With the gradual maturation of numerical control technology, in recent years, five-axis simultaneous CNC machining centers have been widely used in various fields. In practical applications, whenever people encounter challenges in efficiently and accurately machining complex and irregular-shaped components, the five-axis simultaneous technology undoubtedly becomes a crucial means to address such issues.
In the past few years, with the flourishing development of aerospace, military industry, automotive components, and mold manufacturing industries, an increasing number of prototpye manufacturers are inclined to seek five-axis equipment to meet the demands of high efficiency and quality machining. However, do you truly understand five-axis machining? Now, let’s follow the steps of this article to delve into the world of five-axis machining.
what is 5-aixs machine?
A 5-axis machine allows tools to move simultaneously around 5-axes of an object. 5-Axis machines utilize the typical X, Y, and Z-axes in conjunction with the A and B-axes so that your tools can get to five sides of a part, no extra turning or setup required.
The two rotary axes among A, B, and C have different motion modes to meet the technical requirements of various products. In the mechanical design of 5-axis machining centers, machine manufacturers have consistently been devoted to developing new motion patterns to satisfy diverse demands. Considering various types of five-axis machine available in the market, although their mechanical structures come in a variety of forms, they mainly fall into the following categories:
Types of 5-aixs machine
1. Two rotary coordinates directly control the tool axis direction (dual rotary head).
2. Two axes are located at the top of the tool, but the rotary axes are not perpendicular to the linear axes (tilting rotary head).
3. Two rotary coordinates directly control spatial rotation (dual rotary table).
4. Two axes are on the worktable, but the rotary axes are not perpendicular to the linear axes (tilting rotary table).
5. Two rotary coordinates, one affecting the tool and the other affecting the workpiece (one rotary, one tilting).
After seeing these structures of five-axis machines, I believe we should now have a clear understanding of how five-axis machines move and operate.
However, with such diversified machine structures, what characteristics can they demonstrate during machining? In comparison to traditional three-axis machines, what advantages do they offer? Next, let’s take a look at the highlights of five-axis machines.
aDVANTAGE of 5-Axis Machine
When discussing the advantage of five-axis machine, it is important to compare them with traditional three-axis equipment. In production, three-axis machining equipment is commonly used, with various forms such as vertical, horizontal, and gantry. Common machining methods include end milling, side milling, and ball-end cutter contouring.
However, regardless of the form or method, they share a common feature: the direction of the tool axis remains unchanged during the machining process, and the machine tool can only achieve the movement of the tool in the spatial Cartesian coordinate system through interpolation of the X, Y, and Z linear axes.
Therefore, when facing the products below, the drawbacks of low efficiency, poor surface quality, and even inability to process using three-axis machine tools become evident. Compared to three-axis CNC machining equipment, five-axis simultaneous CNC machine have the following advantages:
1.Maintaining the optimal tool cutting state
As shown in the above picture, in the left image with the three-axis cutting method, the cutting state gradually deteriorates as the cutting tool moves towards the top or the edge of the workpiece. To maintain the optimal cutting state even in this region, the worktable needs to be rotated. And if we need to fully machine an irregular surface, the worktable must be rotated multiple times in different directions. It can be seen that a five-axis machine tool can also avoid the situation where the centerline speed of the ball-end mill is zero, resulting in a better surface quality.”
2.Effectively Avoid Tool Interference
As shown in the picture above, for components such as impellers, blades, and integral disks used in the aerospace field, three-axis equipment cannot meet the process requirements due to interference issues. However, a five-axis machine can fulfill these requirements. Additionally, a five-axis machine can use shorter tools for machining, enhance system rigidity, reduce the number of tools, and eliminate the need for specialized tools. For business owners, this means cost savings in tooling expenses with a five-axis machine.
3.Reduce the Number of Setup Steps
As shown in the picture above, a five-axis machining center can also reduce the need for reference changes, thus enhancing machining accuracy. In practical machining, only one setup is required, making it easier to ensure machining precision. Additionally, due to the shortened process chain and reduced equipment count in a five-axis machining center, the number of fixtures, workshop floor space, and equipment maintenance costs are also decreased. This means you can achieve more efficient and higher-quality machining with fewer fixtures, less factory space, and lower maintenance expenses.
4.Improve Machining Quality and Efficiency
As shown in the picture, five-axis machine tools can utilize side-edge cutting for higher machining efficiency.
5.Shorten Production Process Chain
The complete machining of a five-axis CNC machine significantly shortens the production process chain, leading to simplified production management and planning. The more complex the workpiece, the more evident the advantages compared to traditional scattered production methods.
6.Reduce New Product Development Cycle
For industries such as aerospace and automotive, some new product components and molding shapes are complex and require high precision. Therefore, a five-axis CNC machining center with high flexibility, precision, integration, and complete processing capabilities can effectively address the precision and cycle issues of machining complex parts in the new product development process. This significantly shortens the development cycle and increases the success rate of new products.
Simultaneous 5-Axis vs 3+2 Axis Machining
Simultaneous 5-axis CNC has RTCP capability.RTCP, short for “Rotational Tool Center Point” according to Fidia, essentially means “Rotational Tool Center.” It’s commonly interpreted in the industry as “Rotating Tool Center Point” or sometimes “Rotational Tool Center Point Programming,” but these interpretations capture the result of RTCP.
A true five-axis system with RTCP capability can automatically calculate toolpaths based on the spindle’s swing length and the mechanical coordinates of the rotary table. When programming, you only need to consider the workpiece coordinates, without the need to account for the spindle’s swing length or the rotary table’s position. This allows for indexing machining, where setting a single coordinate system and tool alignment is required only once.
Challenges of 5-Aixs CNC machining
CNC Programming: Abstract and Challenging
This is a headache for every traditional CNC programmer. While three-axis machines have linear coordinate axes, five-axis CNC machines have diverse structures. The same NC code might yield the same results on different three-axis machines, but a specific five-axis machine’s NC code might not work for all types. CNC programming involves coordinating rotational movements alongside linear motions, such as angle rotation, non-linear error correction, and tool rotation calculations. The sheer volume of information makes CNC programming highly abstract.
The skills for operating and programming five-axis CNC machining are closely related. If special functions are added to the machine, programming and operation become more complex. Only through repeated practice can programmers and operators acquire essential knowledge and skills. The lack of experienced programmers and operators is a significant obstacle to the widespread adoption of five-axis CNC technology.
Strict Requirements for NC Interpolation Controllers and Servo Drive Systems
Five-axis machine motion combines movement across five coordinate axes, including rotational ones. However, this addition of rotational coordinates increases the complexity of interpolation calculations and decreases machining precision due to tiny rotational errors. Therefore, controllers require higher computational accuracy, and servo drive systems must possess excellent dynamic properties and a wide speed range.
Importance of NC Program Verification
To enhance machining efficiency, the traditional ‘trial cutting’ method must be replaced. In five-axis CNC machining, verifying NC programs has become essential due to the high cost of workpieces and collision risks. Collisions can occur during tool entry, high-speed movement, collisions with the machine, fixtures, or other equipment, and clashes between moving and fixed machine parts or workpieces. As predicting collisions in five-axis CNC is difficult, verification programs must comprehensively analyze machine kinematics and control systems.
Unlike three-axis CNC, where CAM-detected errors can be instantly rectified in the tool path, in five-axis machining, errors found in the NC program during machining cannot be directly modified like in three-axis CNC. Adjustments directly impact subsequent rotational movement trajectories due to changes in tool size and position.
Tool Radius Compensation
In five-axis linked NC programs, tool length compensation remains functional, but tool radius compensation is lost. For using a cylindrical milling tool for contouring, separate programs are needed for different tool diameters. Current CNC systems lack the capacity for tool radius compensation due to insufficient data in ISO files to recalculate tool positions. Users often need to adjust tool dimensions during CNC machining, leading to recalculating tool paths in the CAM system and reduced machining efficiency.
Addressing this issue, Norwegian researchers are developing LCOPS (Low Cost Optimized Production Strategy). LCOPS transfers data for tool path correction from the CNC application program to the CAM system, and the recalculated tool path is sent directly to the controller. LCOPS requires third-party CAM software that connects directly to CNC machines, transmitting CAM system files rather than ISO code. The ultimate solution relies on introducing new-generation CNC control systems capable of recognizing universal format workpiece model files (such as STEP) or CAD system files.
Distinguishing five-axis machines from their three-axis counterparts is the addition of two extra rotational coordinates. Moving tool positions from the workpiece’s coordinate system to the machine’s coordinate system requires multiple coordinate transformations. Existing post-processor generators in the market can create post-processors for three-axis CNC machines by inputting fundamental machine parameters. However, for five-axis CNC machines, only a limited number of enhanced post-processors are currently accessible. Further advancement is necessary to develop post-processors tailored for five-axis CNC machines.
Nonlinear Errors and Singularity Issues
The introduction of rotational coordinates makes the kinematics of five-axis CNC machines much more complex than three-axis machines. The first issue related to rotation is nonlinear errors. Nonlinear errors are considered programming errors and can be controlled by reducing step sizes. During the pre-computation phase, programmers cannot determine the magnitude of nonlinear errors. Only after generating machine programs using the post-processor can nonlinear errors be calculated. Linearizing tool paths can solve this problem. Some control systems can perform tool path linearization during machining, but this is usually done in the post-processor.
Another issue caused by rotational axes is singularity. If a singularity point is located at the extreme position of a rotational axis, even minor oscillations near the singularity point can result in a 180° flip of the rotational axis, which is extremely dangerous.
Requirements for CAD/CAM Systems
For five-axis machining operations, users must rely on mature CAD/CAM systems and have experienced programmers to operate CAD/CAM systems.
In the past, there was a significant price difference between five-axis and three-axis machines. Now, adding a rotational axis to a three-axis machine is almost equivalent to the price of a standard three-axis machine. Such a machine can achieve the functionality of a multi-axis machine. Meanwhile, the price of a five-axis machine is only about 30% to 50% higher than that of a three-axis machine.
In addition to the investment in the machine itself, upgrades are necessary for CAD/CAM software and post-processors to adapt to the requirements of five-axis machining. Verification programs must also be upgraded to enable comprehensive simulation of the entire machine.
Future Trends in Intelligent Five-Axis Machining Centers
The control modes and human-machine interfaces of intelligent equipment will undergo significant changes. The improvement in network performance, such as WiFi broadband and Bluetooth short-range communication, will lead to the increasing popularity of network-based mobile control methods using devices like tablets, smartphones, and wearables.
Progressive touch screens and multi-touch graphical interfaces will gradually replace buttons, switches, mice, and keyboards. People, especially the younger generation, are accustomed to the operation of smart electronic consumer products, enabling rapid responses, screen switching, data uploading, and downloading. This greatly enriches the content of human-machine interaction and significantly reduces the rate of operational errors.
Get Start With KUSLA 5 Axis Machining
5-axis CNC machining streamlines the machining process, enhancing its ease, speed, and cost-effectiveness. This approach also elevates precision and accuracy. To fully leverage these benefits, you require the expertise of a leading global CNC machining service provider. With our 5-axis CNC machines, we deliver high quality components, competitive pricing, and rapid turnaround.
Beyond 5-axis machining, KUSLA stands as a pioneer in technological advancement, offering diverse machining options and solutions. For inquiries or specific needs related to precise 5-axis machining, don’t hesitate to reach out to us or request a quote.