Machining Tip: How do I get started?

You probably know that VoluMill is designed to be run at feeds and speeds much faster than traditional toolpaths. But if you're just starting out, how can you select the best parameters for your machine?

In a series of tests, we've come up with some rules of thumb to help get you started. Of course, after dialing in these parameters, you can use your own instincts and experience to fine-tune things.

The four most important parameters to set when programming a VoluMill toolpath (or, really, any toolpath) are the spindle speed, feedrate, radial depth of cut (or stepover), and axial depth of cut. The spindle speed and feedrate are computed from two fundamental parameters: the surface speed and the chip load. We recommend the following rules to get started:

1. Maintain the chip load recommended by your cutting tool manufacturer for your material.
2. Double or triple the surface speed recommended by your cutting tool manufacturer. If you have a good tool and a good holder, you can probably triple it.
3. Use a stepover between 6% and 40%, depending on the material (see below).
4. Cut axially as deep as your part and the flute length of the tool will allow.

Of course, you can determine your spindle speed rpm and feedrate based on the chip load and surface speed with these well-known calculations or their metric equivalents:

1. rpm = (3.82  x  surface feet per minute) / (tool diameter in inches)
2. feedrate, inches per minute = chip load x rpm x number of flutes

 Determining a good stepover depends on the material and how easy it is to machine. You might use 40% stepover in aluminum, 6% in inconel, and 7% in 6Al4V Titanium. For different types of steel, good numbers seem to be somewhere in between; for example, you could cut 4140 steel at 15%-20%  of tool diameter, softer steels like 1018 at 30%, and 17-4ph stainless at 9%.

  These are only starting parameters, and you may find that you can easily dial the parameters up after your first try. If you feel like you want to get still more performance, try increasing the chip load, particularly if you are using a small stepover. If you are cutting less deep axially, you may be able to increase your stepover as well.