Large circle outside tool path of spline region

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Arctic_Eddie
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Large circle outside tool path of spline region

Post by Arctic_Eddie » Tue Dec 15, 2020 4:34 pm

I'm trying to set up the laser path for an airplane rib. The shape is a spline for the top and bottom region with straight line notches at both ends. If I select "On" for my path, the simulator works fine but with a red message "Undefined contour orientation". If I select inside or outside, I get huge circles below the shape that the simulator follows. It's attempting to use arcs for some of the splined region but attempts to cut the whole circle and not just the arc. I'm using GrblMM as that's what the 3018 laser CNC uses.

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andrew
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Re: Large circle outside tool path of spline region

Post by andrew » Tue Dec 15, 2020 6:46 pm

I'd recommend to adjust / increase the tolerance for exploding splines under:
Edit > Application Preferences > Modify > Explode > Spline approximation tolerance

Then, explode the splines into a polyline and check the result. The thing to avoid are very short arc segments with huge radii.

Alternatively, you could choose to explode the spline into small line segments instead of arcs which is less error-prone when offsetting:
Edit > Application Preferences > Modify > Explode > Explode splines to polylines with line segments

In your follow-up post, please:
- indicate if you want to cut on the path or right or left of it
- attach your DXF file (with the tools and toolpaths)

Arctic_Eddie
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Re: Large circle outside tool path of spline region

Post by Arctic_Eddie » Tue Dec 15, 2020 7:27 pm

A wing airfoil does have very short and sharp turns at the nose and very large arc radii at the underside of the tail. Sometimes there's a reverse curve in this same region. I changed the tolerance to 0.001 and set explode to polylines but it did not fix the problem. Fortunately, the laser beam cuts a very narrow track so the "On" setting is acceptable instead of the desired "Outside". The DXF file is attached.
s3021-rib-3028-test.dxf
(216.14 KiB) Downloaded 142 times

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andrew
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Re: Large circle outside tool path of spline region

Post by andrew » Tue Dec 15, 2020 8:31 pm

The lower spline seems to be the issue.

I'd proceed as follows:

- Edit > Application Preferences > Modify > Explode > Spline approximation tolerance
Change to 0.1 (i.e. "increase")

- Select the lower spline

- Modify > Explode

- Click the toolpath "Profile 1" in the toolpath list

- Double click the exploded lower spline to select the whole contour (or select all)

- Right-click on toolpath "Profile 1" and choose "Update Toolpath from Selection"

Result is also attached.
Attachments
s3021-rib-3028-test.dxf
(208.79 KiB) Downloaded 138 times

Arctic_Eddie
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Posts: 28
Joined: Sat Dec 12, 2020 5:23 pm
Location: St. Petersburg, Florida

Re: Large circle outside tool path of spline region

Post by Arctic_Eddie » Tue Dec 15, 2020 9:04 pm

It works now but only for a climb/left cut. If you try to go the other way, conventional/right, the problem remains. The nature of the spline being quite flat in certain regions is stressing the calculations.

While investigating this problem, I've found two other related problems.
1. Where is the default cutting depths stored? For a laser and thin material, there is no Z motion. I would like to make that the default, 0/0/0/1

2. On the complete rib, there are several holes in the shape. I select them in the order I want them cut but the simulator shows a different sequence. Is there some kind of optimizing turned on. I want to set the sequence as the actual operation has three ribs stacked and I want to cut all the holes in a serpentine fashion then the outside perimeters.

Arctic_Eddie
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Posts: 28
Joined: Sat Dec 12, 2020 5:23 pm
Location: St. Petersburg, Florida

Re: Large circle outside tool path of spline region

Post by Arctic_Eddie » Tue Dec 15, 2020 9:19 pm

I just discovered that if I also explode the upper spline then it will work correctly going the other direction. Both splines are stressing the calculations.

CVH
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Re: Large circle outside tool path of spline region

Post by CVH » Sat Dec 19, 2020 9:19 am

See my post here:
viewtopic.php?f=74&t=7902&p=30902#p30902

Regards,
CVH

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