From selecting a nutrunner to designing and installing a nutrunner

Here.Basic information on how to select, design, and install a "nutrunner."notes.

You may have heard of the "nutrunner" tool, but may not know exactly how to install it or which manufacturer's product to choose.　You may also be looking for detailed information on how to design and install them to suit your own production line, and what kind of peripheral equipment you will need.

In this article, we will try to resolve such questions and concerns by noting as clearly as possible from a professional perspective, from basic knowledge of nutrunners, to specific implementation processes, and even information on costs.

Understanding the basics of nutrunners and finding the best one

What is a nutrunner?

In a nutshell, a nutrunner is "a specialized power tool for tightening bolts and nuts at a pre-set precise force (torque) and angle.　It is.

It is used for fastening important parts that determine the quality of products on factory assembly lines.What makes it significantly different from ordinary electric screwdrivers is that it can not only turn screws, but also control and record the entire fastening process with a high degree of accuracy.

For this reason, it is appropriate to view them not as mere "tools" but as "precision fastening systems" that play a part in quality assurance systems.　In the fields of automobiles and precision equipment, a single faulty fastening of a single screw can lead to a recall or other serious problems.　That is why using nutrunners to guarantee "the same quality no matter who does the work" is indispensable in today's manufacturing industry.

Nutrunner Mechanism

The secret behind the nutrunner's ability to achieve high-precision tightening lies in its internal "planetary gear" mechanism.　This is,A device that converts the high-speed rotational force generated by a motor into a powerful and controlled rotational force (torque) by combining multiple gears structured like a planet orbiting the sun.　It is.

Whereas the impact wrench that many people imagine applies force intermittently by striking with an internal hammer, the nutrunner does not use blows.　Instead, a planetary gear mechanism tightens to the target torque with smooth, continuous force.

This "non-impact" and "continuous" force application is the most distinctive feature of the nutrunner, and is at the core of its ability to enable extremely precise torque management while reducing noise and vibration.　It can be said to be the most reliable and reliable fastening system in the industry.　Thanks to this mechanism, reliable fastening can be achieved without damaging sensitive parts.

Type of power to move nutrunner

There are two main power sources for nutrunners: electric and pneumatic (air).　They are broadly classified into the following categories, each of which has its own advantages and disadvantages³。

Electric Nutrunner

The current mainstream is the electric type.　In particular, models equipped with AC servo motors are suitable for work that requires high quality because torque, rotation angle, and speed can be controlled very finely digitally.　Another major advantage is that they are quiet in operation and have excellent functions for recording and managing fastening data.In recent years, cordless types equipped with batteries have also become popular　The new system is designed to provide great mobility when working in areas where cable routing is difficult or while moving around.

Pneumatic nutrunner

This type is powered by compressed air. It is not as good at precise control as the electric type, though,Simple and sturdy structure is an advantage.　It is.　Therefore, they still play an important role at special sites where the use of electrical equipment is restricted, such as in places where fire is strictly prohibited or in environments where there is a risk of explosion.

It is important to make a decision on which type to choose, taking into consideration the required fastening accuracy, the work environment, and the need for data management in a comprehensive manner.

List of things you can do with Nutrunner

The introduction of nutrunners offers many advantages over simply tightening screws.　The main advantages include the following

• High-precision fastening management: Bolts and nuts can be tightened very precisely at preset torques (screw turning force) and angles.　This prevents human error such as over-tightening or forgetting to tighten, thereby stabilizing product quality.
• Improved work efficiency:Unlike hydraulic tools and other tools, continuous rotation completes the tightening operation at once, thus significantly reducing working time.
• Quiet and safe work environment:No loud impact noise or vibration like impact wrenches, reducing the burden on the operator and creating a quiet working environmentI will do so.
• Automatic detection of abnormal fastening:It monitors changes in torque and angle during fastening and can automatically detect abnormalities such as "missing parts" and "galling of screws. This prevents the outflow of defective products.
• Ensure traceability of quality:All data on "who tightened which parts, when, and under what conditions" can be recorded. This "traceability" helps to quickly identify the cause of a product defect by tracing back the records in the unlikely event of a defect.

Also,By changing the sockets and bits at the end, the nutrunner can be used for a very wide variety of fastening parts, including common hex bolts, nuts, and small screws.　However, there are some caveats.

For example, it is not possible to tighten "Torsia type high strength bolts (shear bolts)" which require special tools. Also,Retightening," in which a bolt that has been tightened once is tightened further, requires loosening the bolt and then retightening it due to the control mechanism.　When tightening soft materials such as resin, it is important to select a model with delicate control to prevent damage due to excessive torque.

Critical differences between nutrunners and impact wrenches

As mentioned a bit earlier, there is a difference between a nutrunner and an impact wrench!

The biggest difference lies in the method of applying force. As mentioned above, the nutrunner uses a planetary gear mechanism to generate "continuous and smooth rotational force" to quietly tighten the bolt to the target torque. On the other hand, an impact wrench has an internal hammer that delivers a "gung-ho" blow in the direction of rotation, and the impact intermittently turns the bolt　It is.

This difference in principle leads to the following differences

• Accuracy:Nutrunners have very high precision in torque management, whereas impact wrenches rely on impact force, resulting in large variations in tightening torque. For this reason, impact wrenches cannot be used for fastening critical parts that require precise torque management.
• Noise and vibration:Nutrunners are quiet and low-vibration, while impact wrenches produce loud blows and vibration.
• Reaction force:Since nutrunners generate continuous forces, they may require a counter-force receiver (such as an arm that supports the tool to prevent it from rotating backward) to counteract the forces. Impact wrenches are difficult to apply large counter-forces except at the moment of impact, which is an aspect that makes them easy to handle by hand.

In short, the basic rule is to use a nutrunner when quality and precision are the highest priority, and an impact wrench when ease and speed are important.　The first two are the following.

Difference between nutrunner and shear wrench applications

The difference between a nutrunner and a shear wrench is clear: "The type of bolt used is completely different.

A shear wrench is a special tool for tightening a specially shaped bolt called a "torsia-type high-strength bolt (shear bolt). The tip of this bolt has a part called a "pintail," and when the appropriate torque is reached during tightening, this pintail is automatically threaded and breaks off.

The operator only needs to visually confirm that the pintail has been broken to determine that accurate tightening has been completed. It is mainly used in bridge and steel construction sites.Nutrunners, on the other hand, are used to tighten common hex bolts and nuts that we usually see, based on torque values and angles set by an external controller.

Therefore, the two are rarely confused.　A clear distinction exists between shear wrenches for handling Torsia type high strength bolts and nutrunners for tightening other general bolts with high precision and control.

Optimal Nutrunner implementation and utilization practices

Characteristics of major nutrunner manufacturers

Here we summarize the major manufacturers widely known in Japan and their characteristics.

Each of these manufacturers has a different philosophy and technical background.　It is important to select the manufacturer that will be the best partner for your company, taking into consideration their production methods, level of quality control, and future scalability.

General Installation and Nutrunner Pricing

There are several ways to implement a nutrunner and a corresponding price range.

General introduction

Nutrunners are specialized industrial tools and are rarely found in home centers.　The main routes of introduction are as follows

1. Purchased from a manufacturer or specialized trading company:This is the most common method. Consult with the manufacturer's sales representative or a trading company that specializes in tools, receive suggestions for products that suit your application and budget, and then make your purchase. The advantage is that technical support and after-sales service are available.
2. Use of rental services:Rental services are an effective option when you want to use the equipment for a short period of time for a specific project, or when you want to reduce the initial investment.³The purpose of this service is to test the performance of a product before purchasing it. It is sometimes used to test performance before purchase.

Price Range

Prices for nutrunners vary very widely depending on their performance and functionality, and it is difficult to generalize.

• Entry models:. Simple electric drivers for integration into automatic machines, for example, can be found starting in the tens of thousands of yen range. For example, electric drivers for robots handled by MonotaRO can be found in the 40,000-yen range. These are mainly designed to function as part of a system rather than as stand-alone highly functional fastening management.
• Standard Model:. General AC servo nutrunners and cordless models with basic torque management functions are mainly in the 100,000 to 500,000 yen price range. Nitto Seiko's "NX Driver" and "KX Driver" series fall into this price range. TONE's cordless simple torque converter "CST20" and others are also typical examples in this class, starting at about 350,000 yen.
• High-function, high-torque models:. It is not unusual for a complete system or product with advanced data management functions or that supports extremely high torques of several thousand N-m to exceed one million yen. For example, Bosch Rexroth's "Electric Cordless Nutrunner NEXO" angle head type is priced at approximately 1,200,000 yen, and TONE's "Electric Power Digit Torque PDX301A" which is capable of 3000 N-m is priced at approximately 840,000 yen.

It is important to note that the price of the tool itself is only part of the installation cost.In particular, when an automated system is assembled, robots, peripheral equipment, and system design costs are required separately, and the total cost may far exceed the price of the tool itself.　Therefore, it is necessary to plan not only for the immediate price, but also for the total cost of ownership (TCO) of the entire system, including post-introduction maintenance and operation costs.

How to automate screw tightening with Nutrunner

Using a nutrunnerAutomated screw tighteningTwo major approaches exist to　The first is the "production method".　Each has its advantages and disadvantages, and the best method depends on the characteristics of the product to be produced.

Multi-axis fastening system

This is,A method in which multiple nutrunners (equipment built-in type called spindles) are fixed to a special jig plate to simultaneously tighten a number of bolts at once.　It is　For example, it is used to fasten all bolts at once in the assembly of a product in which many bolts are arranged in a fixed pattern, such as automobile engine parts.　Examples of actual equipment can be found on the manufacturer's website.

Reference:Tohnichi Corporation Multi-axis type tightening device

• Benefits:Cycle time (time required to produce one product) can be reduced to the limit, resulting in extremely high productivity. It is ideal for lines that produce large quantities of the same product, such as automobile engine assembly.
• Disadvantages:If the position or number of bolts changes, the expensive jig must be rebuilt, which is inflexible. Not suitable for switching between varieties.

Robot Systems

This is,A single nutrunner is attached to the arm of an articulated or SCARA robot, and bolts are tightened one by one in sequence according to a program.　The company has been working to improve the quality of work and shorten working hours.　In fact, there is a case in which a dual-armed cooperative robot was introduced into the screw tightening process of precision machinery to improve work quality and shorten work time, against a backdrop of labor shortages and quality stabilization.

Reference:Kawasaki Robot Introduction Case Study - Fujisen Gikou Co.

• Benefits:Flexible enough to accommodate a variety of products and bolt positions simply by changing the program. We are also good at accessing complex angles.²⁹. Especially with cooperative robots, it is possible to work side by side with people without safety fences.
• Disadvantages:Since each piece is tightened one at a time, the overall working time is longer than that of multi-axis systems.

The main criteria for choosing either method are "production volume" and "variety".　The system will be a "robot system".　　It is advisable to choose a multi-axis system for high-mix low-volume production and a robot system for high-mix low-volume production.

Difference between nutrunner tightening and robot tightening

Closely related to the aforementioned "how to automate," this note focuses on the ideological difference between "fastening by a dedicated machine" and "fastening by a robot.

Tightening by special machine (multi-axis nutrunner)

This is a "specialized" and "efficient" approach　It is　　It is designed for the sole purpose of fastest possible tightening of a bolt in a specific position on a specific product.　Once set up, the same job can be repeated endlessly at high speed and with high precision, but because it is specific to that product, it is not versatile.　It is a very good specialist-like unit, optimized for a specific task.

Robot tightening

This is a "flexible" and "versatile" approach.The robot arm has a high degree of freedom like a human arm and can be programmed to tighten screws in various locations and angles.We can handle product model changes without major facility changes.　Even if there is a product model change, it can be handled without major equipment changes.　It can switch between different tools (in this case, nutrunners) to perform a variety of tasks,A multi-skilled worker.　It is.

Thus, the difference between the two is not merely a difference in performance, but reflects a difference in strategy in terms of what is required of the production line.Choose a dedicated machine for stable mass production, or a robot if you want to be resistant to change and prepared for future product diversification.　will be.

How do I install a nutrunner on an automatic machine?

In order to incorporate nutrunners into automated machines and robots to achieve stable production, careful preparation from the design stage is essential, rather than relying solely on tool performance　It is.　In particular, the concept of "Design for Automated Fastening," or DFAF for short, may be unfamiliar to the average designer, but it can make or break a project.

Why do we need "Design for Automation"?

Simply put, DFAF is the concept of "designing the product side so that it can be easily assembled by a machine (robot) rather than a human.　It is.　　A human being can tighten a screw in a tight space by adopting a slightly unreasonable posture and slightly adjusting the angle of the tool.

However, robots can only move as programmed.　Therefore, if the design is still based on the assumption that the robot will be assembled by a human, a fatal problem can occur: "We introduced a high-performance robot, but it cannot fasten because the tools do not physically fit.　It is no exaggeration to say that the success of automation is determined at the product design stage, before tool selection.

Point 1: Secure a "pathway" and "work space" for tools.

The most basic and most important is to ensure that the nutrunner tip (socket) or body has enough space to physically reach the bolt or nut to be tightened.　At the product design stage, sufficient clearance (gap) must be provided around the bolt and the "swing" for the tool to turn. For example, a situation where a bolt is placed too close to a wall and there is no room to turn a wrench must be avoided.

Point 2: Design that takes into account the "reaction force" generated

Nutrunners generate a large reaction force (force that tries to reverse the tool) when tightened.　The frame of the robot arm or specialized machine should be able to take this reaction force,The design must be sufficiently rigid.

Especially when fastening with high torque, if this reaction force is not adequately calculated, there is a risk that the robot will be misaligned, resulting in inaccurate torque fastening, or in the worst case, failure.It is important to predict the reaction force generated from the torque value of the nutrunner to be used and select a robot and mount with the appropriate rigidity.　It is.

By incorporating these points into the design process from the initial stages, rework in later processes can be eliminated and automation can be launched smoothly.

Peripheral equipment required for nutrunner installation

To build an automated system by introducing a nutrunner, various peripheral devices are required in addition to the main unit, and only when these devices are integrated can the system function as a whole.³¹The Major peripherals include

• Controllers This is the "brain" of the nutrunner. It is responsible for setting fastening torque, angle, speed, and other conditions, as well as monitoring and recording the results of the operation.
• Screw Feeder (Parts Feeder):. This device automatically aligns screws and supplies them to a position where they can be easily grabbed by a robot. Essential equipment for full automation.　It can be said that
• Sockets and bits This is a tip tool that engages directly with the screw head. Although consumable, it is an important component that determines the accuracy of the system.When handling screws of different sizes, the robot also utilizes devices such as a "socket tray" to automatically change sockets　The following is a summary of the results of the project.
• Reaction Force Receiver (Torque Arm) This arm is designed to safely catch the reaction force generated, especially when using high-torque nutrunners by hand.　It helps reduce the burden on the operator and prevent injury.
• Safety devices In areas where robots are used, to ensure worker safety,Light curtain　and area sensors, emergency stop buttons, and other safety devices are required by law.

Proper selection and combination of these peripheral devices is very important to build a reliable automation system.

Final check for optimal nutrunner implementation

We have covered the basics and applications of nutrunners.　　As a final checklist, we summarize the important points.

• Nutrunner is not just a tool, but a fastening system capable of precise torque and angle management
• Its mechanism is based on non-impact, smooth, continuous rotation by planetary gears
• Power source can be either a high-precision electric type or a robust pneumatic type, depending on the application.
• The biggest difference between impact wrenches and impact wrenches is precision and reaction force, which can be used according to quality requirements.
• Shear wrenches are exclusively for Torsia type high strength bolts, and the target bolts are fundamentally different.
• Each major manufacturer has its own strengths, including low-force technology and total supporthave
• Consider the cost of the entire system, including not only the tool itself, but also peripheral equipment and design costs.
• Automation includesThere are multi-axis specialized machines suitable for mass production and robot systems that excel at handling a wide variety of products.
• Robotic systems are flexible for future product changes because they can be adapted through program changes
• The key to successful automation lies in designing the product itself in a "form that is easy to automate.
• Design.It is essential to provide sufficient space for tool access in the initial stages
• such as controllers, screw feeders, and safety devices.Peripherals support the entire system
• Countermeasures against generated reaction forces are an important design item directly related to worker safety and equipment protection.
• Collecting and utilizing the conclusion data can ensure traceability and improve the quality assurance level.
• Need to select the optimal configuration based on a comprehensive evaluation of the company's production volume, quality requirement level, budget, and future plans.

Relevant or cited WEB sites

Finally, in preparing this article, we have consulted the following manufacturers' official websites and technical information sites to provide accurate and reliable information. Please refer to these sites to learn more about the product details and latest technologies of each company.

1. Estic Corporation
   • Description: Manufacturer of a wide range of products from hand nutrunners to servo nutrunners for equipment and robot systems. The company is particularly strong in "pulse tightening" technology, which suppresses reaction forces.
   • URL:. https://www.estic.co.jp/
2. Nitto Seiko Corporation
   • Description: A manufacturer offering "total solutions for fastening" from the manufacture of screws (fasteners) to screw fastening machines and automatic assembly equipment.
   • URL:. https://www.nittoseiko.co.jp/

Sites that cite specific case studies

Next,How Nutrunner is actually utilized　The following case study websites are useful to get a concrete image of what is being done.

1. Yamazen Corporation (Example of automated screw tightening for electronic circuit boards)
   • Description: This is an example of automated screw tightening for electronic circuit boards by combining a cooperative robot, a screw feeder, and a screwdriver for automatic machines. This is a very informative example of a smart factory.
   • URL:. https://tfs.yamazen.co.jp/works-robot/neji.html
2. Example of Quality Control and Traceability] Estic Co.
   • Description: This is a case study of how the introduction of a nutrunner solved the problem of data collection, which was difficult with electric screwdrivers, and improved the level of quality control by linking it to a manufacturing execution system (MES). It shows how fastening data can be used to ensure traceability.
   • URL:. https://www.estic.co.jp/case-study/1186/
3. Example of Automation by Cooperative Robot] Universal Robot
   • Description: This video shows how cooperative robots are used for screw fastening work at various sites around the world. You can see various applications such as tightening screws to vehicle frames and attaching to motorcycle cases, and get hints for automation.
   • URL:. https://www.universal-robots.com/ja/%E6%A4%9C%E7%B4%A2/?query=%E3%83%8D%E3%82%B8%E7%B7%A0%E3%82%81

That's it.