Machining path deviation

[RoboTomo]

Hello,

I have a problem creating straight machining paths in Fusion. I use the Steep and Shallow method for 5-axis lead and lean machining. The machining direction in the Y-axis is fixed, so it would be desirable that the software could create straight lines in this direction, but this is not the case.

1. We can already see visually that in some cases, in the curved area, the line in the middle of the workpiece is going left and right, but ok, this is not a big deal yet (Picture 1).

2. The problem arises when I export the machining path/points that Fusion generated and plot the results. Here, we can clearly see the path deviation since it creates a Zig-zag pattern in the middle of the workpiece (Picture 2). 

I calculate the optimal direction and minimal speed in this Y-direction. I now have to generate a machining path in this direction and verify the minimal speed, but this speed is always incorrect because it is caught in that Zig-zag Fusion pattern.

Why is Fusion doing that and how to eliminate it?

[seth.madore]

Would you be able to share your Fusion file here?
File > Export > Save to local folder, return to thread and attach the .f3d/.f3z file in your reply.

[RoboTomo]

Thank you for your answer. I am attaching the file.

So the goal is to obtain straight machining lines for different stepovers (2, 1, 0,5, 0.1 mm). In this example, we have a stepover of 2 mm and for this case, I tried changing tool diameter, tolerance, and smoothing but was unsuccessful.

[RoboTomo]

I am still struggling with this problem and have additional question.

How exactly are toolpaths generated in this Steep and shallow strategy and if this is different for other strategies? Are they generated directly on the 3D surface with offset curves, or are they generated on the XY-plane and then projected onto the 3D surface?

Thanks.

[a.laasW8M6T · Accepted solution]

Hi

I have made a video that hopefully explains what is going on with the toolpath there

[RoboTomo]

Thank you very much for your answer; you provided a very good explanation! I have been trying all sorts of parameters and did additional tests after your video, and the results are better. However, in some cases, there are still very sharp declines, as in my original post (Figure 2) when we zoom in. 
I noticed that if I use the tool diameter the same as stepover distance, the results also improve.
As you mentioned, the part itself can have an impact on the machining path. Here, originally, I had the .stl part, but I converted it into a solid body in Fusion; maybe it will be better to do machining directly on the original .stl part with a more dense triangulation?

[a.laasW8M6T]

Hi

whether the original .stl will be better I am not sure, it will really depend on the quality of the original.

The toolpath will re-mesh it when it calculates, but it can't Improve the quality better than the original.