MULTIPURPOSE OILS IN THE METAL WORKING INDUSTRY ADVANTAGES IN ECONOMICAL, ECOLOGICAL AND HEALTH AND SAFETY ASPECTS

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1 MULTIPURPOSE OILS IN THE METAL WORKING INDUSTRY ADVANTAGES IN ECONOMICAL, ECOLOGICAL AND HEALTH AND SAFETY ASPECTS J. MÜLLER, S. JOKSCH Oemeta Chemische Werke GmbH, Ossenpadd 54, D Uetersen, GERMANY; joksch@oemeta.com SUMMARY The idea to design multipurpose lubricants is nothing new, but in the past there were only a few successful applications in the metalworking industry. The main problem was to cover the various and different requirements on the fluid properties with only one product system. Costs caused by mutual effects of non-compatible metal working fluids mostly are an unused potential to save money. Now a new generation of multipurpose lubricants brings the break through for the general applicability not only as water mixed but also as non-water mixed metalworking fluid. Field applications of this advanced product have proven a lot of technological and economical benefits. Keywords: Multipurpose, ester, 2-component-cuttingfluid, cleaneremulsion, recycling 1 WHY USE MULTIPURPOSE OIL ()? Increasing worldwide competition forces even the metalworking industry to try and stay one step ahead of the competitors. In order to achieve this aim, production costs must be minimised whilst maximising productivity. Highly efficient, complex process equipment with high availability is used and requires an inconceivable multitude of specialised process materials. Alongside product assurance as the main requirement when using metalworking fluids / lubricants, requirements are also on the increase regarding prevention of waste, industrial health and safety and protection of the environment. All potentially hazardous substances used generate costs which are only indirectly connected to their intended application, whether this be in the field of logistics, storage, disposal, monitoring, the creation of operating instructions, absence of personnel due to illness, etc. In the past few years, a trend towards reducing the amount of process materials used in the operations as far as possible and better adapting them to each other has been observed. However, a considerable reduction of the employed mediums can only be achieved if the available products, on the one hand, are multi-purpose and, on the other hand, assure the full performance of the individual processes. dirt on machines neat less lifetime of cutting fluid slide tramp on surface falling of in production leakage hydraulic more waste more substandard parts Illustration 1: changes in properties The basic approach of demanding multi-purpose lubricants is supported by the possibility of lessening interface problems. Interface problems arise when two incompatible mediums come into contact with each other and experience changes in property due to this contact / mixing (Illustration 1). The effects on the process results and costs can be dramatic. 2 WHAT IS MULTIPURPOSE OIL? The term multi-purpose means nothing more than that it is a product which can be used in various types of application. Regarding the metalworking industry, there are two basic different definitions of the term: A. Non water-miscible product system with compatible basic s and additives for use as a hydraulic, slideway, spindle and processing. Problem: the various applications are not generally covered by a viscosity stage. This means that a multiproduct system has to be used so that a change in viscosity of the working occurs when a large amount of leakage is added. B. Water-miscible product system which can be used as hydraulic when not mixed with water and which can be used as a metalworking emulsion when mixed with water. Problem: different viscosities for slideway and hydraulics required, therefore a multi-product system is required, but there is no change in the product properties of the emulsion by the addition of various multi-purpose viscosities. There are currently no generally valid specifications or standards for multi-purpose s. A specifications plan based on DIN T2 which was presented in 1991 by the Verbraucherkreis Industrieschmierstoffe (VKIS) has not been passed yet nor has it had any influence on any standards.

2 The reasons for this are the complexity of the subject and the current lack of experience in use. 3 DEVELOPMENT OF One of the greatest problems in the field of application of metalworking fluids is the unavoidable leakages of hydraulic and slideway s in the coolants. Studies in the automobile industry have shown that the annual hydraulic leakages in coolants make up between 3 and 10 times the hydraulic filling volume, whereby a 7 10 times larger amount of water-mix coolant compared to non water-mix coolant can be assumed [2]. The first developments of water-miscible hydraulic during the 1980s showed the difficulties of the practical use of multi-purpose : The complete product requirements of the machine tool hydraulics on the one hand and the completely differently constructed coolant product profile for the cutting process on the other hand, were not compatible with each other. biological and physical stability no health hazard good corrosion protection good foam behaviour good residue behaviour good storage stability good compatibility with machine materials easy to treat and dispose (ultrafiltration) Illustration 2: profile for water-mixed coolants If we consider the secondary requirements (Illustration 2) of water-mix coolants, it is corrosion prevention and bio stability which chiefly necessitate the use of a variety of chemical substances, which can cause problems in hydraulic systems. This was clearly demonstrated in test applications of a mineral -based in machine tools as the hydraulic ISO VG 46 and as a water-mix coolant: in a type of pump in which the hydraulic medium can be heated to well above 80 C in its operating state, the unit broke down after only a short amount of time. t max = 80 C constant stream pump Control valve t max >> 80 C t max = 80 C Self-ruled pump Illustration 3: pump control systems The cause was the cracking of the contents and the resulting residues which led to its failure. In case of pumps which work on a different control principle and whose top temperatures < 80 C, operation was perfect (Illustration 3) [3]. A further field test in which a mineral -based (viscosity 11 mm²/s at 40 C), non water-mixed, was used for drilling in camshafts in order to cut off the contamination of the emulsion processing due to displaced cutting, led to skin and respiratory tract problems of the machine operators. The test on this machine had to be aborted. Outstanding results were achieved on another machine using this medium but where the operators were not subject to direct contact. The test results led to the recognition that the aforementioned type which is in principle a mineral -based coolant concentrate has to remain limited to a few fields of application. The requirements on a widely-useable led to the developers having a re-think regarding the basis of raw materials and the principle construction of the product: rawmaterials with good thermal stability and ageing properties use of physiological uncritical substances high performance base choose rawmaterials regarding health / safety and environment f.e. biological degradibility construction of a 2-component multi-purpose based on synthetic esters The need to use a highly efficient basic fluid which also corresponds to the latest state of information regarding industrial health and safety and protection of the environment led straight to synthetic esters. The advantages of synthetic esters over mineral s justify the higher purchase price, especially in the case of s (Illustration 4). + high viscosity index + good lubrication properties + low evaporation loss + good compatibility with requirements of health and safety and environment + good oxydation-stability at high temperature (Polyolester) sometimes less compatibility with seals and coatings Illustration 4: properties of synthetic esters In order to overcome the balancing act between hydraulic and coolant requirements, there is no other choice but the formulation of a 2-component system (Illustration 5). 1-component -System watermixed water base-, emulsifier,corrosion protection, biostability 2-Komponenten-System + Additive watermixed water base-, emulsifier, stabilising agents corrosion protection, biostability Illustration 5: 2-component -system

3 The result was an ester-based 2-component system with a universal, additive component to be used in an aqueous matrix and a range of compatible, emulsifying high performance s with different viscosities and settings. This system s basic product is the HVLP-D hydraulic with a viscosity of 46 mm/s at 40 C. The hydraulic, like all of the system s other products, is a stable O/W emulsion, so that leakages of the various MFOs in, for example, a water-mix coolant, do not cause significant changes in property. The application possibilities are numerous (Illustration 6) and, as we know today, practical application results not only in economical benefits but also partially in astonishing technological advantages. forming Coolant, watermixed cleaneremulsion Multipurpose Quenching agent hydraulic neat slideway Illustration 6: application of an 2-component There are, however, some features to observe in the application of non water-mix ester-based multi-purpose s. Sealing and cable materials, lacquers, coatings and metallic materials in hydraulic components should be ester-compatible. Otherwise, under certain conditions, it could lead to serious malfunctions [4]. It is possible to equip a machine tool exclusively with ester-compatible materials. New machinery, however, is still often equipped for mineral use. Older systems can be converted at great expense. Practical experience, however, shows that s with mild ester-based s do not cause any problems e.g. for standard NBR sealing materials. 4 EXAMPLES OF APPLICATION 4.1 Interface hydraulic / water-mixcoolant Cutting prod. machine tool A motorbike manufacturer used an ester-based 2-component as an hydraulic and as a watermix coolant. In a testing period of 24 weeks, 2 structurally identical Heller machining centres were observed. One machine was operated with conventional lubricants, the other with. Despite the considerably higher purchase price of the compared to the conventional hydraulic, a considerable reduction in costs could be ascertained by using the (Illustration 7). 2- comp.- as water mix coolant (8 % + 2 %) and hydraulic [ Euro ] Conventional coolant costs hydraulic costs coolant (incl. additives) costs of discharge total costs Illustration 7: Comparing - konv. Products, Al-Si-alloy The significant advantage here is in the fourfold emulsion service life due to the cessation of damage due to foreign s and the resulting lower disposal and cleaning costs Hydraulic presses in hydroforming Hydroforming is an innovative manufacturing process for the economic production of components from tubular hollow parts or sheet metal. The force is exerted onto the work-piece by a fluid pressure-exchanging medium of up to 10,000 bar (Illustration 8). pressuretransformer filter Low pressure High pressure ~ 2000 bar tool workpiece High pressureemulsion / solution filtersystem Axialcylinder Hydraulicoi Illustration 8: IHU System The high pressure is built up in a 2-stage hydraulic system via a booster. Conventional mineral -based hydraulic s are used on the low-pressure side, aqueous hydraulic mediums are needed on the highpressure side. A further interface results from forming lubricants which are added to the pressure exchanger fluid from the work surface. The use of multi-purpose s in low and high-pressure hydraulics and as forming lubricants avoids interface problems such as a short service life of the aqueous pressure fluid or difficulties in cleaning of the parts. 4.2 Interface slideway / water-mix coolant On the basis of its basic conception as lubricant loss (Illustration 9), the slideway lubrication has a particularly large portion of damage by foreign of the water-mix coolant. The use of the VG 68 with a conventional coolant improved the service life at one hydraulic component manufacturer regarding coolant (increase from 12 weeks to over one year), reduction of

4 the amount to be disposed of and this in return led to noticeable reductions in costs. DM Illustration 9: open slideway-system When developing an as a slideway, the balance between adhesive power on the metallic surface and the emulsive quality is particularly important. Only then can the uninterrupted operation of the slideways and prevention of damage by foreign be achieved. 4.3 Interface machining / water-mix cool. A changeover from machining to an emulsion machining is often unavoidable within a process due to the various requirements. The s stuck to the workpieces lead to damage by foreign s in the water-mixed coolant. This makes an intermediate washing of the parts or a more frequent changing of the water-mixed coolant necessary. The use of an at a car manufacturer s resulted in the machining of a camshaft, for example, considerably cheaper. Washing between the machining processes was eliminated and the s stuck to the work-pieces served to refresh the emulsion in the following emulsion machining. There was a reduction in energy and disposal costs, and the consumption of cleaners and coolant concentrations was also reduced. 4.4 Conversion of an engine and gearbox works to using multi-purpose Ester-based multi-purpose s have been consistently used in areas of the engine and gearbox works of a car manufacturer where advantages were expected to be shown for approx. 2 years. On the basis of its special properties, ester-based s are also an interesting alternative to conventional lubricants from a singlepurpose point of view. The direct and indirect coolant costs could be considerably reduced by the conversion of the watermixed coolant used for cutting the gearbox components to an emulsion. Particularly lower consumption due to reduced dragging out via chips and foam as well as cleaner processing equipment makes a significant positive difference to costs (Illustration 10). By using s in the hydraulics and as a coolant, a considerably safer operation can be made possible where problems with service life or stability with watermix coolants occur through contamination with foreign s Stück 1-comp./base Min.- 1-comp./ base Ester 2-comp-base Illustration 10: costs after changing to, producing gearboxes, Al-alloy The addition of water-mix coolants to cutting or grinding s can also cause problems. Ester-based multi-purpose s absorb up to 4% water without causing any change in the properties of the, so that work-pieces wet with emulsion can also be machined with non water-mixed coolants without requiring intermediate washing. If the addition of an aqueous medium per unit of time is not too high, a stable balance is set via water vaporisation. Finishing and / or honing of camshafts is a process whose aforementioned problem could be solved by the use of. The service life of a honing stone can be decisively extended (> 20%) on stone finish equipment. The cause of this is the excellent washing and rinsing properties of the mixture of polar ester s and highperformance emulsifying agents. Regarding industrial health and safety, a positive mention should be made that identification with R 65 (Xn) necessary for low viscose honing and finishing s is not applicable to ester-based multipurpose s. Furthermore, injury to workers can be significantly reduced with coolant vapours, thanks to the comparatively favourable vaporisation conduct of low viscose ester s (Illustration 11). 100% 80% 60% 40% 20% 0% Evaporation loss at 250 C (DIN 51581) 19% ester 12 mm²/s 68% neat mineral 12 mm²/s 83% ester 6 mm²/s Illustration 11: evaporation loss 91% honing mineral 6 mm 2 /s An application which promises a great savings potential for the future is the use of the multi-purpose as an emulsion cleaner (Illustration 12).

5 as neat as water-mix coolant as cleaner emulsion Overload cleaner emulsion Washing machine Less waste because of longer lifetime and Recycling less need of energy and chemicals Illustration 12: as cleaner-emulsion Initial uses of the product have put technical suitability to the test. The advantages here are the recyclability and extended service life of the cleaning emulsion. A further application for water-mix multi-purpose s is use as a quenchant for inductive hardness. The high physical stability makes it possible to substitute the usual polymer solutions used for inductive hardness. Without cutting back the hardness results of the workpieces quenched at approx. 900 C, numerous advantages were achieved such as significantly extended service life of the bath, cleaner parts and machines, and lower consumption. Thanks to the radical reduction of the types of process materials, this user was able to introduce a comprehensive recycling system. With this system, which has been awarded an environmental prize, almost all water-mixed multi-purpose s are reprocessed at the end of their usable life and are assigned a new use instead of being disposed of (Illustration 13). collecting CS = central system Mother-system " carestation Emulsion, 25 cbm mixdevice 3% mixdevice 4% CS 5m³ CS 7m³ 56 singlemachines 28 singlemachines 2 MA 7 MA 159 MA individual filled machines individual filled washmaschines CS 15m³ 40 WM 30 MA 22 MA Illustration 13: Recycling system Processing, quenching and washing emulsions are transported to a centralised recycling machine via pipes or a suction carriage and from there are made fit for a second use via filtration, the addition of biocides and concentration setting. This allows certain areas of production to be produced free of waste water. It is also planned for the future that chips from the processing will be integrated with non water-mixed via aqueous degreasing into the recycling system. This is a particularly interesting project for companies producing large amounts of y sludge. 5 CONCLUSION The break-through to extensive usability has been achieved with the youngest generation of multi-purpose s. Referring to the consumption of water-miscible coolants within Germany, the share of multi-purpose s is currently on the increase at 1%. The ester-based s also exhibit a series of advantages from a single-purpose point of view, which makes their use even more attractive. There is currently a great deal of interest in reducing costs and volumes of waste by using s amongst many metal-working consumers. In this context, a higher degree of commitment from the part of machinery and component manufacturers in the future is desirable in order to establish releases and standards / specifications for this product grade. Interdisciplinary co-operation is necessary in order to exhaust the entire potential of the multi-purpose s. It is the ideal scenario that multi-purpose s are included right at the planning and designing stages of processing

6 equipment in order to reduce investment and production costs. Several car manufacturers are already ordering their machine tools with ester-proof sealants. Multi-purpose s will undoubtedly play a greater role in the future than process materials in the metalworking industry. 6 REFERENCES [1] VKIS-Spezifikationsentwurf Multifunktionsöle 11/91 [2] T. Mang u. C. Freiler, Fuchs Petrolub AG Oel + Chemie, Trends bei der Kühlschmierung: Neue Fluidfamilien für die spanende Fertigung und Konzepte für die Minimal-mengenschmierung, Sonderdruck aus Spanende Fertigung, 2.Ausgabe Vulkan Verlag Essen [3] Dr. rer. nat. Jürgen Müller, Oemeta Chemische Werke GmbH, Lösung von Schnittstellenproblemen in der metallbearbeitenden Industrie durch Einsatz von Multifunktionsölen - Praxiserfahrungen Praxis-Forum 1996 [4] J. Nätscher, Mannesmann Rexroth GmbH, Lohr, Erfahrungen mit Multifunktionsflüssigkeiten als Hydraulik-medien aus der Sicht des Anlagenherstellers Schriftreihe Praxis-Forum