Milling
Milling cutters are fundamentally either shank- or arbor-mounted tools with one or more cutting edges. In addition to insert-based cutter bodies, shank mills are also available as high-speed steel and solid carbide shank mills. The use of high-speed steel shank mills has steadily decreased in recent years, and they are now mainly used with manual milling machines. The quality and price of solid carbide shank mills, in relation to the productivity of the tool and the machining methods enabled by modern machining machines, have established this tool type as the most common shank mill model. There is a wide range of shank mills for various applications such as traditional straight shank mills for corner milling and slot milling, long-cut shank mills with multiple cutting edges for dynamic milling, shank mills with a large face radius for high-feed milling, radius or barrel mills (barrel cutters) for 3D surface milling, and various rounding, chamfering, T-slot, and dovetail slot mills. Insert-based cutters refer to steel cutter bodies to which replaceable insert blades (inserts) are attached with screws. Insert mills are cost-effective, and due to the replaceable inserts, maintenance of the tool is easy. Different insert geometries can be used with different qualities and coatings for machining various materials. Insert mills come in both shank and arbor models and are generally larger in size than solid carbide shank mills. Examples of insert mills include face mills, shape mills, corner mills, high-feed mills, drill mills, slot, and disc mills, etc.
Dynamic milling is a machining method developed jointly by tool manufacturers and CAM software creators. Dynamic machining methods were originally developed for the roughing of hard-to-cut materials like hard steels and heat-resistant superalloys, but they are also well-suited for milling other materials. The method utilizes the full depth of cut of the tool, allowing for even wear across the entire cutting length and improving tool life.
The basic principle of dynamic milling is a large axial (ap) and small radial (ae) depth of cut compared to traditional machining methods. In dynamic milling, full-width tool cutting and linear movements are avoided, and material removal occurs through smooth machining motions.
Dynamic machining typically occurs in what is called climb milling, meaning the tool always returns to the start of a new cut at high feed (non-machining feed) after finishing a chip. The approach and exit movement to the machining path are always performed with a curved path (approx. 10% Dc). In dynamic milling, the tool diameter (Dc) can be at most 70% of the width of the area being machined. The side step in dynamic high-speed milling ae is usually about 5-20% Dc, depending on the tool and the material being machined.
Common cutting tools can be used in dynamic milling, but the best benefits of the method are achieved with long-cut solid carbide shank mills designed specifically for dynamic milling, which are equipped with multiple cutting edges and chip breaking grooves. Examples include shank mills from Walter Tools' MD133 product series, which offer 3xD, 4xD, and 5xD cutting lengths. The side step used in dynamic toolpaths is influenced by factors such as tool depth, the material being machined, the machining machine used, the machine's spindle taper, the tool holder, and the workpiece clamping. To ensure a successful machining process, always use tool manufacturer machining value calculators that consider these aspects. Examples of such calculators include Walter GPS.
