End Milling 101: A Complete Guide for Machinists

Regarding manufacturing, various machining processes are available to ensure we achieve parts with the right profile.

End milling is one of these vital processes. In this guide, we will look at some critical processes in the end milling process. From definition, classification, advantages to limitations, you will find all information about en milling process.

What Is End Milling

We can describe it as a machining process that uses a cutting tool called an end mill in the form of a cylindrical shape having numerous cutting edges.

The motion of this end mill can be in an up and down direction, side to side, or a combination of all these directions to provide you with the desired profile shape.

You can easily differentiate from other milling because the axis of the cutting tool is oriented parallel to the plane of the machined surface. Contrary to this, in end milling, the axis of the cutting tool has a perpendicular orientation to the machined surface.

Advantages of End Milling

The reason why end milling is the preferred machining method across various industries is due to the numerous benefits you can achieve from it. Here are some of the benefits you can enjoy from end milling:

You can use end milling to carry out various machining operations such as contouring, profiling as well as facing and slotting.
You achieve higher degrees of precision with minimal error margins which are a requirement for complex components.
It can deliver smooth and accurate finishing that does not require additional secondary finishing operations such as grinding.
It has a wide material compatibility and you can use it on metals, plastics, and various types of composite materials
With the right material and optimum operation parameters, you can achieve tool durability and extended service life. This reduces the frequency of tool replacement and tool-changing time.
The process is fast and efficient which is favorable for production lines

End Milling Process

This is not a very complicated process and you can carry end milling out using the following key steps:

Tool Selection: you need to select the right kind of end mill that will suit the material and produce the right cut. The type of tool you go for defines the production speed of your final workpiece, its accuracy, and how good it looks.
Machine Setup: make all the possible adjustments on your milling machine by ensuring that your workpiece is well secured and the cutting tool is well placed. It is essential that you get the right alignment for you to achieve the perfect dimension and surface finish.
Cutting Parameters: some of the recommended parameters that require your adjustment are the spindle speed, feed rate, and cutting depth. These parameters are responsible for the cut-rate, cutting tool condition, and the surface finish of your workpiece.

Cutting: the cutting will take place after the end mill achieves a high speed and comes into contact with your workpiece, it follows the laid down path while cutting. This tool may cut in several axes to achieve your desired workpiece design.
Chip Removal: you can use either air, a coolant, or even vacuum systems to remove the metal cuttings that are produced in this process. This reduces instances of re-cutting and prolongs the tool’s life while giving you a clean finish.
Inspection: after milling, investigate to ascertain whether your workpiece has achieved dimensional accuracy and proper finishing. You can carry out any corrective adjustments to attain the required specifications.

Classification of End Milling Based On Categories

There are several ways in which we can categorize end milling based on various aspects. Let us analyze some of the categories that we can group them in and what we consider:

Based On Tool Geometry

Flat End Mills: they are designed with a flat cutting edge and we mainly use them when we want to achieve flats, slots, and pockets. They are very crucial, especially in applications demanding accurate angles and measurements such as computer manufacturing.
Corner Rounding Mills: they have a radius on their cutting edge that they use in rounding off corners on your workpiece. We mostly use them in final operations since they can enhance the sturdiness of the workpiece.
Chamfer End Mills: their design includes a side-cutting tool whose sole purpose is to create a taper or bevel in addition to chamfering your workpiece. We mostly apply it when we want to deburr sharp edges and give your workpiece an aesthetic appeal.
Ball Nose End Mills: it is endowed with a rounded cutting-edge feature that works well in finishing and when cutting 3D contoured shapes. You will find their application mostly in mold-making and production of aircraft components.

Based On Material

Cobalt End Mills: their wear resistance is very high making them your best bet when handling hard workpieces. Their application areas are mostly in instances where there is heat generation during cutting.
High-Speed Steel End Mills (HSS): they are very tough and cost less making them widely used in ordinary milling operations. You can use them in milling operations involving relatively soft materials such as mild steel and aluminum.
Carbide End Mills: they are extremely hard and can easily machine difficult-to-cut materials such as titanium. Their high-speed cutting operation serves to improve their cutting performance.

Based On Number of Flutes

Two-Flute End Mills: they are best for slotting operations that heavily rely on the precision of the chip clearance. They achieve this using two cutting edges on their surface.
Three-Flute End Mills: they have varying characteristics between good chip evacuation as well as good surface finish. We mostly employ them for intermediate items that are neither very stiff nor overly flexible.
Four-Flute End Mills: with four cutting edges, they can provide you with the perfect surface finish having a very smooth texture. They work best with hard workpieces such as stainless steel.

Based On Application

Roughing End Mills: they incorporate finely rippled cutting edges for the purpose of removing large volumes of material at once. We normally employ them in the first stages of machining operations where the cutting rate is more important than surface finish.
Finishing End Mills: with their smooth cutting edges, they are designed to give you a smooth final surface finish. They provide very accurate dimensions and the right surface flatness where required.

Limitations of End Milling

Just like any other process, end milling comes with its fair share of disadvantages. Some of them include:

It results in rapid tool wear due to cutting hard materials at high velocities requiring you to change or sharpen it frequently
You require a complex setup procedure to run the whole end milling procedure such as choosing the right tool and cutting parameters among others
High-end quality end mills such as such as cobalt and carbide are relatively expensive and you may spend a lot on the end mills alone
When handing long workpieces, frequent vibrations usually result in poor surface finish and improper dimensions
You may not be able to achieve certain cuts on complex designs because they are limited by the tool geometry of the end mill

End Milling Vs. Traditional Milling

Both end milling and traditional milling are machining processes that we apply widely across many industries. They may sound similar but they differ in several key aspects that we are going to take a closer scrutiny of.

· Tool Orientation

The design of the tool placement in traditional milling is in such a way that the axis of the tool lies in the same plane as the surface of your workpiece. This differs from the end milling whose tool axis lies on another perpendicular plane.

· Versatility

With end milling, the versatility is on another level since you can perform many sorts of operations such as face milling or slotting with a single cutter. Traditional milling has more focused operations with alternating tools for different operations.

· Complexity of Shapes

You can easily machine three dimensional shapes with contours and cutting forms using end milling with precision. On the other hand, traditional milling works best when you are cutting flat forms.

· Surface Finish

In general, end milling normally comes out as the best in terms of surface finish, especially in cases where you apply finishing end mills. Normal milling may require you to apply additional finishing procedures such as smoothening.

· Material Removal Rate

Due to the possibility of using more cutting edges at once, you can achieve a higher material removal rate compared to traditional milling. This is more evident, especially at the roughing stage of milling.

Comparing End Milling vs. Drilling

We can classify end milling and drilling under the same category since in both instances, we are dealing with rotating tools and material removal. However, both of them serve different purposes that we are going to briefly have a look at such as:

· Cutting Motion

The direction of motion when you are drilling is normally in a vertical axis which results in the creation of cylindrical holes on your workpiece. On the other hand, end milling involves several movements in different directions that enable you to create various 3D shapes and contoured surfaces.

· Tool Geometry

Drills are equipped with sharp ends that are meant to make the hole creation process easier. This is in contrast to end mills which feature a flat or rounded cutting end on the sides as well as on the ends.

· Application

The sole purpose of the drilling process is to create holes for various applications. On the other hand, end milling can get you more operations such as drilling, slotting, facing and even contouring.

· Accuracy and Finish

When we compare these two, you are highly likely to achieve a better surface finish on your workpiece using end milling. This is in addition to the process being more accurate than drilling.

· Tool Wear

You will experience a higher local wear on the tips of drills during your operations. On the other hand, end mills wear from the periphery cutting edge which has different impacts on the tool life and cutting capacity.

Best Practices for End Milling

If you want to achieve optimal results during end milling, there are several best practice procedures that you need to follow. Let us dive straight into some of them and how they can help you achieve this:

Tool Selection: ensure that you have settled for the most appropriate end mill to use to enhance the cutting efficiency as well as durability of the tool. Having the correct tool reduces abrasion and you can achieve the required surface texture.
Cutting Parameters: you can achieve a longer tool life with maximum cutting ability by choosing both the right spindle speed and feed rate. You can cut down on tool breakages and standardize your rend milling by properly adjusting the settings.
Coolant Use: by adding cutting fluid or coolant to both the workpiece and cutting tool, heat generation and friction are greatly reduced. You can achieve a better surface finish with a reduction in the accumulation of chips on the cutting tool.
Tool Maintenance: it is advisable that you periodically check and change worn-out end mills to ensure smooth cuts. Regular maintenance ensures that your tools are sharp enough to provide an accurate cutting edge that minimizes errors.
Chip Management: you can adopt proper ways of handling chips that may include vacuums or air blows.
Vibration Controls: if you want to achieve minimal vibrations, go for proper tool length with proper cutting conditions to reduce the cutting forces.

Applications of End Milling

End milling is a very critical process that has a great impact on the operations of various industries. Some of its most notable applications include:

In aerospace manufacturing, it creates small and complex components such as turbine blades and precision fittings
Automotive manufacturers use it to produce engine components and various transmission assemblies
In the medical industry, it produces healthcare equipment such as body implants and general operational tools
In general machining, we use end milling to create brackets, housings, and various custom works
The tool and die-making industry uses it in producing molds, dies, and tooling used in mass production

Conclusion

It is important that you have a clear understanding of the types of end mills, their uses, and proper methods of application to yield the best results. This is because the end milling technique helps create accurate and detailed components across different fields.

Related Resources:

Thread Milling – Source: TSINFA

3-axis, 4-axis and 5-axis Milling – Source: TSINFA

Climb Milling vs. Conventional Milling – Source: TSINFA

Milling Process – Source: WIKIEPEDIA

Dynamic Milling – Source: TSINFA

Horizontal vs. Vertical Milling – Source: TSINFA