High-feed milling is a process that maximizes the removal of material in the shortest amount of time. If not applied properly, high-feed milling can create some improper results, which is why some manufacturers have begun to move away from the process due to what they consider reliability concerns.
For machinists that would like to take the risk, the benefits of high-feed milling can significantly outweigh the potential challenges. The process offers amazing productivity, nearly triple the metal removal rate of conventional methods, and increases tool life. Although, there are a few things you should know in order to make high-feed milling a successful part of your work
Machine Tools
Sturdy and highly capable machine tools are imperative when it comes to high-feed milling because the cutters run at high feed rates, which require the machine and the control to keep up with these demands. New equipment is a lot more advantageous when dealing with high-feed milling technology.
Inserts
The inserts used in HFM are crucial. They are thick with a large radius and strong geometry at the cutting zone. This means you can work at high speed and still have reliable and safe machining. For most HFM operations, trigon-style inserts are preferred over round. The reason is that the main cutting forces are located at the bottom of the cutting edge. Of course, there are situations when you use square inserts, but with a small setting angle.
The lower lead angle also directs the cutting forces in the axial direction, pushing up into the spindle, which is more stable and easier on the machine. Higher lead angles create thicker chips requiring less adjustment in feedrate. They also produce more radial force causing vibration and stress on the spindle bearings.
Insert Grade
Choosing the correct insert grade for the type of material you are machining can increase tool predictability, resulting in fewer tool changes, less rejects and less reworking. You don’t want your tool to fail prematurely, especially if you’re performing a lights-out operation.
Programming
Optimize the cutter path through proper programming, so you don’t put any unrealistic demands on the cutting tool. For example, when you are in a mold and come to a corner, changing directions without using a smooth transition is very hard on a tool because it creates a large angle of engagement. A good rule of thumb is to program an arc that is 50 percent larger than the cutter diameter. If using a 2.0” cutter, program a 3” diameter arc. Programming an arc in pocket corners reduces the angle of engagement and avoids overloading the cutter. Machine tools can also have problems in this area because several calculations are involved in generating an arc. If the machine tool can’t properly calculate the arc, the toolpath can become erratic.
Summary
Although HFM is not an end-all, be-all solution, it is a great method to achieve high metal removal, utilize the full capability of today’s machines and achieve long tool life.
