DI - shortening ARC

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Krischu
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DI - shortening ARC

Post by Krischu » Tue Sep 17, 2019 2:02 pm

Bildschirmfoto 2019-09-17 um 14.57.01.png
Bildschirmfoto 2019-09-17 um 14.57.01.png (77.02 KiB) Viewed 6216 times
The red piece is an arc( cut off of a circle). The green pieces are radii, broken out by using D2.

Now I want to shorten the total length of the arc to 2.8 with the green line pieces following the endpoints of that arc.

How does the DI (DIVIDE) protocol exactly work? shortening the arc piece shortens it one sided only. So I have to split in in halves and shorten the single halves?

How do I make follow the green pieces the endpoints of the arc?
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Krischu
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Re: DI - shortening ARC

Post by Krischu » Tue Sep 17, 2019 3:08 pm

Bildschirmfoto 2019-09-17 um 16.01.13.png
Bildschirmfoto 2019-09-17 um 16.01.13.png (84.47 KiB) Viewed 6214 times
I got a bit further. Somehow I managed to DI the arc. Is it correct to select the entity (arc) and then choose DI?
Still not clear to me how to specify the entity that does the division. A point? A line?

Anyway, I divided, deleted the right segment of the arc, then shortened the left one (using the properties dialog), then mirrored the left and now it's looking like in the above screenshot.

Now, how do I snap the green lines to the arc endpoints of the red arc? The line pieces should stay with one point anchored at the circle ends (white circle) .
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Husky
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Re: DI - shortening ARC

Post by Husky » Tue Sep 17, 2019 7:07 pm

Krischu wrote:
Tue Sep 17, 2019 3:08 pm
Is it correct to select the entity (arc) and then choose DI?
DI doesn't needs a previously selection. Just launch DI, select the entity which has do be divided and watch the mouse pointer - it will partly change to a dash dash point line which indicates the divide (or cut) position. That is as usual snap sensitive.

Husky-2019.09.17-01.png
Husky-2019.09.17-01.png (22.19 KiB) Viewed 6205 times

Krischu wrote:
Tue Sep 17, 2019 3:08 pm
Now, how do I snap the green lines to the arc endpoints of the red arc? The line pieces should stay with one point anchored at the circle ends (white circle) .
If I understand the task correctly then I would use the rotate tool for the green lines and then trim the white lines to merge again with the green lines. The Center point for the rotation is the center of the red arc.
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Husky
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Re: DI - shortening ARC

Post by Husky » Tue Sep 17, 2019 7:26 pm

Krischu wrote:
Tue Sep 17, 2019 2:02 pm
Now I want to shorten the total length of the arc to 2.8 with the green line pieces following the endpoints of that arc.
Should 2.8 be the length or the cord of that arc? Can you attache an example dxf of this situation?
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CVH
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Re: DI - shortening ARC

Post by CVH » Thu Sep 19, 2019 7:49 am

The greens are radii with a center.
Here appropriate 'moving' is to rotate.

You can select the uncut red and enter a new sweep angle or arc length in PropEdit.
Or, you can reduce/enlarge this arc in any way that suites your needs.
Symmetrically as your solution or not.
To alter the actual chord of the arc you need some contruction lines.
Cutting up the red might only serve something if you really need two co-radial arcs.

You'll end up with gaps or crossings as yours.
Done asymmetrical firts rotate your red by mouse around the center as you would like it.
Mid straight up in your case.
Now rotate the greens by mouse around the center so you rejoin them with the ends of the red.
The larger diam. is simply trimmed to the greens.

All that rotating requires lots off clicks.
Sometimes it may be easier to simply redraw new radii and trim them.

Regards,
CVH

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Krischu
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Re: DI - shortening ARC

Post by Krischu » Thu Sep 19, 2019 10:12 am

Husky wrote:
Tue Sep 17, 2019 7:26 pm
Krischu wrote:
Tue Sep 17, 2019 2:02 pm
Now I want to shorten the total length of the arc to 2.8 with the green line pieces following the endpoints of that arc.
Should 2.8 be the length or the cord of that arc? Can you attache an example dxf of this situation?
Despite of the fact that it was easiest to just delete the green lines and draw two new lines letting them snap to the endpoints, I'm passing the dxf anyway, maybe to learn a quicker way. Something like having the red point as center of rotation, grab the white line at the yellow endpoint let it snap to the magenta endpoint of the arc.
Bildschirmfoto 2019-09-19 um 11.10.54.png
Bildschirmfoto 2019-09-19 um 11.10.54.png (102.1 KiB) Viewed 6162 times
The green lines are the desired result.

(N.B. in my example it wasn't that important whether it was the cord length or the arc length I wanted to reduce - it was neglectable in that case)
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chassis_bracket_experiment.dxf
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CVH
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Re: DI - shortening ARC

Post by CVH » Thu Sep 19, 2019 11:47 am

Pls follow layer state setting mentioned in the drawing.
Regards,
CVH

PS
This makes a slot 2.8 wide.
The arc is not 2.8 long!
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chassis_bracket_experiment.rev.dxf
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Krischu
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Re: DI - shortening ARC

Post by Krischu » Thu Sep 19, 2019 4:33 pm

I believe, I did not make clear enough, that the initial green pieces were not going to be radii pieces again.
They simply were intended to connect to the shortened arc ends.

But thanks anyway for the detailed work out.
Bildschirmfoto 2019-09-19 um 17.51.39.png
Bildschirmfoto 2019-09-19 um 17.51.39.png (11.52 KiB) Viewed 6138 times
Last edited by Krischu on Thu Sep 19, 2019 4:52 pm, edited 1 time in total.
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Christoph

CVH
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Re: DI - shortening ARC

Post by CVH » Thu Sep 19, 2019 4:38 pm

Click them
Pick the end marker
Tow

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Krischu
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Re: DI - shortening ARC

Post by Krischu » Thu Sep 19, 2019 4:55 pm

CVH wrote:
Thu Sep 19, 2019 4:38 pm
Click them
Pick the end marker
Tow
Thanks. That's exactly what I wanted to know. And where can read about the markers and their meaning? How to swap the meaning of the markers? What is the red and what the blue marker?
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Husky
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Re: DI - shortening ARC

Post by Husky » Thu Sep 19, 2019 6:45 pm

Krischu wrote:
Thu Sep 19, 2019 4:55 pm
And where can read about the markers and their meaning?
I read it in the QCAD Book ... e_surprised
Krischu wrote:
Thu Sep 19, 2019 4:55 pm
How to swap the meaning of the markers?
With the Reverse (RV) tool. But that is pretty irrelevant for CAD. If the drawing is meant for further CAM processing then we have a different story ... :wink:

Krischu wrote:
Thu Sep 19, 2019 4:55 pm
What is the red and what the blue marker?
Red = start, blue = end of the entity
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