make the new component active and start a new sketch in the design.

Sketch a Rectangle with the lower left corner at the Origin.

What color are the lines?

[TheCADWhisperer]

Now add the two dimensions to the sketch as shown.

What do you observe about the color of the lines of the rectangle after adding the dimensions.

Note the red Lock symbol on Sketch1 in the browser.

[davidmrosner]

yep i'm with you...fully defined/constrained sketch

[TheCADWhisperer]

@davidmrosner 

Now sketch a second rectangle within the first rectangle and dimension as shown below.

File>Export and then Attach your new *.f3d file here for next set of steps.

[davidmrosner]

attached.

[TheCADWhisperer]

@davidmrosner 

Now create a Construction Line Rectangle as you did before (you can toggle linetype using the x key on the keyboard).

Be careful to NOT click on the midpoints of the vertical lines when creating the construction rectangle.

Note the colors of the construction lines.

Add the two missing dimensions.

What do you note about the color of the Construction Lines after dimensioning their position?

Attach the file here for next set of instructions.

[davidmrosner]

the construction lines became fully defined so they turned black...

[TheCADWhisperer]

I am eating lunch as I type these instructions - so my responses might be a little slow.

I think you are getting the idea now that I generally Fully Define each and every bit of sketch geometry as I create it (in most cases) rather than waiting till later. (it is easy to edit the dimensions if I am not yet sure)

Next set of steps to follow.

The process I use is often referred to as the BORN Technique where = Base Orphan Reference Node.

[TheCADWhisperer]

@davidmrosner 

I forgot to mention earlier that I turn OFF the Snap to Grid.

I don't count grid spacing and guestimate - I enter exact Dimensions. (they can easily be edited later)

[davidmrosner]

Appreciate the help! So I get the point that as a best practice I should be fully defining my Sketches as I create them and my current model I still have some constraints to add to get there.

How does that impact the projection i'm trying to do?

I now see what you mean by the timeline and it just hit me....when I edit the sketch the other sketches go away because i'm going back in timeline when I edit that sketch. So do / can I move the timeline around so I can update the earliest sketch with elements from later defined sketches?

[TheCADWhisperer]

@davidmrosner 

Now is where it starts to get interesting.

I very rarely repeat ANY dimensions unless I anticipate that I might not want them equal as I edit the design...

Sketch and dimension the two rectangles as shown in blue.  

Make a vertical line of the left rectangle Equal (=) constraint to a vertical line of the right rectangle.

Make a horizontal line of the left rectangle Equal Constraint to a horizontal line of the right rectangle.

Add a Colinear Constraint between the two bottom horizontal lines of the two rectangles.

If you drag them around in space they should stay the same size and lined up with each other.

Now dimension the location of one of the rectangles.

Everything should turn black (fully defined).

Attach the progress file here.

[TheCADWhisperer]

---

@davidmrosner wrote:

. So do / can I move the timeline around so I can update the earliest sketch with elements from later defined sketches?

---

We will get there.

When robust modeling techniques are used you can often go to the Timeline and Drag and Drop Sketch3 in history to before Sketch1. But you have to be aware of parent/child relationships.

Edit:  BTW your observations of the Timeline behavior is a good sign of your observation skills.

Many users hack around without observing these behaviors.

[davidmrosner]

attached

[TheCADWhisperer]

@davidmrosner 

Click Finish Sketch.

Make sure the component is still active.

Start a New Sketch on the XY plane.

Sketch an unconstrained rectangle in Sketch2.

Finish Sketch.

Click hold drag Sketch2 in the Timeline to occur in history before Sketch1.

Edit Sketch2.

Observe that Sketch1 disappears because it now occurs in history after Sketch2.

[TheCADWhisperer]

Finish Sketch and drag Sketch2 to after Sketch1 in the Timeline.

Edit Sketch2...

Project a line from Sketch1 into Sketch2.

We have now created a parent/child relationship.

The Projected line is a child feature of the line in Sketch1.

Finish Sketch.

Now try to drag Sketch2 in history to before Sketch1.

You will find that you cannot move it earlier because of the dependency.

This might seem very limiting, but as you get more experience you will use parent/child history relationships to your advantage, but in general you should probably avoid these dependencies by using only the Origin as BASE reference.

[davidmrosner]

ok that was super helpful in a few different ways....so the fully defined vs. not sketches though had nothing to do with the projection i was originally trying to do right? it was the timeline behavior that explains it.

That said....is the point of this exercise that while its possible to use projected construction lines to line up objects on different sketches its not the best way to go about it? Instead i should be fully defining every sketch and each sketch should share a common origin and reference off of that? In my case if i did that I wouldn't need the projection in the first place.

Am i interpreting the exercise and its outcome as expected?

I often have sketches that are perpendicular to each other like angle brackets etc. - so aligning the lines/rectangles/etc on each plane is always a need. Seems like projecting construction lines would be easier and creates the parent child relationship I want in case i move stuff in one plane. 

I've added the second perpendicular plane in the model we've been creating and created a rectangle that I want to be aligned with the 2 rectangles from Sketch1. What is best practice to make that happen so if in future i change dimensions in Sketch1 then it reflects in Sketch2?