Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/10—Alloys containing non-metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23C—MILLING
  • B23C5/00—Milling-cutters
  • B23C5/006—Details of the milling cutter body
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23C—MILLING
  • B23C5/00—Milling-cutters
  • B23C5/02—Milling-cutters characterised by the shape of the cutter
  • B23C5/10—Shank-type cutters, i.e. with an integral shaft
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
  • C23C30/005—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process on hard metal substrates

Definitions

• the present invention relates to an end mill tool which through material and cutting geometry attains an improved result.
• End mills according to the invention belong to an advanced group of tools which shall be able to both drill and mill. They shall manage the most changing working conditions at one and the same time. The most distinguishing is that it is required good cutting properties in the form of wear resistance and ability to resist high temperatures at the very periphery, i.e. at full nominal measure at the same time as the tool is capable of generating chips and function as a cutting tool in the center, where the cutting speed approaches zero. Between these a continuous change of the cutting speed is attained through all possible built up edge areas etc.
• End mills are often used in difficult operations, where the requirements are very high in terms of surface smoothness. This is for example the case in the aerospace industry when milling wing spars and the like. Here no unevenness and notches whatsoever are acceptable, since these later may give rise to failure.
• Another important area of application is the finecopying of moulding tools where the requirements of high surface smoothness and shape accuracy, with simultaneous high productivity and predictable long tool life, are specially severe. Further, it is a necessity that the tool does not have to be replaced during the continuous machining operation, something that results in inferior precision of the manufactured article.
• SE-B-392 482 a material is disclosed which contains 30-70 % by volume of sub-micron hard constituents in a metallic binder phase. This material has superior wear resistance compared to advanced high speed steel and can therefore be placed in the gorge between cemented carbide and high speed steel as to material properties. Further, in SE-B-440 753 is disclosed how superior compound tools have been made with, inter alia, the above material in the areas which are subjected to a high cutting speed, with high speed steel in the center for .drilling applications.
• the tools were used in coated condition and the so called PVD-method which is the most used coating method.
• the coating is made mainly with titanium based hard material, such as TiN, Ti(C,N), (Ti,Al)N etc. Particularly good properties have been obtained with 2-4 ⁇ m Ti(C,N) .
• the hard material consists of 30-70 % by volume of hard constituents of mainly TiN in a matrix of high speed steel type, where the concentrated hard constituents have a grain size of ⁇ 1 ⁇ m, preferably ⁇ 0.5 ⁇ m.
• Tools according to the invention function very well not only in normal steels but also in hard metal piece materials, in the range of 250-500 HB, such as tool steel, adhering materials such as stainless steel, aluminum alloys or titanium alloys.
• the hard material is metallurgically bound to a tougher core material, one has obtained a very advantageous combination of wear resistance and toughness behaviour for end mills.
• Fig 1 shows an end mill tool with three cutting edges in a side view
• Fig 2 shows a cross-section of the tool along the line A-A in Fig 1,
• Fig 3 shows an end view of a tool with three cutting edges
• Fig 4 shows an enlarged cross-section view of the tool along the line B-B in Fig 1, radially from the central axis ,
• Fig 5 shows a cross-section along line C-C in Fig 4.
• the tool consists generally of an oblong cylindric body 1 which consists of a compound material according to SE- B-440 753 and which has been made in a way as described in this patent document. Consequently, the tool's core consists of high speed steel or tool steel and an external coating, whose thickness constitutes generally 15 % of the the tool's diameter (however, at least 0,5 mm) , consisting of an above more closely specified hard material. Helically along the tool's central axis run a number of protruding lands 2, usually two or three. The protruding lands 2 are delimited by flutes 3. According to the invention, it has been proved to be surprisingly advantageous to arrange these helically formed protruding lands and flutes with 40 ⁇ 5 degrees helix or pitch angle, suitably 40 ⁇ 3°, and preferably 40 ⁇ 2°.
• Each protruding land is along its whole fore edge, seen in the direction of rotation, equipped with a main cutting edge 4 with a positive rake angle ⁇ .
• this main cutting edge has turned out to be surprisingly advantageous to arrange this main cutting edge with 12 ⁇ 5 degrees positive rake angle, more exactly 12 ⁇ 3°, and preferably 12 ⁇ 2°.
• the clearance angle a of the main cutting edge 4 varies depending upon the tool's diameter. The following values illustrate this variation:
• the tool's cutting edges have an edgerounding of 10-30 ⁇ m, preferably 10-20 ⁇ m.
• end cutting edges 5, 5' corresponding to the number of protruding lands 2 are provided at the tool's tip. These end cutting edges are formed obliquely inwards and downwards in an angle of about 1,5° in relation to a radial plane that is perpendicular to the central line.
• each reinforcing chamfer 6 is arranged on the corner between each main cutting edge 4 and the adjacent end cutting edge 5, 5' .
• This reinforcing chamfer is there to diminish the strains that these corners are submitted to when they are in contact with the workpiece. They are suitably angled at an angle y of 20° ⁇ 10° in relation with the central axis of the end mill, preferrbly 20° ⁇ 5°. Generally, this pitch angle of the reinforcing chamfer amounts to roughly half the helix angle of the main cutting edge 4. Further, each reinforcing chamfer 6 is inclined by an angle ⁇ in relation with the adjacent end cutting edge 5,5'. This angle can generally be 0° ⁇ 10°, preferrably 0° ⁇ 5°.
• the maximal axial width of the reinforcing chamfers can vary within a wide range and depends inter alia on the diameter of the tool. Generally it should be between 0,05 and 1,5 mm, suitably between 0,10 and 1,0 mm and preferrably between 0,15 and 0,50 mm. Owing to these reinforcing chamfers, a number of inconveniences have been overcome in a surprisingly simple manner, such as damages and chippings in these corner parts, as well as vibrations. In order to enable the end mill tools to hold the dimension tolerances even at requirements of long tool life and high cutting data, they are also covered with a thin layer of TiN, Ti(C,N) and/or Ti(Al)N.
• TiCN is used, in a thickness of between 2 and 4 ⁇ m; specially with regard to the very good adhesiveness which has been achieved with specifically this material.
• Coating of the hard material with a thin layer is effected with the so called PVD-procedure, which is well known for the man skilled in the art.
• Tool A End mill with three cutting edges according to the invention, with pitch angle 40 degrees, chip angle + 12 degrees, as well as a reinforcing chamfer between main and end cutting edges.
• Tool B Tool according to A but without reinforcing chamfer.
• Tool C Tool according to A but with a pitch angle of 45°.
• Tool D End mill with three cutting edges of a material according to the invention but with a pitch angle of 30 degrees.
• the chip angle is +12 degrees; a reinforcing chamfer between main and end cutting edges is foreseen.
• Tool E An HSS end mill with three cutting edges and with a pitch angle of 35 degrees, a chip angle of +10 degrees, without any reinforcing chamfer.
• the tools were tested in medium coarse milling with an axial cutting depth of 8 mm and a radial cutting depth of 2 mm.
• the durability criterium was an average flank wear of 0,08 mm or chippings.
• Cutting data were choosen according to the manufacturer's recommendations. Cutting data and results ax 3 shown in the table below.
• test showed that the test tools according to the invention clearly offered the best result in the sense of long tool life and good reliability.
• End mills according to the invention with two cutting edges with a diameter 8 mm were produced in agreement with Example 1 and were tested in grooving in stainless austenitic steel SS 2343 in comparison with other coated conventional end mills of high speed steel or cemented carbide.
• Tool A An end mill with two cutting edges according to the invention, with a pitch angle of 40 degrees, a chip angle of +12 degrees and a reinforcing chamfer between main and end cutting edges.
• Tool B An end mill with two cutting edges of solid fine-grained cemented carbide, with a pitch angle of 40 degrees, a chip angle of +12 ' degrees, without any reinforcing chamfer.
• Tool C An end mill with two cutting edges in a solid, highly alloyed high speed steel with a pitch angle of 40 degrees, a chip angle of +13 degrees and without any reinforcing chamfer.
• the tools were tested in grooving at am axial cutting depth of 6 mm.
• the durability criterium was an average flank wear of 0,06 mm or an interrrupted test due to chippings, tool damage or unacceptable notches
• Tools B and C exhibited a considerably larger spread in tool life because of a large percentage of chippings on the tools' corners.
• Tool A according to the invention gave the clearly best results in the sense of high productivity, long tool life and safety.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Milling Processes (AREA)
• Drilling Tools (AREA)
• Physical Vapour Deposition (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 1992
  • 1992-10-15 SE SE9203024A patent/SE500134C2/sv unknown
• 1993
  • 1993-10-13 EP EP93923695A patent/EP0726828A1/en not_active Withdrawn
  • 1993-10-13 JP JP6509907A patent/JPH08502213A/ja active Pending
  • 1993-10-13 WO PCT/SE1993/000835 patent/WO1994008745A1/en not_active Application Discontinuation

Non-Patent Citations (1)

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