Newbie, creating a section of curved plate.

[joepesterey]

Hello, I am trying to create a drawing of a curved plate with an inside diameter of 7000mm and a thickness of 12mm. 

I lay out two circles and construction draw the required cord. I then proceed to draw the ends; my problem is the lines from the inner circle will not exactly snap to the outer circle, hence I cannot isolate the section for trimming. 

I have read all the solutions proposed by the faqs and made the suggested changes but the same problem manifests itself.

The casting end of the drawn line from the inside radius refuses to snap to the outside circle.

Thank you for your help.

[hamid.sh.]

Could you please share your file (export to *.f3d) and attach here?

[jeff_strater]

weird.  It works for me:

sample model is attached.

[joepesterey]

Thanks for your reply Hamid, maybe it's the way I have approached the
design. When I try to link I can see the box or the x mark, but the line
never ends up on the radius. The line seems to want to attach itself to the
grid lines and not the actual radius itself.
I have tried entering the distance ie;12mm, it either overshoots or
undershoots, unlucky for me, never on the line.
Thank you for your time.
Kind Regards
Joe

[hamid.sh.]

Are you sure it's not really on the line? Because I guess it's just a graphic thing (especially because diameter and line length are orders of magnitude different). You check if a closed profile (darker blue) is formed by the two arcs and two lines:

You can also be sure of coincidence between line end and arc by checking Coincident icon (it appears after you select line's end point). Also see this screencast in which I show above points. In it line seems not snapping on the arc but in fact it does.

[etfrench]

Do you have Snap to Grid turned off?

If you have Layout Grid enabled, I would also turn that off.

[etfrench]

You could try creating the lines in a different order as in the screencast.

Another way to ensure the endpoints are coincident with the outer circle is to extend them past the circle (draw a line outside the circle to extend them to) then trim the lines back to the outer circle.

[jeff_strater · Accepted solution]

"I have tried entering the distance ie;12mm, it either overshoots or undershoots"

That is likely the source of the problem.  Do not try to create those lines by specifying the length of the lines.  That will force the line length, and may not pick up the coincident constraint to the other circle.  Look for the "X" inference, which indicates snapping to the outer line:

The fact that you get the white dot is indicative of not having made that connection.  See the screencast:

[joepesterey]

Yes,

[joepesterey]

Thank you for your help. It's good to know that the platform has lots of support and therefore is worth investing in. They say men are unable to multitask, but that's not true. I took some time away from the project and had an idea. I made two concentric circles and created a vertical construction line, a center-constrained rectangle with one dimension being the cord. I pushed it up to the inner arc to create the connection between the two circles. I only partially cast the line and then I used the extend command and realised that wysiwyg is not necessarily true. At full zoom the line shot past the radius drawn. I was able to select the part I wanted. What Hamid said is the answer; you have to look for the connection sign, not necessarily what the screen shows you. Thanks for all your help.

[etfrench]

If you will be making this from flat plate, your method won't give  you 90 degree sides.  Instead of drawing a rectangle, draw two lines from the center of the circle to the outer circle.  Dimension the distance between the end points to the chord length. Draw a construction line vertically from the center to the circle.  Set the angles between the center line and the other lines equal to each other.  Offset the outer circle 12mm towards the center.  Extrude the profile.  When this is converted to sheet metal you'll find the angle of the sides to the top is 90 degrees.