The open and intersection of two vectors bring uncertainty to the creation of CNC toolpaths. The CNC software tries to figure out the result you want to achieve but often needs help understanding.
Open Vectors and CNC Project Designs
In the simple vector design, below are two circles; one is slightly smaller than the other. The objective is to create a V-Groove between the two circle vectors.
It's a simple toolpath. All that is needed is to select both circle vectors and click on the V-Carve toolpath option. But when the software attempted to calculate the toolpath, an "open" vector error message was displayed.
I ignored the message and clicked the Ok button. But the toolpath simulator result gave me something I was surprised to find out. The result was more like a bowl than a V-Groove. The software did what it said it would do. It ignored the open vector and carved out all the material inside the one closed vector that was left.
This example also illustrates the usefulness of having a toolpath simulator as part of your CNC software. It allows you to catch issues like this before ruining a piece of wood.
Finding the "open" vector is easy using the Vectric software. Vectric CNC software provides a menu option that selects all "open" vectors.
The software function selects the one inner circle vector below.
While you might see a portion of the vector missing in many cases, this vector looks normal. It is open because I cut one of the vector nodes using the node editor.
But with CNC wood machining, it does not matter whether it looks normal but if it's mathematically "normal.
Fortunately, the Vectric software provides a Join Vector function to solve this problem. In this scenario, I selected both of the vectors. You can see below that it found one open and one closed vector. The result after joining would be two closed vectors.
Now, when I calculate my V-Carve toolpath, I no longer receive an error message. Instead, the toolpath simulator shows me the V-Groove result I was expecting.
The Intersection of Two Vectors
The intersection of two vectors introduces similar kinds of problems. The difference is that the CNC software does try to adjust for the issue.
The example below shows two V-Groove shapes I want to carve. One shape is a circle, and the other is a square.
However, these two shapes overlap, and the software gives me a warning message. So I chose to continue anyway, and the result turned out fine. It's what I was expecting.
So I decided to press my luck and try something more complicated. I duplicated the square V-Carve vectors and intersected those also.
This time the toolpath simulator gave me a result I was surprised to find out. The toolpath carved out two shapes entirely, only one as a v-groove.
A Solution to the Intersection of Two Vectors
The solution to this problem is the same as before, fix the intersection of two vectors. It's easy, at least with my example, as Vectric CNC software has an interactive vector trim tool.
Trimming the intersecting portions of the vectors takes a few minutes. The corners are automatically joined, and then you clean vectors to V-Carve. Better yet, you'll know what the result will be.
A More Complex Intersection of Two Vectors
A better example of what can happen with actual designs with intersecting vectors is a Yoda drawing I reviewed earlier. It had some vector intersections, which I ignored when calculating the V-Carve toolpath.
As a result, two of these vectors were the cause of the top of his head not being v-grooved properly.
If I zoom into those two intersections, You can see that the designer did not correctly join the two different rectangles, causing the two vector intersections.
It only takes a minute or two to node edit these vectors and join them properly. Once done, then Yoda's head v-carves correctly.
So remember, if you find a vector design you like but it has problems, you may still be able to fix them. But be careful; node editing is tedious, and you want to spend only a little bit of time with it.