Additive Toolpath Tangent Offset Distance Setting

[Anonymous]

Hi all,

I am trying to create additive toolpaths where the distance between the paths is constant, not in the z-direction, but tangentially along the surface of the part that I am creating. I am using the "Feature Construction" tool, which deals exclusively in distances along the z-axis. Unfortunately, the only way I can currently conceptualize getting the spacing that I want is by manually setting each of the layer heights, and I would rather not do that as it precludes me from creating a generalized macro for creating these additive toolpaths for a variety of shapes. Does anyone have suggestions for creating Profile additive paths with constant distances between layers in 3D, rather than just along the z-axis? Is there maybe a subtractive toolpath that I can use, then convert to additive?

The image below is an example part, a dome. The layers near the top of the part should get closer together as their xy-offset increases, but they remain constantly offset in the z-direction.

[kelvin.hamilton · Accepted solution]

Hello @Anonymous,

That's a great question and one that has been coming up from time to time.

Indeed those types of toolpaths are very interesting but unfortunately not yet possible with Feature Construction.

There are two options for creating this type of toolpath. I call the toolpath Chord Length Slicing toolpath:

A - Use Surface Finishing Toolpath

In PowerMill

- select surface

- set surface units to distance

- step over in this case is the layer thickness

- set tool axis to Lead/Lean and a 90deg lean angle

B - CAD patterns to CAM toolpaths

- Use PowerShape to create patterns that will be used for toolpath creation later in PowerMill

- copy patterns to PowerMill and embed them on the revolved surface. Embedding ensure that surface normal information are given to the patterns.

- use Embedded Toolplath (no gouge checking)

- set tool axis to Lead/Lean and a -90deg lean angle

General notes:

- this type of toolpaths only make sense when the geometry is rotationally symmetric or not too far from that. So any shape that has a profile that can be revolved about a central axis of rotation

- because there are likely to be areas with undercuts in the revolved geometry, you will need to use a barrel tool

- there will be a slight deviation between the surface or pattern and the resulting toolpath due to the tool diameter. Smaller tools will have less deviation. I typically use D0.2mm tool to get good toolpaths

- these two methods are best suited to single bead builds. Multiple side by side builds are possible but will become tricky to manage

- you can convert to Additive afterward to had other options be made available. Unfortunately things like layer splitting wont work well as the layer height in z-axis will not be constant