I want to stepdown in Z only, not X/Y

[BbellYS6XC]

I'm trying to carve some "prismatic" letters with a 120-degree V-bit. The carving isn't modeled, so 2D contour is my toolpath of choice. Because the bit is so wide and shallow, I want multiple depths.

The toolpath that is generated starts in the middle of the contour and then steps outward as it steps down. This creates the correct shape, but with each successive step down the tool is taking a full cut on the "outside" of the contour and a partial depth cut on the inside. What I really want to do is to keep the center of the tool on the contour, and step down in depth only.

If I use a straight end mill, it steps down while keeping the middle of the tool on the contour, which is what I want it to do with the V-bit.

Is there any way to force F360 to keep the tool's center on the contour, regardless of which tool I'm using? I can't think of any problems in actually using a different tool than what was specified in F360, but that seems like an accident waiting to happen. Is that my only option? Thanks!

[brad_francola]

I think you may be happier with the engrave toolpath.  But, I see there is an issue when the tool is at 120°.  I set it to 119.5° and it is happy.  This needs further investigation.

You can have multiple depths

[brad_francola]

@seth.madore do you know why the tool can't be set to 120°

[brad_francola]

@seth.madore figured it out.  Changing the length below holder seems to do the trick.  There may be an explanation for this but for now, you can make your cut.  

[BbellYS6XC]

Yeah, I guess I should have included more information. Engrave is kind of the opposite of what I'm trying to achieve. I didn't include the clearing operations, so it wasn't obvious what the end result should be:

I've attached this sample project that includes the clearing operations.

I increased the length below holder in the 2D Contour path, but it still wants to "step down" the slope. I don't want it to do this because it takes a huge bite of the material on the outside of the shape as it steps down. Here is the current toolpath:

And here is the toolpath I want (generated by changing the tool to a flat endmill):

If you simulate the 2D contour path and watch how much material is cut on both sides of the tool, I think you'll see what I mean about it taking a huge bite on the outside.

 

[BbellYS6XC]

In case it's not apparent from the previous images, the letter should stick up out of the material, not be carved down into it.

[BbellYS6XC]

As a solution, I'm going to use 2D Trace for now. It allows multiple depths (although a bit klunky) and a specified final depth. It'll work for now.

[brad_francola]

I see.  You want something more like this:

[brad_francola]

Hi.  This is the best I could do in short notice.  Using some of the features from MFG Extensions like tool path modifications.  

[seth.madore]

Regarding the tool error, I've logged this as CAM-46178

[BbellYS6XC · Accepted solution]

Seth & Brad, thanks for your efforts. I went with using the 2D Trace and stepping down with 120d V-bit. It worked pretty well.

For anyone in the future who comes across this thread wondering how to do prismatic carving, the attached file is a sample of one way to do it. It's setup for a CNC router cutting wood.