Minimum Quantity Lubrication Systems (MQL) – How to reduce energy and consumable costs without comprising machining performance.

MQL as an acronym (Minimum Quantity Lubrication) is becoming slowly more understood in the machine tool industry as its clear technical and cost benefits start to be delivered for users looking to reduce consumption costs and improve technical and environmental factors for their machining processes. Previously MQL had limited applications and was frequently associated with specialist processes such as turning or specialist mould and die finishing with ball end-mill applications. This article aims to explain the basic principles of the system and offers some recommendations on specific savings which may be achieved by users of MQL compared to conventional coolant systems. MQL utilises a soluble and/or bio-degradable cutting oil delivered in a fine mist to the machining area via either externally delivered nozzles or via integrated tooling to the work piece. It is used as an alternative to either dry machining where tool life is reduced or in place of high pressure flood coolant. Firstly, the disadvantages of flood coolant are numerous such as the high running cost of coolant pumps, maintenance of coolant systems, cleaning of the work area of the machine tool and particularly in summer or warm conditions the unpleasant odour sometimes emitted by poorly maintained coolant systems. It is probably a common viewpoint in the machining industry that a frequent observation of machine shops using flood coolant require a high level of maintenance not only in monitoring coolant condition but also clearing up spills from leaks and so on that present a health and safety hazard in the work place. While therefore it would be ideal to implement dry machining the effect on tool life, heat management and process performance means that this is not possible in most cases. Where dry machining is successfully employed, the process performance can be inhibited by the need to balance productivity against surface finish and tool life and maintenance costs. Therefore even where users have a defined dry cutting process, MQL can potentially assist with extending tool life and increase machining performance in terms of surface finish, cutting forces and process capability. To analyse the cost benefits of MQL, it is firstly worthwhile to study the typical categories of costs associated with the running of a conventional machine tool employing flood coolant in a production environment. When most people are asked about their opinion on which element contributes to the most electricity consumption of a typical CNC machine tool, most people may guess that it is either the main machine spindle (Either work holding or tool holding) or an axis servo motor. In reality these elements are much less, according to a study made by Kuroda shown in Figure 1, which identifies for mid-sized CNC machines that the main spindle only consumes about 12% of the total power consumption and around 7% for main axes feed from the servo motors. Comparatively however, the coolant system including chiller, pumps, and so on can contribute over 60% of the total machine power consumption costs. While this figure sounds relatively high, consider that in reality the machine axes are moving not all the time particularly if point to point positioning is being employed and modern servo motor technology actually produces very efficient motors from a power consumption perspective when not under load. Consider also that a spindle will not always be active either only during actual cutting operations ideally. Therefore a coolant pumping system with associated chillers needs to be ran fairly consistently despite the machine not actually cutting or machining and perhaps also off shift if coolant temperature needs to be maintained for optimum machining performance during actual shift hours to reduce idling time. Imagine thenn also larger users of CNC machine tool maybe also with centralised cooling system and you can start to visualise the potential cost implications of flood coolant systems in the overall consumption costs of machining operations.

Figure 1 – Kuroda study regarding the typical distribution of power consumption in a CNC machining system Further investigation by Kuroda also details the cost implications of coolant in the overall product costs associated with machining operations shown in figure 2 below which indicates that an average 16% of product cost from machining operations could be attributed to coolant systems and cutting tools may contribute 4%.

Figure 2 – Analysis of typical costs associated with machining processes It can be concluded that any improvement on consumption costs for machining operations either in power, tooling or maintenance downtime has to have a direct implication for not only revenue costs but direct product costs as well. Based on field study conditions, Kuroda were able to successfully analyse cutting conditions and calculate coolant consumption costs with their customer base. Shown in figure 3 and based on trials conducted with 4 flute 18mm end mills with depths of cut up to 15mm in carbon steel they recorded that the customer was able to reduce consumption of coolant from 18 litres per month to just 0.6 litre per month of soluble oil and from a cost perspective this represented a cost saving on coolant of 54% based on previous consumption.

Figure 3 – Consumption and costs of MQL versus traditional coolant The principle behind the generation of oil mist is well known from engineering principles utilising the Venturi effect. Via a supply of high pressure air flow generally present in most engineering work shops to a regulator on the machine tool, a chamber of soluble oil is pressurised whereby an oil mist is created by the oil being drawn up through a tube from the incoming pressure. As it passes back into the main tank, it is atomised into a mist from a spray nozzle. Heavier droplets will return back into the main tank liquid and lighter atomised droplets or mist will be carried via a port to the delivery point in the machine tool system from the system pressure.

Figure 4 – Principles of an oil/air mist system As the air mist is delivered along the pipes to the work area the ability to form and retain droplets which will stick to the target area is critically linked to flow speed of the air pressure within the lines as well as the diameter of the droplet itself which is defined by the nozzle exit profile and port design to ensure that the droplet formation is reduced to as small a diameter as possible and where droplet exit should ideally be close to the work piece surface.

Figure 5 – Principles of oil mist deposition While uniform droplet diameter distribution will naturally vary within defined limits, the majority of droplet formation will be 1 micron or less when using a tool integrated nozzle option. Another critical parameter is the choice of oil itself which is recommended as a bio-degradable oil with a specific density of 0.95 g/cm3 at 16 Deg C and importantly a kinematic viscosity of approximately 19mm2/s at 40 Deg C. To compare MQL with either dry machining, flood coolant or even air cooling it is necessary to study a number of factors including cutting force on the tool, tool wear, temperature and surface finish. Based on field case studies by Kuroda using end milling, they were able to demonstrate using the MQL process comparable cutting forces to flood coolant with comparable wear rates. Comparison of MQL samples at varying ml/hr delivery rates consistently reduced cutting force on the tool compared to dry machining with air cooling only. At higher rates of 16ml/hr, MQL was able to match the cutting force measured of flood coolant systems which was operating a much higher consumption rate of 258l/hr.

Figure 6 – Comparison of MQL, Coolant and air blow cooling The thermal effect of dry machining can also be compared and contrasted by the application of a thermal camera and temperature probe and based on extensive continuous cutting trials of 12m of continuous machining showed that with MQL the tool reached its working temperature of approximately 240 Deg C at the tool during cutting and thereafter proved very stable as opposed to a continuous growth in temperature profile of dry or air cooled machining.

Figure 7 – Thermal effects of MQL and non-coolant methods While cutting force was comparable with flood coolant and temperature was considered within acceptable limits and stable with the MQL process, tool wear is also an important factor in the cost analysis and process stability. After 12m of machining, flute edge quality was analysed and photographed and showed comparable and low wear conditions the same as flood coolant.

Figure 8 – Effects of cooling method on tool wear Surface finish is the final element studied by Kuroda and this can be influenced by a variety of factors such as the tool itself, material, feed rates and so on. In a separate test conducted by Kuroda, it was established that MQL could achieve a better surface finish for turning of special materials such as Titanium whereby a 60mm blank size was turned with 3 separate diameters and flood coolant versus 3 separate MQL mist pressures. The startling results indicated that the surface finish measured in Ra was actually lower than the performance achieved by flood coolant.

Figure 9 – MQL trials on surface finish machining Titanium To date, the rate of adoption is fairly low but is increasingly rapidly. Historically, the usage of MQL has been for limited applications such as deep hole drilling, mould and die milling and also some applications where coolant systems are not practical such as in robot based drilling of large components. In reality, the benefits of MQL can be applied to many differing industry types and chip forming processes to great effect. Modern MQL systems such as those provided by Kuroda can be directly fitted to CNC machine as a standalone system whereby they can be operated independently of the CNC system and as such can be purchased and installed by the end user of a machine tool without complex machine modification. Ideally however, the system can be incorporated into a CNC system under M Code actuation which requires more specialist integration either via an independent company or via the machine tool OEM. Kuroda Jena Tec principally offer three models of Eco Saver MQL system where two of the systems (KEP4 & KEP-V) can be offered as an integrated CNC version offering separate tank, delivery rate and pressure ranges and the third is a standalone system (KEP-WR) for use with retrofit by end users or manual machines The MQL process is not a universal solution for all machining requirements and does have limitations dependant on the application, material and geometry of the workpiece. For detailed assessment of the application, Kuroda Jena Tec have application engineers available to assist with determining the correct application of MQL and supply of equipment, process, installation and process development.

Innovative Resin Nut Ballscrew offers lightweight, high performance and quiet operation

Kuroda Jena Tec continues to provide innovation in its latest launch of a lightweight resin ballnut and screw assembly that combines the best in ballscrew technology with the lightweight attributes associated with leadscrews incorporating advanced materials technology. While non-metallic leadscrews have been in the market for some time, disadvantages include excessive heat generation and preferential wear and inaccuracy resulting in poor lifetime performance. Kuroda Jena Tec's exciting new product range comprises a specially selected injection moulded ballnut made of Poly-Phenylene Sulfide (PPS) and stainless steel balls and shaft. The new patent pending design therefore incorporates the advantages of low friction and low wear ballscrew technology with materials technology suitable for stringent medical, scientific or corrosive applications. Competitively priced between leadscrew and ballscrew technology, Resin Nut ballscrews offers a sizeable commercial and technical advantage.

Successful field tests performed by Kuroda Jena Tec demonstrate that Resin Nut technology shows minimal wear affecting accuracy and axis performance even after 250km of travel with heat generation levels typically less than half compared to comparable lead screw alternatives typically with a temperature rise of less than 2 Degrees Centigrade above ambient in service. Initial sizes offered by Kuroda Jena Tec are as follows;

Diameter : 8mm Pitch : 2mm Permissible Axial Load : 40N Permissible Rotational Speed : 3000 min-1 Axial Play : 0.030mm or less Shaft Material : Stainless Steel (Grade 304) Ballnut Material : PPS Balls : Stainless Steel (Grade 404) Grease : Alvania S2 or similar For more information, contact us via one of our local sales offices listed at; www.jena-tec.co.uk www.jena-tec.com www.jena-tec.de

New Hard Turning Investment Allows New Ballscrew Sizes

Kuroda Jena Tec's most recent investment in hard turning technology has increased production capacity with the combined benefits of efficiency compared to conventional production methodology as well as the advantage of development of higher diameter to lead ratios than able to be produced by conventional production techniques in a single ballnut housing. The ability to hold precision ground tolerances with turning technology is due to the unique design and capability of a Mikroturn slantbed CNC machine from Hembrug Machine Tools.

Hard Turning refers to the process of single point cutting of hardened pieces within the 2 micron range with hardness between 58 and 62 HRC. Hard turning has proven to be worthy alternative to the more expensive and time consuming grinding. Finish Hard Turning: Why it is the alternative to cylindrical grinding? Greater accuracy Finish hard turning allows you to machine parts in one set up giving greater accuracies especially on features such as concentricity, squareness and roundness. More Flexibility With a single standard tool and clamping set-up you can machine a wide variaty of products with different forms and sizes. This provides more flexibility in production environments and reduces changeovers. Higher productivity Finish hard turning can remove more material per machining operation than grinding. This can make hard turning up to 3 to 4 times faster when compared to cylindrical grinding. Cost saving Multiple operations can be done in one set-up which eliminates the need for a multi-step grinding process that historically would involve two or three seperate operations.

Kuroda Precision Industries Ltd. acquires Jena Tec Group of Companies

The associated companies of Avingtrans Industrial Products Ltd comprising Jenaer Gewindetechnik GmbH, Jena Tec Inc and Jena Rotary Technology Ltd (hereafter referred to as Jena Tec) and Kuroda Precision Industries Ltd.(hereafter referred to as Kuroda) are pleased to jointly announce a change in Jena Tec’s ultimate holding company share ownership.Subject to final completion on 8th November 2012, Kuroda, a company registered in Kawasaki, Japan has acquired 100% of the shares of all Jena Tec companies from Avingtrans PLC. Jena Tec with manufacturing facilities in Germany, the UK and USA are a designer and manufacturer of high quality precision linear and rotary motion components supplying the machine tool, automation and medical industries principally throughout Europe and North America. Kuroda with manufacturing facilities in Japan, China and Malaysia is a designer and manufacturer of precision components and systems including ball screws, press tools, gauges, tool holding system, machine tool and measuring systems. Since 1925, Kuroda has served a wide range of industries including automotive, machine tool, semi-conductor, automation, and electronics principally throughout Asia. The investment and acquisition of Jena Tec by Kuroda is a further positive step in the development of both brand names whereas each have a reputation for high quality products in their respective markets and where the synergies of both groups will allow significant growth to be achieved globally with their combined resources. Operation of all Jena Tec group companies and respective appointed Directors will continue as before. Jena Tec Divisional Managing Director, Paul Ward, commented: “The investment by Kuroda in Jena Tec is warmly welcomed as the positive elements that both companies can share when combined are significant and supports the expansion plans identified by both groups of companies. The commitment, interest and shared historical background of Kuroda and Jena Tec in producing high precision products in a competitive global market place will continue to benefit our customers, employees and shareholders and secure our successful continued growth in thefuture.” Kuroda president, Hiroshi Kuroda, commented: “We are very pleased with Jena Tec joining Kuroda Group. Jena Tec and Kuroda share commitment to precision manufacturing, skilled employees and long-term relationship with our customers. Jena Tec’s high-quality precision products and customer base ideally complements with those of Kuroda. By combining our resources and competencies, we can better serve our global customers with a wider range of products and solutions. I am excited about the wonderful growth opportunities lying ahead of us.”

Sale of Jena Tec to Kuroda Precision Industries Ltd. (“Kuroda”) of Japan

Avingtrans plc, which designs, manufactures and supplies critical components and associated services to the global aerospace, energy, medical and industrial sectors, announces that it has agreed the sale of its Industrial division, comprising the Jena Tec sub-group of companies (“Jena Tec”), to Kuroda, of Japan, for a cash consideration of £13.45 million (the “Sale”). Highlights: • Cash consideration of £13.45 million • Avingtrans now focused on Aerospace and Energy & Medical Divisions • Aerospace continues to thrive with record order book • Board continues to evaluate potential acquisition targets • • Disposal of Jena Tec provides certainty of funding The Board believes that the Sale will enable Avingtrans to fully focus on its two core sectors through its remaining divisions, namely Aerospace and Energy & Medical, which together contributed revenues of £32.2 million and earnings before interest and tax (“EBIT”) of £1.8 million (before group costs and impairment of goodwill) during the year ended 31 May 2012 and currently employ 548 people. The proceeds of the Sale will be used to invest further in the growth of these divisions and to reduce debt, whilst the Board also continues to evaluate acquisition targets that it believes will enhance long-term shareholder value. The Industrial division contributed revenue of £11.8 million and EBIT of £1.3 million during the year ended 31 May 2012. At that date, the gross assets of Jena Tec were £12.6 million. The division was constructed by Avingtrans from a series of small acquisitions over several years, which originally cost approximately £4 million in total. Jena Tec employs 178 people across its operations based in Germany, the UK, USA and China, all of whom are expected to transfer to Kuroda. Jena Tec’s principal business is the design, manufacturing and servicing of Precision Ballscrews, Spindles and Linear Motion actuation systems for automation and control of CNC machines and precision instrumentation. The final procedural steps for the disposal will be completed on Thursday, November 8th. Steve McQuillan, Chief Executive, of Avingtrans commented: “Whilst Avingtrans is in the enviable position of having three solid, profitable businesses, our overall size and corporate structure has meant that we have been unable to invest in each of the businesses to the degree that we would like and thereby maximise the opportunities available in each of our divisions. “The sale of Jena Tec provides us with a more focused business and the proceeds will allow us to invest for future growth. Our Aerospace division has been thriving and our order book at the financial year end remained at record levels. The creation of Sigma Composites in February is evidence of our ability to create value by targeted investment and we will continue to explore opportunities which would improve our customer reach or product offering and thereby further strengthen our position in this attractive market. “The Energy and Medical division had a difficult period last year, but is well placed to recover in the second half of this financial year, as the volume of activity with Siemens increases. We have continued to cement our key relationships within this division and add further customers, which will enable us to prosper in the years ahead. “We are very proud of all that we have achieved with Jena Tec during our stewardship, including consistently improved sales and profitability. We believe it is well positioned to continue on this growth path under its new owners and we wish our friends there, the employees and Kuroda all the very best for the future. ”

www.jena-tec.co.uk

UK Trade & Investment Team Visit Jena Tec in Germany

July saw an important visitor delegation to Jena Tec's German factory located in the town of Jena, Thuringia, in the shape of a team from the UK embassy located in Berlin and the department of UK Trade & Investment with sector responsiblity for the engineering sector. The visit was part of a co-ordinated tour of successful Anglo-Deutsch companies where examples of best practice could be demonstrated. The strength of the German manufacturing industry particularly in relation to export markets is still very relevant in the current economic climate and the Ambassador and UKTI team were keen to learn lessons from successful companies, such as Jena Tec, and the German model with respect to how manufacturers can be better supported in the future. Jena Tec gave an extensive presentation of the high precision ballscrew machining operations in Jena followed by a Q&A session and a practical demonstration of the important factors of ballscrew assembly for the Ambassador and his team.

New design of Brake Caliper requires new Jena Tec Multi Head Spindles

Jena Tec's design, manufacture and retrofit capability for mutli spindle heads for linear and rotary transfer machines led to orders within June for 8 new spindle heads for a tier 1 supplier in the automotive industry to be retrofited to an existing cell of rotary transfer machines. The 8 new units will be designed specifically to produce a new design of brake caliper for a leading international automotive OEM with production facilities in the UK. Jena Tec will provide a complete design, manufacturing and supply solution for the new spindle heads which will be installed and producing parts by October 2012. For more information on Multi Spindle design capability please go to www.jena-tec.co.uk or www.mossgroupautomation.com