Basics of robotics (basics of joint axes robots for welding)

The market has developed an enormous number of different types of robots and appeared the need to divide them in the following main characteristics:​

• Coordinate systems;
• Power source;
• Method of control;
• Programming method.

Articulated Configuration Robots​

Joint-Arm Robot as a welding robot

The main advantages of the Articulated robots are:​

• High speed for three degrees of freedom;​
• High mechanical flexibility;​
• Easy sealing of all joints.​

These robots are usually used for:​

• Die casting applications;​
• Assembly operations;​
• Arc and gas Welding;​
• Spray painting;​
• Fettling machines.​​

The harmonic drive​

The harmonic drive is important for the preciseness of a joint-arm robot because it is a type of gear mechanism that provides ​high reduction ratios, high torque capacity, and high positional accuracy. ​
The harmonic drive achieves this by using a unique operating principle that involves the elastic deformation of a flexible spline. ​
This allows the drive to achieve zero backlash, which means there is no play or lost motion between the input and output shafts. ​
This results in very precise positioning and motion control, making it an ideal choice for joint-arm robots that ​require high levels of accuracy and repeatability.​

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Key advantages of the harmonic drive​

• Compact design with few parts​
• Large single-stage delay from 1 in 78 to 1 in 320.​
• High torsional stiffness​
• Low side clearance​
• Opposite direction of rotation of in- and outgoing movement​
• Reversible drive direction​
• Multiple designs in terms of inward and outward movement​
• Low weight​

RV GEAR as gear box instead of the Harmonic Drive

An RV (Rotary Vector) gear is a type of precision reduction gear that is commonly used in industrial robots. It is similar to a harmonic drive in that it provides high reduction ratios, high torque capacity, and high positional accuracy. However, there are some key differences between the two types of gears. RV gears use a cycloidal mechanism, which consists of an eccentric bearing, a cycloidal disk, and a set of pins. This mechanism allows the RV gear to achieve high reduction ratios and high torque capacity while maintaining a compact size. In contrast, harmonic drives use a flexible spline and a circular spline to achieve high reduction ratios. Both types of gears have their advantages and disadvantages, and the choice between them depends on the specific requirements of the application.​

RV gears and harmonic drives are both types of precision reduction gears commonly used in industrial robots. While they share some similarities, there are also some key differences between them, including their advantages. Some of the advantages of RV gears compared to harmonic drives include:​

• Higher torque capacity: RV gears can handle higher torque loads than harmonic drives of the same size, making them suitable for applications that require high torque transmission.​
• Higher shock resistance: RV gears are more resistant to shock loads and impacts than harmonic drives, making them more durable and reliable in demanding environments.​
• Lower noise: RV gears typically operate with lower noise levels than harmonic drives, making them suitable for applications where noise is a concern.​
• Higher efficiency: RV gears have higher mechanical efficiency than harmonic drives, which means they can transmit power more efficiently and with less energy loss.​

These are some of the advantages of RV gears compared to harmonic drives. However, the choice between the two types of gears ultimately depends on the specific requirements of the application.​​

What to be known?

IWE/IWS/IWT

• Why does a welding robot preferably have a minimum of 6 degrees of freedom?

IWE/IWT only

• Explain the advantages of a harmonic drive and how it works. Are there also disadvantages?  
• What are the advantages of a RV gear box compared to a Harmonic Drive?