En Mecanizado CNC, for roughing workpieces, dynamic milling and layer milling are two common milling strategies. Although both methods aim to remove material, they differ significantly in machining methods, applicable materials, spindle speed, feed rate, and machining efficiency. Understanding their definitions, advantages, disadvantages, influencing factors, and selection criteria can help us make better decisions in different machining scenarios.
Dynamic Milling
Definition:
Dynamic milling is a milling method that maintains high machining efficiency and reduces tool load by continuously adjusting cutting parameters such as cutting depth and feed rate. By flexibly adjusting the toolpath, each cut maintains a relatively small engagement, avoiding excessive load on the tool caused by deep cuts and reducing heat accumulation during machining.
Materiales aplicables:
Aluminum alloys, copper alloys, plastics, soft steel, titanium alloys, and other relatively soft metals or polymer materials. Dynamic milling is suitable for soft or medium-hard materials, especially in scenarios where a large amount of material needs to be removed quickly.
Spindle Speed Range:
Dynamic milling typically uses higher spindle speeds, generally between 5000–12000 RPM. The specific speed should be adjusted according to the tool and material hardness.
For hard materials such as titanium alloys, the spindle speed should be reduced appropriately to avoid tool breakage.
Feed Rate:
The feed rate of dynamic milling is relatively high, usually between 2000–8000 mm/min, depending on material characteristics, cutting depth, and machine performance.
Advantages and Disadvantages:
Ventajas:
- Lower tool load, extending tool life.
- High efficiency, especially suitable for removing large areas of material.
- Provides better cutting stability and higher material removal rates.
- Reduces heat accumulation and tool wear.
Desventajas:
- Higher requirements for machine tools, including stability and spindle speed.
- In some cases (such as complex shapes), dynamic milling may generate looping toolpaths that create idle tool movement.
- Surface quality during finishing is relatively poor.
Machining Efficiency:
Dynamic milling shows high efficiency when removing large amounts of material. Because of its high feed rate and deeper cutting engagement, it can significantly improve machining efficiency. However, it may be less stable than layer milling in fine machining operations.
Factors Affecting Machining Efficiency:
Machine performance: High spindle speeds and good machine stability are required. Dynamic milling performs especially well on five-axis machines.
Material characteristics: Softer materials such as aluminum and copper alloys are most suitable.
Tool selection: Tool size and type influence dynamic milling performance, particularly when machining harder materials.
Layer Milling
Definition:
Layer milling is a machining strategy that divides the cutting depth into multiple thin layers. Each cut removes a small amount of material, which effectively controls tool load, reduces excessive tool wear, and maintains high machining accuracy.
Materiales aplicables:
Hard steels (aceros para herramientas, alloy steels), stainless steel, cast iron, titanium alloys used for finishing, and other hard materials.
Layer milling is generally suitable for materials with higher hardness and machining tasks requiring higher surface quality and precision.
Spindle Speed Range:
Layer milling usually operates at relatively lower spindle speeds, typically between 3000–8000 RPM.
For hard materials such as titanium alloys and hardened steels, spindle speeds should be reduced appropriately to minimize tool wear.
Feed Rate:
The feed rate of layer milling is generally lower, usually 500–5000 mm/min. Lower feed rates help ensure cutting stability and machining precision.
Advantages and Disadvantages:
Ventajas:
- Stable machining conditions, suitable for hard materials and finishing operations.
- Small cutting depth per pass reduces tool load and improves surface quality and dimensional accuracy.
- Provides high precision and is suitable for precision machining.
Desventajas:
- Shallow cutting depth leads to a lower material removal rate and lower efficiency.
- Because each cut removes only a small amount of material, machining cycles are longer and not suitable for quickly removing large volumes of material.
Machining Efficiency:
Layer milling has relatively lower efficiency, especially when removing large volumes of material, due to slower feed rates and lower material removal rates. However, in precision machining and high-accuracy requirements, it can provide better results.
Factors Affecting Machining Efficiency:
Material hardness: Hard materials are suitable for layer milling, but efficiency is low when machining softer materials.
Tool selection: Tool geometry, cutting depth, and feed rate influence efficiency and precision.
Cutting parameters: Proper cutting depth, feed rate, and spindle speed determine overall machining performance.
CNC Dynamic Milling vs Layer Milling: Which Is More Efficient?
To compare the roughing efficiency of both methods, we create a cavity workpiece measuring 10 mm × 10 mm with a depth of 25 mm. The workpiece material is Aluminio 7075, with overall dimensions of 150 mm × 150 mm × 30 mm and an internal cavity. The machining allowance of the workpiece blank is set to 5 mmy 25 mm needs to be removed from the edges.
Material removal rate (Q) is used as the comparison metric. The greater the volume of material removed per unit time, the larger the Q value. The unit is cm³/min.
The other two influencing parameters are cutting depth (AP) y cutting width (AE).
Known formula:
Q = (F × AP × AE) / 1000
Dynamic Roughing Calculation
Tool diameter: 10 mm standard tool, cutting edge length 30 mm.
Since dynamic machining requires slightly larger tools to reduce breakage risk, the tool diameter is selected as 12 mm.
Velocidad del cabezal S = 8000
Average feed rate F = 5000 mm/min
Profundidad de corte AP = 30 mm (single pass)
Cutting width AE = 2.5 mm
Calculation:
Q = 5000 × 30 × 2.5 / 1000
Resultado:
Q = 375 cm³/min
Layer Roughing Calculation
For layer roughing, an insert cutter is used. The tool diameter must cover the cutting width, so a 32 mm diameter cutter is selected.
Velocidad del cabezal S = 4500
Feed rate F = 4000 mm/min
Profundidad de corte AP = 2 mm
Cutting width AE = 25 mm
Calculation result:
Q = 200 cm³/min
From the calculation results, the material removal rate of dynamic milling is indeed higher than that of layer milling, and the theoretical machining speed is faster. However, in actual machining, dynamic milling is not always faster. During cavity machining and surrounding roughing, there are often many looping movements and idle toolpaths, which waste machining time. In addition, dynamic roughing conditions are not always stable. When removing large portions of material, the tool load can suddenly increase and cause tool breakage.
In contrast, layer milling has fewer looping movements and shorter idle toolpaths, resulting in a more stable machining rhythm. Some may consider using climb and conventional milling to improve the speed of dynamic roughing, but this increases tool load and accelerates tool wear, ultimately raising machining costs.
However, when the material changes from Aluminio 7075 alloy to titanio alloy (such as TC-4), the situation becomes different. Titanium alloys have low thermal conductivity. If layer milling is used, tool heat dissipation becomes difficult, and about 80% of the heat concentrates at the tool tip, causing rapid tool wear and reducing machining stability and cost efficiency. With dynamic milling, the cutting mainly uses the side edge of the tool. As long as the material removal rate is controlled and excessive engagement is avoided, heat dissipation improves and machining speed increases.
Therefore, the material removal rate is only one reference factor. It must also be combined with the material type and machining features to determine the best strategy. For example, when machining aluminum alloy parts, cavity roughing can use layer milling, while the remaining R-corners or fillets at the workpiece edges can be cleared using dynamic milling, which can save more machining time.
Selection Criteria for Dynamic Milling and Layer Milling
Choosing between dynamic milling and layer milling mainly depends on the following factors:
Material Type:
For soft materials such as aluminum and copper alloys, dynamic milling provides higher efficiency.
For hard materials such as titanium alloys, stainless steel, and hardened steel, layer milling is more suitable because it maintains higher machining accuracy and surface quality.
Machining Objectives:
If the goal is to remove a large amount of material quickly, dynamic milling is more suitable after optimizing idle toolpaths and looping movements because it offers higher removal rates and faster feed speeds.
If the goal is precision machining with high surface quality or accuracy, layer milling has advantages, especially for complex finishing operations. However, attention must be paid to heat concentration at the tool tip to avoid rapid wear.
Machine Tool Performance:
Dynamic milling requires higher spindle speeds and better machine stability, making it more suitable for five-axis or high-precision machines.
Layer milling has lower machine requirements and is suitable for most conventional three-axis machines.
Machining Efficiency:
Dynamic milling is more efficient for removing large volumes of material, while layer milling is more suitable for finishing operations, offering lower efficiency but higher precision.
Conclusión
Both dynamic milling and layer milling have their own advantages in CNC machining. Dynamic milling is suitable for softer materials and fast material removal, while layer milling is better for harder materials and precision machining. Choosing the right strategy depends on the material, machining features, and machine capability.if you want know more details or get custom manufacturing price,you can póngase en contacto con con nosotros.
