What's the Differences Between Milling and Shaping Operations ?

Abstract: 

Milling and shaping are two different machining operations used to remove material from a workpiece and shape it according to desired specifications. While both operations involve cutting tools and material removal, they differ in terms of process, tooling, machine type, and the nature of the resulting surfaces.

Keywords:

Milling, Shaping, Process, Tooling, Machine Types,  Resulting Surfaces

Learning Outcomes

After undergoing this article you will be able to understand about the differences of milling and shaping operations. 

1. What's Milling Operations?

2. What's Shaping Operations?

3. Why milling and shaping operations are carried out?

4. What's the differences of milling and shaping operations?

5. Conclusions

6. FAQs

References 

1. What's Milling Operations?

Milling is the process of machining using rotary cutters to remove material by advancing a cutter into a workpiece. This may be done by varying directions on one or several axes, cutter head speed, and pressure.

A modern milling machine is often paired with Computer Numerical Control (CNC) for automated control over the whole process.

There are many different types of milling operations. Each of these types can create different components of shapes. These different types are:

• End Milling: An end mill is similar in shape to a drill bit. However, end mills are able to cut radially and axially. The drilling machine can only cut in the axial direction. A conventional milling machine can cut only in the radial direction.
• Face Milling: A face mill is used when working on the surface finish of a workpiece. Face mills can turn an uneven surface into a flat surface. It can also create very smooth surface finishes. There are different automatic and manual milling options for face milling.
• Chamfer Milling: Chamfer milling machine is used to make chamfers and bevels. A chamfer mill is also known as a chamfer cutter. Chamfer mills also have other applications like deburring, countersinking, and spotting.
• Slot Milling: Slot milling uses a long rotary cutting tool to create grooves in a workpiece. It is also known as groove milling. The slots made by this machining process are deeper than what end mills can create. The grooves can be closed or open, with many options for shapes.
• Peripheral Milling: In peripheral milling, the cutting tool is placed parallel to the workpiece. Therefore, the sides of the cutting tool grind against the work surface instead of the tool tip. This is the opposite of the face-milling process. Peripheral milling is preferable when a large amount of material removal is required.
• Climb Milling: In climb milling, the cutting tool rotates in the feed direction. This is the opposite of conventional milling operations, where the cutting tool rotates opposite the feed direction. The cutting tool climbs over the workpiece resulting in an accumulation of chips behind it. This eliminates the problem of chips obstructing the cutting tool.
• Profile Milling: The profile milling process is used when machining vertical surfaces or vertically inclined surfaces. It can be used in the roughing as well as the finishing stage. Different types of cutting tools in profile milling are based on roughing or finishing operations.
• Helical Milling: Helical milling makes helical pathways, channels, and holes in a cylindrical workpiece. The workpiece is present on rotary tables. The rotating cutter moves along a helix angle along the workpiece. Helical milling is a common type of process for making lubrication holes and path on a workpiece.

• Plunge Milling: In plunge milling, the feed is in the same direction as the tool axis. This process is also known as z-axis milling. Plunge milling is commonly used in the roughing stage. The cutter plunges into the workpiece and carves out pockets in the material.
• Thread Milling: Thread milling is used to make threads inside a workpiece. Thread mills work on predrilled holes only. The thread mill rotates as well as revolves around the interior surface. Thread turning is more commonly used than thread mills.
• CNC Milling: CNC stands for Computer Numerical Control (CNC). CNC milling utilizes computer programs to control the cutting tool’s motion. It can create parts of high complexity at fast speeds. Depending on the complex shapes required, there are multiple axes options for CNC milling machines.

2. What's Shaping Operations?

A shaping operation is a process that uses a tool to create a smooth, flat, and sculpted surface on a workpiece. The tool is positioned with the workpiece, then repeatedly moves in a straight line while the workpiece is fed into the tool's path. The tool may reciprocate across the stationary workpiece, and it may be tilted or lifted after each stroke to prevent chipping. 

Here are some details about shaping operations: 

Tool

The tool is a single-point reciprocating tool that cuts metal when the ram moves out of the column. The tool's cutting velocity is important. During the cutting stroke, the tool should travel at the optimal velocity to remove material from the workpiece. During the return stroke, the tool should travel at maximum velocity to reduce idle time and increase production. 

Machine

Shaping operations are performed on a machine tool called a shaper. The shaper's main components are the ram and the worktable. The ram has a toolpost with a cutting tool mounted on its face. The worktable holds the part and moves it into the tool's path. 

In shaping, the cutting tool rotates while the workpiece remains stationary. Shaping is used to change the size and shape of a workpiece. Like planing, it will remove material from the workpiece. The cutting tool will press against the stationary workpiece while removing material from it.

The following are the shaper machine operations:

1. Machining horizontal surface
2. Vertical surfaces
3. Angular surfaces
4. Irregular surfaces
5. Cutting slots, grooves, and keyways
6. Machining splines or cutting gears.

Operations on Shaping Machine

With the knowledge of the parts of the shaping machine, we can now learn the operations that are generally performed on it. Refer to the diagram of operations as we discuss them.

Machining Vertical Surface

When finishing a workpiece, a block, or cutting a shoulder, the vertical surface machining process is employed. The surface that needs to be machined is properly aligned with the ram axis and positioned in a tight vice or clamp or directly on the table.

Machining Horizontal Surface

A shaper is mostly employed in horizontal operation to create a flat surface on a workpiece, held in a vice. The table is raised until there is a 25 mm to 30 mm gap between the tool and the workpiece.

The position of the stroke is adjusted such that the tool moves 12 mm to 15 mm before the shaping operation. The stroke should be 20 mm longer than the work. For roughing work, the depth of cut often ranges between 1.5 and 3 mm, whereas for finishing work, it typically ranges between 0.075 and 0.2 mm.

Machining Angular Surface

An angular cut is produced at any angle other than 90 to the horizontal or vertical plane in the shaper. The workpiece is placed on the table, and the tool head vertical slide is rotated to the required angle, either to the left or right, from its vertical position.

Cutting Slots, Grooves, and Keyways

A shaper can easily machine slots, grooves, and exterior and interior keyways on shafts and pulleys or gears with the right equipment (Eg. Gear shaping machine). A square nose tool is used to machine slots or keyways.

Machining Splines or Cutting Gears

With the help of an index centre, a gear or spline with identical spacing can be cut on a shaping machine. The workpiece is positioned between two centres, and a spline is cut in the shape of the keyway. 

3. Why milling and shaping operations are carried out?

Milling and shaping are two different machining operations used to remove material from a  and shape it according to desired specifications. While both operations involve cutting tools and material removal, they differ in terms of process, tooling, machine type, and the nature of the resulting surfaces.

4. What's the differences of milling and shaping operations?

The differences of milling and shaping operations are as follows:

Milling:

1. Process: Milling involves the use of a rotating multi-point cutting tool (milling cutter) to remove material from the workpiece's surface. The workpiece is typically held stationary while the milling cutter moves across it, creating various shapes, features, and contours.
2. Tooling: Milling cutters come in different types, such as end mills, face mills, ball mills, and more. These cutters have multiple teeth or cutting edges that interact with the workpiece to remove material in the form of chips.
3. Machine Type: Milling can be performed on various types of machines, including vertical milling machines, horizontal milling machines, and CNC machining centers.
4. Flexibility: Milling operations are highly flexible and capable of creating a wide range of shapes, sizes, and features. They can be used for both flat and curved surfaces.
5. Material Removal: Milling gradually removes material in layers, allowing for controlled depth of cut and feed rates. This results in smoother surface finishes compared to shaping.
6. Applications: Milling is suitable for producing complex shapes, pockets, slots, threads, and other intricate features on a workpiece. It's commonly used in industries such as manufacturing, aerospace, automotive, and mold making.

Shaping:

1. Process: Shaping involves the use of a reciprocating single-point cutting tool (shaper tool) to remove material from the workpiece. The shaper tool moves in a linear back-and-forth motion, cutting material as it passes over the workpiece.
2. Tooling: Shaping employs a single-point tool called a shaper tool. The tool's cutting edge is shaped to match the desired profile or contour.
3. Machine Type: Shaping operations are primarily performed on shaping machines, which are specifically designed for this purpose.
4. Limited Shapes: Shaping is more limited in terms of the shapes it can create compared to milling. It's generally used for simpler shapes and profiles.
5. Material Removal: Shaping removes material with each pass of the tool, resulting in a surface finish that may be less smooth than that achieved with milling.
6. Applications: Shaping is used for producing relatively simple flat and contoured surfaces, keyways, and straight-sided grooves. It's often employed when milling may not be practical due to the shape or size of the workpiece.

5. Conclusions

Conclusions about milling and shaping operations: 

Precision

Milling is one of the most precise manufacturing technologies, especially when using CNC milling tools that are directed by a computer program. This high precision can lead to consistent parts and is required in industries like aerospace and medical. 

Versatility

Milling can create complex shapes and features on a wide range of materials, including hard materials like titanium and Inconel. 

Efficiency

Milling has a high production rate and low labor costs, which can lead to cost-effective operations. It can also save time and improve operational efficiency, which can lead to faster product-to-market delivery. 

Safety

Turning-milling machining can reduce the need for operators to handle heavy or awkward parts, which can reduce the risk of injury and improve overall safety. 

6. FAQs

Q. What are the Different Stages in the Milling Process?

Ans.:

Here is a step-by-step breakdown of the working process of milling machines:

1. Workpiece Loading: The preliminary setup involves keeping the workpiece on the machine table feed and securing it. Wobbly fixtures will result in machining errors and poor precision.
2. Tool Selection: Many different types of milling machine tools exist. Choose the right tool for the job, which depends on the workpiece materials and the required result.
3. Machine Setup: Machine setup involves adjusting parameters like spindle speed, coolant flow, feed rate, cutting depth, etc.
4. Milling Execution: The operator starts the actual milling operation once the setup is complete.
5. Roughing: Roughing is the process of removing abundant material from the workpiece. This is done to get the workpiece into a vague resemblance of the required shape. This is done at a high cutting speed and feed rate.
6. Semi-finishing: Once roughing completes, the speed of the milling machine is reduced. The workpiece is shaped identically to the final part.
7. Finishing: Finishing occurs at a very slow feed rate and low depth of cut. The aim is to improve the dimensional accuracy of the part and make it as close as the machine possibly can.
8. Unloading: The operator removes the finished part from the milling machine.
9. Inspection and Quality Control: The final part is inspected to ensure there are no flaws. In case of any defects or further machining requirements, the operator loads the part on the machine and goes through a further finishing pass. This stage repeats until the part meets the required standards.
10. Post-processing: The part can undergo any secondary machining requirements after milling. Common post-processing steps are deburring, cleaning, grinding, surface treatment, etc.

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