Chronological order for Toolpath

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Husky
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Chronological order for Toolpath

Post by Husky » Wed Jan 12, 2022 8:01 am

Hi,
I need to follow a chronological order in a milling process. In a test drawing I reordered the entities, created a path and was surprised that my order wasn't used by QCADCAM. How can I tell QCAD/CAM to follow "my" chronological order?

On the right side a screenshots shows my "wish" order and on the left side the created order from the Toolpath tool.

Husky-2022.01.11-08.png
Husky-2022.01.11-08.png (32.41 KiB) Viewed 1247 times
Win10, QCAD/CAM Version: 3.27.1.0
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andrew
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Re: Chronological order for Toolpath

Post by andrew » Wed Jan 12, 2022 9:45 am

The contours in a single toolpath are ordered automatically for shortest path. If you need to be in control of the exact order, you need to create an individual toolpath for each contour.

CVH
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Re: Chronological order for Toolpath

Post by CVH » Wed Jan 12, 2022 9:56 am

Husky,
It's probably just an example ... Have a closer look at the lead in-outs.

Regards,
CVH

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Husky
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Re: Chronological order for Toolpath

Post by Husky » Thu Jan 13, 2022 12:01 am

Thanks for the info!
andrew wrote:
Wed Jan 12, 2022 9:45 am
The contours in a single toolpath are ordered automatically for shortest path.
Ok, as you know it is debatable what is the shortest or best path and in my case the created optimum isn't usable. However - I also learned that I haven't understood the QCAD/CAM Reference Manual explanation for "Reorder": Quote - ... for certain types of further processing (such as CAM), the order of entities can be crucial. End Quote. Well - I thought with Reorder I can control the order for all paths but my reordered entities are always overwritten by QCAD :( .
andrew wrote:
Wed Jan 12, 2022 9:45 am
If you need to be in control of the exact order, you need to create an individual toolpath for each contour.
That works ................ but that is really labor-intensive. In my simple example I have to ...
select 1. contour,
launch "Add Profile Toolpath", file dialog, confirm with ok,
select 2. contour,
launch "Add Profile Toolpath", file dialog, confirm with ok,
select 3. contour ....

... and I have to do this ~ 70 more times!!! :shock:

Next idea: In my case I can use the same tool for every path. I hoped that I'm able to "trick" QCAD for this task with a different approach, selected the contours one by one in the order I need, launched "Add Profile Toolpath" to created the Toolpath for all contours all together what would shorten the user input in around the half. Well, QCAD noticed it is a single toolpath, took over and created again the "shortest" Toolpath. :(

I assume that is a great achievement in the eye of a programmer but the problem is I can't control this "Artificial Intelligence" - I need to use "Natural intelligence" in this case. :wink:

This said ...
Would it be possible to make the "shortest Toolpath" optional (on/off) so that my "Trick" works for the path order?
... I'll file a Feature Request. :wink:
https://www.qcad.org/bugtracker/index.p ... sk_id=2330
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Re: Chronological order for Toolpath

Post by CVH » Thu Jan 13, 2022 4:59 am

Husky,
Andrew's answer was basically the same as here:
https://www.qcad.org/rsforum/viewtopic. ... 867#p30867

I assume that a certain TSP algorithm is implemented to reduce the traveled G0 paths.
https://en.wikipedia.org/wiki/Travellin ... an_problem

With closed sub-paths it is a typical TSP but CNC can also include open paths.
Using in/out leads that already can be open cutter paths.
For a 146 point problem there might be several minimal solutions and many near minimal.
The outcome will then depend on the used algorithm and possibly on the seed.
In most basic cases there is only one.

One can fool this a bit with grouping things.
Then again, it could turn out less optimized in a minor to major degree.
I would also like to compare it with the outcome of nesting shapes.

Another advice is to position the start point of a closed contour on a long and steady side.
Some CAM automatically choose the mid point of the longest (near) straight edge.
Or that of the inner cutter path while pocketing.
In QCAD one needs to define it as a polyline with a certain start-end point.
The chosen point will have an influence on the sequence.

From writing scripts that handle a selection, I know that the order of selected things is not very predictable.
I assume there will be some logic, but it still eludes me.
The drawing order can also be renumbered 0...NNN when saving a file.
e.g. Open a file, select 10 entities, MB, all 10 have order -1, save & close, re-open ...
The new drawing order of those 10 is 0-9 and correlates with their handles, the rest is shifted.

From a selection QCAM generates individual cutting path segments, each having a handle and a drawing order.

I can understand your request that is similar as in the first link. :wink:
The question remains what to use as path sequence. :?
There is no selection order, the drawing order is uncertain, that of a contour can be a mix, a handle is fixed on creation.

Regards,
CVH

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