Any high speed machining operation demands high quality carbide cutting tools. To attempt saving money on inferior end mills is setting yourself up for failure. Not only must the cutters be quality, but the spindle, CNC operating system, machine tool itself and toolholder, such as HSK, must be designed for HSM.
If any one of these components is lacking, the process will break down and fail. You just cannot take a conventional CNC mill and attach a high speed spindle and crank up the speeds and feeds. The entire process must be integrated in order to succeed.
Many HSM applications include fine details, such as those found in a complex plastic injection mold. The miniature end mills required must be able to stand up to the rigors of speeds such as 60K or higher. Many operators find that coated carbide end mills which are specifically designed for this purpose perform much better than uncoated.
Recommendations from leading carbide tooling manufacturers
- Carbide cutters should have a micro grain substrate and coating of TiAIN for high wear resistance and hot hardness.
- High precision grinding with a runout of less than 3 microns.
- A minimum overhang as possible in the toolholder to provide maximum stiffness.
- As large a body diameter as possible to ensure stiffness and minimize distortion.
- Short edge and contact length for lowest possible risk of vibration, cutting forces and distortion.
- Holes for coolant and air blast.
- Geometry specifically designed for HSM applications.
- Symmetrically designed tools that are balanced by design.
The use of coolant in HSM with carbide
- Normally carbide cutters do not require the use of coolants. Experience and tests show that the use of coolants is ineffective.
- The cutting action of high speed machining results in very high temperatures at the point of shear between the metal and the cutter. Any coolant coming into contact at this point will immediately be turned into steam and have no cooling effect.
- An air blast is much more effective because it clears the chips out of the cutting area much better. Recutting chips is one of the easiest ways to destroy your cutter. It is also rather easy to remedy with a good air blast.
Using indexable cutting tools in HSM
- An indexable end mill or face mill can work very well, provided it is designed for high speed machining.
- Cutter geometry must be specific to avoid rubbing when the tool deflection (cutting forces) disappear.
- Must have holes for air blast or coolant.
- The maximum allowable rpm should be marked on the cutter body.
A reputable manufacturer will have a specialist available to assist you and adequate videos and reading material to educate everyone concerned. Companies such as Sandvik, OSG, Ingersoll, Morse, Kennametal, Accupro, SGS and Widia have great resources available to teach you the ins and outs of high speed machining.
Another use for HSM is in woodworking. These CNC wood machines use carbide router bits to produce the moldings, dado and rabbet joinery, hand rails, tables, trim and even guitar components.