Trochoidal Milling Below 10% Radial Engagement

Categories: MillMax Tips

In order to automatically generate Dashboards in an acceptable amount of time, we plot and analyze stability lobe diagrams at 10% increments of the Ae or width of cut from 0% to 100% (full slot). The range from 0-10% is complicated as explained below.

This is for testing an existing tool cutting at below 10% engagement. Best practice would be not to RECOMMEND such a light cut. Here's why:

With very small (<10%) stepovers, the cutting edges spend less and less time inside the cutting area. Hence, the cutting forces lose their sinusoidal (wavy) shape and become similar to impacts of grinding, which excite the modes of the system. This is chatter, but the cut is so light you cannot hear it. If you tap test an application like this, the Dashboard will show chatter at <5%. It is not incorrect. Again, the user can't hear it, but the surface finish will show chatter marks.

Long axial depths of cut, especially with smaller diameter endmills, cause a lot of deflection, are prone to chatter (heard or not heard), leave poor surface finishes and inaccurate walls. 

Our current solution is this:

1. Tap the tool
2. Enter the customers current conditions
3. Send us the TXF file
4. We will generate our new Trochoidal Stability Lobe Diagram and provide recommendations for optimization.

Note that the difference is the depth of cut is set at the maximum (in this case 2.75") and the right axis is radial width of cut.

The SLE and CDD gages will probably not be very good because of the bouncing nature of this cut, but you can refer to them.

Use THIS CALCULATOR to optimize feed rate and SFM limit of below 10% engagement.

You can also use the following chart to increase SFM limit.