Milling cutters with inserts are widely used in various industries, including the automotive industry, for face milling applications. One of the main uses of these cutters is to create surfaces on engine blocks. Tool manufacturers like Sandvik Coromant even offer specific tools for engine block face milling, such as auto cutters.
The number of inserts on a face milling cutter is directly proportional to the working feed, which means that more inserts allow for faster cutting. However, a higher number of inserts also leads to higher machining forces, which can cause vibration and poor surface finish or tolerances. Therefore, it is important to consider the strength of the fixture or machine spindle when selecting a cutter with the appropriate number of inserts to avoid excessive cutting forces.
Two important cutting data in milling are diagonal engagement (ae) and depth of cut (ap). Diagonal engagement represents the portion of the cutter that is engaged with the workpiece diagonally, while depth of cut shows the engagement of the cutter along its axis or length. Another important feature of a face mill is the entering angle, which is the angle between the insert cutting edge and the workpiece. Different entering angles, such as 45 and 90 degrees, are available for different applications.
When the entering angle is small, for example, 10 degrees, the entry and exit from the workpiece are more gradual and smooth, and milling diagonal forces are lower. This allows for higher feed rates, making high-feed face milling cutters ideal for small entering angles. On the other hand, 45 degree angle cutters are considered general-purpose cutters, and 90 degrees entering angle face mills are used to make right angle edges or steps.
Wiper inserts are another type of insert that can be used in face milling cutters. Wiper inserts have a larger cutting edge compared to standard inserts, which can result in increased machining forces. However, they can also provide better surface finishes or allow for higher cutting feed rates. Wiper inserts are not limited to face milling cutters and can also be used in turning applications. For example, they can be useful in turning gearbox components made from low carbon steels to improve chip breaking and increase feed rates.
There are also face milling cutters that use round inserts, which have a strong cutting edge and are suitable for machining tough materials such as stainless steel and super alloys. Some inserts, whether in turning or milling, are coated with layers of ceramics to increase their wear resistance and temperature resistance. Common coating materials include titanium carbide (TiC), titanium nitride (TiN), aluminum oxide (AL2O3), and titanium carbon nitride (TiCN).
Coating thicknesses depend on the coating process and can range from two to twelve micrometers. There are two main types of coating processes for inserts: chemical vapor deposition (CVD) and physical vapor deposition (PVD). CVD coating is done through chemical reactions of gases, while PVD coating is done by depositing gases over the tool. PVD coatings are generally thinner compared to CVD coatings and are preferred for tools that require sharp cutting edges or low cutting forces, such as end mills, drills, or turning inserts for heat-resistant super alloys. On the other hand, CVD-coated inserts are usually thicker and offer higher wear resistance. The type of coating also affects coolant usage, with PVD coatings being more preferable when coolant is used.
Understanding the different types of milling cutters with inserts and their applications, as well as the factors to consider when selecting the appropriate cutter, can greatly impact the success and efficiency of face milling operations. Careful consideration of factors such as the number of inserts, entering angle, and type of coating can help achieve desired results in terms of cutting performance