Common line Removal, hull vs align nesting

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chrispedersen
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Common line Removal, hull vs align nesting

Post by chrispedersen » Thu Oct 21, 2021 9:23 pm

If you have two rectangles and they are placed abutting with 0 margin, does QCadCam remove the common line between?

I read the online help, and purchased the manual - and for the life of me I haven't found the difference between the Hull and Align nesting method?

Thanks

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Husky
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Re: Common line Removal, hull vs align nesting

Post by Husky » Thu Oct 21, 2021 9:55 pm

chrispedersen wrote:
Thu Oct 21, 2021 9:23 pm
If you have two rectangles and they are placed abutting with 0 margin, does QCadCam remove the common line between?
No. But you could run after nesting the "Detect duplicates" tool ...
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andrew
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Re: Common line Removal, hull vs align nesting

Post by andrew » Fri Oct 22, 2021 9:53 am

chrispedersen wrote:
Thu Oct 21, 2021 9:23 pm
I read the online help, and purchased the manual - and for the life of me I haven't found the difference between the Hull and Align nesting method?
The "Align" strategy moves the parts closest to the chosen edges resulting in a rectangle shape hull, squeezed to the first priority alignment edge.

The "Hull" strategy tries to first of all minimize the total surface area occupied by the parts. You will more likely end up with a roundish cluster of parts.

Please post one question per topic, thanks.

chrispedersen
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Re: Common line Removal, hull vs align nesting

Post by chrispedersen » Fri Oct 22, 2021 9:06 pm

Husky wrote:
Thu Oct 21, 2021 9:55 pm
chrispedersen wrote:
Thu Oct 21, 2021 9:23 pm
If you have two rectangles and they are placed abutting with 0 margin, does QCadCam remove the common line between?
No. But you could run after nesting the "Detect duplicates" tool ...
if a common line is 2 " long and it coincides with a line 4" long, will it flag the 2" as duplicate and remove?

CVH
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Re: Common line Removal, hull vs align nesting

Post by CVH » Sat Oct 23, 2021 6:30 am

chrispedersen wrote:
Fri Oct 22, 2021 9:06 pm
if a common line is 2 " long and it coincides with a line 4" long, will it flag the 2" as duplicate and remove?
Called a partial duplicate.
No, that is one of the known limitations of the MD method.
One would have to set the tolerance to 2" or more in your example.

Several feature requests handle over this.
See forum and: https://qcad.org/bugtracker/

I usually fall back on closed contours as polylines.
What is not part of any polyline is then not a contour and probably a left over.
Still, a polyline can retrace over itself ... It is not watertight. :wink:

Regards,
CVH

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Husky
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Re: Common line Removal, hull vs align nesting

Post by Husky » Sat Oct 23, 2021 8:17 am

chrispedersen wrote:
Thu Oct 21, 2021 9:23 pm
If you have two rectangles and they are placed abutting with 0 margin, does QCadCam remove the common line between?
1. May I ask you at which CNC machine (Laser, Milling, Waterjet etc) you want to use an nesting arrangement with 0 margin alignment?
2. How many possible overlaps we're realistically(!) talking about? 5? 50? 5000?
3. Do you have an example drawing which you can show us?
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chrispedersen
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Re: Common line Removal, hull vs align nesting

Post by chrispedersen » Mon Oct 25, 2021 5:40 pm

Husky wrote:
Sat Oct 23, 2021 8:17 am
chrispedersen wrote:
Thu Oct 21, 2021 9:23 pm
If you have two rectangles and they are placed abutting with 0 margin, does QCadCam remove the common line between?
1. May I ask you at which CNC machine (Laser, Milling, Waterjet etc) you want to use an nesting arrangement with 0 margin alignment?
2. How many possible overlaps we're realistically(!) talking about? 5? 50? 5000?
3. Do you have an example drawing which you can show us?
Hi Husky,
Thanks again for all your help. I have a Golden Laser 180W 2500 x 3000(mm) table.
I am completely self (mis)taught. At this point I've done probably 10,000 parts. I'm cutting mostly fabric. My laser manufacturer suggested that in the fabric industry it is common to remove common lines.

I've adapted/written some code that removes common lines - but it doesn't nest as well as QCad does - specifically it optimizes for left/right not top bottom. And its more of a can of worms to resolve than I am competent to do.

On a typical cut file approximately 33% of the cut lines are common. (I pulled up one 36 cut lines, 12 common).
On the other hand, I cut that cut file 30 times a day... Each cut file takes 5:46 seconds to complete. So on a yearly its pretty hefty.
It would save an hour a day, I'm guessing.


The advantages to removing the common lines are
a): Saves laser time. CO2 laser tube good for roughly 3000 hours. Eliminating 1/3 of the usage ... is a good thing.
b): Cut quality. Going over the coincident edges can cause warping/discoloration on the edges. In the cases where I am using QCADCAM, I give up on saving laser time, and separate the parts by a fraction.

I'll generate and load up some test files later this afternoon, so you can see what I'm talking about.

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Husky
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Re: Common line Removal, hull vs align nesting

Post by Husky » Mon Oct 25, 2021 6:24 pm

Thanks for the extra explanation. Looking forward for the example files ...
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chrispedersen
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Re: Common line Removal, hull vs align nesting

Post by chrispedersen » Thu Oct 28, 2021 7:58 pm

So here is method 1, generating the .dxf programmatically: (should have no common lines)
992-test-test-10.dxf
(5.32 KiB) Downloaded 289 times

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Husky
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Re: Common line Removal, hull vs align nesting

Post by Husky » Thu Oct 28, 2021 9:06 pm

chrispedersen wrote:
Thu Oct 28, 2021 7:58 pm
So here is method 1, generating the .dxf programmatically: (should have no common lines)992-test-test-10.dxf
Sorry but I don't understand this example! It doesn't looks like it is done by nesting and the two common lines are easily removed with "Detect Duplicates". Please elaborate the purpose of this example. Where do we have to look at ... :oops:
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chrispedersen
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Re: Common line Removal, hull vs align nesting

Post by chrispedersen » Thu Oct 28, 2021 9:12 pm

Here is method two, using a public domain software I modified.
Here, its specified to remove the common lines.
Example 2 common line removal.dxf
(7.3 KiB) Downloaded 293 times

chrispedersen
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Re: Common line Removal, hull vs align nesting

Post by chrispedersen » Thu Oct 28, 2021 9:41 pm

Qcadsolution.dxf
(116.97 KiB) Downloaded 299 times
And here is the QCadSolution.
Distance between parts set to zero.

Now, running the removal you suggested would remove a good number of the common lines - maybe half, but not all.

CVH
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Re: Common line Removal, hull vs align nesting

Post by CVH » Fri Oct 29, 2021 6:00 am

Hi,
Method 1 = 48 pieces of 13.3640 by 7.5180
Both other examples are 12 by 8 mixed with 6 by 4.
Like comparing apples with ... :wink:

I don't think method 2 (62 by 24) and the QCAD solution (78 by 20) used the same target sheet.
BTW: For method two I had to set all polyline Global Width to zero instead of 0.013889 so QCAD could render it. :wink:

I can fit them snugly on a sheet of 60 by 24, 13 cuts, in under 3 min.
QCADsolution-CVH.dxf
(98.14 KiB) Downloaded 300 times

Sure there is nesting and nesting and partially common lines removal would be nice. :wink:

Regards,
CVH

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Husky
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Re: Common line Removal, hull vs align nesting

Post by Husky » Fri Oct 29, 2021 8:47 am

chrispedersen wrote:
Thu Oct 28, 2021 9:41 pm
Qcadsolution.dxfAnd here is the QCadSolution.
Distance between parts set to zero.
Here is the bitter pill: A CAD nesting function is fascinating but only a mathematically solution. QCAD has no idea what you will do next with the result and how to optimize it for your further processing goals. This said - with all nesting option in QCAD you can make your life easier if you force the nesting tool in the right direction.

Your example files are inconsistent. Nevertheless my example will show the process to meet your goals: No common lines, less laser time, less maintenance.

We know that the tool "Detect Duplicates" can't find reliable partial duplicates. To avoid that we can minimize the outcome of partial duplicates with a smart part arrangement. In my example I nested by size to have most of the expected duplicates as a same length duplicate.

Nesting.gif
Nesting.gif (2.36 MiB) Viewed 8272 times
chrispedersen wrote:
Thu Oct 28, 2021 9:41 pm
Qcadsolution.dxfAnd here is the QCadSolution.
Distance between parts set to zero.
Now, running the removal you suggested would remove a good number of the common lines - maybe half, but not all.
Now with this arrangement we can use common sense where to look for duplicates. No need for endless looking behind the curtains ...
There are only two lines suspicious where partial duplicates could be exist and the rest will be find by "Detect Duplicates". You agree?

Husky-2021.10.28-03.png
Husky-2021.10.28-03.png (5.25 KiB) Viewed 8272 times
Ok, let's do it! If I now run the "Detect Duplicates" tool I'll find 56 duplicates - I delete them. The rest is hidden in only two lines - I clean it manually.

cleaning.gif
cleaning.gif (1.23 MiB) Viewed 8272 times

How much work (Time) is needed to do it this way? Nesting took me around 1:50 min. Cleaning around 50 seconds = 2:40 min. I'm faster when I don't have to document it .... :lol:
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