Another Newbie Center-Alignment Question

[jdsilver]

Hello. I'm brand new to Fusion. I'm used to drawing shapes in Adobe products and cetering them using some pre-set alignment buttons. I can't seem to do the same in Fusion 360 when sketching.

I am trying to draw a trapezoid and center it to a circle. I do not know the angles of the trapezoid, but I do know the lengths of each of the horizontal lines. I also want these lines to be on the same center line as the circle. Is there a way to do this?

I've tried constraints. I've tried the construct line (which I found in another post). I just can't get it to work the way I want/ I can't even get the shape to be a proper trapezoid without it flailing around. This is such a simple task, yet I'm a confused newb. Thank you in advance!

[TrippyLighting]

You should really watch some of the video tutorials in the learning section because they cover how to sketch with Fusion 360 and how to work with constraints. Of course they do not exactly cover how to tackle your particular problem, but after watching the tutorials you have the necessary basics so we can have a more productive conversation. 

[jdsilver]

Thanks, yes. I've watched about 7 videos already. And like you've said, none of them really cover my question.

[davebYYPCU · Accepted solution]

I had a quick fiddle with your sketch as presented, there are about 3 solutions depending on your desired end result,

From where your screen shot is now, lock the shape, making the top and bottom lines parallel, and the other line perpendicular to the parallel ones, keep their dimensions,

do you want the top line coincident with the vertical centre line?

Do you want the vertical line coincident with the horizontal centre line?

I am new but the way I did it

If so I put a sketch point on the mid point of those two lines and make them coincident, to the centre lines.  Results with your trapizoid being moved down and across.

But, If you also want that mid point of the 45mm line coincident with the vertical centre line, it (c/L) will have to be extended down through the circle, then make it (mid point - 45mm line) coincident with that lower part of the centre line, it worked for me,

but had to remove horizontal and vertical constraints to the three orthagonal lines first.

[TrippyLighting]

The reason why I suggested for you to watch the videos is so you can get your head around how to constrain sketch elements properly, so I woukld not have to explain basics that are covere there.

You just have to give yourself some time for learning and failure.

The rhomboid shape over the circle is not constrained enough, which is why it "flies"all over the pace. How to best constraint is really depends on your design intention.

I personally would constrain one of the horizontal lines with the horizontal/vertial constraint.

Then you can use a parallel constraint between the top horizontal line and the bottom horizontal line.

Use a perpendicularily constraint to constrain the vertical line to one of the horizontal lines. I'd use the top line as that seems to be your reference element.

That's another tip that I'd have. Think about what are the reference points and elements in your sketch and use those to constain against and dimension from.

Then you already have a midpoint constrint from the top horizontal line to the center of the circle and perpendicularity constrinaint to the vertical construction line to the top.

So, now if you stretch the top horizontal line by just picking an end point of the line and draggin it, then the top horzotal line should stretch equally to the left and right of that circle.

Of course you'll beed one morre constrint so the angled line will not change the angle while you chenge the size of the shape.

[jdsilver]

Thanks! Doing a sketch point in the middle of the line helped! I didn't realize you needed to put a point in the middles of lines to mark a midpoint in Fusion.

[TrippyLighting]

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@jdsilver wrote:
I didn't realize you needed to put a point in the middles of lines to mark a midpoint in Fusion.

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You don't have to do that! There is a midpoint constraint that works on lines as well.

[davebYYPCU]

I haven't been able to reliably use the midpoint constraint to do what I want, so putting the sketch point on helps me a lot, 'cause I do a fair bit of lofting, and rails and sketches use the sketch point so much easier.  Project - Include, etc.

There is always more than one way to get it done, I haven't taught myself how to get that midpoint constraint to work yet, to be honest.

cheers

[TrippyLighting]

Yes, that constraint only works within the same sketch.