Climb Milling vs Conventional Milling
Continue reading to discover more about each kind of CNC milling and its applications.
Understanding Milling Basics
CNC milling is a subtractive manufacturing process that employs a rotating cutting tool to carve away material from a workpiece. It enables the creation of intricate shapes with high precision and plays a critical role in producing various components. Modern CNC mills, ranging from 3 to 6 axes, can handle complex geometries with ease, ensuring repeatability. Today’s advanced CNC machinery can tackle even the most intricate tasks.
To CNC mill a component, the workpiece is first securely clamped in the machine. The cutting tool then removes material in successive passes. This material removal can happen in two ways: either a moving tool impacting a stationary part or a stationary tool impacting a moving part. In both cases, the cutting tool rapidly rotates to eliminate material, shaping the workpiece into the desired part.
Different surface finishes, cutting styles, and machine requirements result from variations in how the cutting tool moves over the workpiece. Certain components benefit from specific CNC machines; for instance, Swiss machines excel at crafting small parts with tight tolerances. Sungplastic provides a range of CNC options to manufacture even the most complex parts at remarkable speeds.
Conventional CNC milling involves the cutting tool rotating in the opposite direction to the feed, a practice sometimes referred to as “fighting the feed.” This process is known as up milling because the cutting tool starts at the bottom of the cut and moves upward through the workpiece. Typically, manual CNC milling employs conventional milling.
The enduring appeal of conventional milling lies in its numerous advantages, including:
- Greater control over the cutting tool, leading to higher accuracy.
- Reduced likelihood of the tool pulling into the workpiece.
- Suitability for less powerful machines.
- Effectiveness in handling larger cuts.
- Diminished chattering and tearing, particularly at the micro-surface level.
Conventional milling remains a dependable method even with less precise and less powerful CNC machines. The direction of the cutting edge’s rotation minimizes the tool’s tendency to pull into the workpiece, preserving accuracy and minimizing errors.
Nonetheless, conventional milling has its drawbacks, such as:
- Rougher surface finish.
- Increased chances of recuts due to the direction of chip ejection, negatively affecting surface quality and tool longevity.
- Elevated heat generation, reducing tool lifespan and potentially warping the workpiece.
- Transfer of higher forces to the workpiece.
In conventional milling, the cutting tool’s rotation relative to the workpiece leads to chip ejection in the same direction as the tool’s movement. Many of these chips get recut as the tool passes over them, resulting in a diminished surface finish and quicker tool wear.
Conventional (up) milling also necessitates higher clamping forces. The cutting tool naturally tends to lift the workpiece away from the table as chips are removed. In situations where machines are susceptible to backlash or materials are prone to tearing or chattering, the advantages of conventional milling often outweigh the disadvantages. Manual machines predominantly utilize conventional milling techniques.
Climb Milling: Enhancing Machining Quality
Climb milling, also known as down milling, closely resembles conventional milling, with the primary distinction being the cutting edge’s rotation concerning the workpiece. In conventional milling, the cutting tool rotates “up,” while in climb milling, it rotates “down,” causing the tool to ascend or pull into the workpiece. In essence, the direction of the cut aligns with the cutting tool’s rotation, working harmoniously to lift the mill up and away from the workpiece.
No additional equipment is required for climb milling; the machinist simply alters the workpiece’s feed direction. Despite the seemingly minor change, climb milling significantly influences the finished part’s quality.
Advantages of climb milling include:
- Improved surface finish as the chip width narrows throughout the cut.
- Reduced risk of recuts due to more efficient chip ejection.
- Lower cutting forces, which stabilize the workpiece and lessen clamping requirements.
- Heat dissipates from the part thanks to chip formation.
- Lower power consumption during cutting.
- Increased tool lifespan due to reduced chip recutting.
Climb milling, with its aggressive entry angle, efficiently removes material but may lead to backlash or chatter. This is why conventional milling was historically used to mitigate these issues. However, with modern machines featuring backlash eliminators, concerns about backlash during climb milling have diminished, although surface quality can still be affected if not carefully managed.
The same forces that reduce clamping requirements can also lead to drawbacks. The tool’s inclination to pull into the workpiece can result in over-cutting. Additionally, the difficulty in controlling the process arises from the tool and workpiece moving in the same direction. Modern machine tools and CNC controls address many of these challenges.
When to Choose Conventional or Climb Milling
Selecting between conventional and climb milling depends on the material being machined and the desired surface quality. Soft materials like aluminum are well-suited for climb milling. Some materials that perform favorably with climb milling include:
Harder materials like cast iron and hot-rolled steel are typically better suited for conventional milling, though some softer steel variants respond positively to climb milling. Conventional milling is ideal for materials prone to chatter or tearing. Climb milling is advantageous for workpieces that tend to lift since the forces push the workpiece onto the table.
A helpful tip: Choose climb milling for cutting less than half the cutter tool’s diameter, while conventional milling is more suitable for cutting over 75% of the cutter tool’s diameter due to potential issues with negative rake.
Climb milling is often employed as a final pass to enhance surface finish. Conventional milling performs the bulk of material removal, with climb milling used toward the end to achieve the final dimensions with superior surface quality. This approach is common in aerospace applications, even for harder materials like titanium, where a final climb milling pass is utilized.
Start Your Next Project With Sungplastic
For all your CNC machining (conventional, climb, or otherwise) and finishing needs, Sungplastic has you covered. We’re experts at producing custom CNC machined tight tolerance parts, involving a variety of materials, including CNC milling, CNC turning, CNC EDM and other processes, providing advanced CNC mill machines, CNC lathe, EDM tools and so on.
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