Opening the door to collaborative automation 


Tanaka Iron Works Co, based in Kobe City, Japan, manufactures precision machined parts for industrial robots, medical devices, aircraft and nuclear power plants. The company had already constructed a production system that operates unmanned 24 hours a day in its plant for cutting processes using dedicated machine tools. However, it had not been able to automate its finishing process, where the main work is performed manually. When exploring what could be done to introduce industrial robots into a space where people are performing the main part of the work, the company turned to the duAro collaborative type dual-arm SCARA robot from Kawasaki, as MEPCA discovered.

Tanaka Iron Works is a professional in the field of precision metal processing.

The company started business in 1938, with the production of the main landing gear for the Kawanishi N1K fighter plane. For more than 80 years since, it has continued to produce precision processed components that are used in aircraft, medical devices, nuclear power plant components and the like.

It also built up a relationship early on with Toa Medical Electronics Co., Ltd. (currently Sysmex), which developed the first automatic blood cell counter in Japan.

Components from Tanaka Iron Works are used in the current blood cell counting inspection equipment from Sysmex.

The company has also been a supplier to Kawasaki Robotics since 1977 and has delivered the mechanical components for the arms, etc., which can be described as the heart of industrial robots.

The strength of the company is its flexible multi-product variable quantity production, which merges 17 machining centres with skilled craftsmanship.

The company is engaged in the ever-expanding businesses of industrial robots for manufacturing automobiles, semiconductors, and medical device components. President Yoshinobu Tanaka explained: “In recent years, we seem to be operating in a 120% utilisation situation, and we have really struggled with a shortage of labour.

For this reason, we have always been searching for work that robots can perform instead of people.”

The first floor of the two-story plant is filled with dedicated machinery where the cutting processing for precision processed components is performed unmanned 24 hours a day.

On the other hand, people are mainly performing the work on the second floor, where finishing processes are performed.

When President Tanaka looked at that workplace, where there were multiple technicians in front of workbenches silently performing the final processing work, he thought there must be some elements that could be automated.

However, introducing an industrial robot to a workplace where human workers are the main element requires large-scale improvements, such as the installation of safety fences.

President Tanaka continued: “If you ask what the biggest issue is for a small factory, it is, of course, space. This is why the majority of locations where industrial robot use is possible are large-scale manufacturing lines, such as in the automobile and semiconductor industries. I had never considered that we would be able to introduce one to our factory.”

That was until President Tanaka came across the duAro collaborative type dual-arm SCARA robot launched by Kawasaki in 2015.

“I heard that it is a robot that can be outside of a fence and coexist with humans, so I thought that it might be something that we could use.

The installation was only possible because of duAro,” added President Tanaka.

Precision and reliability

At Tanaka Iron Works, duAro performs the assembly work for critical components used in Sysmex products. Specifically, the work is to press fit two parallel pins made of stainless steel into aluminium blocks about the length of the back of a human hand.

President Tanaka explained that: “In recent years, the production (for these components) has been increasing. The production used to be 2,000 per month, but it increased to 5,000 per month three years later. When making 5,000, the pin press-fitting requires 10,000 points.”

The pins have a correct up/down orientation and must be inserted in the correct direction, at the correct pressure, and to the correct depth. It seems to be simple but requires skilled techniques. In addition, it is monotonous, repetitive work, so it is also a process where human errors can easily occur.

“If we prioritise speed, then people are faster at inserting them. However, it was not speed we required; it was precise and reliable work,” President Tanaka added.

The first idea was for a simple system where a human worker places the pins in a line, and the duAro would pick them up and insert them into the blocks.

President Tanaka examined that idea and had doubts because there was more preparation work by people than originally thought.

In response to this, he consulted Yasuhiko Hashimoto, then General Manager of the Robot Division, Precision Machinery and Robot Company (currently President of Kawasaki Heavy Industries, Ltd.). The response was quite clear. ‘Please make the robot work harder.’

A pin press-fitting robot system that combined the seven elements was developed. The elements comprised a supply unit to set the pins in the correct orientation, a surface area sensor to double check that the orientation of the pins is correct, duAro to set the blocks and pins on jigs, a press-fitting unit, a load cell to measure the press force, a contact type sensor to measure the height to check that the pin has been inserted to the correct depth, and a system to store the inspection records for all products.

The supply unit devised to set the parallel pins in the correct orientation uses a unique idea to sort the pin orientations with a simple mechanism.














Overcoming challenges

The supply unit has a mechanism that exploits the profile of the pins, where one end is rounded, and the other end is flat.

First, pins that have been placed in a receptacle shaped like a funnel go down into the tube one at a time.

There is a dividing plate placed at an angle part-way along the tube. If the lower end of the pin that comes down is flat, then it will not tip over when it hits the dividing plate. The dividing plate opens, and the pin goes straight down as it is to the discharge port and is set.

However, if the pin comes down upside down, the rounded end of the pin hits the dividing plate, and the pin falls over. It then branches off to the side route as it changes direction to the correct orientation. Air is used to send it off from there, and then it is discharged.

In preparation for the small possibility that a pin with the wrong orientation may pass through, a double-check mechanism is installed. A surface area checker reads the profile of the pin end and removes it if there is a doubt.

The failure rate by manual work was 0.05%. However, through automation, 100% of errors in pin orientation, pressure failures and insertion failures have been eliminated. Between 2016 and 2021, around 100,000 pieces went through the manufacturing process, but there have been zero defects.

President Tanaka says that more than anything else, it is significant that having duAro take on simple work tasks makes it possible for the employees to engage in more sophisticated and skilful work.

The business creed of Tanaka Iron Works is ‘a company is its people’. duAro helps the company put that principle into practice.

Future plans

To develop this project, Tanaka Iron Works collaborated with the system integrators Nanbokusangyou Co., Ltd. and KSS Co., Ltd. President Tanaka believes that the existence of the integrators was essential in making the automation of the pin press-fitting a reality.

“A lot of the specialist terminology related to robotics is impossible to understand unless it is explained in a way that even we can understand. The system integrators are something like an interpreter, connecting the company installing the robots and the robot manufacturer. If you have somebody to act as a bridge like that, then I think that there are still a lot of opportunities for robots to spread in small factories,” he concluded.

Today, right next to a technician who is concentrating on the delicate work at hand, the duAro is quietly working monotonously on the pin press-fitting work.

President Tanaka believes they should be able to use duAro to automate the processes before and after the pin press-fitting work too. For example, the block masking processing and the inspections of components before shipping. Furthermore, there is also now a possibility of introducing duAro for lens assembly work.

The planning for these developments is well underway.



About Author

Comments are closed.