MMC Magazine

Cooperation: Citizen Machinery Co., Ltd.

Fundamentally changing chip control

Chip control is one of the problems to be addressed in the use of small automatic turning machines employed in automobile parts production and small precision machining of parts in the manufacture of medical equipment and OA devices. If chips are not produced or handled well, they can become entangled and result in reduced tool life, damaged product surfaces and even machine breakdowns. In other words, chip control is a priority factor for improving tool life. This in turn promotes a stable level of quality and for optimisation of machining efficiency, high pressure coolant that breaks chips directly and inserts with suitable chipbreakers should be used. Citizen Machinery took a completely new approach to chip control with low frequency vibration cutting technology. In autumn 2013, Citizen Machinery attracted attention both at home and abroad by introducing a machine that incorporated this technology. Yoshimitsu Oita of Mitsubishi Materials Sales Division and Akira Sato of Mitsubishi Materials Development Division visited Takaichi Nakaya and Kazuhiko Sannomiya at the Citizen Machinery Development Division to interview them about the concept and future of low frequency vibration cutting technology.

Low frequency vibration cutting LFV*

Citizen Machinery’s unique control technology synchronizes the vibration of the servo axis with the revolution of the main axis. LFV breaks chips into small pieces and discharges them during operation. This addresses all the problems caused by entangled chips during difficult-to-cut material machining and deep hole drilling. LFV is the most advanced machining technology and has the advantage of applicability to a wide range of cutting materials and geometries.

Applying neutralisation to completely break chips

Oita (Mitsubishi Materials): Chip control is an important problem that machining tool manufacturers need to address, and my interest in Citizen’s machine development is rooted in this problem.

Nakaya (Citizen Machinery): It started with a request from our customer and some proposals involving the application of LFV. We were aware of the need for chip control and our discussions led to the idea that LFV would provide a solution, this prompted us to work on joint development.

Sato (Mitsubishi Materials): Generally, machine tools should not vibrate, right?

Nakaya: Sure. It is important that machine tools do not vibrate. When the customer made the request involving LFV, I wondered whether it would be possible to maintain the accuracy of machining and whether the machine would be able to withstand the vibration. However, I understood the potential of LFV technology, which gave me the confidence I needed to work on this technical development.

Sato: The biggest problem with automating manufacturing sites is chip control and the biggest problem with chips is the damage they do to tools. There are many other problems with chip control, problems such as rough surface finishes and shortened tool life, etc.

Oita: Machine operation rates are the key to productivity (cost) in machining mass-production parts on automatic lathes. Once chips get entangled in the machine, the flow of chips changes and this causes surface damage. In the worst case, this may cause machine stoppage. Being able to discharge chips reliably, surface finishes are guaranteed, general problems during machining decrease and overall productivity increases. We are very excited about using LFV and it helps to achieve good results.

Nakaya: We think that cutting processes that we developed utilizing the LFV would make it possible to break and discharge chips utilizing neutralisation during cutting, prevent the increase of temperature on the cutting edge and lead to expanded tool life.

Shifting to a time in which difficult-to-cut materials become easy-to-cut materials

In 2014, Citizen Machinery released the VC03, a two-axis lathe with LFV. What was the most difficult challenge during the development of the VC03?

Nakaya: The major characteristics of the VC03 are shown in the bottom figure on page 27. The basic concept is zero vibration in machine tool development, so it was very difficult at first for us to accept the idea of actually trying to cause vibration. What I mean is that if the LFV vibration frequency matches the vibration of each component, the machine itself will vibrate, making machining impossible. In spite of this, we proceeded with development. LFV can completely break chips, reduce cutting resistance under specific conditions, reduce temperature at the cutting edge and increase tool life. LFV has proved to be an innovative solution for manufacturing.

Sannomiya (Citizen Machinery): I feel that we have achieved something great if the technology we develop can solve problems for our customers. It is a great pleasure for us to see that LFV technology has made our customers happy and it has been highly regarded since we launched the product.

VC03 – Mechanism for high precision

Symmetric heating system frame and bed, wing-type head stock and external coolant tank are basic VCO3 specifications required to prevent time dependent thermal displacement and processing heat from being conducted to the machine body. Its built-in motor is equipped with a forced cooling function, is beltless and vibration resistant, which promotes smooth revolution and highly precise product formation. The combination of peripheral devices such as an in-out stocker and a high speed gantry loader, whose service time is only 3.5 seconds can respond to a wide range of systematic automation.

How do you think manufacturing will change in the future?

Nakaya: Citizen Machinery set the goal of “Ko No Ryosan”*, mass customization in Citizen style as a business concept in 2013. The concept promotes innovative manufacturing for customer-oriented production and was established to achieve high productivity while ensuring the same level of efficiency in both mass and small-lot production. A wide range of forms and materials will be processed in product lines, this requires a unified chip control system such as LFV that applies to all materials and machining. We need to continue with the development of new machining technology to expand this concept.

Sannomiya: We are dreaming about expanding our technology to make difficult-to-cut materials into easy-to- cut materials in the near future. LFV has significantly reduced the length of chips and has made it possible to reduce chip entanglement even with difficult-to-cut materials so that chips are easy to remove. This reduction in length of the chips also leads to easier disposal by recyclers, which makes it environmentally friendly.

Nakaya: I believe that LFV will change the concept of machining technology significantly. Based on the concept of LFV, tool geometries and design changes; and as soon as we reduce chip entanglement to zero, design flexibility can also increase. The future is filled with potential. We have a wide range of ideas that we are looking into and tool manufacturers will also be engaging in research and development.

Oita: Innovation will come if we can discuss tool geometries, design and parts with manufacturers and identify the ideal match between technology and individual tools. This could fundamentally change machining strategies at manufacturing sites.

Nakaya: In the manufacture of large machines, safety becomes an issue when operators leave the cover open during manufacturing to remove chips manually. They do this because they want to prevent damage caused by entangled chips, but it is dangerous. LFV provides excellent chip control to enable safe and automated machine operation. We will continue to expand the application of LFV technology in VC03 to other machines to promote safe operation in other manufacturing processes.

Sato: We also put energy into tool development from the standpoint of our customers and want to provide innovative machining methods that prove valuable for manufacturing sites around the world.

Oita: Mitsubishi Materials has established a cutting-edge technology development team and our young engineers are also engaged in tool development.

Sato: LFV technology made it possible to discharge chips completely, which showed us the possibility of producing new tools with a wide range of functions such as tools exclusively for LFV cutting. Considering the progress of such new technology and machine tools, we would like to continue developing tools that are useful at actual customers manufacturing sites.

Ko No Ryosan, mass customization is a registered trademark of Citizen Holdings Co., Ltd.