Exploding Splines

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andrew
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Exploding Splines

Post by andrew » Mon May 08, 2017 2:10 pm

Splines are convenient drawing elements to represent non-circular, non-elliptical curves. Unfortunately, when drawings are further processed for example through CAM (G-Code or similar), splines often need to be broken down into simpler elements. Since most CNC machines do not support splines, splines are often automatically converted into tiny line segments which has the potential to slow down the machine substantially.

To prevent this, you can convert splines in QCAD before handing the file to the CNC processor. QCAD can convert splines into polylines with tangentially connected arc segments (fewer nodes, guaranteed smoothness, i.e. no "kinks").

First, please check your preferences under:
Edit > Application Preferences > Modify > Explode
Make sure that Explode splines to polylines with line segments is unchecked as shows in this screenshot:
Screen Shot 2017-05-10 at 14.47.33.png
Screen Shot 2017-05-10 at 14.47.33.png (141.7 KiB) Viewed 4135 times
Adjust the spline approximation tolerance (maximum error). The larger this value, the fewer nodes you will get. Try a value of 0.01, 0.1 or 1.0 and check the different results.
Screen Shot 2017-05-10 at 14.49.53.png
Screen Shot 2017-05-10 at 14.49.53.png (141.29 KiB) Viewed 4134 times
To convert splines into polylines with arc segments, simply select the splines and choose Modify > Explode.
Screen Shot 2017-05-08 at 15.09.15.png
Screen Shot 2017-05-08 at 15.09.15.png (25.64 KiB) Viewed 4176 times
Original spline (top) and exploded spline with 14 nodes (bottom).

ross
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Re: Exploding Splines

Post by ross » Mon May 08, 2017 4:05 pm

Hi Andrew

Thank you

Ross

CVH
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Location: Belgium; Antwerp

Re: Exploding Splines

Post by CVH » Sat May 19, 2018 11:42 pm

Hint
Keep a copy off your spline(-s) to revert to.
There ain't no easy way back from polys to splines exept undoing all the changes you made in between.
nor after closing.

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