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What is 3,4, and 5-Axis CNC Machining?
CNC is widely used across the manufacturing industries for fabricating complex metal parts. CNC machining has varied axis capabilities, i.e., 3, 4, 5, 7, or 9. More axes means the ability to create complex parts.
In this article, we provide comprehensive information about 3-axis, 4-axis, and 5-axis machining. You’ll get to know their advantages, limitations, and factors to consider when choosing one technique.
What is 3, 4, and 5 Axes in Machining?
Axis basically means the direction in which the machine can move or rotate. The rotatory axis helps in shaping the material precisely. More axes means the machine can move the tool or workpiece in more directions. There are two types of axes:
- Linear Axis: Linear axis means straight line motion. There are 3 linear axes:
- X-axis: left ↔ right
- Y-axis: front ↔ back
- Z-axis: up ↕ down
- Rotatory Axis: The rotatory axis allows rotational movement. The rotatory axis moves in degrees. Here are its types:
- A-axis: Rotates around X-axis
- B-axis: Rotates around Y-axis
- C-axis: Rotates around Z-axis
What is 3-Axis Machining?
In 3-axis machining, the cutting tool uses three different axes of motion (X, Y, Z) and remains vertical during machining. The workpiece remains fixed to the CNC work table throughout the machining process. This type of machining is best suited for machining flat surfaces or geometries that are simple to machine.
Advantages of 3-Axis Machining
3-axis machines offer several benefits for manufacturers:
Cost reduction: Compared with multi-axis machines, the total cost of acquisition and
maintenance of 3-axis machining is low. It makes them affordable for small/medium-sized businesses.
Ease of programming: In many cases, programming is very easy for many 3-axis machines. Thus allowing operators to learn programming with minimal training.
Speed of setup: The time required to position or mount the workpiece to the machine is less than for multi-axis types. And 3-axis machines do not require a complicated calibration before production.
Availability: Most machine shops employ 3-axis machines. It’s easy to find service providers or replacement parts is easy.
Reliability: Since 3-axis machines have fewer components than multi-axis machines, the potential for failure is less. if maintained regularly, they can provide reliable and consistent service for multiple years.
Limitations of 3-Axis Machining
Here are some limitations of 3-axis machining:
- The vertical tool cannot cut through undercut or create a shaped surface
- Holes in deep pockets or angled holes may also not be accomplished with a 3-axis machine
- Parts with features on different sides need repositioning. Each repositioning adds time and reduces accuracy.
Applications of 3-Axis Machining
Here are some applications of 3-axis machining:
- Flat metal plates
- Metal enclosures and housing components
- Gears
- Flanges
- Heat sinks
- Simple molds for plastic injection molding
- Nameplates and engraved identification tags
- PCB boards (printed circuit boards)
- Spacers and washers with precise dimensions
What is 4-Axis Machining?
4-axis machining has a rotational axis in addition to the three existing linear movements. The workpiece can rotate on an axis most commonly referred to as the A-axis. The addition of this rotation allows the machine to machine curved surfaces or multiple faces of an object. It does not need to reposition the object manually.
Advantages of 4-Axis Machining
Let’s look at some advantages of 4-axis machining:
Less Time-consuming Setup: With the 4-axis machine having the additional rotation axis, you don’t have to remove and remount parts. Thus, you can machine multiple faces at once, saving you several hours of handling manually.
Machining Curved Surfaces: Looking for smooth curves or cylindrical features? The rotational axis allows you to easily create these features. 4-axis machining allows for seamless, continuous engraving around parts without having to pause to readjust for proper positioning.
Increased Tool Life: The cutting tools approach the workpiece at optimal angles during the machining process, thus reducing wear. This increases the overall tool life, leading to more money saved on tool replacements.
Faster Production Times: Because of the reduced handling time between each work process, you will finish jobs much faster.
Limitations of 4-Axis Machining
4-axis systems have the following limitations:
- The cost associated with acquiring 4-axis machinery is higher than that of 3-axis machinery.
- If your part is complex and contains multiple angles, you may experience difficulty accessing those areas.
- Tool path development will take more time and effort. The programmer needs additional time to learn the complexities of the CAD program.
Applications of 4-Axis Machining
Applications of 4-axis machining include:
- Crankshafts with curved profiles
- Shaft used in turbines in the production of electrical power
- Cylinder-shaped custom engraved products (i.e., custom pen and tube)
- Helical gears
- Pump impellers with curved blades
- Medical screws
- Custom rifle barrels
- Cylindrical molds to manufacture bottles
- Couplings and connectors
What is 5-Axis Machining?
A 5-axis machine has the same capabilities as the 3-axis and 4-axis systems, but it adds two rotational axes to the linear axes. The cutting tool can rotate and tilt as it approaches the workpiece, allowing you to access almost any angle on the part.
Additionally, 5-axis machining can produce highly complex shapes without requiring the part to be moved to a different position.
Here’s how the 5-axis capability is used:
- 3+2 Axis (Positional) Machining: In positional machining, the rotatory axes are used to orient the tool or part to a fixed angle. Then, the cutting is performed using the linear axes. The rotary axes remain stationary during the cutting process.
- Simultaneous 5-Axis Machining: In simultaneous 5-axis machining, all five axes move continuously at the same time during cutting. The machine can approach the workpiece from all five sides. This is an advanced method that enables the machining of highly complex, freeform geometries and superior surface finishes.
Advantages of 5-Axis Machining
5-axis machining has unique advantages over other methods:
One Setup: 5-axis machining allows you to create all sides and features of complex parts in a single setup.
Superior Surface Finish: The tool maintains an optimal contact with the workpiece during the entire cutting cycle, which results in smoother surfaces with fewer visible tool marks and less finishing work.
Precision: The ability to tilt the head gives you the ability to use shorter and more rigid tools. This decreases tool vibrations and deflections, allowing you to achieve a higher level of precision when machining deep features.
Faster Machining: Although programming takes longer at first, part production time significantly decreases with a single-programmed tool.
Limitations of 5-Axis Machining
The 5-axis machining capabilities have certain drawbacks, including:
- A 5-axis CNC machine costs 3 to 5 times more than a comparable 3-axis CNC machine.
- A 5-axis machine requires highly skilled computer-aided manufacturing (CAM) programmers to program. Hiring experienced CAM programmers or training in-house programmers will incur high additional costs.
- The more 5-axis moving parts increase the possibility of a tool or tool head colliding with a fixture or workpiece. Therefore, 5-axis Machinists must take care to simulate the program before running it.
- If you manufacture only simple parts, using a 5-axis machine is not efficient due to the amount of setup and programming time compared to the speed at which the machine can process the part.
Applications of 5-Axis Machining
Here are some applications of 5-axis machining:
- Titanium medical implants
- Aerospace turbine blades
- Automotive body panel molds
- Prosthetic components
- Prototype engine components, including internal cooling channels
- Marine propellers
- Compound angle tool and die components
- Military aircraft structure components with weight-reducing pockets.
Key Differences Between 3, 4, 5-Axis Machining
In the following section, we have discussed the key differences between 3, 4, and 5-axis machining:
Part Complexity
- 3-Axis Machining: 3-axis machining can make flat parts with simple features (holes, pockets), but it can’t do undercuts or complex angles
- 4-Axis Machining: With 4-axis machining, you can make cylindrical parts/circular-shaped parts with curvature, and parts with features on multiple sides.
- 5-Axis Machining: With 5-axis machining, the most complicated, complex shapes can be manufactured. Compound angles, deep pockets, and organic curvatures are manufactured in a single setup.
Cost
- 3-Axis Machining: Is typically very affordable ($20k on average), and has very low ongoing operational costs.
- 4-Axis Machining: 4-Axis machining will set you back more ($75k-$250k), with reasonable maintenance costs.
- 5-Axis Machining: Can cost anywhere from $200k to $1M+), with significant ongoing operational/maintenance costs.
Time Taken
- 3-Axis Machining: Is capable of making simple, fairly quick-turnaround parts. However, making more complicated parts requires multiple setups that can affect your overall schedule.
- 4-Axis Machining: Eliminates downtime by allowing you to rotate the parts in the fixture rather than having to completely re-mount the part.
- 5-Axis Machining: Handles complex parts the fastest, as the entire part is made in a single setup.
Programming Requirements
- 3-Axis Machining: Only requires basic training of the operator within 2-3 weeks using a standard CAM Package
- 4-Axis Machining: Requires the person(s) performing the programming to have an understanding of rotary toolpaths, so they will require a few months of training.
- 5-Axis Machining: Requires highly skilled personnel with advanced CAM programming and collision avoidance skills.
Setup Time
- 3-Axis Machining: The time it takes to set up and run your job with a 3-axis machine is between 15 minutes and 30 minutes.
- 4-Axis Machining: For a 4-axis machine, it takes 30 to 60 minutes because you have to attach the rotary fixture and place the part into position.
- 5-Axis Machining: It takes between 1 hour and 3 hours initially, but you don’t have to reposition it again after this.
Accuracy
- 3-Axis Machining: Tolerances maintained when using 3-axis machines are ±0.005 inch range.
- 4-Axis Machining: You have more precise tolerances of ±0.002 inch because your part is in this position longer during machining.
- 5-Axis Machining: 5-axis machining has even stricter tolerances of ±0.0005 or tighter.
Surface Finish Quality
- 3-Axis Machining: Due to the use of 3-axis machines, flat surfaces appear good; however, angled surfaces show clear tool marks.
- 4-Axis Machining: Cylindrical surfaces produced from a 4-axis setup provide a very smooth finish around all of the curves.
- 5-Axis Machining: The ultimate finish quality is produced on the 5-axis because the tool maintains the optimal cutting angle on the part.
Conclusion
Understanding about 3-, 4-, and 5 Axis CNC machining helps people in manufacturing select the correct technology for them. Having a greater number of axes will allow for more movement and flexibility. It also allows for the use of more complex geometries and fewer setups. However, those machines with more than three axes will cost more money and require more skill in programming.
FAQs
What is the difference between 3/4 and 5-axis machining?
The difference between 3, 4, and 5-axis machining is the direction in which the tool or workpiece can move. With three axes, the machine can only move along three straight lines. With four axes, the machine can also rotate about the axis. With a five-axis machine, the machine can tilt as well as rotate.
Is there a 6-axis CNC machine?
Yes, six-axis machines have been specifically designed to provide additional flexibility. However, these machines are used for specialized applications, such as those involving the pairing of robotic machining with additive manufacturing processes.
How much does CNC machining cost per hour?
CNC machining prices vary based on the number of axes on the machine. For example, 3-axis machines will generally cost between $40-$75 per hour, 4-axis machines will cost between $75-$150 per hour, and 5-axis machines will generally cost between $150-$300 per hour. The cost depends on the machine’s capabilities and geographical location.
How expensive is a 5-axis CNC machine?
The price of a 5-axis CNC machining machine will generally range between $200,000 and greater than $1,000,000. The entry-level desktop versions of these machines will generally cost at least $50,000, but they will typically have very limited capabilities. Industrial machines that have higher levels of precision, on the other hand, will cost many times more than that amount.
