Method and device for manufacturing a tool

(54) (56) (57)

INVENTOR

REPRESENTATIVE TITLE

CALLED PUBLICATIONS:

SUMMARY:

Johnny Bruhn, Norberg SE, Mattias Puide, Fagersta SE, Mikael Grönkvist, Norrköping SE

Sandvik AB Patent department

Method and apparatus for manufacturing a tool

The present invention relates to a method and apparatus for manufacturing a tool. The method and apparatus permits a drill (10) comprising a central portion (12) of relatively tough hard material connected to a peripheral portion (13) of relatively durable hard material. The drill chip channels (18) in their entirety consist of relatively durable hard material.

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The numbers in brackets indicate international identification code, INlD code. Letters in clamps indicate international document code.

514 558,

Field of the Invention

The present invention relates to a method and apparatus for manufacturing a tool.

Prior art

It is previously known, for example, by WO 98/28455 to compress a core and an enclosing tube of material powder in two stages. The material powder consists of tungsten carbide (WC) together with cobalt (Co), which is compressed between a stamp and a pad and then sintered so that the binder metal melts and binds the carbides to form tool material for chip separating processing. The object of the prior art is to achieve two different properties depending on the radial position in a solid body. The known technology causes a number of disadvantages, among other things, in the production of long slender bodies. The powder ponds and the formed green body (pressed but not sintered material) does not withstand handling to any appreciable degree. In addition, chip channels must be ground and the method is time consuming. The problems have been partially solved by the injection of cemented carbide mixed into a support as disclosed in SE-B-9501687-9. The injection molding method entails high degrees of freedom from the geometry point of view, but involves difficulties in the production of long slender bodies and involves costly investments in molding tools.

US 4,779,440 discloses a tool for forming a blank for a spiral drill. An extruded drill bit whose chip channels have a uniform pitch along the perimeter of the blank is obtained by heating a cemented carbide powder to extrusion temperature, pressing the heated powder under high energy consumption through a space defined

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S-515EN 00-08-14 2 of a mandrel and a nozzle during rotation of the blank. The blank is guided by extrusion in the direction past a helical ridge disposed on the inside of the nozzle to form chip channels along the blank. A disadvantage of the prior art is that the tool produced does not have optimum life.

Objects of the invention

The present invention has as an object to provide a method and a device, whereby said problems according to the prior art are overcome.

It is another object of the present invention to provide a method and apparatus whereby elongated tools of optimum service life can be manufactured.

These and other objects have been achieved by a method and apparatus for manufacturing a tool as defined in the following claims with reference to the drawings.

List of Figures

Figures 1A-1C schematically show a drill in side view and in perspective views front and rear respectively. Fig. 1D shows a cross-section according to the line DD in Fig. 1 A. Fig. 1E shows a cross-section according to the line EE in Fig. 1 A. Fig. 2A shows a device according to the present invention for producing elongated green bodies, in front view. Fig. 2B shows the device in cross-section according to line IIB-IIB in Fig. 2A. Fig. 2C shows the device in end view. Fig. 2D shows the device in cross-section according to the line IID-IID in Fig. 2A. Fig. 3 shows the device and a feeder part.

Detailed description of the invention

The embodiment of a tool shown in Figs. 1A-1E is a so-called spiral drill. The drill 10 comprises a generally solid shaft 11 with a first tip-forming end, comprising at least one cutting edge 19, a number of chip channels 18 corresponding to the number of cutting edges. The drill comprises a central portion 12 of relatively tough hard material connected to a peripheral portion 13 of relatively durable hard material. The drill bit 10 is made of solid hard material such as

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S-515EN 00-06-14 3 extruded or extruded cemented carbide and includes helical chip channels 18 and these may extend along the entire body or along a portion thereof. The shaft 11 is to be secured in a rotatable spindle, not shown. The drill has two upper release surfaces 15. The drill is extruded from two different materials where the difference mainly consists in the balance between hard substance (for example tungsten carbide, WC) and bonding phase (for example cobalt, Co). All outer surfaces and associated edges are made of the same material, ie extruded durable carbide with relatively low cobalt content. The chip channels 18 in the tool 10 as a whole consist of durable hard material which gives both rigidity and durability to the drill. As can be seen from the cross sections of Figs. 1D and 1E, the tough portion 12 constitutes the majority of the cross section, regardless of where the cut is taken. In addition, the cross-section of the tough part 12 varies at the same time as it is completely surrounded by the durable part 13 at the ends, thereby obtaining a torsion-resistant and hard "shell" of the drill. Furthermore, the coil ducts 14 are preferably performed only in the tougher part. Cutting lines between the chip channels 18 and the release surfaces 15 form the main cutting edges 19, preferably via, not shown, reinforcing phases.

In Figures 2A-2D there is shown a device ~ 20 according to the present invention for the production of elongated green bodies. The device 20 consists of a rectangular housing 21 made of steel, which is intended to be secured by, for example, bolts to a machine for extrusion, not shown. The housing 21 accommodates two bolts 22 for attachment to the machine and has a rear surface 23 for sealing against said machine. The housing has a central recess 24 through which at least two masses are to be pressed. The recess 24 is turned into a diameter-reducing throttle 27 in a circular nozzle 28. The nozzle 28 is made of a durable material such as cemented carbide. The recess 24 then proceeds in a cylindrical inner centrally located hole 30 in a circular nozzle 29, which is disposed adjacent and adjacent to the nozzle 28. The position of the nozzle 29 is determined by the interaction of a stop screw 31 in the housing and a hole 32 across the main masses. feed direction F. A rod-shaped core 33 is recessed into the nozzle. The core is rectangular and includes two holes 34 for attaching elongated pins 35. The pins 35 are intended to protrude from the core in the feed direction F in the case of

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S-515SE 00-06-14 4 coil ducts shall be formed in the blank. The recess 24 then proceeds in a lid 36 in the form of a coaxial hole 37. The lid 36 is secured to the housing by means of two screws 38 and the screws 22. The lid 36 is provided with a T-groove 39 extending between two long sides of the lid 36. The groove 39 is intended to accommodate two jaws 40, 41, the basic shape of which is substantially formed in Fig. 2B. Each jaw 40, 41 comprises a cavity 42 facing the other jaw. The cavity 42 includes a helical ridge 43 so that when the slopes abut each other, the cavities form the cross-section of a spiral drill with chip channels. The jaws are pressed against each other by means of power means, not shown, and the same means are used in the case where the jaws are to be moved apart, such as when the blank must be partially cylindrical, for example at the drill shaft. Preferably, a flat table is placed adjacent to the slopes to support the hot, extruded blank.

In Fig. 3, a feeder member 50 is shown connected to the housing 21. The feeder member 50 consists of at least two separate chambers 51,52. A central chamber 51 is arranged substantially symmetrically about the feed direction F and comprises a central nozzle 53 facing the housing 21. At least a second chamber 52 is arranged substantially perpendicular to the feed direction F and comprises a nozzle 54 disposed adjacent to the nozzle 28. The nozzle 54 is arranged coaxially with the nozzle 53 but axially closer to the housing 21 than the latter. The first chamber 51 is intended to contain a first mass 55 of relatively high cobalt content while the second chamber 52 is intended to contain a second mass 56 of relatively low cobalt content. The chambers include feed screws 57, 58 intended to drive the two masses forward in the feed direction F. Each feed screw is driven by a motor 59, 60. The granules are fed into funnel-like openings 61.62. The chambers are surrounded at least partially by heating elements 63, 64.

The drill bit or stick cutter is manufactured as follows. Carbide powder with a certain cobalt content and a carrier, for example plastic, are mixed and formed into pellets or granules. This is done so that at least two different pellets or granules are obtained, the difference being in the amount of cobalt. The carrier will form the matrix of the green body. The difference in binding phase is in the range of 1-10

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S-515SE 004) 6-14 5% by weight units. By "cobalt" is meant here a metallic bonding phase which can alternatively be exchanged for or include other metals, for example nickel, Ni. Thereafter, the mixtures are preheated to temperatures suitable for the mixtures, preferably the same temperature, and introduced into a machine for extrusion. Then the mixtures in respective chambers 51.52 are pressed under high pressure and a certain temperature, about 180 ° C, to respective nozzles 53 and 54, whereby said second plastic mass comes into contact with said first plastic mass during extrusion, thereby forming a substantially cylindrical rod. 65. Then, the hot masses reach the core 33 and pass through the two formed on either side of the core, essentially semicircular openings. Core width (see Fig. 2A) is preferably smaller than the diameter of the inner mass. Behind the core in the feed direction F, the pulp again collapses into a cylindrical rod. If the pins 35 are arranged in the core, then voids are formed in the body which will later form flushing channels. The pegs are thus chosen long enough for the pulp to cool enough to not collapse again. By selecting the parameters for the extrusion and, in particular, the diameter of the nozzle 53, the environment of the coil channels can be selected to consist solely of one or the other mass or a combination of both. Thereafter, the pulp reaches the cavity 42 as defined by the slopes 40, 41 whereby the pulp, due to the ridges 43, is screwed through the slopes and receives the cross section of a spiral drill. Unlike the prior art, the chip channels in the drill made with the method of the present invention as a whole will consist of the more durable hard metal. When the pulp comes out of the slopes, the pulp is quickly cooled by the ambient temperature and the material continues to be extruded until the chip channeled portion is long enough. Thereafter, the jaws 40,41 are pulled apart and engaged with the mass to form a cylindrical shaft portion. The length of the shaft portion is determined either by how long the extrusion continues or by reversing the jaws inwards so that a new blank is started. In the latter case, two or more topics are related. The solidified substance can then be cut or broken off, for example by hand, at suitable lengths.

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S-515SE 00-06-14 g

Then, the substance is heated in a separate oven so that the carrier is burned and the binder melts and binds the carbides. Subsequent machining such as sanding, for example, on edge parts, shaft part and release surfaces. Thus, the tool's periphery achieves higher wear resistance due to the lower bonding phase content, for example cobalt, while the center part consists of a tougher more cobalt-rich cemented carbide.

By means of the present method, a tool with a good service life can be produced with or without chip channels and with or without shaft part and means easy handling at a low cost. This is done without dust being generated.

In addition, at least one of the slopes can be used to make markings in the shaft part of the blank where the plane is to be ground for holding in the chuck. Thus, the abrasive volume can be reduced.

The invention is in no way limited to the above-described embodiments but can be freely varied within the scope of the following claims.

The invention is also applicable to solid cutters. The tool can be coated with layers of e.g. AI₂O₃, TiN and / or TiCN.

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S-515SE 004) 8-14 γ