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Hello,
Tool exceeds the boundary limit, “Tool Center on Boundary” mode, in situations when boundary segments face each other and the “Additional Offset” exceeds the (distance between the opposing segments) / 2 value.
It seems that the “Tool Center on Boundary” mode of the limiting mechanism offsets the boundary by the tool radius value and then implements the “Tool Inside Boundary” algorithm instead of using the true tool center value. It is obvious from the tool paths in the attached project which I generated using both limiting modes and respective boundary offset values.
Please tell me if I'm missing something, I am totally new to Fusion, maybe there is an option setting or workaround that I am not aware of. Thank you in advance.
P.S. I zipped the *.f3d, it doesn't let me upload otherwise for some reason.
Solved! Go to Solution.
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Help me out a bit here, I'm not entirely sure what you're asking....
The toolpath you highlighted WILL cut outside of the model silhouette because you have asked it to, by invoking the "Additional Offset" text box.

Seth Madore
Customer Advocacy Manager - Manufacturing
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I have highlighted the sketch (pic.1, pic.2) which I am using as a boundary. With “Tool Center on Boundary” turned on the tool center must not exceed the boundary, at least this was the case with my old CAM.
I assume that (“Tool Center on Boundary” algorithm = “Tool Inside Boundary” + boundary with tool radius offset) because a respective offset to this boundary merges it in the problematic areas causing a similar result with “Tool Inside Boundary” turned on (pic.3).
I have mentioned the “Additional Offset” because “Silhouette” + “Additional Offset” + “Tool Center on Boundary” behaves the same way.
P.S. I had the toolpath settings mixed up in the *.f3d project, sorry for that. A fixed project is attached.
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@Anonymous
Like Seth I am unsure exactly what you are asking for, see images below, are they anything like your needs ??
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Hello, engineguy. I am saying that the the tool center exceeds the boundary in the example I have posted and it should not do that if I'm not mistaken (pic.1).
Yes, it is possible to prevent the tool from machining in the narrow area by lowering the boundary offset value like in your example. But there are a couple reasons why this is a problem for me, one of them being that I will have to double check my toolpaths knowing that this feature exists.
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@Anonymous
As I have explained it is the way you are selecting things, if you are selecting a sketch that is already larger than the model then even without any "Additional Offset" it will be over the edge, if you select the edge of the model shape and then add 3mm then of course the center of the tool will be outside the Boundary so why would you set an "Additional Offset" in the first place ??
If you only want the tool to go outside the Boundary by a small amount as in the image below then set your "Additional Offset" to a Minus (-) value, this will move the tool center inwards, just for illustration I used a -3mm value on the 8mm tool and as you can see the tool has only gone over the Boundary of the Model by a small amount, by using the offset (+/-) you do have full control of where your tool will go to ![]()
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Please excuse me my stubbornness, but the thing is that I am intentionally applying a 3mm offset to a 8 mm mill toolpath so that I still have a 1 mm overlap with the model which must prevent the tool from exceeding the edge of the part along Z axis (pic.1).
This is a trick I currently use to automate my work flow, lets me generate typical roughing, finishing toolpaths via macro and do the non standard work afterwards. Guess it is a matter of different software solving tasks differently.
Thank your for your time, Seth and Engineguy!)
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@Anonymous
Ok, so, I am thinking that you wish to machine outside the edge of your Model, yes??
That is easy enough on your File, you can set the "Additional Offset" to anything you like, I have set it to +6mm as shown in the image below so the whole diameter of the tool is outside the Model, but it isn`t diving down the slots in the Z axis, that is because for that Operation I set the Bottom Height to the top of the model, this stops the toolpath going down any further than the top of the model, if you do want the toolpath to go down the sides of the model then adjust the "Bottom Height" to where you want the toolpath to go to ![]()
This is with the "Bottom Height" set to the Model top with -4mm ![]()
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@Anonymous what bug are you referring to exactly? Nothing I've seen thus far in the conversation jumps out at me as a bug...

Seth Madore
Customer Advocacy Manager - Manufacturing
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Tool center exceeding the boundary is a bug in my opinion because it should be limited by the boundary according to the “Tool Center on Boundary” option description (pic.1).
You can see form (pic.2) that the tool center is not limited by the boundary.
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@Anonymous
Agreed, if you had set a Boundary then I would agree that there is a problem, but you have not set one, however if you do set a boundary with the "Stock Contour" then what you get is the image below where you can see the 3mm addition and the toolpath not diving down the slots, the software is working correctly, I would not expect the toolpath to respect a Boundary that is not there, nor should I
![]()
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Okay, I think I see what you are saying now. Fortunately, this isn't the only way to accomplish what you are looking for, as @engineguy laid out in his posts above

Seth Madore
Customer Advocacy Manager - Manufacturing
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@Anonymous
Yes, for sure it isn`t easy, don`t know if you have used any other CAM software but if you haven`t then it is a very steep learning curve ![]()
Good luck, you know that you will always have the support of the Fusion Community so always ask
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