First, we need to correct this view: the more axes a robot has, the more flexibly it can reach spatial locations, but it is absolutely wrong to say that the more axes a robot has, the better.
A robot's axis is commonly known as a joint, much like a human arm. Naturally, the more joints a robot has, the more flexible it is, and the more positions it can rotate and reach. This should be self-explanatory!
Six-axis robot
However, we can't say that the more axes a robot has, the better. Why? Let me explain!
The more axes a robot has, the more complex its control system becomes, and the higher its cost. It also undoubtedly allows the robot to reach more points in three-dimensional space and provides greater flexibility. From this perspective, it's true that more axes mean a more advanced robot, but it's not necessarily better. Why?
6-axis welding robot + external axis = 7 axes
Case Study 1: Palletizing Application. In palletizing applications, goods do not require three-dimensional rotation; they only rotate horizontally. The placement is simply a matter of front-back, left-right, and right-side movement. Therefore, a four-axis palletizing robot is sufficient to complete these actions. Using a six-axis robot would actually increase the palletizing cycle time. A four-axis palletizing robot typically performs 1000 palletizations per hour, while a KUKA six-axis robot's fastest is only 700 palletizations per hour. Furthermore, a six-axis robot with the same load capacity is significantly more expensive than a four-axis robot. Can we then say that six-axis robots are better?
Case 2: The Scala robot only has three axes, limiting its working range to the horizontal plane. However, its cycle time is much faster than any six-axis robot. Typically, a Scala robot's combined XY-axis speed can reach 5 m/s, and its Z-axis (vertical) speed can reach 1.6 m/s. The KUKA robot (world-renowned for its superior linear speed) has a maximum linear speed of 2 m/s. Does this mean that more axes are always better?
Case 3: The DELTA robot is a three-degree-of-freedom parallel robot with a cycle time of several times per second. Its repeatability is far higher than that of a six-axis robot. Can we say that more axes are always better?
In summary, it is advisable to select the appropriate model of industrial robot based on its intended use. Robots are now categorized according to different working conditions:
1. Palletizing is generally done using a four-axis palletizing machine, which has the advantages of large load capacity and high speed.
2. For general welding, a six-axis small-load robot, such as a 6kg robot, is generally selected because the robot only needs to support the weight of the welding torch and wire feeder, and a 6kg load is sufficient. The difference in selection lies in the robot arm length, i.e. the working range, which is commonly 1200mm, 1400mm, etc.
3. For butt welding, such as spot welding of car body shells, a high-load six-axis robot is generally selected because the robot needs to support the weight of the welding clamp.
4. For spraying, grinding, loading and unloading, etc., a six-axis robot is generally selected. The robot with different load and arm length can be selected according to the working conditions and working range.
5. Scala robots are generally used for assembling electronic components because they are fast and have high precision.
6. Delta robots are generally used for food packaging and sorting, but SCRA robots can also be used, as they are fast and have high precision.
Therefore, in practical industrial applications, more axes are not necessarily better. It depends on the specific usage. Some prioritize speed, others precision, load capacity, and still others arm length. Different brands also have different focuses. For example, within the same brand, a 165kg robot might be more expensive than a 50kg robot. However, some brands may specialize in high-load robots, and their 50kg robots are rarely produced. In such cases, their high-load robots might be cheaper than their low-load ones. Mass production is a crucial factor. Therefore, it's essential to compare different options when choosing a robot, especially given the emergence of numerous domestically produced robots this year, which has impacted the market. We should have a correct understanding of this!
Additional answer:
First, let's explain the function of the shaft.
The number of axes refers to the number of movable axes a robot has, that is, axes around which it can rotate.
Axis is closely related to the Cartesian coordinate system. A three-axis robot, also known as a Cartesian robot, allows the robot to move along three axes; while the six axes in a six-axis robot are the XYZ axes in the Cartesian coordinate system, plus the UVW axes for rotation around the XYZ axes. Currently, robots on the market range from one to seven axes, including both single-axis and seven-axis robots.
II. Single-axis robots
Also known domestically as linear modules or electric slides, it is a mechanical structure that can provide linear motion and can be combined to complete more complex tasks. The name also indicates that it can complete specified tasks in a modular way, and at the same time, it shows that single-axis robots have been developed to a high level of maturity.
Advantages of single-axis robots:
1. It has a simple structure, consisting of profiles as the main body and internal transmission components such as guide rails and lead screws. Its linear structure means that it can only perform simple point-to-point movements.
2. It has no complex components and does not require long-term maintenance; it usually only needs to be lubricated on time.
3. We usually see that multi-axis robots are not very fast, but these problems do not exist for single-axis robots. Single-axis robots are generally driven by motors and their speed can easily reach several meters per second.
4. The single-axis slide is linear in shape, and the required stroke and installation method can be selected according to the actual situation. Compared with multi-axis robots, it is more flexible in terms of space utilization.
III. Determine the number of shafts based on requirements.
Multi-axis robots can perform fully automated work through free programming, which can significantly reduce the error rate in production.
However, this comes with high operating costs and a lengthy programming and simulation process before formal use. Furthermore, it is essential to ensure that the device does not malfunction, otherwise the maintenance and repair costs during use will be substantial, and a professional engineer responsible for maintenance is required.
At the same time, operators using multi-axis robots must undergo long-term training to master them; otherwise, even a simple operational problem could lead to irreparable losses or even personal injury.
Therefore, it's not true that the more axes a robot has, the better; the number should be determined based on the actual tasks and environment the robot will be working in.
