BRIGHTSTAR
PROTOTYPE CNC CO., LTD
+86 137 5010 5351
EN
May. 29, 2026
Have you ever received a CNC machining quote and found the price to be shockingly high, only to learn that the part requires 5-axis machining? Or have you designed a complex part but are unsure whether it really needs 5-axis, or if 3-axis with a few setups could also work?
These questions are encountered by almost every engineer who purchases CNC parts. 5-axis machining sounds advanced, but it also costs more. So, when is 5-axis really necessary? When is 3-axis sufficient? What can 5-axis do that 3-axis cannot?
This article will help you answer these questions. Starting from the fundamental differences between 3-axis and 5-axis, we will analyze which features absolutely require 5-axis, which features are better with 5-axis, which situations are fine with 3-axis, and how to determine whether your part needs 5-axis machining.
To determine whether you need 5-axis, you first need to understand the fundamental differences in capability between 3-axis and 5-axis.
3-Axis CNC Machining
3-axis machining is the most common CNC machining method. The machine moves along three linear axes: X, Y, and Z. The tool always remains in a vertical orientation. To machine the sides or bottom, the workpiece must be manually repositioned.
3-axis machining is suitable for parts with relatively simple shapes where all features can be accessed from the top, such as flat parts, brackets, and housings. Its advantages are lower equipment cost, simpler programming, and easier operation. The disadvantage is that multiple setups are required to machine multiple faces, and each setup introduces positioning errors.
5-Axis CNC Machining
5-axis machining adds two rotational axes to the three linear axes. Depending on the machine configuration, these two rotational axes can be A-axis, B-axis, or C-axis.
5-axis machining is divided into two modes:
Simultaneous 5-axis moves all five axes at the same time, allowing the tool to continuously change angle. This is suitable for machining complex curved surfaces such as turbine blades, impellers, and propellers. This is something 3-axis cannot do at all.
3+2 positioning machining first uses the rotational axes to position the workpiece at a compound angle, then locks them, and then uses the three linear axes for cutting. This method is suitable for machining angled holes, undercuts, and features on multiple faces. Although not as complex as simultaneous 5-axis, it can already handle many tasks that 3-axis cannot do efficiently.
Summary of core differences:
3-axis can only machine from the vertical direction; 5-axis can machine from any angle.
3-axis requires multiple setups for complex parts; 5-axis can complete them in one setup.
3-axis requires long tools for deep cavities; 5-axis can tilt the workpiece to use short tools.
3-axis cannot machine undercuts or complex curved surfaces; 5-axis can.
Some parts simply cannot be made with 3-axis at all. The following situations absolutely require 5-axis machining.
Parts such as turbine blades, impellers, propellers, and complex mold cavities have complex freeform surfaces. These surfaces require the tool to maintain the optimal attitude at all times; otherwise, overcutting or substandard surface quality will occur.
When machining curved surfaces on a 3-axis machine, the tool is vertical, and only ball nose end mills can be used to approximate the surface through layer-by-layer passes. This method has two problems: first, scallop marks remain between each pass; second, the tool tip has zero linear speed, resulting in poor surface quality.
On a 5-axis machine, the tool can always remain perpendicular to the surface, achieving perfect surface quality. For parts with high aerodynamic requirements, 5-axis is the only choice.
If a part has a very deep cavity, 3-axis machining requires long tools. The longer the tool, the poorer the rigidity and the more prone it is to chatter. To control chatter, cutting speed must be reduced, resulting in longer machining time and poorer surface quality.
5-axis can tilt the workpiece, allowing short tools to access deep cavities from the side. Short tools have better rigidity, allow higher cutting speeds, machine faster, and produce better surface quality.
Undercuts are areas that are blocked by other features and cannot be accessed directly from the top. On a 3-axis machine, undercuts simply cannot be machined because the tool is blocked.
5-axis can rotate the workpiece to expose the undercut area to the tool. For example, if a part has an internal boss pointing inward, a 3-axis machine cannot machine it, but a 5-axis machine can tilt the workpiece to allow the tool to enter from the side.
If a part requires drilling angled holes on multiple faces, 3-axis requires multiple setups, each requiring a complex angle fixture. This is not only time-consuming but also makes accuracy difficult to guarantee.
5-axis can machine all angled holes in a single setup. Simply rotate the workpiece to the correct angle, drill, rotate to the next angle, drill again. High accuracy and high efficiency.
If a part requires machining features on multiple faces, and those features have strict relative positional requirements, the advantage of 5-axis is very clear.
On a 3-axis machine, each repositioning introduces positioning errors. Even if each error is only 0.01 millimeters, the accumulated error from two setups can exceed 0.02 millimeters. If features are on three faces, the error is even larger.
On a 5-axis machine, all features are machined in a single setup using the same coordinate system, so positional accuracy is higher.
Thin-walled parts are prone to deformation during machining. On a 3-axis machine, using long tools to machine deep cavities generates large cutting forces, causing more severe deformation.
5-axis can use short tools, which generate smaller cutting forces and less deformation. Additionally, by tilting the workpiece, the cutting force direction can be directed toward the thicker supporting structure, further reducing deformation.
Some parts can be done with 3-axis, but are better done with 5-axis. The following situations, while not strictly requiring 5-axis, are strongly recommended for consideration.
If a part requires four to five setups on a 3-axis machine, each setup requiring fixture design, coordinate system recalibration, and critical dimension inspection, the total time may exceed the machining time on a 5-axis machine.
In this case, using 5-axis to complete in one setup, even though the hourly rate is higher, the total time is shorter and the total cost may be lower.
When machining curved surfaces with 3-axis, scallop marks remain between ball nose end mill passes. To reduce these marks, stepover must be decreased, but halving the stepover increases machining time by four times.
5-axis allows the tool to maintain the optimal angle at all times, resulting in a smoother surface that typically does not require additional polishing. For parts with high appearance requirements, 5-axis is the better choice.
If features on different faces of a part have strict positional requirements, the accumulated errors from multiple 3-axis setups may make it difficult to meet requirements. 5-axis with a single setup can easily achieve positional accuracy within 0.005 millimeters.
If your project has a tight timeline, 5-axis can reduce the number of setups, thereby shortening total machining time. For complex parts, 5-axis can be 30% to 50% faster than 3-axis.
5-axis is not a panacea, and not all parts need 5-axis. The following situations are fine with 3-axis.
If all features of your part can be accessed from the top, with no undercuts, no angled holes, and no deep cavities, 3-axis is completely sufficient. For example, a mounting plate with through holes and counterbores can be easily done with 3-axis.
If part tolerances are ±0.05 millimeters or looser, 3-axis can fully meet the requirements. Properly calibrated 3-axis machines can achieve ±0.01 millimeters or even higher precision.
For high-volume simple parts, 3-axis is very economical. Dedicated fixtures can be designed for fast loading and unloading, even enabling unattended automated production.
5-axis machines typically cost two to five times more than 3-axis machines, and their hourly rates are also higher. If your project budget is limited and the parts are not complex, 3-axis is the more economical choice.
In the early prototype phase of product development, using 3-axis to quickly and inexpensively validate design concepts is common practice. Only when the design is finalized and requires complex features that only 5-axis can machine should you consider upgrading to 5-axis.
Here is a simple decision process to help you determine.
Does the part have complex curved surfaces (such as turbine blades, impellers)? Does it have undercut features? Does it have multiple angled holes at different angles? Does it have multi-face features that need to be machined in one setup?
If the answer to any of these is yes, your part may need 5-axis.
Does the part require four, five, or even more setups? Does each setup require a complex angle fixture? Are there strict positional requirements between features on different faces?
If the answer to any of these is yes, 5-axis may be the better choice.
If 3-axis can do it but requires many setups and long machining time, calculate the total cost. Although the hourly rate for 5-axis is higher, the total cost may be lower and the lead time shorter.
If unsure, the best approach is to consult an experienced machinist. Send your 3D model and drawings to Brightstar, and we can evaluate whether your part needs 5-axis and provide quotes and lead time comparisons for both options.
Many customers assume that 5-axis machining is always more expensive than 3-axis. This is not completely correct. For complex parts, 5-axis may actually be cheaper.
Cost components of a 3-axis solution:
Multiple setups mean multiple setup times. Each face may require a separate fixture. Multiple setups lead to higher scrap rates. Total machining time may be long due to multiple setups and calibrations.
Cost components of a 5-axis solution:
Single setup means short setup time. Fixtures are simple, often just a vise or vacuum chuck. Scrap rate is low because setup errors are reduced. Machining time is short because short tools allow high-speed cutting.
Cost comparison example:
Assume a complex part requires five setups on a 3-axis machine, total machining time 4 hours, scrap rate 8%. On a 5-axis machine, only one setup is needed, total machining time 2.5 hours, scrap rate 2%.
Although the hourly rate for the 5-axis machine is higher, total machining time is shorter and scrap rate is lower. Calculating it out, the per-part cost of 5-axis may be 20% to 30% lower than that of 3-axis.
Therefore, when deciding whether to use 5-axis, do not look only at the hourly rate; look at the total per-part cost.
Machining Capability
3-axis can only machine from the vertical direction. 5-axis can machine from any angle.
Number of Setups
3-axis requires 3 to 10 setups for complex parts. 5-axis typically requires only 1 to 2 setups.
Positional Accuracy
3-axis has accumulated errors from multiple setups, so accuracy is moderate. 5-axis has single setup, so accuracy is high, within 0.005 millimeters.
Curved Surface Quality
3-axis leaves scallop marks and requires subsequent polishing. 5-axis produces smooth, continuous surfaces with little or no polishing needed.
Undercut Capability
3-axis cannot machine undercuts. 5-axis can.
Deep Cavity Machining
3-axis requires long tools that are prone to chatter. 5-axis can use short tools from the side, providing better rigidity.
Programming Difficulty
3-axis programming is simple with a short learning curve. 5-axis programming is complex and requires experienced programmers.
Equipment Cost
3-axis is lower. 5-axis is higher.
Per-Part Cost (Simple Parts)
3-axis is lower. 5-axis is higher.
Per-Part Cost (Complex Parts)
3-axis is higher (due to multiple setups). 5-axis is lower (due to single setup).
Q: What is the difference between 3+2 and simultaneous 5-axis?
3+2 positions first then machines, suitable for angled holes, undercuts, and multi-face features. Simultaneous 5-axis moves all five axes at the same time, suitable for complex curved surfaces like turbine blades. 3+2 programming is simpler than simultaneous 5-axis and costs less.
Q: What accuracy can 5-axis machining achieve?
5-axis machining completes all features in a single setup with no accumulated errors, so positional accuracy can reach within 0.005 millimeters. The dimensional accuracy of individual features depends on the machine itself and is similar to 3-axis.
Q: Is 5-axis machining always more expensive than 3-axis?
Not necessarily. For complex parts, 5-axis may be cheaper because it reduces the number of setups and scrap rate. It is recommended to calculate the total cost for your specific part.
Q: Can my part be done on a 3-axis machine?
If you are unsure, send your drawings and 3D model to Brightstar, and we can evaluate for free.
Q: What is the minimum part size for 5-axis machining?
5-axis machines can machine very small parts, down to a few millimeters for precision medical parts. They can also machine larger parts, depending on the machine's work envelope. Brightstar's 5-axis equipment can machine parts up to 800 millimeters in diameter.
Q: Do you have 5-axis CNC equipment?
Yes. Brightstar has multiple 5-axis CNC machines that can machine complex curved surfaces, deep cavities, undercuts, and other features. We can recommend the most suitable machining solution based on your part requirements.
5-axis CNC machining is not a panacea, but for certain parts, it is indispensable.
When your part has complex curved surfaces, deep cavities, undercuts, angled holes, or requires machining features on multiple faces with strict positional requirements, 5-axis is the best choice, and sometimes the only choice.
When a part requires multiple setups on a 3-axis machine, resulting in long machining times and high scrap rates, 5-axis may be more economical and efficient.
When a part has a simple shape, loose tolerances, and high volume, 3-axis is still the more economical choice.
The key to determining whether you need 5-axis is to analyze the part's geometric features, calculate the total cost for both 3-axis and 5-axis, and consult a professional machinist if necessary.
Brightstar has both 3-axis and 5-axis CNC equipment and can provide the most suitable machining solution based on your part requirements. Whether you need 3-axis or 5-axis, we can provide high-quality services.
Ready to Determine Whether Your Part Needs 5-Axis?
Whether your part is suitable for 3-axis or requires 5-axis, Brightstar can provide professional advice and services.
Email Amy: amy@brightstarprototype.com
Call or WhatsApp: +86 13750105351
Send us your CAD files and drawings for a free process evaluation and quote.
Brightstar – Precision CNC Machining. 3-Axis and 5-Axis. The Right Choice for You.
