Laser Technology

Welding robots are the core execution units of modern automated welding production lines. Their motion accuracy, response speed, and load-bearing capacity largely depend on the performance of the drive system. The drive system is responsible for translating control commands into the joint movements of the robot.

The drive methods of welding robots are mainly classified into the following basic types:

1.Hydraulic transmission robot: As the name suggests, this type of robot uses hydraulic power to execute mechanical movements. Its characteristics include: a gripping capacity of over 100 kg, smooth transmission, compact structure, and sensitive movement. However, it has very strict requirements for sealing devices.

Advantages:

High power-to-weight ratio: Output force is much greater than pneumatic and electric drives for the same volume.

Smooth movement: Hydraulic oil has damping characteristics and strong impact resistance.

Self-lubricating: Hydraulic oil lubricates moving parts and has a long service life.

Limitations:

Prone to leakage: Wear of seals can easily lead to oil leakage, contaminating the welded workpiece.

Temperature rise sensitivity: Changes in oil temperature cause changes in viscosity, affecting control accuracy.

Complex maintenance: Requires a hydraulic station, cooling and filtration system, and occupies a large area.

2.Pneumatic manipulators are those that use compressed air to drive their actuators. Their main advantages are: readily available air source, low output force, rapid pneumatic action, relatively simple structure, and low cost. However, their disadvantages include poor stability in operating speed due to the compressibility of air, significant impact, and a generally limited gripping weight of around 30 kg due to the relatively low air pressure. Compared to hydraulic manipulators, pneumatic manipulators are more suitable for high-speed, light-load, high-temperature, and dusty environments.

Advantages:

Low cost: Inexpensive air source and actuators, simple maintenance.

No overheating: Good heat dissipation, suitable for auxiliary actions in high-temperature welding environments.

Clean: Pollution-free exhaust.

Limitations:

Poor positioning capability: Difficult to achieve arbitrary intermediate point positioning; only suitable for endpoint positions.

Low-speed crawling: Unstable movement at low speeds.

High noise: Exhaust noise typically exceeds 75 dB.

3. Mechanical Transmission Robotic Arm: This type of robotic arm is driven by a mechanical transmission mechanism. It is a specialized robotic arm attached to a main machine tool, with its power primarily transmitted from the working mechanism. Its main characteristics are accurate and reliable movement, high frequency of action, but it has a larger structure and its motion program is fixed. It is often used for loading and unloading materials on the main machine tool.

Advantages:

High precision and accurate transmission ratio: Mechanical transmission is based on rigid meshing or contact, with no slippage (such as gears or lead screws), enabling precise transmission ratios and high repeatability. It avoids the leakage or hysteresis problems common in hydraulic systems.

Fast response speed: Mechanical components have high rigidity and lack the compressibility of hydraulic oil or gas, resulting in direct motion transmission and rapid response in starting, stopping, and reversing, suitable for high-speed operation.

Strong load capacity: Through a well-designed gearbox or linkage mechanism, it can withstand large static and dynamic loads, and has high transmission efficiency (especially gear transmission, with efficiency reaching over 90%).

High reliability and long service life: Under good lubrication and normal operating conditions, mechanical components have a long fatigue life, clear failure modes, and are easy to predict and maintain.

Advantages: Strong environmental adaptability: Unlike electric drives, which are susceptible to electromagnetic interference, and unlike hydraulic drives, which are vulnerable to oil contamination, pure mechanical transmissions have a certain tolerance to harsh environments such as high temperatures, dust, and radiation.

Limitations: 

Complex structure and large size/weight: Achieving multi-degree-of-freedom movements requires complex combinations of links, joints, and gears, resulting in a bulky robot with a large moment of inertia, limiting high-speed dynamic performance.

Poor flexibility: Once the design and manufacturing of pure mechanical transmissions (such as cams and linkage mechanisms) are completed, the motion trajectory and stroke are fixed, making it difficult to adapt to the flexible production needs of multi-variety, small-batch operations. Changing the motion usually requires replacing the cam or adjusting the linkage, which is time-consuming and labor-intensive.

Backlash exists: Gear meshing and hinge connections inevitably have backlash. Long-term wear exacerbates the backlash, leading to decreased transmission travel and positioning accuracy, affecting the quality of welding trajectories.

High manufacturing costs and maintenance requirements: Precision gears, high-precision lead screws, and other parts are difficult and costly to manufacture. Simultaneously, mechanical joints require regular lubrication, dust prevention, and wear monitoring, resulting in a large maintenance workload.

Advantages: Noise and Vibration: During high-speed operation, gear meshing impact and linkage inertia will generate significant noise and mechanical vibration, potentially affecting the stability of the welding arc.

4. Electric Drive Robotic Arm: This type of robotic arm uses a specially structured induction motor, linear electromechanical system, or power stepper motor to directly drive the actuator. Because no intermediate conversion mechanism is needed, the mechanical structure is relatively simple. Linear motor robotic arms, in particular, offer high speed and long stroke, and are very convenient to maintain and use.

Advantages:

Highest Precision: Capable of welding complex spatial curves (such as circular arcs and spline curves).

Flexible Control: Easy to digitize, network, and implement teach programming.

High Energy Efficiency: Energy conversion efficiency can reach over 90%, with low standby power consumption.

Low Maintenance: No hydraulic oil or air hoses required, ensuring cleanliness.

Limitations:

High Cost: Servo motors and precision reducers are expensive.

Overheat Protection: Motor cooling needs to be monitored during prolonged high-speed welding under full load.

Sensitive to Electromagnetic Interference: Requires proper shielding and grounding.

Overall, modern welding robots are developing towards full electrification, high precision, networking, and collaboration. Deep integration of drive and transmission systems (such as eliminating the reducer in direct-drive torque motors and integrating drive modules within the joints) further improves reliability and trajectory tracking performance. In the future, with the combination of servo control algorithms (such as force control and visual servoing) and artificial intelligence technology, welding robots will evolve towards greater intelligence and flexibility to cope with increasingly complex welding processes and production environment requirements.