Multi-axis Machining Explained: 3-Axis to 5-Axis
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Multi-axis Machining Explained: 3-Axis to 5-Axis
The complexity and accuracy needed in today’s precision engineering demand extremely efficient machines and tools. The expectations in the industry are so high that conventional machining methods may not be good enough. Are are looking for the highest level of machining results for your turbine blades, engine blocks, and such intricate components? Multi-axis CNC machining technology may be the answer.
Multi-axis machining, a process defined by multiple tool movement directions, is extremely popular in medical, automotive, defense, and aerospace industries among others. The industries produce many parts using CNC milling machines and other types of CNC machines. There is so much to gain from the technology – faster production, relatively better surface finish, higher accuracy, and more ability.
However, there are differences of 3-axis to 5-axis machining categories. The details of these methods can determine suitability for a particular project. Considering the uniqueness of project requirements, budgets, and user preferences, we present this quick guide that compares three axes, four axes, and five axes machining to help you make an informed choice.
What is Multi-Axis Machining?
Multi-axis machining is a manufacturing process that utilizes multiple rotational axes to enhance the capabilities of conventional CNC machining. It is capable of creating intricate parts with complex shapes, curved profiles, and undercuts.
Multi-axis CNC machining is based on the Computer Numerical Control (CNC) technology. This technology automates the direction and movement of various parts of the machine, including the cutting tools.
With the traditional machining methods, it is almost impossible to achieve such results. The complexity and ultra-precision that comes with multi-axis machining is unmatched. That the process creates parts faster makes this option even more irresistible.
Multi-axis CNC lathe machining may have advanced features, but the foundation of the technology goes back a few decades ago. The multi-axis technology was present before 1952, but that is the time that Richard Kegg introduced the concept of CNC machining. Earlier, machinists relied on the manual operation of CAM plates.
Aviation, medical, and automotive industries have invested a lot in this technology due to the efficiency and versatility it provides. To demonstrate more about the capability of multi-axis machining, let us review how CNC machining works.
How Does Multi-axis CNC Machining Work?
As we review how multi-axis CNC machining works, it would be worthwhile to mention the basics of axes in the machine. CNC machines are within the Cartesian coordinate reference system domain. The basis of this system is the intersection of perpendicular axes at an original or common point. These linear axes are the X-axis, Y-axis, and Z-axis.
Linear Axes and Rotary Axes
For machining to be accurate and have effective cycle times, the linear axes work hand in hand with the rotary axes. The specific rotary axes for CNC machining are A axis, B axis, and C axis. As you would guess, the name of the axes comes from the fact that these axes (A axis, B axis, and C axis) are associated with rotary motion. The rotary motion in this case is around the linear axes.
If you come across the 2-axis CNC machine, know that it can only machine the workpiece on two sides at a time. This typically means a pair of linear axes. Using the same argument, the 3-axis CNC machine is limited to machining three sides – X axis, Y axis, and Z axis.
Rotary Axes Make the Difference
When the rotary axes are added to the mix, this gives rise to multi-axis machining. Multi-axis machining can be 4-axis, 5-axis, and so on, based on the sides of the workpiece that the machine can work on at a time to produce parts.
Multi-axis machining works differently from 2-axis and 3-axis machining in that it can shift the positions of the bed and cutting tool in both linear and rotary positions. It is important to note that the 3-axis CNC machining method is not a multi-axis version. This is because the cutting tool moves in the X, Y, and Z axes only.
Common Steps in Multi-axis CNC Machining
This process involves systematic steps that are largely similar for all setups. Here is a common sequence in all the types of multi-axis CNC machines:
Part Design:
The graphical design of the component is produced. The main features and dimensions of the component are identified.
CAD Model:
Computer Aided Design software is used to develop the CAD model for the part. You can find all the component details in this model, but they are the digital graphic type.
CAD to CAM Conversion
This is a necessary step considering that the CNC machine can only recognize CAM concepts. The CAM software helps in this conversion step.
Setting Up the CNC Machine
Setting up the CNC machine involves part loading, loading the CNC machine with the CAM software, and feeding in the respective operation settings such as work coordinate.
Running the CNC Machining Program
For the CNC machine to work on the workpiece, the operator has to run the program. As long as the program is okay and the machine is in good working condition, the machining process will start and run to the end as programmed.
Final Step
The CNC machining process is complete when the operator inspects and approves the produced part. Removing the part from the CNC machine would be the final step.
For more on the differences between 3-axis machining, 4-axis machining, and 5-axis machining, we now discuss them individually.
3-Axis CNC Machining
The 3-axis CNC machining process involves a vise that holds the workpiece in place. The vise rests on a moving table, which can move on the X (length) and Y (width) axes.
The tool is designed to operate along the Z axis (depth). Consequently, the 3-axis CNC machining method is capable of removing material from the workpiece along the width, length, and depth directions.
This machining method is ideal for jobs where the details are limited or not too many details are needed. It could be used for complex features, but this would take some time. For more details, CNC machines with higher configurations are recommended.
Limitations of 3-Axis CNC Machining
If you are regularly machining highly complex parts, this type of CNC machining may not be good enough. The three axes offer limited movement, a characteristic that makes it difficult to machine intricate contours and 3D designs.
This machining technique typically gives excellent results where a flat surface and limited geometry jobs are involved. It is enough for you if you specialize in simple metalworking, hobbyist woodworking, and basic prototyping.
Furthermore, machining multiple sides of the workpiece simultaneously can be a demanding undertaking. Since executing such jobs on a single setup is practically impossible, you may be required to set up the machine several times before you can achieve the desired part.
The increased setup time can have huge ramifications on production time and consequently, business profitability.
4-Axis CNC Machining
For this one, there is one more axis as compared to the 3-axis machining method. In other words, this type of CNC machine can machine in the X, Y, and Z axes and one more axis. The extra/fourth axis is rotary and connected to one of three axes – X axis, Y axis, and Z axis.
It could be A axis, B axis, or C axis. The 4-axis CNC machines come with a swivel head or rotary indexing tables to support this operation involving a fourth axis.
Limitations of 4-Axis CNC Machining
For many people with job shops, the costly initial investment for the 4-axis CNC machine can be a deterrent. While it is possible to recoup this cost in the long run, there are other limitations.
This method may provide an extra A axis compared to the 3-axis CNC machine, but it still has limitations on angles and geometries. To add to that, there is the aspect of the high level of expertise needed to run the machine.
The operator needs to be well-versed in programming and setting up the machine for the job. Supervision also requires some level of knowledge and skill.
5-Axis CNC Machining
The 5-axis CNC machining method is an improvement of 4-axis CNC machining. It can generate more complex parts more easily because it involves five sides of the workpiece. This ensures continuous contact between the tool and the component.
Using the same concept, the 5-axis CNC machining variety offers two rotary axes to add to the three linear axes to make five axes. The two rotational axes are drawn from the A axis, B axis, and C axis options identified earlier.
That means that the extra axes could be a combination of the A and B axes, or the A and C axes to make the fourth axis and fifth axis. Since the two extra axes use different mechanisms, the result is two varieties of 5-axis CNC machining – Trunnion style and Swivel-rotate style.
The Trunnion style comes with rotary tables and indexers for the formation of the extra rotary axes. This exposes the workpiece to the cutting tool in a way that the geometry of the cutter is optimized. In essence, the goal is maximum exposure of the sides of the workpiece to the cutting tool.
The tilting of the table is on any of the two sides of the vertical axis and around A or B by a given angle. Manufacturers can have different angles so you want to check that out first before buying or using the 5-axis CNC machine. However, the 360º rotation around the C-axis is common for rotary tables.
A rotating swivel head and a rotary table are the main characteristics of the swivel-rotate-style 5-axis CNC machining method. The swivel rotate style applies swiveling rotation to remove material from the workpiece as it sits on a stationary horizontal table. It rotates the A axis on the Y axis and the B axis on the Z axis.
5-axis CNC machining vs. 3+2 CNC machining
There is often confusion between 5-axis machining and 3+2 machining. Well, the two are different because 3+2 machining is a variation of 3-axis machining. It uses a rotary cutting table that fixes the workpiece in one location for 3-axis CNC machining.
This is unlike 5-axis CNC machining, which has five axes moving simultaneously for CNC milling and other processes. Unlike 5-axis machining, 3+2 machining is unable to maintain continuous contact. On the contrary, the workpiece remains in a fixed position.
Limitations of 5-axis CNC machining
To add to the high investment cost, a common drawback with 5-axis CNC machines is related to the perpetual twisting and turning of the components. The potential for tool interference is ever high.
With this level of rotation and general maneuverability, this CNC machine can only support a limited weight of the workpiece. This technically rules out machining most large parts on this machine. No wonder the Trunnion-style machines are typically synonymous with lighter components.
Producing parts using the 5-axis CNC lathe machine is normally more expensive than with a machine with fewer axes. The investment and maintenance costs for the machine are generally higher compared to 3-axis and 4-axis CNC machines. Due to this, small businesses find it hard to use these services.
Programming and setting up the 5-axis CNC machine can be a lengthy process. For projects that have strict timeliness, this can be a drawback. In the same breath, the level of expertise required to operate this setup is relatively higher.
Advantages of Of Multi-Axis Machining
Mechanical engineering and multi-axis machining have increasingly become intertwined. Numerous assembly lines across different industries rely on these types of machines. There are several advantages and benefits that multi-axis machines present.
Higher Precision and Accuracy
The precision and accuracy of machining results on a multi-axis CNC machine are much higher as compared to the 2-axis and 3-axis CNC machines. For the conventional CNC machining setups, the workpiece is restricted to a few points of interaction with the tool. The angles at which the tool can cut the workpiece are limited. This is the main difference between these technologies and multi-axis CNC machining.
To cut at many angles, the position of the workpiece will have to be changed several times. With each repositioning, the precision and accuracy levels usually reduce. The multi-axis CNC machine increase accuracy and offer high precision because the workpiece doesn’t have to be repositioned for complex machine geometries. All can be achieved in a single setup.
Improved Production Speed (Lead Times)
CNC machined parts have all sorts of geometries, so it is worthwhile to consider the type of machine you use to produce parts. If you are manufacturing complex parts, you need a CNC machine with matching turning and milling capabilities. Not all CNC machines can manufacture complex geometries.
To machine complex part geometries, you want to consider the dimensions of the part, the processing time, the cutting tool, and the tolerance. All these factors will suggest the multi-axis CNC machine as the best choice for the operation.
The fact that the multi-axis CNC machine can bring the cutting tool close to the workpiece at various angles is the mainstay of creating more complex geometries. This machine can achieve deep and intricate shapes, which are not possible with conventional CNC machining.
If you want to achieve the most complex part geometries, go for a multi-axis CNC machine with the most axes. That’s because then you don’t have to reposition the workpiece. Precision loss is minimal, if any.
More Complex Part Geometries
CNC machined parts have all sorts of geometries, so it is worthwhile to consider the type of machine you use to produce parts. If you are manufacturing complex parts, you need a CNC machine with matching turning and milling capabilities. Not all CNC machines can manufacture complex geometries.
To machine complex part geometries, you want to consider the dimensions of the part, the processing time, the cutting tool, and the tolerance. All these factors will suggest the multi-axis CNC machine as the best choice for the operation.
The fact that the multi-axis CNC machine can bring the cutting tool close to the workpiece at various angles is the mainstay of creating more complex geometries. This machine can achieve deep and intricate shapes, which are not possible with conventional CNC machining.
If you want to achieve the most complex part geometries, go for a multi-axis CNC machine with the most axes. That’s because then you don’t have to reposition the workpiece. Precision loss is minimal, if any.
High-Quality Surface Finish
A CNC machining process in the shop typically ends with surface finishing, a step that not only removes visual flaws but also modifies the electrical conductivity and enhances the strength of the part. Designers have a myriad of surface finish options. These include powder coating, anodizing, and as-machined.
While the first two are post-processing, the as-machined surface finish remains as it is. This surface finish is preferred where the aesthetics of the part are not a priority, but you can still achieve a relatively high-quality surface finish with multi-axis CNC machining.
These machines can place the cutting tool at different angles and orientations for a better surface finish. This minimizes the need for the sometimes-expensive post-processing steps.
Aria Manufacturing Limited's Multi-Axis CNC Machining
Multi-axis machining is a revolutionary process that has taken modern manufacturing to previously unimaginable levels. It is highly accurate and efficient, leading to higher production volumes.
As with any other manufacturing solution, there are several options for multi-axis machining. Without a proper analysis of the different axis options for CNC machining, one might think that more axes translate to better results.
Our experience has shown us that more axes don’t necessarily mean better. Every setup has its advantages and disadvantages. Rather, it is the combination of expertise and good multi-axis machining equipment that delivers.
But you don’t have to undertake your CNC machining jobs alone in your job shop. ARIA Manufacturing Limited is an experienced and professional manufacturing company. We have the right expertise and CNC machines with the ability to deliver accurate and timely results.
We also have the systems to fulfill your parts needs, whether for volume manufacturing or rapid prototyping.
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.