Face Milling: Process, Types and Tips
Home > Blog >
Face Milling: Process, Types and Tips
Milling is a prominent process that helps create flat surfaces of great quality with unmatched accuracy. If there is one method that will ever feature whenever milling is mentioned, it is the one related to face mills.
Face milling is one of the many milling techniques that have transformed the machining world. Like the rest of the techniques, this milling operation has its approaches and capabilities. Its tooling, cutting speeds, material compatibility, and other elements are recognizable.
In this article, we revisit this vital milling technique. We discuss how it works and outline the various types of the process. You will find out how face milling compares to peripheral milling, plus many other aspects.
What Is Face Milling?
Face milling refers to a machining method that uses a flat-faced milling cutter to remove matter from a work piece. The cutter and the work piece surface are placed perpendicular to each other. The machinist can perform face milling on different CNC machining centers. However, this operation is typically done on the CNC router.
Some people may confuse face milling on these machines with the one done on the CNC lathe machine. Notably, the work piece is rotating on the lathe machine. However, the work piece is stationary during the “real” face milling. It is also noteworthy that the lathe machine uses a single-point cutting tool to machine the material.
The material removal in face milling is due to the grinding action of the milling cutter. The cutter has peripheral cutting edges. These edges do the cutting in face milling.
There are different types of face milling, as we will discuss later in this article. Regardless of the type, a proper milling process should produce a smooth and flat surface on the part.
How Dose Face Milling Work?
Like other machining processes, face milling involves a series of steps. This include tool selection, work piece preparation, machine preparation, and so on.
For face milling, the process starts with the selection of the face milling tool and setting it up. Note that there are different types of face milling tools, but we cover that a little later. Typically, the face mill is slightly larger than the surface to be machined so that the milling can be complete in one pass.
After choosing the face mill, the operator secures the work piece on the fixture or milling machine table. This is followed by the positioning of the machine spindle in perpendicular direction to the work piece surface.
The next step in how does face milling work is the cutting action. In this machining operation, the peripheral teeth do the real cutting. As you may have noted, the mill also has teeth on the tip. These teeth are usually for the finishing step. The cutter in face milling has a tip, which touches the part surface during the process.
During the milling process and like other machining processes, cooling the tool and surface takes place. There is also removal of the chips.
In summary, that’s how the face milling process works.
Types Of Face Milling Cutters
Shell Mills
Shell mills are the most recognizable face milling tools because they are the most common. This milling tool is characterized by the presence of inserts and cutting teeth on the outer edge. There is a reason why most users looking to achieve a smooth surface of the highest quality prefer shell mills. The face milling tools are designed to offer accurate control of the cutting forces and material removal, even at high speeds. The only requirement is that of changing the inserts for different work piece materials.
In face milling, there is one thing or step that you cannot afford to ignore – choosing the type of face milling tool. Let’s see the different types of face milling tools, before we discuss how to choose the right type in the next section. There are three main types of face milling tools namely shell mills, end mills, and fly cutters.
End Mills
There is also the end mill, which has teeth on the end. It uses these teeth to machine along the spindle axis and create flat surface on the work piece. Even before we look more deeply into the anatomy of the end mill, it is important to note that a drill bit is different. The profiles of the two are dissimilar and the versatility of the end mill is higher.
The end mill comprises several distinctive parts. They include the end gash, end teeth, and side teeth.
Fly Cutters
The fly cutter belongs to the rotary cutting tools category. This type is equipped with single-point bits that are affixed to a cylindrical piece. This combination is held by an angled holder, which rotates to face mill a wide range of materials including steel and aluminum. There are different types of fly cutters, including the Single-point fly cutters and rotary curving tools.
How To Choose The Right Face Milling Tools For Your Project?
Before embarking on your face milling project, it’s important to check a few points that can affect the quality of your results. Several factors should inform your choice of face milling tool. These include the type of work piece material and type of mill. That said, follow the following tips for the best face milling tool:
Choose your face milling tool based on work piece material. Since steel grades are harder than other materials, they should be milled using carbide bits. Aluminum is less demanding, so you can easily face mill it using high-speed milling tools.
Face mill the harder surfaces using the shell mill owing to its suitable cutting edge design
End mils have multiple cutting teeth, hence most suitable for eye-catching designs
Mill delicate or softer materials using fly cutters to optimize their low speed suited designs
Consider the entering angle – 45 – 90 degrees is the most acceptable range, but there are exceptions
For a durable cutting edge, use CNC machining instead of manual face milling
Align the machine speed to the spindle speed for tool integrity
Prevent instances of exit and reentry by not face milling holes and slots
Types Of Face Milling Operations
General Face MillingGeneral Face Milling
Any face milling process that does not have any special elements is called general face milling. While there are no special considerations, the entering angle is still a big factor. An entering angle of 45 degrees is the most common.
General face milling is optimized when:
Choose your face milling tool based on work piece material. Since steel grades are harder than other materials, they should be milled using carbide bits. Aluminum is less demanding, so you can easily face mill it using high-speed milling tools.
Face mill the harder surfaces using the shell mill owing to its suitable cutting edge design
End mils have multiple cutting teeth, hence most suitable for eye-catching designs
Mill delicate or softer materials using fly cutters to optimize their low speed suited designs
Consider the entering angle – 45 – 90 degrees is the most acceptable range, but there are exceptions
For a durable cutting edge, use CNC machining instead of manual face milling
Align the machine speed to the spindle speed for tool integrity
Prevent instances of exit and reentry by not face milling holes and slots
Heavy Duty Face Milling
As the name suggests, heavy duty face milling relates to the face milling of large work pieces. More powerful milling machines are used in this case. The machines have to be big because they are holding and machining materials that are significantly larger than normal.
As for the entering angle, the ideal one is 60 degrees. This is where the material removal rate is highest. Optimize heavy duty face milling with the following strategies:
Prioritize decluttering of the workspace
Avoid burns by using gloves during insert changes.
High Feed Milling
When the feed rate and cutting speed are high, we call that high feed milling. The cutting speed can be in the excess of 1000m/min but the entering angle is low. Use 10 degrees as the entering angle for the best results with this type of face milling.
Finishing with Wiper Inserts
Wiper inserts are used where face milling is used to achieve an aesthetically pleasing surface finish. There are different varieties of the wiper inserts. These are in terms of length and hand side.
Face Milling vs. Peripheral Milling: What’s the Difference?
In looking at the differences between face milling and peripheral milling, we must first appreciate that the two processes are closely related. To cement this argument, let’s see how peripheral milling works.
Peripheral Milling Overview
The other name for peripheral milling is plain milling. It is one of the most popular milling techniques. During the peripheral milling operation, the cutter rotation axis is parallel to the workpiece material surface.
The cutter may have teeth at the tip, but it is the teeth at the periphery that do most of the cutting. That’s because the cutter axis is parallel to the surface of the workpiece material.
Comparison between peripheral milling and face milling
Both face milling and peripheral milling are popular in the machining world. However, there are fundamental differences between the operations. To be specific, there is a big difference in the way the cutting tools in the processes are mounted.
In peripheral milling, the axis of the cutting tool is parallel to the work piece surface. The periphery of the tool presses against the workpiece material.
For face milling, the setup is the opposite of this. The cutting tool axis in face milling is perpendicular to the workpiece material surface. The tip of the cutting tool presses against the workpiece material.
Because of this unique setup, peripheral milling is more applicable where the user wants to remove material in large chunks.
Advantages and Disadvantages Of Face Milling
Here are the advantages and disadvantages of this milling technique:
Advantages
Produces a smooth surface finish
The cutting forces in the axial and radial directions are balanced
Spindle bearings experience less force
Chatter is minimal
Versatile machining process
Disadvantages
Not suited for corners
The cutter may produce chips as it exits
Maximum depth of cut is limited
Applications of Face Milling
The versatility of face milling makes the operation applicable in a broad range of projects. Here are a few of the applications of face milling:
Creating Flat Surfaces
In the industry, flat surfaces are necessary in many areas. Popular ones are steps and slots. Not even that, some materials are simply too rough or uneven for use. Face milling is used to produce a nice flat surface. The machinist requires to set up the workpiece and cutting tool expertly to attain the flat surface.
The face milling cutter is ideal for this kind of task because it presents a wide cutting surface area. The number of passes needed to complete the job are fewer than for alternative milling processes. With its multiple teeth or inserts, the face milling cutter also results in surfaces that are devoid of defects. This can reduce the need for further processes.
Surface Finishing
There are two main reasons why materials need to have a smooth surface: For aesthetic appeal and to enhance precision in critical industries such as aerospace. Face mills are very effective in creating high quality surface finish. The face mill is designed to remove material uniformly for consistent surface finishes.
Again, this cutting capability is due to the large cutting diameter that the tool features. Apart from ensuring consistent forces, the even distribution of inserts on the cutting tool ensures minimizes surface flaws. The result is a fine surface finish that is applicable in critical industries.
Surface Preparation for Further Processes
The face mill may produce a fine surface finish, but this sometimes is not the end of the processing. Some products need to be processed further, and the the face milling operations shorten the process. Whether you are looking to drill or tap the surface, doing it on well machined surface can make the results more presentable.
Machining Sizable surface areas
Face milling is renowned for removing material very fast and covering large surface areas. This capability is based on the wide cutting path of the process, something that sets it apart from many other processes. When you want to machine large flat surfaces areas fast, you may want to consider this machining process.
With the engagement of the several cutting inserts coupled with a large cutting coverage, the face milling process is typically successful in these kind of jobs. One may wonder, what about the large cutting forces generated due to the large surface area?
Well, the face milling cutters are designed to generate minimal forces. Therefore, you will realize that the cutting tool in this instance lasts longer because tool wear and deformation are not as serious problems as in many other milling cutters.
Tips To Optimize Face Milling Processes
The face milling operation may be versatile and very effective, but it needs the correct execution for the best results. That’s why the following tips are worth considering for this process to be successful:
Proper tool selection
If you find a successful face milling process, the cutter tool selection must have been right. The quality of face milling operations heavily depends on the shape, size, and material of the face milling cutter.
So, when you are selecting the tool, ask yourself a few questions. Is the tool material suitable for machining that kind of workpiece? Does the tool have the design to deliver the desired surface quality?
Considering the association between face milling and fine surface finishes, make sure the tool can deliver such results. Go for a cutting tool with fewer but sharper cutting edges. The rake angle should also be positive because this combination suits finishing machining processes.
Proper Insert positioning
Face milling inserts may be capable of producing excellent surface finishes, but you must choose and position them properly. The diameter of the insert in relation to the size and nature of the workpiece. To add to the surface finish quality, proper insert positioning can enhance tool rigidity, dissipation of heat, and chip removal.
Balance feed rate and speed
The feed rate and speed are two most important cutting parameters during face milling operations. These plus other parameters are adjustable based on the cutting requirements of a specific part. It is upon you to find out the ideal combination of these elements for your part.
That’s because carefree combination of these parameters can affect accuracy of the results. For instance, if you overdo the feed rate and rotation speed, you may as well forget about a quality surface finish.
Apart from the accuracy being affected, overzealous feed rate and speed can also cause the face milling cutting tools to wear faster.
Use of Coolant
The build-up of heat on the tool material and workpiece material can be detrimental to the process. You want to makes sure that the coolant system is working properly. The coolant should also be of the best quality. The intention is to ensure safety of the milling procedures and prolonged tool life.
Proper chips removal
For better chips removal, you want to relook into the quality of the coolant system. Are the cutting tool and workpiece materials well cooled to aid in chip removal? Other aspects that may affect chips removal are the chip removal slots, your face milling parameters, and milling machine enclosure.
Cut dimensions
With optimized cut dimensions, the overall face milling process will also be more optimized. Here are some steps you could take:
Secure the workpiece properly to minimize vibrations
As part of quality assurance, check the dimensions of the product regularly
Avoid tool overhang as much as possible
Use face milling tools with the right inserts, cutter diameter, etc.
Overhang Best practices
With optimized cut dimensions, the overall face milling process will also be more optimized. Here are some steps you could take:
Secure the workpiece properly to minimize vibrations
As part of quality assurance, check the dimensions of the product regularly
Avoid tool overhang as much as possible
Use face milling tools with the right inserts, cutter diameter, etc.
Quality of Inserts on Cutting Tool
There are many ways investing in high quality inserts can optimize your face milling operations. Consider the impact this decision has on tool life. Due to higher wear resistance, the amount of downtime is minimized, thereby adding to the business profitability.
Tool Path Quality
There are many ways to enhance the tool path quality. The simplest or most straightforward one would be to utilize the tool path utilization features available in CAM and CAD software.
Regular Milling Machine calibrationRegular Milling Machine calibration
The success of the face milling operation is related to the machine’s condition. It also depends on the relevance of the machine to the operation. Keep the milling machine well-calibrated. Make sure that the face mill is operating at the right speeds, feed rate, etc.
Conclusion
With this coverage, you can face your face milling projects with more confidence. But if you still need help on face milling in any way, there’s a way out. Aria Manufacturing offers the best face milling services around.
We have the experts and machinery to deliver your custom requests fast and as you want them. Ask for a free quote today.
Author
Gavin Leo is a technical writer at Aria with 8 years of experience in Engineering, He proficient in machining characteristics and surface finish process of various materials. and participated in the development of more than 100complex injection molding and CNC machining projects. He is passionate about sharing his knowledge and experience.