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MOTOREX Magazine 2006 79 EN

  • Text
  • Motorex
  • Motor
  • Oils
  • Engines
  • Bushes
  • Lowsaps
  • Racing
  • Lubricant
  • Diesel
  • Particulate
MOTOREX_Magazine_2006_79_en

Industry Photos: Walter

Industry Photos: Walter Dünner SA, Moutier Industry Correctly adjusted and lubricated guide bushes are an essential requirement if the parts being manufactured are to be dimensionally accurate. This article will tell you what to look out for, and how MOTOREX ORTHO plays a positive role in “guidance.” Perfect lubrication = optimum guidance! The sophisticated MAGIC guide bush system from Walter Dünner SA enables fully automatic opening and precise closing. Guide bushes remain an important topic in any small part turning operation. It is through these bushes that the polished bars are fed to the machining process, with a play that can be precisely adjusted to 1/100th of a millimeter. It is not uncommon for incorrect guide bush diameters or incorrect play adjustment to cause problems in day-to-day production. If cold welding materials, such as stainless steels or titanium alloys, are processed for this purpose, then even the slightest deviations or the use of an unsuitable cutting oil means that there is a risk of “seizing” in the guide bushes. ture severely reduces the viscosity of the lubricant, and demands maximum performance from the machining fluid. For this reason, MOTOREX uses a combination of temperature-stable extreme-pressure additives in its ORTHO cutting oils. With “turning” guide bushes, direct friction between the surfaces can be prevented. The turning movement takes place in the spindle and its ball bearings. However, the spindle bearings must have only minimum play. With “turning” guide bushes the bearings heat up linearly, which need not be considered problematic. Especially for guide bushes, the cheapest way is not always the most cost-efficient. With regard to safety, guide bushes with ceramic guide surfaces are pointing the way. They are extremely temperaturestable, and have outstanding reliability and longevity. However, they are slightly more expensive than conventional guide bushes. Also, vibrations can cause chipping, for example in difficult knurling operations. From a lubrication point of view, ceramic presents absolutely no problems, and is best suited to modern, chlorine-free cutting oils. A sensible option would be to fit special cross-bores to the guide bushes in order to optimize lubricant feed. Your supplier will be happy to help you. Strict demands on cutting oil Chlorine-free, environmentally neutral cutting oils are now the rule. For some time, chlorine has been considered an undesirable additive in modern cutting oils. Previously, the chlorine in the cutting oil gave the lubrication film the desired extreme-pressure characteristics; now, however, all essential characteristics must derive from the basic formulation and a modern package of additives. While leaving out the chlorine means that the machining fluid is indeed “chlorine free,” it no longer has the necessary safety limits with respect to the extreme pressure characteristics. A new additive technology in MOTOREX ORTHO NF-X enables the machining of all materials. In addition, the characteristics of the active substances, including the extreme pressure characteristics, are reinforced within a defined temperature range. This provides maximum process reliability, enhanced cutting values (MOTOREX vmax Technology), and perfect surfaces. With ORTHO cutting oils, outstanding machining results can be obtained without the use of undesirable substances. Optimal lubrication pays off The effects of optimized oil feed to the guide bush also should not be underestimated. Wherever possible, the cutting oil should be supplied in the direction of the bar feed. In this way, the oil is drawn onto the guide surface in a pulsed manner by the new bar. If, in addition, guide bushes with cross-bores are used for improved oil feed, you’re 100% on the safe side! We will be happy to give you information on the new generation of ORTHO cutting oils in connection with the guide bushes that you use. Guide bush checklist: • Choose a suitable type of guide bush for the type of material/machining • Always set the play correctly at the guide • Check for correct concentricity of guide bush/collet/headstock • Use only a high-quality modern cutting oil such as MOTOREX ORTHO • Optimize the oil supply to the guide surface of the bush • Make sure the machine is as clean as possible Cutting oil should also be fed from the rear and in the direction of the bar feet. Thus the oil is “drawn on” by the new bar. Different types of guide bushes When selecting the guide bush, the small part turner can now choose between a large number of types, technologies, and manufacturers. A distinction is made between two basic types: the “fixed” and the “turning” guide bush. With fixed guide bushes, friction occurs on the guide surface as a result of the rotation of the material bar. During turning, the temperature in the bush with a carbide guide surface averages between 30 and 60°C. When parting off, the temperature can very quickly rise to short peaks of between 120°C and 180°C. This precipitous rise in tempera- The latest carbide and ceramic guide bushes For carbide guide bushes, various manufacturers including Walter Dünner SA of Moutier, Switzerland, now use hard metals containing cobalt. Extensive testing has shown that cobalt has a desirable frictionreducing effect. At Dünner, the guide surface is also given a special grinding, which leaves behind the required “micro-recesses.” This gives the cutting oil better adherence and provides a highly stable lubricating film. In all cases, the guide surface should be lapped, but unfortunately this is not always the case with all manufacturers today. Desired micro-recesses The cross-section of a fixed guide bush (left) shows the carbide guide surface marked in blue.The enlarged detail (top) shows the lubrication film (yellow), which hydrodynamically separates the guide surface and the bar material. Because of a special surface structure with “micro-recesses,” the cutting oil has maximum adhesion, and, thanks to special MOTOREX additives, forms a high-performance lubricating film. If desired, additional oil ducts can be provided laterally in most guide bushes. This guarantees better lubrication and cooling. 12 10 13

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