How To Choose a Stepover

This is a guest post by Robert Grzesek, founder of Grzsoftware and creator of the excellent MeshCAM 3D CAM software. This post originally appeared on the Grzsoftware Blog, and I will be incorporating Robert’s excellent article on stepover for 3D profiling into the Milling Feeds and Speeds Cookbook, but I wanted to post it to the CNCCookbook Blog to make sure everyone sees it. It’s a very clear explanation of how to choose a stepover and I particularly like his analysis of the “sweet spot” for stepover. Very useful knowledge to have!

One of the fundamental parameters of any CNC machining, and 3D machining in particular, is the stepover. It is not a stretch to say that it is the single most important parameter in determining the quality of the finished parts you will produce. A machinist can pick a value by feel, based on previous experience, or do the math and calculate the exact value that will give them the finish required. New users generally don’t have the experience and don’t know the math so it takes a while to get an intuitive understanding of of the stepover parameter.

The following post focuses mostly on 3D toolpaths so we’ll be assuming the use of a ball mill. Once you understand the basic concepts it’s easy to apply them to flat end mills and bull mills. We’ll try to build to some rules of thumb rather than derive equations that most users won’t be interested in.

Definition of Stepover

Almost all CNC toolpaths are based on the concept of one toolpath being offset from another by some distance; this offset distance is generally called the stepover. Most CAM software, MeshCAM included, uses a couple toolpath styles in particular with these offsets- the raster toolpath (sometimes called a zig-zag toolpath) and a contour offset.

A contour offset toolpath

A raster or zig-zag toolpath

Adjacent sections of the toolpaths above are separated by the stepover value chosen by the user.

Read the rest of the article in the CNC Milling Feeds and Speeds Cookbook.

Related posts:

1. G-Wizard High Speed Machining Feeds and Speeds
2. Breaking Cutters With Tool Deflection: An Anecdote
3. Ballnose Surface Finishes
4. New Installments for the Milling Feeds and Speeds Cookbook

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  [...] like to post about.  Let’s see what makes sense.  In the past, we’ve had some wonderful guest posts from folks like Robert Grzesek, the founder of [...]

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