Adaptive Milling is new in NX 12 for manufacturing and gives a nice cut pattern that gradually adapts to the shape of a cut region with smooth, flowing motions. Unlike traditional cut patterns, Adaptive Milling doesn't violate the Stepover input from one cut to the next. This makes it ideal for high speed machining.
However, did you know that by maintaining a very small stepover you can greatly increase the feed rate? It also allows the CAM programmer to use a greater axial depth of cut than normal. This is all due to a phenomenon known as radial chip thinning, and the default template settings in Adaptive Milling are guiding users toward this.
In the Path Settings group of the Adaptive Milling operation dialog, you will notice that the Percent of Flat Diameter parameter is set to 7%, and the Maximum Distance is set to 200% of the tool diameter for the cut depth. This is generally a good starting point for taking advantage of radial chip thinning.
The next step is to calculate the proper feeds and speeds for the end mill. The radial chip thinning formula will help in calculating a proper feed rate when using a small stepover input of around 10% or less of the end mill diameter. The formula for radial chip thinning is as follows:
CT = Chip Thickness (The usual chip load at a normal 50% stepover)
D = Tool Diameter
RDOC = Radial Depth of Cut (The Adaptive Milling stepover input as a constant)
The solution to this equation can then be used as the chip load variable of the feed rate calculation.
The video in this post shows an example of Adaptive Milling with a proper feed rate using radial chip thinning cutting 4140 steel. The cutting tool is a solid carbide end mill with a 0.030" corner radius. The spindle is rotating at 8000 rpm, and the feed rate is set to 270 inches per minute. This is actually on the conservative side as it is very likely that the feed rate could be higher.
Notice in the video that no coolant is being used. That's another added bonus to using Adaptive Milling with radial chip thinning. The wonderful effect is that most of the heat generated from the cut goes into the chips, some of it goes into the cutter, and hardly any heat is transferred into the workpiece. When Adaptive Milling is used correctly, the steel workpiece is cool to the touch immediately after the tool path is finished.
Contact your cutting tool providers for the proper cutter speed information and how to properly calculate radial chip thinning feed rates when using Adaptive Milling in NX.
Please leave a comment if you find this article helpful to your understanding of adaptive milling in NX 12.