How do I split/break/trim a spline?

[mab]

Hello,

A newbie here.

I am designing a figure to cut it with a laser. Take the below image as an example. As you can see the spline and circle are tangent (or at least, they are visually tangent). But if I give this to the laser machine, it will cut and separate the circle from the spline and fall off. I would like to make a "bridge" by removing the tangent points so the laser doesn't pass through that zone. The green square is what I would like to remove:



It uses different basic geometric shapes and also splines. I know how to split/break/trim a line that intersects with other line by going to Modify > Break out Segment and clicking on the segment that I want to remove:



But if I try the same for splines, it doesn't work:


In this case, it says: "Entity is not a line, arc, circle or ellipse.".

So, my question is, is there some way to achieve what I want in QCad?

Thank you!

[CVH]

hi,
Break out Segment (D2) works with splines (... in PRO)

If Qcad fails to find the segment or so ...
I have the habit of drawing fast two lines ...
From here ... to there.

If its handier to modify them seperate than I'll do so.

Regards.
CVH

[mab]

hi,
Break out Segment (D2) works with splines (... in PRO)

If Qcad fails to find the segment or so ...
I have the habit of drawing fast two lines ...
From here ... to there.

If its handier to modify them seperate than I'll do so.

Regards.
CVH

@CVH, could you elaborate a little bit on that, please? For example, what do you mean by "drawing fast two lines from here to there"?

[CVH]

See Attached drawing.

Depending the visibility of the layers.
One can cut/break out (D2) a segment from shape1 or shape2 independently between the 'cutter' lines.
Fast = V type => If exact doesn't matter.
Neat = squared => 2 Proper spaced orthogonal parallel lines. (to add roundings or so)

A temporary layer is quickly added and deleted.
An entity to cut/break is quickly swapped to a temporary layer.

- You did mention 'touching' ... the cutout of the touching point is zero long.
serves nothing to make a bridge zero long.
An equal distance from a single cutpoint is a circle as cutter.
- Breaking fit point types splines results in control points types (A math thing)
and it alters the spline(s) a minute bit.

This is only necessary when all fails.
With these shapes you simply choose for screen based linetypes, zoom in and breakout twice.

Regards,
CVH

[CVH]

It uses different basic geometric shapes and also splines. I know how to split/break/trim a line that intersects with other line by going to Modify > Break out Segment and clicking on the segment that I want to remove:

You should use trim there.
Or test your drawings on zero-length entities what can occur with D2 on single-ended.

Regards,
CVH

[mab]

Sorry, I understand how the cutters can work for square and lines, but how do the method of cutters and layers work with splines? I mean, what are the ordered steps.

- Breaking control fit point types splines results in control points types (A math thing)
and it alters the spline(s) a minute bit.

Good catch! I didn't thought on that.

With these shapes you simply choose for screen based linetypes, zoom in and breakout twice.

What are "screen based linetypes"?

Also, all of this is because I need to do it with the free version of QCad. As you said at the beginning of the thread, trimming a spline is possible in the PRO version, isn't it?

[CVH]

Well,
I threw the 'PRO' in regarding it was your first post and a post in the 'QCAD Professional Version' & 'How do I' forum.
At the top of this page the Forum Rules are displayed.
We can't know that you are PRO / Trial or CE ....
I'll mark this topic to be moved.
It may get moved to the 'QCAD Community Edition' forum.

Not PRO ... Then you should not have fitpoints type splines functionality.
https://qcad.org/en/documentation/features
Nor a lot of spline functionalities.

First:
-Do you see two fitpoint splines in the file? (shape1 & 2)
-Do you see the Layer List? Else Menu .. View .. Layer List or simply type GY
If so:
Hide layer 'Cutter' (the red one).
Hide layer1.
Zoom in on the spline segment inside the magenta rectangle what was freely drew as 'Cutter2'
Type D2 (Break out Segment), look at the options bar (left high) and set option 'remove segment'
Now point to the segment inside the rectangle and click.
Normally QCAD will break out a segment near your pointer and between two intersections.
I made those intersections pretty obvious.

If it fails to break out the spline segment from one side to the other ...
Delete my fitpoint spline an draw a new one.
As CE user that can only be a control point type.
Repeat the breakout trial.

If that fails you have two options:
Become PRO or convert (Explode (XP)) the spline to a polyline.
A functionality that is marked as PRO but not that long ago a CE user could do that.
How good the polyline will match the spline depends on settings in the Application Preferences.
Type Ctrl+, (Hold control and type 'comma') .. Modify .. Explode
The smaller the absolute tolerance, the more 'arc-segments' are used for the polyline.
And clear the option poly with line-segments.

What are "screen based linetypes"?

QCAD will render your lines with there lineweights.
These can become very thick while zooming in.
There are more solutions: screen based, draft ... alter weights.

ScreenBased.png (19.3 KiB) Viewed 19618 times

Regards,
CVH

[Husky]

Topic moved to "QCAD Community Edition"

[CVH]

Thanks, Husky
Regards,
CVH

[mab]

Sorry, I didn't see that I was posting in the PRO forum. Will be more careful the next time.

About the steps you described: I'm not sure if we are understanding each other. As far as I can see, "Cutter" (red) is a line and "Cutter2" (pink) is a polyline, but any of them are splines which is what I want to know if is possible to split in QCad Community. With your example, I can split the red figure by using D2 shortcut. But actually it is a line and not a spline and, therefore, not what I am looking for.

I hope I am explaining myself well.

[CVH]

You are not seeing the splines I presume.
Was reading up on it and CE doesn't display controlpoint splines it seems.

Send me the example file of the firts picture.
Regards,
CVH

[mab]

White = spline
Orange = arc
Green = line

I want to remove the little piece of white spline that is between the two green lines.
The purpose is to connect the inner black content of the spline (which is a closed shape) with the inner black content of the arc (which is also a closed shape).

[CVH]

With cutter lines ...
As PRO ...
Simply D2.
CVH

[mab]

Ok, good to know. For the moment, I'm working on a small project and QCad Community is enough for me. I would like to say that I'm very happy with the software, it's so easy to use and has a lot of features! And can imagine that working with PRO must be a delight. This product is worth it.

Just in case this helps someone, finally, I simply deleted the entire spline (white) and manually drew two new halves of that spline but leaving the desired gap connecting their extremes to the extremes of the arcs (orange).

Thanks for your help!

[CVH]

I simply deleted the entire spline (white) and manually drew two new halves of that spline

I doubt the matching accuracy.
CVH