4 Axis CNC Machining - China CNC Machining Service - Sunrise Metal

Why Choose 4 Axis CNC Machining?

Creating a Part With 4 Axis CNC Machining4 Axis CNC machining involves a total of four degrees of freedom. That means either the tool or the workpiece can be moved/rotated along four axes. So, the workability is apparently higher than 3 Axis CNC machining.

Having the 4th axis allows the manufacturing of more complex parts. It is also be used to increase the number of parts you can work with at a time. So, manufacturers highly prefer 4 Axis CNC machining as an economic method for increasing production capabilities.

4th Axis Components

There is some fundamental difference in the construction of a 3 and 4 axis CNC machine. You might want to keep them in mind if you are new to 4 axis CNC machining.


Tombstone of Horizontal CNC Machine

This is something you won’t encounter in 3 axis CNC machining. The tombstone is an exclusive feature of four axis machining. It is a tower-like arrangement with several mounting points for the workpiece. This is comparable with the milling table that holds the workpiece.

But tombstones can be rotated with the 4th axis to give access to more surface area and of course more parts. This is usually seen in a horizontal CNC machine. However, tombstones can be seen in vertical CNC machines as well. But it only allows parts with less clearance.


CNC Machining Lathe Chuck

Chucks or Lathe Chucks are used to clamp the workpiece with the 4th axis when tombstones are not used.  They are utilized when both milling and turning of a part is required.  However, you can only work with one part at a time with this setup.


4 Axis Vertical CNC Machining Vise

The vise works as a mounting surface for the workpiece. They are mainly used for vertical 4 axis CNC machining. Directly clamping a workpiece will only machining of the top surface. Vises give you access to a workpiece from three directions.

Vises can also be mounted on the tombstone surfaces as well. This will allow you to machine more parts in one go.

4 Axis CNC machining Working Principle

 Machining a Part With the 4th Axis

4 Axis CNC machining works almost similarly to 3 axis CNC machining, except that it includes an additional rotational axis for the workpiece. The cutting tool can move along the X, Y, and Z-axis just like how a 3 axis milling machine would perform.

An additional rotating mechanism is set up on the table which functions as the 4th axis. It is also called the A-Axis. Usually, a cylindrical workpiece is clamped into it and the workpiece is rotated to perform machining from different angles. So, the part can be machined without any setup change.

The 4 axis CNC machining process can be divided into the following steps.

  • Programming
  • Workholding
  • Machining

4 axis CNC milling/turning machine programming can be done using a CAM program. It generates a suitable toolpath for the CNC machine. The machining sequence, rotation speed, tool selection, etc. can be defined in the CAM program.


The workpiece is carefully clamped into the chuck of the 4th axis. Sometimes a tombstone is attached to the 4th axis which acts as a mounting surface for multiple parts. So, multiple machining tasks can be done at one go without having to go through the hassle of calibrating the workpiece every time.


4 axis CNC machines can perform both milling and turning operations. Simply replacing the milling tools with a lathe cutting tool will convert the CNC milling machine into a CNC turning machine. The CNC machine is operated by feeding the codes generated by the CAM program.

Here’s a video that explains the 4 axis CNC machining process in brief.

Types of 4 Axis CNC Machining Centers

4 Axis machining is performed on multiple types of machining centers. While all of them have four axes, their construction and functionality are a bit different than one another.

Based on the working mechanism four Axis CNC Machining Center it may be classified into the following categories.

  • Positional (3+1 Axis)
  • Simultaneous (True 4 Axis)
Positional (3+1 Axis)

Positional (3+1) Axis CNC Machining CenterThe Positional 4 axis machining center is basically an upgraded version of a 3 axis CNC machine. Even though there is a 4th axis, the machine would function just like how a 3-axis machine would. The only difference is that the workpiece can be rotated along the X-axis.

You can add a 4th axis to your existing 3 axis equipment whenever you want. However, additional controllers and programming is required to incorporate the 4th axis functionality. But, simultaneous machining is not possible with the 4th axis.

When cutting is complete on one surface, the workpiece is repositioned at a different angle, and the machining continues again. Since the 4th axis operates separately from the rest thus it is known as the 3+1 Axis machining center as well.

Such a setup is more suitable when machining a part with square or polygonal features on the end. It is also good for using along with tombstones.

Simultaneous (True 4 Axis)Simultaneous (True) four axis CNC Machining Center

It can utilize all four axes together. So, it came to be known as simultaneous or true 4 axis machining center. More complex details are possible with a simultaneous four-axis machine as both the tools and workpiece can move and rotate at the same time.

Note that, any machine capable of simultaneous machining will have positional machining capability as well. However, Simultaneous machining supports complex toolpaths that can be quite hard or impossible to execute with positional machining.

It is especially useful for machining intricate details in a cylindrical workpiece.

Based on the construction of the four Axis CNC Machining Center it may be classified into the following categories.

  • Vertical
  • Horizontal
4 Axis Vertical CNC Machining Centers

Vertical CNC Machining Center

In this case, the workpiece is held parallel to the table, and machining is done from the vertical direction. 4 Axis CNC Vertical Machining Centers are more common. Because they are mostly a conventional 3 axis vertical milling machine equipped with a 4th axis.

The 4th axis may support both positional or simultaneous four axis CNC machining depending on the controllers used and how it is programmed.

4 Axis Horizontal CNC Machining Centers


horizontal CNC Machining Center

In 4 Axis CNC Horizontal Machining Centers, the workpiece is held vertically and machined from the horizontal direction. Horizontal machining centers are mostly coupled with a tombstone to support machine multiple parts. And it is usually positional in nature.

Unlike 4 axis CNC vertical machining centers, these are rarely converted from an existing 3 axis machining center. The construction is entirely different and comes embedded with the 4th axis, to begin with.

Which One to Pick?

Among all the different types of four axis CNC machining centers, determine which one you really need can be confusing. You can consider the following things when deciding on one.

  • Assess the geometry of your part to determine whether you will need both milling and turning functionality in the 4 axles CNC machine or just one of them.
  • If you to machine a large batch of parts, consider 4 axles CNC machines with a tombstone.
  • When you are dealing with multiple flat parts and less clearance is needed, you will be fine with a vertical four axis CNC machine. Otherwise, you will need a horizontal four axis CNC machine.
  • If you want to machine curved features, you will probably need a simultaneous four axis CNC machine for this job.
  • Otherwise, go for a positional (3+1) 4 axles CNC machining centers.

 4 Axis CNC Machining’s Common Applications

Before you decide on 4 axis CNC machining, you must know its scope of use. A clear assessment of your part design is needed to determine whether you need 3,4 or 5 axis machining. Some common scenario is described below where 4 axis machining is required.

To Increase the Production Capacity

Well, your part design may not even need four-axis CNC machining. But if you want to increase your production capacity you can use a  four axis CNC machine for increasing the number of parts you can work on at a time.

This is especially useful for machining a large number of small parts. Because setting up the workpiece for each part is quite a time consuming and hampers production. A positional 4 axless CNC machine loaded with a tombstone is all you will need in this case.

Detailing Cylindrical Objects

The 4th axis is a rotational axis. So, the workpiece can be freely rotated like a CNC lathe and machined simultaneously. So, intricate details can be implemented on a cylindrical object with 4 axles CNC machining. The CAM programming is also simpler due to the 4th axis capability.

Machining Sharp Edged Corners

Parts with sharp edges at the end or sides can be easily machined with the help of the 4th axis. The part can simply be rotated at a suitable angle so that it can be end milled without issues. It is especially useful for introducing edged features in a cylindrical part.

The 4th axis rotation allows lathing the cylindrical features and milling the edges at the same time. So, you can complete the part without switching between the milling machine and lathe.

4 Axis CNC Machining Advantages

The major advantages of 4 axis CNC machining over 3 axis CNC machining is described below.

Reduced Setup Change: 4 axles machining allows working on parts from four different angles. This minimizes the need for unnecessary setup changes.

Higher Production Capacity: 4 axis machining can deal with more parts compared to 3 axis machining. Using a tombstone in a 4 axis machine more than quadruples the number of parts you can machine at a time.

More Efficient: Any 3 axis CNC router can be converted into a four axis CNC router. It requires a fairly small investment. But it greatly increases the production speed and capacity compared to the 3 axis CNC router.

Supports Milling & Turning: Machining cylindrical features are much easier with a 4 axis CNC machine. Unlike 3 axis equipment, both milling and turning of parts can be done with a single machine.

4 axis machines are costlier than a 3 axis machine. And adding a 4th axis to the existing equipment will need some investment as well. However, given the efficiency and production capacity of four axis machining, it can prove to be more economical in the long run.

3 Axis vs 4 Axis CNC Machining

Limitations Compared to 5 Axis CNC Machining

5 Axis CNC Machining has more capability than 4 axis CNC machining. It supports the movement of the tool/workpiece in five directions. Three degrees of freedom is along the linear X, Y, and Z-axis, and the other two are rotational axis usually termed as the A and B axis.

5 axis CNC machining almost eliminates the need for unnecessary setup changes. Thus, very complex parts can be machined in a single run. The time required is also significantly reduced in this case.

However, the additional capability of the 5th axis comes with a significant increase in cost. So, manufacturers will not suggest 5 axis machining unless necessary. It is mostly used for prototyping purposes or for creating extremely complex parts.

Besides, you will encounter very few parts that need 5 axis CNC machining to accomplish. 4 axis machining will be more than enough for most of the parts.

4 Axis vs 5 Axis CNC Machining

So, have you decided on going with 4 Axis CNC Machining? If yes, then Sunrise Metal Can Help! We are an ISO9001 & IATF 16949 certified CNC machining professional with first-class 4 axis machining capabilities.

We have 8 dedicated 4 axis machining centers of the latest technology and also have all sorts of quality inspection instruments to ensure the quality of your parts. If you are interested in our CNC machining service, contact our customer support to get a quote.

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