2D Contour toolpath rather unpredictable

[ltomuta]

I have a simple 2D Contour on which the generated path is bit odd if Stock Contour and Multiple Depths are both enabled.

In the attached image, the first row shows the paths generated with Stock Contour OFF and the second row with it ON (no actual contour selection, using setup's stock). I am turning it on as I want to push the start position away from the stock, which does happen as expected but if the multiple depths are used then the starting position (column 2 in image) also jumps on the side of stock.

I tried to correct this by setting an entry position point on that edge but it is ignored.

[seth.madore]

Can you share your file? Right click on the file in the Data Panel and select "Share Public Link"

[ltomuta]

See https://a360.co/35yERmk |
New and simple project, the problem is reproducible there once to turn Stock Contour on/off

[seth.madore]

I too once ran into this issue and reported it as a bug. Verdict? This is intended behavior. 

The solution is to use Tangential Fragment Extension:

One other thing; I couldn't help but notice your selections; there were six of them. This isn't needed. Press the ALT key, select the start. Select the edge again, a new box pops up. Add onto the chain, selecting the "+" when done. Repeat the process for the other side, and now you only have 2 selections. Hopefully this saves you some time in the future!

[ltomuta]

Somehow I'm not sure that the + thing saves many of the Alt+(6 clicks) needed for my selection. But having just 2 chains could maybe help somewhere else.

As for the "feature" it doesn't quite make sense. If I select multiple depths I should see the tool coming multiple times from the same direction where it was coming before making this choice. I may have verified that path against a nearby clamp and after a minor change suddenly I go right through it. Could you still give it another try with a bug report (or reopen the old one)?

Yes, I agree, tangential extensions are the correct solution here. Once you learn about their existence 🙂

[ltomuta]

Now I see that there are two "tangential extensions", one under Geometry and one under Passes. With different behaviors too. Quite interesting.

[seth.madore]

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@ltomuta wrote:

As for the "feature" it doesn't quite make sense. If I select multiple depths I should see the tool coming multiple times from the same direction where it was coming before making this choice. I may have verified that path against a nearby clamp and after a minor change suddenly I go right through it.

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I'm not sure I follow what you are referring to. I'm not seeing a difference between Multiple Depths and not, as far as direction from where it's coming is concerned

[seth.madore]

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@ltomuta wrote:

Now I see that there are two "tangential extensions", one under Geometry and one under Passes. With different behaviors too. Quite interesting.

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Yes. The one on the Geometry tab has zero effect when you have "Stock Contours" enabled

[ltomuta]

See in my original image, 2nd row. With one depth, toolpath is basically coming along the body, with just a tiny deviation at the start unlikely to hit anything there.
When multiple depths are ON, the path goes first perpendicular to the body for a long stretch (basically as wide as the stock is on that side of the body) before entering the stock to go alongside the body.  During that first part of the move it may accidentally hit something.

[daniel_lyall]

If you do a top view you can see the toolpath is cutting to the selected stock contour as if it is a block of material.

Stock contour ticked so the stock is defined in the toolpath.

Not ticked

If the stock is not defined in the toolpath it gives this result.

To put it simply you have told it to cut this out of this block of material, 2D toolpaths are not model aware so you have to define the item to be cut and the stock material also It should cut or move around what is defined as it is in your case.

[ltomuta]

What I question is the difference in behavior between one depth vs multiple depths when stock is on.

Whether stock contour is on(4) or off(1) the resulting paths should all start from the same position. So what you see in (5) should never happen instead it should look like (2) but with an offset reflecting the offset between (6) and (3).

Alternatively, if there is justification for it, then (6) should also look like the bottom path of (5) since other than the multiple depths all else is equal.



And no, I did not ask for any additional stock to be cut. I asked for the current toolpath to be extended outside the stock, alongside the selected edge. Similar to a tangential extension. In fact this technique is specified as an option in the tooltip shown for tangential extension. Because otherwise the tool plunges into material at the start and that's not cool.

However I look at it, this has to be a bug.

[daniel_lyall]

It is not a bug, 5 is traveling around the stock to the start point how can that be a bug when a 2D toolpath can only do what it is set to do you say do this it does just that if it happened in a 3D toolpath that would be a bug.

It starts inside the stock because it is not set in the toolpath as a stock contour, 2D toolpaths are not model aware so the user has to fully define it, hands down that is how to do it. If this happens with a 3D toolpath it would be a bug.

[daniel_lyall]

This is what you posted 

What is A 2D toolpath set to what is in the pic as this is what you set

A 3D toolpath with only the tool selected 

It starts outside the stock as it is model awear.

Now when fusion stop crashing I can show you how I do it what is close to how you want it.

Attached is how I have done it for years, the first toolpath is what I always do minus multiple depths with even step-downs and whatever machine I am programming for max depth of cut.

I have dumped leads as I do not use them but if you added them back all is well and good.

IF there is a bug it would be in the extensions for the start and end extension.

[ltomuta]

@daniel_lyall either (5) is a bug or (6) is a bug. Because nothing justifies them being different other than with regards to the number of entries along the Z axis. If (5) is not a bug then (6) should look like this:

Yes, the tool moves outside the stoc and does not cut anything. Unless along that useless path it runs into a clamp. Which I did not check against since I only looked closely at the single depth scenario (6) and I was not expecting this stroll around the stock that happens in (5).

[daniel_lyall]

Enjoy life.