Explaining the types and features of robot cables! What is the difference between movable and fixed cables?

Robots are used in factories. In fact, their movements are supported by special cables called "robot cables." They supply power to the joints and sensors of the robot arm, enabling precise movement.

In this article, we will explain basic information about robot cables, such as their structure, types, and standards. Let's take a look at the world of robot cables, which support the movements of robots behind the scenes.

What is a robot cable?

Robot cables are used in the moving parts of FA equipment, including industrial robots. It is important that they can withstand the bending and twisting loads that occur every time the robot moves, and can stably supply power and signals for a long period of time.

Compared to ordinary cables, the conductor is made of multiple thin wires twisted together to make it more resistant to bending, and the insulator and outer jacket are made of carefully selected materials to enhance oil and heat resistance.

In addition, in many cases, a strong shielding structure is used to prevent communication failure, minimizing the effects of noise even in harsh factory environments. These designs significantly reduce the risk of disconnection, creating a system that can minimize losses due to operational downtime.

In addition, because abrasion resistance and operating life are also important for robot cables, they tend to be required to meet stricter test standards than general electric wires. With the aim of exporting to overseas markets, an increasing number of products are being produced that comply with various international standards, and thorough safety and quality control is being implemented.

It is against this background that robot cables play an important role in today's world, where industrial robots are becoming increasingly sophisticated.

You can get a better understanding of its importance if you think of it not just as an electrical transmission line, but as a lifeline that delivers energy and commands to the heart of the robot.

Robot cable structure

Robot cables are constructed more precisely and sturdily than general wiring cables to accommodate the complex movements of moving parts.

Robot cables have four elements - conductor, insulator, shield, and sheath - that complement each other to minimize mechanical stress and the effects of the external environment.

• conductor
• Insulation
• shield
• sheath

We will explain each one in detail.

conductor

A conductor is a metal part that carries electricity and is generally made up of multiple thin copper wires twisted together.

In robot cables, the cables are twisted in the optimum diameter, pitch length, and pitch direction to increase bending resistance.

Generally, the thinner the wire diameter, the more flexible it becomes, but at the same time, the strength and resistance of the copper wire itself must also be taken into consideration. Therefore, finding the optimal combination of twist pitch and strands is a major challenge in product development.

Using many small diameter wires helps to disperse metal fatigue caused by repeated bending, reducing the occurrence of wire breakage. It is also important to control the current capacity and ambient temperature so that the conductor does not become overheated.

In cases where the working environment of the robot tends to be high, the conductor cross-sectional area is designed to have some margin to accommodate the temperature rise. This reduces problems during long-term operation and leads to stable operation of the production line.

Furthermore, by performing surface treatment or plating on the conductor, it is possible to prevent performance degradation due to oxidation or corrosion and reduce the risk of the robot stopping.

Insulation

The insulator is a layer that prevents contact between conductors and protects against electrical short circuits and leakage current. At the same time, it must have the property of not sticking even when the moving parts move significantly, and it can be said that this determines the lifespan of the robot cable.

Thermoplastic elastomers (TPE) and polyvinyl chloride (PVC) are the most common, but in some cases high-performance materials such as fluororesin are used depending on the environment they are used in. All of these materials are flexible and tear-resistant, and are characterized by their ability to minimize friction inside the cable while maintaining high insulation properties.

For example, if you want to improve oil and chemical resistance, it is important to choose a chemically stable resin and optimize the hardness by adjusting the composition. Furthermore, the design must be able to withstand heat caused by repeated operation and external shocks, and some manufacturers even conduct repeated field bending tests.

Using carefully selected materials and manufacturing processes, we are able to create robot cables whose insulation performance does not deteriorate even during long periods of operation.

shield

A shield is a protective layer that suppresses external noise and electromagnetic interference. In situations that require high-speed communication and precise control, it is an essential element in preventing communication failures.

In particular, in industrial robots, which require high-precision control, even minute signal disturbances can lead to a decrease in precision.

Therefore, a shielding layer made of metal braid or aluminum foil is placed inside the cable to reduce the effects of electronic noise.

sheath

The sheath covers the outermost layer of the cable and serves to physically protect the insulation and shielding.

If the sheath peels off, the internal structure will be exposed, which may lead to a break or short circuit.

For this reason, many products have a smooth finish to prevent unnecessary pressure from being concentrated on the surface even when the cable moves.

When the robot arm has a wide operating range or in an environment where multiple cables interfere with each other, it may be necessary to take into account the surface resistance of the sheath and devise measures to prevent the coating from rubbing against each other.

Features of Robot Cable

Compared to general cables, robot cables have the following features:

• Bending resistance: Because it is used in moving parts such as robot arms, it is resistant to breakage due to repeated bending
• Twist resistance: Resistant to cable twisting caused by the robot's rotational movements
• Durability: Able to withstand high speed, high acceleration and high frequency operation
• Environmental resistance: Heat resistance, oil resistance, chemical resistance, etc., depending on the usage environment

These features ensure that robot cables can operate stably even in harsh environments. The durability and reliability of robot cables are especially important on factory production lines, where equipment stoppage can lead to major damage.

For this reason, many factories tend to actively select high-quality cables with long life while still placing emphasis on cost performance.

Against this backdrop, robot cables have become a key component of industrial automation, and the race to develop products incorporating the latest technology is on.

Robot Cable Standards

There are various standards and certifications for robot cables to demonstrate their safety and quality. JIS standards are widely used for domestic use, while compliance with UL standards is emphasized when exporting overseas.

• JIS standards
• UL standards

Both standards have strict regulations for product design and testing methods, and obtaining certification increases reliability. This time we will explain the two standards in detail.

JIS standards

JIS standards are standards that define quality and testing methods that have long been used in Japanese industry.

In the field of electric wires, JIS C 3005 and JIS C 3521 are representative examples, and products that pass tests in accordance with these are given the JIS mark.

Robot cables are also evaluated based on factors such as insulation performance, durability, and flexibility, so if they have the JIS mark, domestic users can feel at ease.

Furthermore, the evaluation criteria are sometimes updated in line with revisions to JIS standards, and manufacturers are always making efforts to meet the latest requirements.

UL standards

The UL standard is an American safety standard established by Underwriters Laboratories Inc. The UL standard is more commonly used when exporting overseas.

Many electrical products, including robot cables, undergo multifaceted testing, such as combustion tests and dielectric strength tests, and products that pass are given certification such as UL Listed.

There are two types of UL standards: "UL Recognized" and "UL Listed."

In the case of robot cables, the intended use is clearly defined, so they are "UL Listed" certified.

Furthermore, certifications are divided according to the application, such as MTW (Machine Tool Wire), TC (Tray Cable), and CMX (Communication wires and cables).

Robot Cable Types

There are several types of robot cables with different characteristics depending on the application. Roughly speaking, there are two types: movable cables used in places that move frequently, and fixed cables used in parts that hardly move at all.

Below, we will explain the structure and usage of each in an easy-to-understand manner.

• Movable Cable
• Fixed cable

By using these appropriately, you can reduce unnecessary maintenance and replacement and improve operating efficiency.

Movable Cable

Dynamic cables are used in parts that are constantly bent and twisted, such as robot arms and cable bears. The conductor is made of thin strands twisted together to increase flexibility, making it easy to handle high-speed and repeated movements.

For example, by dividing the copper wire into small pieces and then twisting them, we create a structure that is less likely to concentrate stress.

For the insulation, we select a material that is resistant to heat and oil, and we formulate it so that it does not stick inside the cable.

The outer sheath is also designed to be wear-resistant, making it less likely to crack or peel off even with frequent movement.

In addition, there are types that incorporate woven shielding to suppress noise, which helps send high-precision control signals.

The larger the bending radius and stroke length, the more the quality of this flexible cable affects the operating rate. As a result, the frequency of wiring replacement can be reduced and stable operation can be maintained for a long time.

Fixed cable

The fixed cables are installed in parts that barely move, such as the robot's base and control device.
Its distinctive feature is that the twist pitch is slightly coarser than that of the movable type, and the outer covering is made of a harder material.

In factories, oil and chemicals can splash around, so resins with high oil and chemical resistance are used for the insulators.
On the other hand, since the cable does not move, it does not need to be resistant to twisting, and long-term environmental measures are important. In places where the cable comes into contact with the floor or equipment, materials that are resistant to friction can be used to reduce the risk of damage.
If the device is susceptible to external noise, a type with a shielded structure is chosen.

Because there is little handling, thicker and heavier conductors are used in some cases to ensure ample power supply. As a result, stable current flow and a long life are ensured, improving the reliability of the equipment.

Robot cable share

The global market for robot cables is expanding year by year as automation advances rapidly. This is due to the growing demand for industrial equipment not only in developed countries where factories are becoming more unmanned, but also in emerging countries.

Japanese manufacturers have earned a global reputation for providing high-quality, durable products. In particular, the detailed quality control and bending resistance technology that Japanese manufacturing is known for are highly regarded by users overseas.

The global market size in 2023 is expected to be approximately 225 billion yen, with the Asia-Pacific region accounting for approximately 2023% of the market share as of 40.

In addition, overseas manufacturers have also entered the market, taking advantage of cost advantages, and the market is being divided according to use and price range. Japanese companies still hold a large share of the high-value-added cable market, which emphasizes communication and control performance.

On the other hand, in the general-purpose field, the influence of Asian companies is expanding, and in some cases they are capturing demand for low-priced products. In the future, it is expected that the demand for cables with higher functionality will increase as robots become more precise and energy-efficient.

Summary

With the spread of factory automation and industrial robots, robot cables have become indispensable components.

Its special structure and outstanding features ensure stable operation even in harsh environments, contributing to factory automation.

As industrial robots become more sophisticated, the demands on cables are also increasing day by day, but the range of applications is expanding thanks to improved performance through technological innovation.

This evolution will support further automation and labor-saving through the use of robots, leading to increased competitiveness in a variety of industries.

Therefore, the robot cable market is expected to continue growing in line with the spread of robots and the advancement of IoT.