Mastercam Dynamic Milling
Dynamic milling is a machining method developed in collaboration with tool manufacturers and CAM software developers. Dynamic machining methods were originally developed for the roughing of difficult-to-machine materials, such as hard steels and heat-resistant superalloys, but they are also well-suited for milling other materials. The method utilizes the full cutting depth of the tool, resulting in even wear across the entire cutting length and extending the tool's lifespan.
The fundamental principle of dynamic milling is a large axial (ap) and small radial (ae) depth of cut compared to traditional machining methods. Dynamic milling aims to avoid milling at full tool width and linear movements, achieving material removal with smooth machining movements.
Dynamic machining is generally performed as so-called climb milling, where the tool returns to the start of the new chip with a high feed (so-called non-cutting feed) once the chip ends. The approach and departure movements to the machining path are always performed on a curved trajectory (about 10% Dc). In dynamic milling, the tool diameter (Dc) should be at most 70% of the width of the area being machined. The side shift ae of dynamic high-speed milling is usually about 5-20% Dc depending on the tool and the material being machined. The use of external cooling emulsions should be avoided in dynamic milling of closed pocket shapes, as the liquid pushes the chips down into the pocket, interrupting the machining process. It is recommended to use air cooling during dynamic milling.
In dynamic surface leveling, the optimal cutting width of the tool is normally used according to the tool manufacturer's instructions (around 60-90% Dc). The advantage of dynamic leveling over traditional leveling methods (one-way or zigzag) is a smooth machining path that follows the surface to be leveled. In dynamic leveling, the tool is always engaged with the material being machined, and the cutting direction remains constant with the cutting width continuously at the optimal given value. Using dynamic methods ensures a stable chip flow and machine load during the machining process, allowing for higher machining values to be applied.
Advantages and Disadvantages of Dynamic Milling
Advantages:
- Higher cutting speed
- Larger feed per tooth
- Greater chip flow
- Shorter machining time
- Better chip management
- Less heat generation
- Lower tool costs
- Process reliability
- Only one cutting edge is engaged at a time, reducing vibration
- Lower power requirements compared to traditional machining methods
Disadvantages:
- NC code length
- Complex machining program readability without CAM software
- Impossible to manually edit NC code
- Memory required for the NC code in the machine control
- Older machine control's ability to read long NC codes
Cutting Tools and Tool Holders in Dynamic Milling
In dynamic milling, common cutting tools can be used, but the best benefit from the method is achieved by using solid carbide end mills with long cutting lengths specifically designed for dynamic milling, equipped with multiple cutting edges and chip-breaking flutes. These include, for example, the Walter Tools MD133 series end mills, available in 3xD, 4xD, and 5xD cutting lengths. The lateral shift used in dynamic toolpaths depends not only on the tool used but also on machining depth, the material to be machined, the machine tool used, the machine tool taper, the tool holder, and the workpiece clamping. To ensure the effectiveness of the machining process, always use the tool manufacturer's machining value calculators, which take these aspects into account. Such calculators include, for example, Walter GPS.
The significance of the right tool holder in dynamic milling should not be underestimated. Since tools designed for dynamic milling are often more expensive than traditional end mills, tool clamping has a significant impact on the cost-efficiency of the process. The recommended tool holder for dynamic milling is a hydraulic power chuck. For example, Walter Tools AK182. A hydraulic power chuck provides a good and stable clamping for the tool, maintaining high rotational accuracy. A secondary option for dynamic milling tools is a Weldon holder, which also provides firm clamping but not as good rotational accuracy, which affects tool life and workpiece surface quality. When using shrink-fit holders or other slender tool holders, it is often not possible to use the maximum machining values of the tool. ER collet chucks should be avoided, as the tool can pull back from these holders as machining forces increase. If necessary, ER collets designed for dynamic milling can be used, locking the tool to prevent pulling out.
