Up Milling vs Down Milling: Difference and Comparison

Key Takeaways

1. Direction of Cutter Rotation: In up milling, also known as conventional milling, the cutter rotates against the direction of the workpiece’s feed. In contrast, in down milling, also referred to as climb milling, the cutter rotates in the same direction as the feed. The names “up” and “down” refer to the direction of the chip thickness, which increases in up milling and decreases in down milling.
2. Surface Finish and Tool Wear: Down milling provides a better surface finish and less tool wear than up milling because the force on the cutting edge is not as abrupt. However, in up milling, the cutting forces vary from zero to maximum, leading to more tool wear and vibration, which can affect the finish.
3. Applications and Equipment: Up milling is used when the machine or the equipment setup isn’t robust, as it tends to have less aggressive cutting action and is less likely to pull the workpiece. Down milling is preferred when the setup is sturdy, and the machine can handle the potential for higher forces. Also, down milling is used when the surface finish is a critical concern.

What is Up Milling?

Up milling is a machining process that is used in milling operations. It is also known as conventional milling. In up-milling, the cutter’s rotation is against the feed’s direction. The chip formation in up milling is gradual chip thickness decreases during cutting. 

It is used or preferred for materials to achieve good surface finish requirements or materials for work hardening. Moreover, the tool used in up milling has a long life. Besides this, up milling has its own limitations, like it gives a rough surface finish. 

What is Down Milling?

Down milling is another machining process that is used in milling operations. It is also known as climb milling. In this machining process, the rotation of the cutter rotates in the same direction. The cutting direction in down milling is the same as the feed. The chip formation in down milling the thicker chips that reduce during cutting.

The advantage of down milling is that it provides an improved surface finish if compared to up milling. Down milling the tool means life is shorter because of the rigorous use. Also, the heat generation in the case of down milling is low. 

Difference Between Up Milling and Down Milling

1. In up milling, the cutter’s rotation is against the feed’s direction. Whereas, in the other hand, in down milling, the rotation of the cutter rotates in the same direction.
2. The cutting direction in up milling is opposite to the feed direction. Whereas on the other hand, the cutting direction in down milling is in the same direction as the feed.
3. The chip formation in up milling is gradual chip thickness decreases during cutting. In contrast, the chip formation in down milling the thicker chips that reduce during cutting.
4. In up milling, the cutting forces tend to move the workpiece slightly upwards. At the same time, in down milling, the cutting forces tend to push down the workpiece.
5. The tool life of up milling is longer in comparison to down milling tool life, and it is shorter because of the rigorous wear.
6. The surface finish of up milling tool is rough. At the same time, the surface finish of the down milling tool has an improved surface finish.
7. In up milling, the heat generation while cutting is very less. On the other hand, in down milling, the heat generation while cutting is more.
8. Up milling is suitable for flexible or thin workpieces. Comparatively, on the other hand, down milling is suitable for rigid or sturdy workpieces.
9. The application efficiency of up milling is lower because of the potential vibrations. Contrastingly, the application efficiency of the down milling is higher because of the reduced vibrations.
10. Up milling is safer to use because of less aggressive cutting. In contrast, on the other hand, down milling is a high risk involved.
11. Up milling requires less machine power, whereas, comparatively, on the other hand, down milling requires more machine power. 

Comparison Between Up Milling and Down Milling

Parameter of Comparison	Up Milling	Down Milling
Cutter Rotation	It rotates against the direction	It rotates in the same direction
Cutting Direction	Opposite	Same
Chip Formation	Gradual chip thickness decreases during cutting	Initially, the thicker chips reduced during cutting
Cutting Forces	It tends to move the workpiece slightly upwards	It tends to push down the workpiece
Tool Life	Long	Short
Surface Finish	It can be rougher	It has an improved surface finish
Cutting Heat	Less	High
Suitable For	Flexible or thin workpieces	Rigid or sturdy workpieces
Application Efficiency	Lower because of the potential vibrations	Higher because of the reduced vibrations
Safety	Safe because of less aggressive cutting	Higher risks involved
Machine Power	Less	More

References

1. https://www.sciencedirect.com/science/article/pii/S1877705813020882
2. https://journals.sagepub.com/doi/abs/10.1177/1077546309341131