NSK Feed Drive Adjuster™ — a new paradigm in feed drive design that evokes an exciting future in machine tool technology

Source of information: NSK

Societies globally are undergoing rapid change as we face climate and environmental issues, aging and shrinking labor forces, and the shift to renewable energy. The field of manufacturing is also experiencing significant change.

New trends in manufacturing were prominent at the most recent Japan International Machine Tool Fair (JIMTOF), with industry players from around the world going all out to make proposals toward creating a sustainable manufacturing industry. NSK also exhibited a wide range of new products and technologies contributing to the reduction of environmental impact and sustainable manufacturing.

One of the items NSK unveiled for the first time as a near-future technology is the NSK Feed Drive Adjuster™, a mechanism for maintaining the structural stiffness and enhancing the stability (reliability) of ball screw feed systems.

We talk to Dr. Satoru Arai, Executive Chief Engineer Industrial Machinery Technology Development Center NSK Ltd., the mind who stands behind this unique development.

What does the future hold for machine tools?

Considering the current social and industry climate, manufacturing in the near future will require a healthy balance of advanced automation and environment-oriented technology. To achieve this, we need to transcend the ideas and methods we are familiar with today and rethink machine tools from a more fundamental perspective with systems premised on utilizing big data and digital technology.

It may not be a stretch to say that the significance of manufacturing in developed economies itself could be in jeopardy unless the conventional approach of relying on on-the-fly adjustments by skilled machine operators is fundamentally changed through digital transformation and new value is generated from AI and advanced simulation models.

By making full use of the power of digital technology, we will be able to develop solutions for various pain points that have (until now) been set aside as “just have to live with it” or “good enough” and solve issues that have not been apparent from conventional perspectives.

What is NSK’s role regarding the future of manufacturing and machine tools?

NSK has developed a uniquely deep knowledge of friction (tribology) through its involvement in a broad range of global industries. We believe that in the coming era of manufacturing, which will be supported by advanced digital technology, it will be vital to integrate this understanding to create highly accountable machine tool solutions strongly grounded in scientific and technological understanding.

That is to say, the systems and technologies that make up present-day machines tools are surprisingly entangled with manual processes executed by skilled operators. In other words, machining can often rely on on-the-fly shop-floor tuning and trial-and-error adjustments. Leaving the specifics of various adjustments and settings to the shop floor has worked until now, but as the digital transformation and further automation of machine tools advances, we will need to explain in more detail the “why” (the basis of our assumptions) in order to reduce reliance on these manual processes by skilled operators.

Naturally, in explaining this, one must be able to speak with a perspective on the overall performance of the machine, not just individual component parts such as bearings and ball screws. With a view to support the development of future machine tools, we would like to closely support our customers by understanding deeply their business philosophy and the essence of their machine design, so that “machine + component parts” can create more value than 1 + 1 = 2, such as a creating machines that do not breakdown, do not stop, and do not require human intervention.

What is the NSK Feed Drive Adjuster and why should I want it?

The NSK Feed Drive Adjuster is a mechanism that minimizes variation (deterioration) in machining accuracy and quality caused by thermal expansion (elongation) of the ball screw shaft due to temperature rise in the machine tool feed drive system. It fulfills vital prerequisites for advanced automation of machine tools and offers considerable environmental benefits. In other words, it has been developed as a solution to reduce reliance on manual processes by skilled operators while also reducing environmental impact.

To elaborate on the mechanism, in a ball screw feed system, heat generated by linear motion of the ball screw nut also heats the screw shaft, causing it to elongate in the axial direction. Here a support bearing structure is typically installed at one end of the screw shaft that can be released to relieve the elongation of the shaft in order to prevent feed system failures and abnormalities in the support bearing.

However, relieving shaft elongation inevitably reduces the support stiffness of the feed system, resulting in a deterioration of machining accuracy and quality. The NSK Feed Drive Adjuster is unique in that it aims to solve this problem from what is essentially an overall machine tool design perspective.

Comparison of ball screw feed system

Comparison of ball screw feed system

In a ball screw feed system equipped with the NSK Feed Drive Adjuster, the support bearing can remain consistently preloaded while stably maintaining axial stiffness, even when the ball screw shaft has elongated due to thermal expansion. In other words, because the stiffness does not change even if the machine (component) deforms, using a simple displacement measurement system in conjunction with the NSK Feed Drive Adjuster reliably secures ideal conditions for maximizing machining accuracy and quality.

Conventionally, ball screw shaft elongation has required manual adjustments to the machine by skilled operators to maintain accuracy and quality, but with the technology of the NSK Feed Drive Adjuster it may not be a dream to eliminate the need for such manual adjustments.

In terms of configuration, the NSK Feed Drive Adjuster requires no external power source and can be retrofitted onto existing machine tools (i.e. the machine tools in your shop right now). It also further improves control characteristics when combined with NSK ball screws.

The NSK Feed Drive Adjuster is not just a highly performant component. We would like to develop this product as an essential item that enhances overall machine tool and sub-system design to ensure human-intervention-free stability and reliability, which is a prerequisite for further digitalization and automation in machine tools. The NSK Feed Drive Adjuster reflects our desire to work closely with customers to crack open the future of machine tools from a fresh perspective.

How does it benefit the end user?

The NSK Feed Drive Adjuster offers tremendous benefits to machine tool owners and operators. It eliminates the need for warm-up programs, enabling machining from a “cold-start” right after powering the machine tool on. Today, machine tools often require that a warm-up program is run prior to doing any work in order to stabilize thermal expansion and reduce fluctuations in the stiffness of components in the machine tool during work.

Further, today’s high-accuracy machine tools are installed in thermostatic chambers that perform strict climate control (temperature control). However, with the NSK Feed Drive Adjuster, it may be possible to achieve high-precision machining of dies and molds in any place where the temperature is relatively stable, without using an energy-consuming climate control solution. This would enable high-precision finishing even in mid-summer or mid-winter temperature conditions, eliminating or reducing the cost of maintaining a thermostatic chamber.

The solutionis not simply a component you install to increase the performance of a machine tool. We are confident that this solution will bring significant new value by enabling an unprecedented level of machine tool automation and reducing environmental impact by realizing cold-start machining as has never been seen before.

Example of Benefits to Machine Tool Owners/Operators

Example of Benefits to Machine Tool Owners/Operators