Last Updated on November 23, 2023 by assistant
In the field of machining, there are many operations that require the removal of large amounts of workpiece material on a face milling machine. These operations are performed to remove excess parts from different raw materials to obtain machine parts designed for the project. These operations are collectively called milling. There are many types of milling, and in this article, we’ll discuss what face milling is, its definition, the machining process, some technical operating tips, and more. If you want to complete some milling projects, our online CNC milling service may be able to help you. Next, let’s learn about face milling.
What is face milling?
Face milling is an efficient CNC machining process. The workpiece to be processed is fixed on the lathe. At this time, the milling cutter faces the lathe workpiece. After calculating the feed per tooth, the multi-point cutting tool of the face mill cuts on the plane of the workpiece. Face milling focuses on producing a flat and uniform workpiece surface perpendicular to the spindle axis. By removing material in a sweeping motion, face milling produces a smooth surface and ensures precise dimensions, hence why face milling is also called “surface milling.” The figure below shows the process of surface milling to remove workpiece material.
As shown in the figure above, when the workpiece is in contact with the tool, the horizontal surface after the counterclockwise rotating facing mill removes the workpiece material is very flat, like a flat plate but does not show the appearance of a complete part. Therefore, face milling is also called slab milling.
What is the process flow of face milling?
The face milling process involves removing material from the flat surface of a workpiece using a rotating milling cutter called a face milling cutter. Here is a step-by-step overview of the face-milling process:
Workpiece mounting: Securely mount the workpiece to the milling machine’s table or fixture. Ensure proper alignment and clamping to maintain stability during machining.
Tool selection: Select the appropriate face milling cutter according to specific processing requirements. Consider factors such as workpiece material, required surface finish, material removal rate, and cutting conditions.
Tool installation: Install the face milling cutter onto the milling machine spindle. Make sure tools are properly tightened and aligned to prevent vibration and runout.
Tool Positioning: Positioning the face milling cutter at the desired starting point on the workpiece surface. Adjust the machine’s axes, such as X, Y, and Z, to align the tool with the workpiece.
Cutting parameter setting: Set cutting parameters according to processing requirements. These parameters include cutting speed (the surface speed of the tool), feed rate (the rate at which the tool advances into the workpiece), and depth of cut (the amount of material removed in each pass). The setting of parameters is very important for the quality of the presented artifacts. If the face milling tool speeds and feeds of the face milling cutter are not set well, it may have a relatively large impact.
Workpiece movement: Start the milling machine and start the face milling operation. The machine will move the face mill along a predetermined tool path across the workpiece surface. This path can be linear, circular, or a combination of both, depending on the specific machining strategy employed.
Material Removal: As a facemill rotates, its cutting edges engage the workpiece material, removing material in the form of chips. The cutting edge shears and plows through the material, generating heat and force.
Chip Evacuation: Proper chip evacuation is critical for efficient face milling. A machine tool’s chip management system, such as a chip conveyor, auger, or coolant flush, helps remove chips from the machining area to prevent chip recutting and tool damage.
Multiple passes and finishing: Depending on the desired surface finish and material removal requirements, multiple passes may be required. Each subsequent pass removes additional material until the desired dimensions and surface quality are achieved. Finishing passes can take advantage of smaller depths of cut, reduced feed rates, or special tool geometries to improve surface finish.
Inspection and Quality Control: After completing the face milling operation, inspect the machined surface for accuracy, dimensional consistency, and surface finish. Use appropriate measuring tools such as calipers, micrometers, or surface roughness testers to verify the quality of the workpiece.
Post-processing operations: Depending on the specific application, additional post-processing operations may be required. These can include deburring, chamfering, or other secondary operations to remove sharp edges, improve aesthetics, or prepare the workpiece for subsequent assembly or finishing operations.
What face milling tools are used for face milling?
The cutting tools used in face milling are called face milling cutters. These tools are designed for machining flat surfaces. The success of every face-milled part depends on a dedicated milling cutter. Let’s take a look at these commonly used face milling cutters.
Shell Mills: Jacketed milling cutters are widely used in face milling. They consist of a cylinder with multiple cutting teeth around its circumference. Set milling cutters are available in a variety of diameters and widths to suit a variety of machining applications. They are usually mounted on or fixed within the milling machine spindle. As follows.
Indexable Face Mills: Indexable face mills have replaceable carbide inserts that are fixed to the face mill body. These inserts have cutting edges on multiple sides, allowing for multiple cuts before replacement. Indexable face mills are versatile and cost-effective because the inserts only need to be replaced when worn or damaged. As follows.
Solid Carbide Face Mills: Solid carbide face mills are made from a single piece of carbide material. They are known for their high rigidity, excellent wear resistance, and cutting performance. Solid carbide face mills are typically used in high-speed machining applications and can provide excellent surface finish and dimensional accuracy. As follows.
High-Feed Face Mills: High-feed face mills are designed for high-speed machining with extremely high material removal rates. They feature a unique cutting-edge geometry that enables high feed rates and shallow depths of cut, minimizing cutting forces and optimizing chip evacuation. High-feed face milling cutters are often used for roughing operations and can significantly reduce machining time. As follows.
Fly Cutters: A Flying Knife is another type of face mill cutter. They consist of a single cutting tool that rotates on the spindle of a milling machine. Fly Cutters are often used for light-duty face milling operations to achieve a good surface finish. They are often preferred for smaller workpieces or when a simple, low-cost solution is required. As follows.
These are just a few examples of face milling cutters commonly used in machining operations. Tool selection depends on factors such as the specific application, the material being machined, the surface finish required, cutting conditions, and machine tool capabilities. To get the best results, it is important to choose the right face milling tool based on these factors.
So, how do we choose the right face-milling tool? Don’t worry, here are some scenes compiled by the Ruitai Platform. You can choose the right tool based on these scenarios. These are some practical tips from CNC operators.
How to choose the right face milling tool?
The face milling tools mentioned earlier, such as shell mills, indexable face mills, solid carbide face mills, high-feed face mills, and fly cutters, are typically used for cutting a variety of materials in face milling operations. Here’s a summary of the materials these tools are commonly used for:
Shell Mills: Shell mills are versatile and can be used for machining a wide range of materials, including ferrous and non-ferrous metals, such as steel, stainless steel, aluminum, brass, and copper. They are also suitable for cutting softer materials like plastics and composites.
Indexable Face Mills: Indexable face mills with carbide inserts are suitable for machining various materials, including steels (carbon steels, alloy steels), stainless steels, cast iron, aluminum, and non-ferrous metals. The specific insert grade and geometry can be selected based on the material being machined.
Solid Carbide Face Mills: Solid carbide face mills are commonly used for high-speed machining of materials such as steels (tool steels, alloy steels), stainless steels, cast iron, titanium alloys, and heat-resistant alloys. They are also suitable for machining non-ferrous metals and some composites.
High-Feed Face Mills: High-feed face mills are often used for roughing operations in materials like steel (carbon steels, alloy steels), stainless steels, cast iron, and non-ferrous metals. They are designed to handle high chip loads and can be effective for materials that require aggressive material removal rates.
Fly Cutters: Fly cutters are generally used for light-duty face milling operations in softer materials such as aluminum, brass, plastics, and wood. They may also be suitable for facing operations in mild steels or low-carbon steels.
The tool selection tips above include a comparison between the shell mill vs face mill. In the actual face milling process, we also have many practical milling skills that can help us avoid some common processing problems.
Practical Milling Tips
1. Select appropriate cutting parameters
When face milling, you should choose your cutting speed, feed rate, and depth of cut based on the material you’re working with, tool capabilities, and the desired surface finish.
2. Ensure correct tool settings
When performing face milling operations, mount the face milling cutter securely and ensure proper alignment and runout. Using the correct tool holder, spindle or adapter can minimize vibration and runout, which can affect surface finish and tool life.
3. Keep knives sharp
You should regularly inspect and replace worn or damaged blades or cutting edges. Blunt or damaged cutting tools can result in poor surface finish, increased cutting forces, and shortened tool life. Following proper tool maintenance practices can extend tool life and ensure consistent performance.
4. Optimize chip removal
Effective chip evacuation is critical to maintaining machining efficiency and preventing chip re-cutting. You should use appropriate chip management techniques such as spindle center coolant, air blowers, or chip conveyors, depending on the capabilities of the machine tool and the material being machined.
5. Consider workpiece fixation and stability
Properly secure the workpiece to minimize vibration and movement during milling. When performing face milling, appropriate clamping methods or fixtures should be used to ensure the stability and accuracy of the workpiece.
6. Monitor cutting conditions
Technologies such as tool condition monitoring, vibration analysis, or power consumption monitoring are used to detect tool wear, tool damage or machining abnormalities. Adjust cutting parameters or replace tools as needed to maintain optimal performance.
7. Consider coolant or lubrication
Depending on the material being machined and the specific cutting conditions, appropriate coolants or lubrication methods can improve cutting performance, chip evacuation, and tool life. Select the correct cutting fluid or lubricant based on the material and machine settings.
8. Perform post-processing inspections
Inspect machined surfaces using appropriate measuring tools to verify dimensional accuracy and surface finish. This can help identify any potential issues or changes that may require corrective action.
Keep in mind that these tips provide general guidance, and it is important to refer to the specific tool manufacturer’s recommendations, machining guidelines, and best practices for the specific face-milling operation you are performing.
How many different types of face milling operations are there?
There are many different types of face milling operations, each with its own specific characteristics and machining directions. The main machining directions for these face milling types include:
Perimeter Milling: In perimeter milling, the face mill rotates around its axis and the cutting edges on the tool’s perimeter remove material from the workpiece surface. The machining direction is primarily radial, moving from the center of the face mill toward the periphery. This type of face milling is typically used for roughing and general-purpose machining.
Conventional Face Milling: Conventional face milling is similar to perimeter milling in which the cutting edge removes material from the workpiece surface. The machining direction is primarily radial, moving from the center of the face mill toward the periphery. This type of face milling is used in semi-finishing and finishing operations to obtain the desired surface finish and dimensional accuracy. For this kind of ordinary face milling, it is generally best to choose a face milling cutter with a leading angle of 45°.
Clockwise face milling: In clockwise face milling, the face milling cutter rotates in the opposite direction compared to conventional face milling. The cutting edge engages the workpiece material at the periphery and moves toward the center of the face mill. The machining direction is mainly axial, moving from the outer circumference to the center. Climb milling can offer benefits such as reduced cutting forces and improved surface finish, but it requires careful machine setup and tool selection to prevent tool deflection or workpiece movement.
High-feed milling (HSM): “High-feed milling” is a specific face milling technique that focuses on achieving high material removal rates using shallow depths of cut and high feed rates. The goal is to maximize productivity and reduce processing time. An entry angle of 10° was chosen for optimal feed rate. HSM effectively removes chips and reduces cutting forces while maintaining a good surface finish and tool life.
Heavy Face Milling: “Heavy Face Milling” refers to face milling operations that involve machining with higher depths of cut, heavier chip loads, or more aggressive cutting parameters. It is typically used when material removal rates need to be maximized or tougher materials processed. The machining direction can be radial or axial, and tools with a 60° entering angle generally provide the best feed rates and increase milling efficiency.
Face Milling Using a Bevel Mill: In some cases, a face milling operation may involve the use of a face mill with a bevel cutter. These tools have spiral or angled cutting edges that eject chips more efficiently and reduce cutting forces. The machining direction can be radial or axial, depending on the specific design and geometry of the bevel mill.
Finishing with Wiper Inserts: “Wiper insert finishing” is a technique used in face milling to improve surface finish. Wiper inserts modify the cutting-edge geometry to help smooth machined surfaces and reduce surface roughness. They are typically used in the finishing phase of face milling operations. In this process, the higher the feed per revolution produced by standard inserts, the greater the need for wiper inserts. The machining direction can be radial or axial, depending on tool design and desired surface finish requirements.
What is the difference between face milling and perimeter milling?
Face milling and perimeter milling are two distinct machining processes that differ in their objectives and cutting approaches. Here’s an explanation of the differences between the two:
Face Milling: Face milling is a machining process primarily focused on machining flat surfaces on the workpiece. It involves using a specialized cutting tool called a face mill that has cutting edges on its periphery. The face mill rotates on its axis, and the cutting edges remove material from the workpiece, creating a flat surface. The primary cutting direction in face milling is radial, moving from the center of the face mill towards the outer periphery. Face milling is commonly used for tasks such as roughing, finishing, and creating flat surfaces with high precision and surface quality.
Perimeter Milling: Perimeter milling, also known as periphery milling or contour milling, is a machining process that involves machining the outer profile or periphery of a workpiece. Unlike face milling, which focuses on flat surfaces, perimeter milling is concerned with creating contours, features, or profiles along the perimeter of the workpiece. Perimeter milling typically uses end mills or specialized contouring tools to cut along the edges or contours of the workpiece. The cutting direction in perimeter milling can vary depending on the specific contour or profile being machined. It can involve both radial and axial movements to follow the desired shape. Perimeter milling is commonly used for tasks such as creating complex shapes, machining curved surfaces, or adding features to the workpiece periphery.
In summary, the main difference between face milling and perimeter milling lies in their objectives and cutting approaches. Face milling focuses on machining flat surfaces using a face mill with cutting edges on the periphery, while perimeter milling aims to create contours or profiles along the outer periphery of the workpiece using specialized contouring tools.
What are the cutting speed and feed formulas?
The cutting speed and feed formulas are used to determine the appropriate cutting parameters for machining operations. Here are the commonly used formulas:
Cutting Speed (CS):
The cutting speed refers to the speed at which the cutting edge of the tool moves relative to the workpiece surface. It is typically measured in surface feet per minute (SFPM) or meters per minute (m/min).
The formula for cutting speed is:
CS = (π * Cutter Diameter * RPM) / 12
π is approximately 3.1416
Cutter Diameter is the diameter of the cutting tool in inches or millimeters
RPM is the rotational speed of the cutting tool in revolutions per minute
Feed Rate (FR):
The feed rate is the linear speed at which the workpiece moves relative to the cutting tool. It is typically measured in inches per minute (IPM) or millimeters per minute (mm/min).
The formula for feed rate is:
FR = Feed per Tooth (fz) * Number of Teeth (Z) * RPM
Feed per Tooth (fz) is the distance the workpiece advances during one revolution of the cutting tool per tooth, measured in inches or millimeters
Number of Teeth (Z) is the total number of cutting teeth on the tool
RPM is the rotational speed of the cutting tool in revolutions per minute.
Face Milling FAQs
Can a face mill be used for boring?
Yes, face mills can be used not only for boring but also for drilling.
How much does face milling cost?
The initial cost of face milling will be higher compared to other milling processes because it requires unique face milling tools, but also because these tools can be easily switched between different machining scenarios, making it cost-effective in the long term investment.
What is the difference between face milling and end milling?
Face milling and end milling are two common types of milling operations. Although they have some similarities, face milling, and end milling differ in cutting direction, application, tooling, and machining strategies. Face milling is primarily used to machine flat surfaces, while end milling is versatile and suitable for creating specific shapes and contours. In a previous blog, we made some comparisons between them.
This article introduces face milling, explains it, discusses its machining process, and more. However, knowledge is always endless. If you would like to know more about face milling, you can contact our team.
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