3 years ago

MOTOREX Magazine 2003 69 EN

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Industry Industry 10 12

Industry Industry 10 12 Nowadays, the only way to economically yet accurately machine castings is to combine expertise in machine tools and machining fluids. If you can do this, you’ll be successful before long! Unmachined valve block castings made of EN GJS-400-15 (GGG40) arrive in mesh bulk containers for machining in Frutigen. The proven MAPAL principle embodies maximum precision: Cutting tool tip (1) with guide pads (2). A = support Fp = passive force Combined competence in machining and lubrication The Bucher Hydraulics plant in Frutigen is one of four production sites; it focuses its activities on the development and production of a broad range of hydraulic valves and valve blocks. The hose-burst safety valve shown here is manufactured for the world-renowned CASE and CATER- PILLAR excavators, and it must meet a series of tough quality specifications. Since manufacturers are required to comply with precise dimensional specifications they are extremely interested in production cycle times and tool lives. This is where MOTOREX, working together with the renowned precision tool maker MAPAL Schweiz AG, came to the rescue by putting synergistic effects to work in a unique way. More and more spheroidal graphite cast iron being used Spheroidal graphite cast iron belongs to the iron carbon group of alloys. Unlike steel, the carbon content of this material can be up to 4%. The properties of the material depend on the shape, distribution and size of the graphite and the metallic matrix (ferrite and pearlite 1:100). With ductile cast iron (i.e. a material that can yield or flex under loads), the graphite appears in spheroidal, ball-shaped form. The specific structure of the spheroidal graphite cast iron results in particularly advantageous mechanical properties such as high tensile strengths, good elongation at break, and extremely low notch sensitivity. In addition, the material offers good vibration deadening and excellent limphome characteristics. Furthermore, improved dense-feed characteristics produce greater manufacturing reliability. Thanks to its excellent mechanical properties, the material is suitable for highstress parts such as safety parts used in automobiles and engines, as well as for thin-walled, lightweight designs. However, a great deal of skill is required to machine it economically. Properties of EN-GJS-400-15 spheroidal graphite cast iron Material designation as per DIN EN 1563 EN-GJS-400-15 (previously GGG40) Tensile strength R m N/mm 2 400 – 550 0.2%-yield point R p0.2 N/mm 2 250 – 350 Elongation at break A 5% 27 – 15 Brinell hardness HB 30 135 – 185 The MAPAL precision step drill With its high-precision adjustable and exchangeable indexable inserts with two cutting edges, the MAPAL precision step drill (diameter of the first step: 31.8 mm/30°, diameter of the second step: 30 mm H6, and diameter of the third step: 18 mm H6) which is being used to machine the part shown here represents the latest generation of cutting tools used to machine EN-GJS-400-15 (GGG40). The unmistakable MAPAL principle, with one tip and three guide pads, delivers absolutely precise machining results. This design was implemented for all three steps in this machining operation. Above all, the quality of circularity is significantly better than that produced by conventional multicut reamers. N6 surface quality can be achieved without difficulty using the selected cutting lead at the guide pads. The finely lapped Cermet guide pads are used to guide the tool precisely and provide support in the bore. The cutting fluid that is used is the key to this final function. The use of high-quality MOTOREX SWISSCUT TWIN 300 cutting fluid greatly extends the life of the guide pads. This is due to the extremely thin lubricating film between the guide pads integrated in the main body of the tool and the wall of the hole, which effectively prevents wear. Additional contributions to extending service life are made by the coating on the indexable inserts and by optimal alignment of the tool. Using the integrated MAPAL adapter, the precision step drill can be aligned to the nearest micron both radially and relative to its angular position. Significantly longer tool lives Compared to the machining of aluminum, where cutting velocities of several meters a minute can be achieved, the machining time for cast iron is limited by the material. This was the challenge that faced MOTOREX and MAPAL: Using the right tool and a machining fluid properly matched to the application, cutting velocities and tool lives were noticeably improved. With the chlorine-free MOTOREX SWISSCUT TWIN 300 high-performance cutting fluid, the experts were able to concentrate on achieving high cutting values with above-average surface qualities and the same long tool lives. The complex chemical processes in the critical temperature ranges were supported by a special high-pressure additive, without which the desired result would not have been possible. This example once again shows that there is a great deal of performance potential that can be unlocked in various machining processes when the right combination of tool and lubricant is found. To learn more, click: and MOTOREX SWISSCUT TWIN 300 cutting fluid and the MAPAL tool significantly optimize machining results. Valuable synergies can only be achieved through close cooperation between tool makers, machine builders, and lubricant producers. Three at one strike – this cutaway model clearly shows what goes on inside a valve block. 13



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