When it comes to CNC machining, two of the most common types of machines you'll encounter are lathes and mills. Both CNC lathes and CNC milling machines are essential tools in modern manufacturing, capable of producing high-precision parts with complex geometries. However, each machine has its own unique strengths and is better suited for specific applications.
In this blog, we'll discuss the key differences between a CNC lathe and a CNC mill, helping you determine which machine is the best fit for your manufacturing needs.
What is a Lathe Machine?
A CNC lathe refers to a computer numerically controlled turning center, a machine tool that shapes a workpiece by rotating it about its axis while employing cutting tools to remove its material to attain the required profile. The workpiece is normally held securely by a chuck or a collet, while the cutting tools are placed on a turret which has the capability of sliding in X and Z plane motions. CNC lathes are best suited in making simple cylindrical work parts with some additional features as threads, grooves and tapers.
Types of CNC lathes
Engine Lathe: This is the most prominent lathe and is often referred to as a center lathe. It’s mounted on a horizontal bed with a headstock and a tailstock for holding the workpiece. Engine lathes are quite adaptable and can perform numerous turning, facing, and threading operations.
Turret Lathe: A turret lathe features a multi-angular turret that accommodates various tools. This facilitates fast alteration of tools enhancing efficiency. Turret lathes are mostly used for mass production of small components.
Swiss-Type Lathe: Built for the precision fabrication of intricate and tiny parts, swiss-types lathes possess a slotted headstock and guide that holds the work near the cutting edge. This design suits the manufacture of elongated parts too thin in diameter like those used in the medical, dental, and electronic sectors.
Vertical Lathe: Vertical turning center is also known as this lathe type. In this case, the lathe spindle holding the work piece is oriented in the vertical plane. The cutting tools are fixed to a turret, which is capable of horizontal movement. Vertical lathes are suitable for large heavy and crazy shaped components which are cumbersome to fit on horizontal lathes.
Multi-Axis Lathe: Such lathes are more sophisticated in design and enhance movement on additional axes such as a milling spindle or axis y. Thus, complex parts can be completed in one operation unit without transferring the job to another equipment. Multi-axis lathes comprise of turning, milling and drilling operations hence minimizing the number of machines needed and enhancing the general efficacy.
Typical Applications of a CNC Lathe
These machines are also responsible for precision turned parts (±0.0005”) used in demanding applications such as power or propulsion systems. In power transmission, there are blanced shafts; there are splines and stepped shafts. Machining of aircraft components involves cutting exotic alloys for turbine engine components and landing gear parts. Medical implants designs combine advanced shapes and biocompatible materials.
In other industries, CNC turning is used in the fabrication of internal parts of valves and rotational fluid control devices. In hydraulic, vales, the internal geometry will include spools of certain diameter and sealing faces. There is always an emphasis on adequate cylindrical tolerance and surface treatment (16-32 Ra) for the bearings manufactured. The manufacture of threads can vary from conventional screwnut to advanced lead screw.
The latest CNC lathes are able to substitute turning for milling as both functions are present in a single unit allowing complexity in shapes to be achieved without the need for multiple work setups. These include, stainless steel, titanium alloys, pre engineered plastics, all of which undergo features for sub sector compliance.
What is a Milling Machine?
A CNC milling machine which is also referred to as a CNC mill is a machine tool where work piece material is removed by using rotating cutting tools in order to produce different features and shapes. In most cases, the workpiece is held down on a table that is capable of moving back and forth on the X, Y and Z horizontal and vertical axes, and the cutting tools are fixed in a high speed rotating spindle. CNC mills are considered to be very efficient machines since they have a number of applications ranging from drilling and boring to milling.
Types of CNC mills
The world of CNC milling machines offers a few distinct classes of machines, all which have their benefits and use cases.
Vertical Mill: The most widely used type of CNC milling machine is the vertical mill where the spindle holding the cutting tool is oriented vertically. The table moves in X, Y and Z axes in order to present the workpiece to the cutting tool. Vertical mills are general purpose and can undertake a great variety of milling processes.
Horizontal Mill: In a horizontal mill, the spindle is placed horizontally and is parallel to the table. Workpiece is placed on the table, which is moved in X and Y directions and the cutting tool is moved vertically in Z direction. Horizontal mills are ideal for cutting operations involving bulk components and deep milling.
Bed Mill: Bed mills are bigger and more durable machines than normal as they are made with fixed spindle and X, Y and Z axes on the table. The area of the table is usually bigger than those of vertical or horizontal milling machines hence its possible to machine larger parts. Bed mills are used more in the production sectors such as aerospace and energy.
Gantry Mill: A gantry mill also called a bridge mill has a frame in a shape of a bridge constructed across the worktable. The spindle is supported by a gantry that is movable in the X and Y axes, while the worktable is Z-axis translational movable. Gantry mills are large and powerful machine tend to have small cutting areas and large envelopes which makes them suitable for the manufacture of large intricate components.
Typical Applications of a CNC Milling Machine
CNC milling machines allow the fast and accurate fabrication of complicated geometries in different sectors of ±0.0002 inches. Aero structures have weight saving machined out pockets and thin walled sections. Injection mould care for well sculptured and smooth 3D shapes, sculptured that are necessary for provision of quality parts. Bio compatible implants are made from materials that have surfaces that facilitate attachment to bone.
In automotive spaces, engines CNC milled for ports shaped to exacting contours as well as valve seats. Transmissions case are designed with oil galleys in addition to pockets for bearings. Suspension parts have tight tolerances for mounting provision and joint surfaces. Brake calipers had to accommodate the invention of fluid channels and different pad retention systems.
In this respect, most manufacturing processes employ CNC milling in constructions of jigs and fixtures consistent in their primary datums. Gears have to be produced with the correct tooth form and concentricity. Volute and seal surfaces are provided in pump housing. Electronic cases are used with shielding and complex board interface arrangements.
Today’s CNC milling equipment makes it possible to carry out 5-axis simultaneous machining work. Consequently, there is no need to repeat machine set-ups for complex parts and this enhances productivity. Materials worked on include aluminum alloys, tooling steel and superalloys that are fabricated to upper performance limits.
CNC Lathe vs Mill: Key Differences
Workpiece orientation and cutting tool movement
One of the primary differences between a CNC lathe and a CNC mill lies in the orientation of the workpiece and the movement of the cutting tool. In a CNC lathe, the workpiece is held horizontally and rotates about its axis, while the cutting tool moves parallel to the axis of rotation (Z-axis) and perpendicular to it (X-axis). This configuration allows for the creation of cylindrical parts with features such as grooves, threads, and tapers.
In contrast, a CNC mill holds the workpiece stationary on a table that moves along the X, Y, and Z axes. The cutting tool, mounted in a spindle, rotates and moves relative to the workpiece to remove material and create the desired shape. This setup enables the machining of parts with complex geometries, including flat surfaces, slots, and pockets.
Suitable applications and part geometries
CNC lathes are primarily intended for turning operations of revolving geometrical form parts like shafts, bushings, and plugs. They particularly address operations like threading, grooving, and tapering the inside and outside of cylindrical components. Lathe machine apart from turning also perform other operations, for instance, facing, boring, and parting off.
It differs from CNC lathe as it can accomodate various part shapes within its range. These machines also excel in these shapes which tempered prismatic features of flat surface wear, slot and pocket machining. They also add features like 3d contouring, cavity and boss formation. Further, since CNC machines are multipurpose, CNC mills do the drilling, tapping and reaming of holes, hence they can produce components that have holes and with threads.
Precision and tolerance capabilities
Accuracy and narrow tolerances are features common to CNC lathes as well as CNC mills. However the exact tolerances that can be achieved differ with respect to the condition of the machine, cutting tool quality and the operator.
By and large CNC lathes are able to retain ±0.0002 inches (0.005 mm) or better tolerances with regard to diameter and length dimensions. They are capable of producing high surface finishes with the Ra values going down to 4 microinches (0.1 micrometer).
CNC mills on the other hand are capable of holding ±0.0001 inches (0.0025 mm) or better tolerances on linear measurements. They are also capable of producing decent surface finishes with the Ra values ranging around 16-32 microinches (0.4-0.8 micrometers).
Which is better for high volume production - CNC lathe or mill?
The selection of either a CNC lathe or a CNC mill for mass manufacturing of parts will be dependent on the shape and features of the manufactured parts. In the case of manufacturing cylindrical parts with uncomplicated shapes such as shafts and spacers, for instance, a CNC lathe will be the preferable choice. Such parts do not usually go through several setups since lathes do these parts on a single setup cutting down on unnecessary handling time thus chances of errors.
On the other hand, for instance, made in a lathe with several set ups complicated shapes which cannot be simply manufactured and carried duplicates a CNC mill will do best in the high demand producing them. CNC Mills can do more complex features in one operation eliminating the need for extra procedures that enhances performance.
A mill-turn center, which integrates the functions of a lathe and a mill may sometimes be the most suitable equipment for producing complex parts in large quantities. These types of machines allow turning and milling within the same fixture reducing cycle time and enhancing productivity.
Eventually, the choice of whether to use a CNC lathe or CNC mill for mass production is based on the characteristics of the parts being manufactured as well as the design of the entire manufacturing process.
Factors to Consider When Choosing Between a CNC Lathe and Mill
When it comes to the question of whether to use a CNC Lathe or a mill for manufacturing processes, consider the following factors:
Complexity of Parts and the Geometries You Want
When it comes to making symmetrical workpieces containing some simple features like threads or grooved shapes, one is likely to opt for the CNC lathe. When working on flat surfaces attached to grooves and pockets, among many other parts, the CNC mill is likely to be more adjusted to such geometries.
Regarding Machinability of the material and its type
In terms of working range, CNC lathes and CNC mills can be designed to use every possible material range from metals, plastics to composites. However, some of the materials may pose difficulties if machine on certain machines than on others. For instance, lathes may not be the ideal machine for making long and slim linear workpieces as they may, wobble or bend during the turning operations inside the machine. Hard and wear resistant materials can easily cause the milling tools to be completely worn out within a short time period.
Production Volume and Speed Requirements
Also think of your production volume and its speed when making a choice in a CNC lathe or a mill. For a repetitive geometric shapes production with prolonged length, the cylindrical turning centers will be the most preferred machine. While for repetitive low volume high mixed production cases with minimal cylindrical turning, lower level axes of rotation CNC milling machines will serve best.
Between a CNC lathe and a milling machine, which is more multipurpose?
In this regard, CNC milling machines are more versatile than lathes. Lathes, for instance, are only capable of manufacturing cylindrical objects, while mills can be used even for elemental geometrical shapes that have flat surfaces, grooves and hollows. In addition, operations like drilling, boring, and tapping can also be carried out on the CNC milling machine as well thus it makes it less restrictive in many aspects of manufacturing industry.
Combining CNC Lathe and Milling Capabilities
For some applications, it might be worthwhile purchasing a CNC turning center with a milling capability rather than having a separate lathe and a mill. Turn-mill centers or multitasking machines, as they are commonly referred to, are capable of doing turning and milling processes in just one machine, making it ideal in situations where several processes are done on a work piece minimizing setups and increasing efficiency.
Why Renting or Purchasing a Lathe and Mill Combined Machine is a Good Idea
A lathe-milling machine has its few downsides like:
Decreased average time taken for setups as well as an overall average increase in productivity
Higher precision and better repeatability as all operations are performed without removing the component from the working holder
More versatility and capability of making more intricate details
Occupies less area when compared to having separate lathe and milling machine.
When would it make financial sense to buy a hybrid CNC machine?
A hybrid CNC machine which is capable of lathe and milling works is worth purchasing whenever:
Parts that are designed are mostly turned and milled
The components to be manufactured are complex and are required to be manufactured within narrow tolerances
The space available is small and maximization in usage of machine is desired
There is a need to minimize the time taken for setup and maximize production in the overall sense
Conlusion: which is better overall - CNC lathe or milling machine?
When it comes to the lathe versus the mill, there cannot be a definite conclusion. For the reasons that the choice of the machine is dictated by the individual manufacturing requirements. In the event that you only produce round simple parts, a CNC lathe would be a better alternative. Nevertheless, if parts with intricate designs and various geometries are required, then a CNC milling machine would be the best option.
Knowing the difference between a CNC lathe and a CNC mill and analyzing the manufacturing needs can help in making the right choice of a machine suitable for achieving production objectives.
Reference Sources
Lathe
Milling(Machining)
FAQs About CNC Lathe and Milling Machine
How does a lathe differ from a milling machine?
A lathe spins the material outwards and the cutting tool remains in a fixed position making it suitable for producing cylindrical parts. On the other hand, a milling machine keeps the workpiece in a fixed position and multi-axis rotating cutting tools move above the surface which is suitable for creating complex shapes or prism shapes parts.
What does a lathe machine do?
A lathe machine holds a workpiece in a rotating chuck allowing cutting tools to be brought into contact with the workpiece to perform operations that produce cylindrical components. Lathes support a number of other operations apart from turning, and these are: facing, boring and also in threading cutting tools.
What is the operation of CNC lathe?
Computer numerical control (CNC) converts machining from manual to machine-based processes in a CNC lathe. It works in such a way that the object to be machined is held in a chuck or collet and rotated about an axis of rotation while a tool, which is fitted in a turret or tool post, is fed in the axial direction to remove the material in a pre-determined tool path.
What about milling with a lathe?
In some cases, advanced lathes, a term known as mill turn centers or multitasking machines should be used. Such machines are capable of both lathe and mill functioning at the same time. Hence, it will enable the turning of parts and milling of features that are mixed on the same part in the same set up.
Which is more accurate, a CNC mill or lathe?
CNC lathe and milling machine offer the capability of operating within tight tolerances, typically ±0.0001 inches (0.0025 mm) or even narrow, with regards to efficient practice. In reality, the achieving accuracy in machining operations depends on the state of the machine, the condition of cutting tools, the skill of the operator among other considerations.
