Milling tools wear with extended use. Millalyzer contains a tool life estimation that predicts for how long an endmill will remain useful, in terms of
- the total length of the cut;
- cutting time (minutes);
- volume of material removed.
Life prediction is available for most metals, but not for other materials at this time. Calculations for titanium and stainless steels (such as 1.4301 / 304) assume that flood cooling with a suitable emulsion is used, as tool life would be extremely short otherwise. Flood cooling (or rather lubrication) will also improve tool life in aluminium, as it drastically reduces friction between tool surface and stock material. Effective minium quantity lubrication (MQL) can have a similar effect.
The underlying model used to predict tool life is empirical and attempts to account for tool wear only. That means that factors which can drastically reduce life such as chip re-cutting or clogging of flutes due to insufficient chip evacuation, are not considered. The following machining parameters have a strong influence on wear:
- Feed per tooth [FZ] will increase tool life expressed in total length of cut. This is because the amount of wear caused by each tooth engagement is typically less than the increase in feed. This effect is especially pronounced in brass and aluminium but present in all metals.
- Cutting speed negatively affects tool life once a certain limit is exceeded. This limit may increase with lubrication. The decrease is more or less linear for brass, aluminum and steel (ISO P) but much more radical for titanium and stainless steel.
- Lower radial engagement [AE] increases tool life expressed in cutting length and time. Beyond a certain point it may however reduce the amount of material removed within that tool life, all else being equal.
- Axial engagement has no impact on tool life expressed as length or time, because the same wear occurs along the entire exposed tool edge. This means that the volume of material removed during the useful life of the tools scales directly with axial depth of cut.
The prediction methods assumes good-quality tools that are designed for the workpiece material. With a non-descript general-purpose tool that is advertised as being suitable for all materials, tool life will be much shorter than predicted here. Furthermore, the predictions are only available for carbide tooling, simply because there is not enough data available for HSS endmills.