DE10260136A1 - Extrusion process and sintered blank or tool body produced by this process - Google Patents

Abstract

An extrusion process is described for the continuous production of fully cylindrical sintered blanks (24) with at least one internal, helically extending channel (3) of predetermined cross-section, in which the plastic mass (12) forming the blank (24) from a die mouth (DM) of an extrusion die (10) is pressed out in the form of a tube which is essentially circular cylindrical, preferably smooth on the inside. The plastic mass, which essentially enters the nozzle mouthpiece (DM) without swirling, flows along the axis of at least one helically twisted pin (400, 420) held in place on a nozzle mandrel (18) and at least in sections into the nozzle mouthpiece (DM) protrudes. The process is characterized by the fact that the pin (400, 420) does not rotate, the plastic mass (12) in the nozzle mouth (DM) into one of the helix shape, so that fully cylindrical sintered blanks can be produced with high accuracy even with difficult to create cooling channel geometries the twisted flow corresponding to the pin (400, 420) is displaced, and the rotational movement of the plastic mass (12) is supported by a rotatably driven section (140) of the nozzle mouth (DM) engaging on the outer circumference of the mass such that the pin (400 , 420) is essentially not subject to any bending deformation.

Description

The invention relates to an extrusion process, especially for the production of a sintered metal or ceramic blank for a Tool or a tool part in which the plastic forming the blank Mass pressed out of a nozzle mouthpiece being twisted helically along the axis of at least one, on a nozzle mandrel held pen flows. Furthermore, the invention relates to a producible with this extrusion process Extruded green body or sintered blank and one that can be produced from the sintered blank Cutting tool and a component of such a tool.

From a plasticized ceramic or powder metallurgical mass continuously, for example Extruded cylindrical sintered blanks with internal, at least in sections, helical channels predetermined cross-section are increasingly, for example in the tool industry, and especially in the manufacture of Drilling tools needed the one inside cooling or detergent supply have so that the cooling or detergent in the immediate vicinity of the cutting edge can come out of the tool. The helical course of the at least an internal cooling channel is required if on the tool to be manufactured, such as z. B. helical flutes are provided on a drilling tool, are ground in, for example.

Such high performance tools are also to cope with the high loads that are encountered in hard machining, Dry machining, low-quantity lubrication (MQL) and high-speed machining (HSC) occur. It has also been recognized that the objectives are MMS capability and significantly higher Cutting performance are not contrary, but can be realized at the same time. Drilling tools for use developed with MMS, for example, run at significantly higher feed rates than Tools for conventional cooling lubrication. Here comes the supplied Amount of coolant a crucial role too. In so-called high-performance cutting (HPC) processes tried today considering the manufacturing costs of all involved process parameters reduce. For In addition to their manufacturing costs, tools are mainly those Main times and downtimes are decisive, which in turn are decisive depend on the mobile feed speed and thus on the existing machine tools / high-performance spindles Speeds. The feed speed is not only of the speed is limited, but also because of that to pay attention to is that there is no chip jam during chip removal. In contrast for straight-fluted tools, coiled tools are decisive Benefits. Because the coiled design allows due to the cheaper Rake angle a higher Cutting performance and due to the twist angle of the flute one easier removal of the mixture of chips and lubricant. Also spiral tools are advantageous with regard to centering accuracy, since these tools are over their entire outer circumference support in the hole can.

It is not just the axial length of such drilling tools has been increased significantly in the meantime. Latest developments are increasingly moving also very small cutting tools, especially drills, with To equip internal cooling ducts, a special one with regard to the stability of the drill Attention to the particularly thin wall thicknesses between the cooling channels and flutes must be placed. It is therefore particularly important on, the slope of the at least one internal helical cooling channel to control and monitor precisely during production, so the location of the cooling duct in over the drill or tool bars the entire length of the cutting part is in the range of predetermined, narrow tolerances.

To remove the chips from the flute must, especially when drilling deep holes, the coolant partially under high Pressure are supplied, the inner cooling channel or the drill corresponding pressures destructively endure. One is in the process of spreading Minor lubrication strives to design the cooling channels as large as possible. moreover there is a need to be able to drill smaller and longer holes. With increasing length and decreasing diameter of the drilling tool, it will always be more difficult to close the internal cooling channels dimension that a corresponding coolant throughput or coolant pressure is provided without the stability of the drill suffering. Because the size of the cooling channels is limited by the distance to the back of the drill or chip space. At too thin Bridges cause cracks and tool breaks. For multi-edged tools have to the cooling channels also one have a certain minimum distance from each other, otherwise impairments the drill face geometry, i.e. e.g. the chisel edge or a point are caused. You also toast process-related limits, as with common powder metallurgical Procedure none for Such tools suitable blanks can be produced.

For example, the course of the internal cooling channels cannot be monitored during machining on the sintered blank. It is therefore necessary to manufacture the blank so that it is possible in the area of the inner channel The smallest possible tolerances with regard to cross-section, pitch circle diameter and eccentricity of the pitch circle to the axis occur in every radial section of the blank, which furthermore requires precise adherence to a predetermined helical pitch.

Otherwise, the case may arise that especially when grinding flutes into longer sintered ones Blanks the groove comes too close to the inner channel, which either leads to a loss of strength or but leads to- that the entire blank is no longer usable. This problem occurs independently on how much internal coolant or detergent channels are formed in the drill and what shape these channels are have as a further consideration in the manufacture of metallic or ceramic blanks to take into account is that the blanks Significant shrinkage in the drying and / or sintering phase subject to regular structure-dependent expiry. It is therefore important to extrude the plasticized Taking carbide or ceramic mass measures that ensure that the extruded blank not only with great dimensional accuracy, but also with maximum homogeneity of the structure over the Cross section can be produced.

Known methods only insufficiently meet these requirements. So is already in the U.S. Patent 2,422,994 described an extrusion process in which a plasticized powder-metallurgical mass is pressed through an extrusion die, the inner surface of which have projections in the shape of the flute cross section. In the area of the center of the extrusion die, straight, rod-shaped bodies extend in the axial direction, which are attached to a mandrel lying in front of the extrusion die and surrounded by the plasticized mass. This process works in several stages, in that the plasticized raw material is first formed into a drill blank which has at least one rectilinear outer groove which corresponds to the shape of the flute cross section and at least one straight rod which corresponds to the shape of the cooling channel cross section. In a second step, the green body designed in this way is twisted by a relative rotary movement between the extrusion die and the raw material. A blank is created in the form of a spiral helix with an embossed inner channel. However, modern cutting tools are required to have the tool shank made of fully cylindrical material except for the internal cooling channels that are stamped in, since this is the only way to ensure that the coolant is completely introduced into the coolant channel or channels. The cutting part produced from the spiral helical blank must therefore be soldered to a separate, fully cylindrical shaft, which - apart from the increased manufacturing costs - also results in less stability of the tool. In addition, it has been shown that such a two-stage shaping process is out of the question for most of the raw materials used in the meantime, because the blank emerging from the extrusion die is regularly so sensitive to pressure that even the smallest forces acting on it result in undesirably large deformations leads not only to the outer contour, but also to the inner, molded channels, as a result of which the reject rate increases excessively.

It is already in the meantime Multiple attempts have been made to produce an economical extrusion process to find, made with the fully cylindrical, rod-shaped blanks can be which is a manufacture of one-piece Tools with later allow incorporated flutes.

In the DE-PS 36 01 385 For this purpose, a method for producing a drilling tool with at least one helical internal coolant channel is already presented, in which the helical course of the at least one internal coolant channel is generated simultaneously with the extrusion of the plastic compound. For this purpose, the nozzle mouthpiece is equipped on the inside with a helical profile, the helical pitch of these projections being adapted to the helical pitch of the internal cooling channels to be aimed for. In the center of the extrusion die, elastic pins are provided, which are attached with their upstream ends to a die mandrel and whose elasticity is chosen so large that the pins can follow the swirl flow induced by the inner contour of the die mouthpiece. In addition to the fact that a relatively large amount of energy has to be applied in this type of production in order to impart a homogeneous swirl flow to the entire flow cross-section, it has been shown that in the blanks produced by this known method, the pitch of the cooling channel helix often depends on the helix pitch of the projections or Indentations on the inner surface of the nozzle mouthpiece deviates. The consequence of this is that the projections or depressions on the inner surface of the nozzle mouthpiece had to be formed in large numbers, but with a relatively small depth, in order to keep the material losses as small as possible. Accordingly, the finished sintered parts are regularly ground on the outside before the flute is inserted.

In order to save the process step of grinding the finished sintered cutting part blanks externally, in the DE-OS 40 21 383 or in the EP 0 465 946 A1 proposed a method in which the inner surface of the nozzle mouthpiece is formed by the outer surface of a circular cylinder. A swirl device located within the mass flow is connected upstream of the nozzle mouthpiece. According to an alternative, the extrusion by means of this swirl device, a swirl movement which acts uniformly over the cross section of the strand is forced, while according to the second alternative of the swirl device, a swirl or rotary movement is forced by the extrusion molding compound. To form the inner channels, the following thread-like material protrudes into the mass flow of the swirling or rotating movement. In this case, the circular diameter on which the cross-sections or the cross-section of the at least one internal coolant channel comes to lie in the extruded blank is influenced by the flow speed and by the friction losses in the nozzle mouthpiece, which is particularly the case when changing the extrusion mass from one batch to another can have a negative impact. According to a further variant of this method, it is therefore proposed to design the nozzle mouthpiece to be rotatable, wherein the rotational movement of the nozzle mouthpiece is intended to correct the swirl movement of the mass flow. However, since the necessary correction can only be recorded in an area downstream of the nozzle, dead time inaccuracies cannot be avoided. Also, a relaxation movement of the extrusion mass against the twisting direction of the twisting device after the mass exits the nozzle, which depends on the individual properties of the respective mass batch, makes the method difficult to control, so that inaccuracies in the position of the helix of the inner channels predetermined by the threads cannot be avoided. In addition, round, coolant channel-forming material can only be hung on the threads in the flow cross-section, since - if no material is used in the flow cross-section - it cannot be defined how the material hung in the flow comes to lie on the flow cross-section.

From the document EP 0 431 681 A2 a method and a device for producing a cylindrical, metallic or ceramic blank of the type described at the outset has also become known, in which at least one twisted center pin made of a rigid material extends through the center of an internally smooth, circular-cylindrical nozzle mouthpiece. This at least one twisted center pin is attached to a stationary mandrel in front of the inlet area of the nozzle mouthpiece. The pins are thus preformed helically in this process and made of a rigid material such as. B. made of hard metal or steel. With a certain, relatively small ratio between the inner diameter of the nozzle mouthpiece and the outer diameter of the at least one central pin, it is possible to dispense with additional twisting devices. It is approximated that the rigid center pins are able to force the mass flow over the entire cross-section to have a uniform swirl movement. For larger values of the above-mentioned ratio, the swirl of the blank must be increased by additional guide vane-like swirl aids in the nozzle, which impose a swirl direction on the flow. It has also been shown that it is regularly necessary to twist the center pins more than the twist of the helical channels actually present in the blank. This requires extensive tests for each extrusion compound, which make the manufacturing process more expensive and necessitate complex quality assurance measures.

In order to produce extrusion blanks with a precisely defined course of internal, helical cooling channels with the highest degree of reproducibility and with high structural quality, there should be no restrictions with regard to the scope of the method with regard to the composition of the extrusion mass, the process parameters or with regard to the geometry of the blank in their own patent DE 42 11 827 proposed to produce the inner channels without plastic deformation of the mass located in the nozzle mouthpiece in the primary molding process, preferably the mass entering the nozzle mouthpiece essentially without swirl, flowing over the entire flow cross section essentially swirl-free either the at least one pin and this when passing through the nozzle mouthpiece into one continuous rotary movement corresponding to the pitch of its helix, or flows past a pin suspension which can be driven as a function of the flow velocity.

According to a variant, the device is characterized in that the at least one pin is connected in a rotationally and axially fixed manner to a shaft which is rotatably mounted in the nozzle mandrel about an axis parallel to the nozzle axis and is twisted in such a way that the plastic mass flowing along its axis is essentially over it the entire length impresses a constant angular momentum defined by the pitch of its helix. The corresponding extrusion head is in 1 shown, to which reference is already made here:
According to a further variant, the shaft carrying the at least one pin, the connection point to the pin lying radially inside the pin in the nozzle mouth, has an additional drive, in which case the pin can be flexible and the drive can be controlled independently of the desired pitch. According to one in the additional patent DE 42 42 336 The further development shown here is additionally flowed against by a friction-reducing fluid.

Here, one basically frees oneself from the idea of imparting a swirl movement corresponding to the helix pitch to be generated to the highly viscous mass flow during extrusion, and thereby plastically verifying the mass relatively strongly to form. The method works on the reversal of a corkscrew effect, whereby the corkscrew coil is compared with the flow around the pin and the cork with the plastic extrusion. The at least one inner helix is created using the primary molding process. A high accuracy of the cooling channel was achieved, namely with regard to the slope, radial position, angular position and cross section. The possibility of producing cylindrical extruded bodies with helical cooling channels, which have a cross-sectional shape that deviates from the circular shape, for example a rectangular, polygonal or elliptical shape, has already been mentioned in principle.

But it has been shown that this Process especially for small nominal diameters and in relation to Nominal diameter large cooling channel cross-sectional areas not leads to success there the energy of the flow the extrusion in this case is not sufficient to the or to set the rigid pins in a rotary motion and thus accordingly used cooling channels in the pushed out green compacts memorize. On the contrary, the coiled pins can be bent straight come.

The object of the invention is therefore to further develop the above method such that fully cylindrical Sintered blanks with embossed helical Cooling channels too with difficult to create cooling channel geometries can be manufactured with high accuracy, as well as a sintered blank, a cutting tool which can be produced therefrom and a component of a to create such a tool that meets the requirements of today Manufacturing tasks.

This task is related to the Method with the features of claim 1 solved with respect to the sintered blank the features of the claims 4 and 5, regarding of the tool with the features of claim 19 and with respect to the component with the features of claim 24.

According to the invention, a method for manufacturing fully cylindrical extruded green parts or Sintered blanks with at least one helically stamped channel proposed. Such blanks are used, for example, in the manufacture of drilling tools needed. In the extrusion process according to the invention flows the plasticized mass in the extrusion head initially essentially swirl-free in a nozzle inlet, around then along the longitudinal axis of at least one, on the nozzle mandrel positionally fixed pin in the nozzle mouthpiece to the outlet of the Nozzle and to be pressed through them. The nozzle mouthpiece has a circular cylindrical, preferably essentially smooth surface so that the resulting Blank has a fully cylindrical outer contour. The flowed pen does not rotate with the mass, but projects rigidly into the nozzle. It is preferably attached to the nozzle mandrel in a rotationally fixed manner. alternative this can also be done by possibly producing the sintered blanks according to the invention existing arrangement can be used, in which the pin is rotatable on the nozzle mandrel is stored, but the pin due to the small nozzle cross-section or high pin cross-section in relation to the nozzle cross-section rotates. The flow in the nozzle mouthpiece on the one hand by the pitch of the coils of the pin and on the other hand, by a rotating portion of the nozzle Radial component induced.

This results in an overall helical flow, which were rotating when the speed of rotation was adjusted Section on the slope of the spiral shape of the in the nozzle mouth protruding pin so that the flow of the extrusion of the Helix pitch essentially follows, i.e. that the particles on radial height of the pin a flow direction corresponding to the course of the pin have, whereby a bending deformation of the pin or pins despite their positionally and rotationally fixed arrangement can be avoided. Also a plastic deformation of the extrusion or an uneven structure or density distribution in the mass can be avoided because the Radial component of the flow not through swirling devices or deflection devices like guide vanes etc., but only by the Rotational movement of the rotatable portion of the nozzle is achieved. The radial movement the current is therefore not by redirection at one of the flow in the Standing obstacle causes, but only that of the extrusion inherent Frictional forces that cause the mass from the rotational movement of the nozzle section is taken, whereby the thus induced rotational movement of the nozzle wall starting independently to the inside of the nozzle propagates until a steady helical flow occurs, that of the slope the helix corresponds. The flow is related to viscosity and toughness the extruded mass.

So it largely comes to a structure of the extruded material freed from tension and inhomogeneity in density, so that after the blank has been ejected from the nozzle, there is also no subsequent Whirl up like a swirling device Helical flow too fear is. With the method according to the invention can be green parts manufacture with high helix accuracy.

It is advantageous if the rotationally driven section of the nozzle extends over the section penetrated by the coiled pin, since in this way an interaction between the pen coil and the rotational movement is ensured represents is. By arranging the rotated section over a forward area of the pin and over the length of the section of the nozzle mouthpiece that is penetrated by the pin, the mass can move in a helical shape before reaching the pin, thus effectively preventing bending of the pin. An advantageous additional lubrication of the pin according to claim 3 can further reduce the load acting on the pin.

As material for the production of the extruded green compacts hard metal is preferably used, for example based on tungsten carbide, because carbide tools are widely used in manufacturing technology have found. The plasticized mass for the extrusion is thereby under permanent Walk through from a hard metal powder with the addition of a binder, e.g. cobalt, and a plasticizer, e.g. Paraffin, produced. The extrusion process according to the invention could, however just as well with other sintered materials such as ceramics or cermet can be used in which the cooling channel cross-sectional geometry can already be defined for the still soft raw material.

The proposed extrusion process is suitable for the production of extruded green compacts for rotary-driven cutting tools, in particular Drills and milling cutters, for example end mill. In addition, it is also used for the production of green extrusions for step tools, for example step drills can be used.

The extrusion process follows first a drying or pre-sintering process before the corresponding deflected blank bars be subjected to the actual sintering process. The finished sintered Blanks are then regularly cut edited by in the outer surface of the Blanks at least one helical Flute is ground in.

Because of the advantages outlined above of the method according to the invention are also blanks with small diameters and circular shape deviating cooling channel contour as well as with large ones Cooling channel cross-sectional areas manufacture, where previous methods could not lead to success, in particular Sintered blanks according to claims 4 or 5th

This is of enormous importance since especially with small tool diameters on or Tool bars available standing area in compliance with necessary Minimum wall thickness for one optimal coolant supply Completely must be exploited, on the other hand there are process limits in common manufacturing processes. With regard to optimal use of what is available on the dock In this way, space gains a design that deviates from the circular shape the cooling channel contours in importance. On the other hand, one tries in this sense, the wall thicknesses between cooling channel and flute and outer tool circumference preferably narrow, i.e. Sintered blanks in relation to the Blank cross-sectional area huge Cooling channel cross sections manufacture. Here is the helix accuracy or the size of the deviation crucial from the target helix. This applies in particular to blanks with small diameters and with large cooling channel cross sections, because here small wall thicknesses between the flute and the molded cooling channel, so that already small deviations lead to scrap production.

According to the invention, for the first time these requirements for sintered blanks for tool making to wear.

So point with the method according to the invention blanks according to claim 5 which can be produced for the first time have a ratio of Blank-sectional area to the cross-sectional area of the molded channel or channels on a molded channel with a value of 20:80 or better, in particular 30:70, for example 50:50, at several molded channels 20:80 or better, especially 30:70, for example 40:60. "Better" is in the sense preferably greater Cooling channel cross sections to understand.

The blank according to the invention according to claim 5 makes it possible to produce tools which, compared to tools made from conventional sintered blanks, have outstanding coolant throughput rates. the production of such blanks is only possible through the method according to the invention. Because such large cooling duct cross sections result in an extremely thin minimum wall thickness between the inner cooling duct helix and the coiled flute, which requires that extremely precise tolerance limits for the duct helix be met. With a process with forced swirl, this cannot be achieved due to the problems inherent in the process described above with regard to structural, stress and density inhomogeneities in the plasticized mass. At most, with the acceptance of high reject rates, one can count on non-reproducible random hits. With your own procedure according to DE 42 42 336 on the other hand, the force required to drive the pin cannot be applied, since the pin becomes thicker and therefore more stiff as the desired channel diameter increases, while at the same time the mass usable for driving the pin decreases.

Blanks with a diameter of less than 12 mm and a cross-sectional contour of the cooling channel that deviates from the circular contour can also be produced for the first time using the method according to the invention. As mentioned above, cross-sectional contours deviating from the circular contour offer considerable advantages in terms of space utilization on the tool bars and thus in terms of lubricant supply optimization Advantages, which is particularly important with small tool diameters.

According to the known method EP 465 946 blanks with such small diameters could also be produced. However, only round, coolant channel-forming material can be hung on the threads in the flow, since - if no balls are hung in the flow - it cannot be defined how the material suspended in the flow comes to lie on the flow cross-section. In addition, only relatively small cooling channel cross sections are to be produced, since otherwise the minimum wall thickness between the cooling channel and flute becomes so small in the tool to be produced from the blank that the helix tolerance of the cooling channels that can be maintained with the thread method is too large.

Tests also showed that with the own procedure according to DE 42 42 336 with outside diameters under 12 mm with large cooling channel cross sections the force necessary to drive the pin cannot be applied with certainty (see above), whereas with smaller dimensions of the cooling channel cross sections and thus the pins protruding into the flow, the force acting on the pins quickly bends to a straight line Leads leads.

With future materials for the extrusion, optimized lubrication of the pins according to DE 42 42 336 etc., however, it cannot theoretically be ruled out that blanks with outer diameters of less than 12 mm could also be produced with the older proprietary process. In the area below 8 mm, for example below 4 mm, the use of this method seems impossible.

The blanks according to the invention are therefore suitable for the production of tools with increased coolant supply compared to known tools.

The sintered blanks are used for this their outer circumference reground, whereupon the required number of helical ones Chip flutes are incorporated, for example ground or milled. The resulting tools then have at least one web, which is traversed by at least one coiled internal cooling duct, the Slope of the at least one internal cooling channel in synchronism with the slope which runs at least one flute.

The from the sintered blank according to claim 4 manufactured tools according to the invention is particularly suitable for use as a deep hole drilling tool with diameter-length ratios over 1: 5 and particularly suitable for deep hole drilling of steel, at which so far despite poor chip removal due to the side rake angle from 0 ° and poorer centering accuracy (due to the one-sided on sides support in the borehole) with straight flutes had to be worked since cooling channel contours deviating from the circular shape and smaller ones Tool diameters than 12 mm, in particular less than 8 mm, for example tools smaller than 4 mm do not coiled with those for maximum loads required accuracy could be established. The same applies to Tools from a sintered blank with the features of the claim 5th

This also applies to shorter cutting tools the extrusion process according to the invention achieved high accuracy in terms of location and area of the Cooling channels on the Tool bars help with a sufficient tool strength optimal lubricant supply is ensured. This enables machining tasks solved that cannot be managed with today's tools, in particular regarding smaller bore diameters, longer stroke lengths without intermediate retraction and poorly machinable materials such as CFRP sandwich materials etc.

With the tool according to the invention can hence the trend towards ever smaller bore diameters longer drilling stroke lengths, increased feed speeds and optimized coolant throughput be met. For example, drill holes are used to drill holes a relationship drill length to diameters of up to 200: 1, in individual cases up to 100 times Stroke diameter drilled in one go and sometimes even without pre-drilling. Such Tools are used today, for example, in engine and shipbuilding, and used in the manufacture of fuel injection systems. Here there is a requirement to drill holes with very small diameters (in the range of 1 mm) and in relation to very large bore lengths finished.

For tools with diameters smaller than 12 mm, in particular less than 8 mm or 4 mm, it is in the sense of optimization the cooling channel cross-sectional area and so that the sufficient Lubricant supply also advantageous if both of the Circular deviating cross-sections as well as the cooling channel cross-sectional areas according to claim 5 are provided.

The rake angle on the cutting edge is determined by the side rake angle of the drill helix and thus by the spiral angle of the inner cooling channel formed in the sintered blank certainly. It has a decisive influence on chip formation and chip removal and therefore depends on the properties of the material to be processed Material. In the advantageous embodiment according to claim 8 it assumes values greater than 10 °.

According to an advantageous embodiment according to claim 21, the tool is provided as a two-lip or multi-lip tool. Sintered blanks with cooling channel contours in the form of an ellipse or a trigon according to claims 17 and 18 and mixed forms according to claims 12 to 15 are particularly suitable for their production, since with these forms the one on the respective Tool space available space can be used optimally and with certain minimum wall thicknesses for the cooling channel. Trigon in the sense of the invention is understood to mean a triangular shape with slightly rounded corners with a minimum radius in the range of 0.2 times the circle enclosed by the triangle.

With a single-lip design according to claim 22 appears in particular a kidney-shaped cooling channel design according to claim 16 suitable. Alternatively, the coolant supply can be in certain circumstances Trigonal or elliptical cooling channels take place.

Extensive tests have shown that with a trigonal cooling channel cross section compared to a circular cooling channel cross section, a very good utilization of the area on the tool web can be achieved while observing the minimum distances to the flute and the outer circumference of the tool that are necessary from a strength point of view. With regard to coolant throughput and tool strength, cooling channel shapes with rounded radii have proven to be even more favorable:
It was recognized that the stresses occurring at the cooling channel depend on the shape of the cooling channel and mainly result from the notch effect of the cooling channel at its smallest radii in the load direction. It was also recognized that for the resistance that a cutting tool, for example a drill or milling cutter, can counteract these voltage peaks, ie for its stability and ultimately for whether the tool is cracked or prematurely broken, in addition to the voltage peaks occurring on the cooling channel the distance between the cooling channels and the chip space and thus the position of the cooling channel on the web is decisive.

Extensive tests and simulations resulted an advantageous cooling channel cross-sectional geometry, i.e. Sintered blanks according to claim 15 with minimum radii of the cooling channel contour in the range of 0.35 to 0.9 times, in particular 0.5 to 0.85 times, preferably 0.6 to 0.85 times, particularly preferably 0.7 to 0.8 times, for example 0.75 times the radius of one enclosed by the contour Circle.

For a tool made from the sintered blank turned out to be Minimum wall thicknesses between the inner cooling duct and the outer circumference of the drill, between Internal cooling channel and rake face and between the inner cooling duct and chip clearance as cheap, those in a range between a lower limit and an upper limit lie, the lower limit being 0.08 × D for D <= 1 mm and 0.08 mm for D> 1 mm, in particular at 0.08 × D for D <= 2.5mm and at 0.2mm for D> 2.5mm, preferred at 0.08 × D for D <= 3.75mm and at 0.3mm for D> 3.75mm, for example at 0.1 × D for D <= 3mm and at 0.3mm for D> 3mm, and where the Upper limit at 0.35 × D for D <= 6mm and at 0.4 × D-0.30mm for D> 6mm, in particular at 0.2 × D, preferably at 0.15 × D for D <= 4mm and at 0.6mm for D> 4mm.

With this experimentally determined cooling channel geometry and position of the cooling channel on the web, surprisingly positive results can be achieved, particularly in terms of their size:
It was found that the tool with the cooling channel profile according to claims 15 and 23 has high throughput rates under load, dramatically lower stress loads than with trigonal tools. The correspondingly higher strength values of the insert tool according to the invention were confirmed in breaking tests. The tests were carried out on tools made of a common hard metal with values of 0.5 to 0.85 times the radius of a circle enclosed by the contour for the narrowest radius of curvature. Values of 0.6 to 0.85 times, in particular 0.7 to 0.8 times the diameter of the enclosed circle appeared to be particularly suitable. For example, with a drill with a nominal diameter of 4mm, there was a minimum radius of 0.75 x the diameter of the enclosed circle on the side of the cooling channel facing the flute, with approximately 35% lower voltage peaks with the same cooling channel cross-sectional area. As a result, a value of only 0.3 mm could be achieved for the minimum wall thickness there without having to accept insufficient drill strength. For tools made of a different material, values in a range of 0.35 - 0.9 × circle radius can be useful. When using a material of higher ductility and thus higher tension, in particular tension resistance, minimum radii of curvature down to 0.35 × circle radius of the enclosed circle can, for example, deliver advantageous results. Such dimensioning can also be useful for tools that are exposed to special load conditions.

In addition to the lower notch tensions due to the ratio to conventional Trigon profiles with relatively gentle rounding occurs the additional Effect on the point of the cooling channel contour where the greatest curvature lies from the point where the wall thickness of the web is the least, is offset. It follows that the wall is the most heavily loaded Body is relatively thick and therefore unbreakable.

On the other hand, the throughput quantities of an insert tool with the cooling duct geometry according to the invention increase almost proportionally with the cross-sectional area compared to an insert tool with a round cooling duct geometry, the increase in the notch stresses with increasing cross-sectional area in the area of the cooling duct geometry according to the invention being surprisingly small compared to that in conventional trigon profiles. With The cooling channel profile according to the invention can thus be used to realize cross-sectional areas which, in the case of a round profile with the same coolant throughput, would already lead to tool failure due to insufficient wall clearances.

There was a connection between the sufficient wall thickness to the nominal diameter, which is the case for small tool diameters linearly with an increase in tool diameter. As have been sufficiently stable with extremely high coolant supply in the wall thickness test proven that above a lower limit of 0.08 × D for D <= 2.5mm and at 0.2mm for D> 2.5mm, preferred at 0.08 × D for D <= 3.75mm and at 0.3mm for D> 3.75mm, for example at 0.1 × D for D <= 3mm and at 0.3mm for D> 3mm, where D denotes the nominal diameter. So the one mentioned above had been tested Drills with a nominal diameter of 4mm, for example, a wall thickness of 0.3mm.

Leave with such thin walls due to the stress distribution in the tool bar Great Cooling channel contour design achieve high tool strength and thus tool life. In individual cases it may even be sufficient to provide a minimum wall thickness of 0.08mm for D> 1mm.

On the other hand, the minimum wall thickness only by the one you want Maximum throughput is limited. Here values emerged according to claim 23 by 0.35 x D for D <= 6mm and from 0.4 × D-0.30mm for D> 6mm, in particular of 0.333 × D for D <= 6mm and from 0.4 × D-0.40mm for D> 6mm, preferred by 0.316 × D for D <= 6mm and from 0.4 × D-0.50mm for D> 6mm, particularly preferred by 0.3 × D for D <= 6mm and from 0.4 × D-0.60mm for D> 6mm, for example of 0.2 × D or 0.15 × D for D <= 4mm and from 0.6mm for D> 4mm as suitable maximum values up to which such a cooling channel contour is useful.

It had been shown that the cooling channel geometry according to claim 15 especially for smaller ones Tools where it is particularly important in terms of strength and optimized coolant flow Use of space on the tool bar is appropriate. This Knowledge was gained through the upper limits for the minimum wall thickness according to claim 23 taken into account that above a certain nominal diameter rise more than in the range of smaller diameter values.

In particular, it turned out that with a diameter of 6mm and a linear increase in the cooling channel cross-sectional areas the nominal diameter only for individual applications, such as e.g. with deep hole drills, makes sense because the need for lubricants Covered even with under-growing cooling channel cross-sections can be. Of course but it can also be used for larger diameter values make sense with the minimum wall thickness down to the lower limit according to claim 23 approach to a high coolant supply with sufficient strength to reach.

The values specified in claim 23 for the The upper limit of the minimum wall thickness takes this into account, whereby the Design of the cooling channel contour especially with minimum wall thicknesses in the range below 0.2 × D makes sense. Especially in the minimum wall thickness range below 0.15 × D for D <= 4mm and 0.6mm for D> 4mm it turns out to be by the shape according to the invention and dimensioning of the cooling channels on the available standing installation space achieved flow rate increase with simultaneous good tool strength as surprisingly cheap.

However, it must be considered that tools of different diameters are often made from sintered blanks of the same diameter. That is, for example from a blank with a raw diameter of 6.2mm with tools Nominal diameters of 4mm, 5mm and 6mm can be manufactured. With the 6mm tool with the same cooling channel like the 4mm tool hence the minimum wall thickness between cooling channel and tool outer circumference 1mm bigger. Under This manufacturing aspect also includes upper limits for the Wall thickness of 0.35 × D for D <= 6mm and of 0.4 × D-0.30mm for D> 6mm, in particular of 0.333 × D for D <= 6mm and from 0.4 × D-0.40mm for D> 6mm, preferred by 0.316 × D for D <= 6mm and from 0.4 × D-0.50mm for D> 6mm, particularly preferred of 0.3 × D for D <= 6mm and from 0.4 × D-0.60mm for D> 6mm still in one area, in which the cooling channel geometry according to the invention Brings advantages.

At this point it should be mentioned that the minimum wall thicknesses between cooling channel and outer circumference of the drill, or rake face or chip clearance different, of course chosen can be. From a strength point of view, this is particularly important to the minimum distance or the minimum wall thickness between the cooling duct and rake face to the opposite the minimum wall thickness between cooling channel and chip clearance be chosen larger can. Also opposite the minimum wall thickness between cooling channel and outer circumference of the drill can be the minimum wall thickness between cooling channel and rake face with larger values be provided to the higher Strength requirement to be taken into account. On the other hand, it can for example under the above relevant in practice Manufacturing aspect of blanks of the same diameter for tools different diameters to a minimum wall thickness between Cooling channel and Drill outer circumference come which is bigger than the one between the cooling channel and rake face.

With the advantageous cooling channel profile according to claim 15 and the minimum wall thicknesses according to Proverb 23 thus succeeds in using the available installation space on the web or webs of a rotating cutting tool in such a way that both coolant throughput and strength values are optimal.

Drills with the rounded cooling channel profile can do this both in the case of attacking compressive forces and torques, such as they are typical for drilling as well as for shear or bending moment loads, as they occur when entering the workpiece to be machined, high load values non-destructively over a long period Endure downtimes. Similar shear and bending stresses occur also with parallel or counter-milling cutters. On the other hand the coolant throughput achieved with regard to Amount and pressure drop over the tool length high demands just.

Due to the low notch tensions with the rounded cooling channel geometry on the one hand it is possible the minimum wall thickness between the cooling duct and rake face to be dimensioned smaller, as a result of which the cooling duct cross section and thus the throughput increased accordingly.

To increased coolant throughput with reduced Pressure drop the effect is that due to the large radii there is a cheaper hydraulic Radius, i.e. a based on the enveloping surface of the cooling channel size Cross sectional area of the cooling channel results. The average flow rate that is essential of the pipe friction force and that caused by the pressure drop Counterforce depends is opposite the conventional Trigon profiles higher, so that a higher throughput is achieved with the same cross-sectional area.

The rounded cooling channel geometry is suitable therefore especially for Tools where the conflict between sufficient coolant supply on the one hand and sufficient strength on the other hand particularly problematic is, as a rule, for tools with small diameters and / or long tool lengths.

The two are advantageous curvature maxima of the cooling duct cross section on the same radial coordinate, this radial coordinate being larger or equal to the radial coordinate of the one enclosed by the cooling channel cross section Circle is. The cooling duct cross-section is in the sense of optimal use of space symmetrical to an axis running radially to the drill axis, so that the radius applied is the same at the two curvature maxima. This Developments carry the essentially symmetrical shape of the Tool bars and thus that in compliance with the minimum wall thickness to disposal standing space for the cooling channel cross section bill on the dock. Next to it would be but also - especially if the web widening in the radial direction on the side of the main cutting edge is faster than on the side facing the bridge back - an asymmetrical shape the cooling channel cross sections conceivable to the available use the available space optimally. Also under the aspect that the highest Load on the side of the cooling channel facing the main cutting edge occurs while on the one facing the bridge Relatively low loads can be withstood must, can asymmetrical designs can be considered.

The elliptical cooling channel shape has proven to be particularly advantageous in terms of a simultaneously high coolant supply and sufficient strength of the tool. Preferred values for the ratio of the major axis / minor axis are 1.18 to 1.65, particularly preferably 1.25 to 1.43, for example 1.43. In the context of the invention, the ellipse is not only a mathematically exact ellipse (x ² / a ² + y ² / b ² = 1), but also a production-related, ie approximated, ellipse.

With elliptical cooling channel cross sections can the cooling channel due to the low notch stresses at the maximum curvature with a smaller one Minimum wall thickness between the cooling duct and main cutting edge are dimensioned as for designs in which the curvature maxima radially further outwards are offset because there are narrower radii than the elliptical one Design.

In addition to the elliptical cooling channel shape but there are also others, particularly in manufacturing technology In terms of advantageous tool designs, in which the cooling channel contour does not describe an ellipse.

A cooling channel geometry in which the curvature maxima across from offset the center of the enclosed circle are under the aspect of easier controllability of the Manufacturing process used in the extrusion process according to the invention Advantageous pins that specify the helix of the internal cooling ducts. Because the coiled used in extrusion to produce the cooling channels Pins that are arranged on a mandrel in front of an extrusion die and so in the incoming Form the cooling channels, are relatively complex to manufacture in elliptical form, while the Manufacture of coiled pins with maximum curvature offset due to the relatively large contour sections on the inside of the wires, which are available for a precisely fitting system on a drawing die, is comparatively simple.

Particularly advantageous in this regard it is when the extruded green compacts with a radial cooling channel contour are formed according to claim 11 straight leg sections, on which the wires at Can securely support the spirals in the drawing form.

Experiments and simulations made it clear that even with such cooling channel cross sections, similarly good results in terms of notch stress and coolant throughput can be achieved as with elliptical cooling channel cross sections as long as sufficiently large minimum radii and wall thicknesses are observed. However, due to smaller radii at the curvature maxima than with the elliptical shape, the minimum wall thicknesses are larger.

The sintered blanks according to the invention are suitable but not only for the production of complete tools, but also for the production of tool components according to claim 24. For example Deep hole drills often from a locally limited to the drill tip Drill head and one over the length of the drill extending shaft soldered together. At least it can a cutting edge can be formed directly on the drill head or a Drill head with screwed indexable or indexable inserts for Come into play. The drill head and the shank are quite different Requirements. While at Drill head especially wear resistance and hardness in the foreground, the shaft must have high toughness and have torsional rigidity.

According to the invention, the sintered blanks can be used with the geometry according to claims 4 to 18 also tool components such as shanks, drill heads etc. manufacture, in the embodiment according to claim 25 with a Flute or in the embodiment according to claim 26 with several flutes.

From a stability point of view, one is in the Tool manufacturing, however, endeavors especially in deep hole drills, which due to their large length in relation to Diameters have to endure high loads, as few as possible prone to errors strength-reducing solder joints to have. This requirement is met with the advantageous further training of the cutting tool according to the invention according to claim 18 taken into account.

Let the characteristics of the claims combine as much as it makes sense.

Otherwise, the tool according to the invention can or tool component with usual Coatings be equipped, at least in the area the sharp edges. If it's a hard material layer, it is preferably thin executed the thickness of the layer preferably in the range between 0.5 and 3 µm.

The hard material layer consists for example of diamond, preferably monocrystalline diamond. However, it can also be designed as a titanium nitride or titanium aluminum nitride layer, since such layers are deposited in a sufficiently thin layer. But also other hard material layers, for example TiC, Ti (C, N), ceramics, for example Al ₂ O ₃ , NbC, HfN, Ti (C, O, N), multi-layer coatings made of TiC / Ti (C, N) / TiN, multi-layer Ceramic coatings, in particular with intermediate layers made of TiN or Ti (C, N), etc. are conceivable.

Alternatively, it is conceivable to use the sintered blanks according to the invention To create tools or tool components that can be used to hold screws or to be soldered Indexable or interchangeable inserts are intended.

Additionally or alternatively, a soft material layer can also be used, which is present at least in the area of the grooves. This soft material coating preferably consists of MoS ₂ .

Below are schematic drawings preferred embodiments the invention closer explained. Show it:

1 shows a known extrusion head according to its own patent DE 42 42 336 ;

2 shows an extrusion head according to an embodiment of the invention for performing the extrusion method according to the invention;

3 shows a side view of a sintered blank according to an embodiment of the invention;

4 shows an isometric view of an embodiment of a tool according to the invention with two webs;

5 shows an isometric view of a further embodiment of a tool according to the invention with two webs;

6 shows possible cross-sectional geometries of a tool in an embodiment with two webs;

7 shows further possible cross-sectional geometries of a tool in an embodiment with two webs;

8th shows further possible cross-sectional geometries of a tool in an embodiment with two webs;

9 shows an isometric view of an embodiment of a tool according to the invention with a web;

10 shows an isometric view of a further embodiment of a tool according to the invention with a web;

11 shows an isometric view of a further embodiment of a tool according to the invention with a web;

12 shows a schematic cross-sectional view of a further embodiment of a tool according to the invention with a web;

13 shows a schematic cross-sectional view of a further embodiment of a tool according to the invention with a web;

First, referring to 1 that from our own patents, e.g. DE 42 42 336 Known extrusion processes and the extrusion head provided therefor, to which the method according to the invention is then based on the in 2 illustrated embodiment of the extrusion head is compared.

In 1 is with the reference symbol 10 on Extrusion head is called, that from right to left of a highly viscous, plasticized metallic or ceramic mass 12 is flowed through. With 14 is a nozzle mouthpiece, which is integral with a nozzle support part 16 is trained. The extrusion die has two sections, namely a die mouth DM and a die inlet area DE, in which the plastic mass 12 is funnel-shaped into the nozzle mouth. In the center of the nozzle inlet area DE is a nozzle mandrel 18 provided that on its downstream side a conical surface 20 has so that between the nozzle mandrel 18 and the nozzle support part 16 an annulus 22 is formed, which opens into the nozzle mouth DM.

The extrusion tool or the extrusion head 10 or the extrusion die 14 . 16 is used for the continuous extrusion of cylindrical rod-shaped bodies 24 with at least one, internal and helical, left or longitudinal channel 3 ,

In the known extrusion tool 10 according to 1 is in the center of the nozzle mandrel 18 a wave 30 rotatably mounted. The wave 30 extends over the front end 32 of the nozzle mandrel 18 out into the nozzle mouth DM and carries a plate-shaped hub body at the downstream end 34 that over its radially outer side surfaces 36 . 38 firmly with helically pre-twisted pins 40 . 42 connected is. Two such pens 40 . 42 are point symmetrical to the axis 44 the wave 30 and thus the hub body 34 ,

The pencils 40 . 42 have essentially the length of half a spiral pitch WS / 2 and the arrangement is such that the pins 40 . 42 at least up to the front 48 of the nozzle mouthpiece 14 extend so that from the bars 40, 42 inner channels formed during the extrusion process 3 maintain their shape and position outside the nozzle.

The hub body 34 sits in the nozzle mouth DM so that it has a predetermined axial distance AX from the front end 32 of the nozzle mandrel 18 Has. This axial distance AX is preferably adjustable to the flow conditions of the nozzle mouth DM and thus the at least one pin 40 . 42 to be able to influence.

As with the arrows 50 in 1 indicated the pens 40 . 42 defined, and flowed axially in the area of the nozzle mouth DM. The flow thus hits the pins at the angle PHI determined by the slope WS and the pitch circle diameter 40 . 42 , Since this is over the hub body 34 and the wave 30 around the axis 44 are rotatably fixed in the nozzle mouth DM, the pins 40 . 42 when passing through the plastic mass 12 through the nozzle mouth in a continuous rotary movement corresponding to the pitch of the helix of the preformed pins with the angular velocity OMEGA. The force components acting in the circumferential direction caused by the inclination of the helical pins in relation to the flow direction add up over the length of the pins 40 . 42 on.

The arrangement of rotatable shaft 30 , Hub body 34 and at least one helically twisted pin 40 . 42 performs a uniform rotational movement of the pins, predetermined by the flow velocity 40 . 42 , the bending stress of the pins 40 . 42 is kept relatively small. The pencils 40 . 42 act in this way on the principle of an axially flow-through turbine with the output shaft 30 , but the medium is not formed by an ideal, incompressible liquid, but by a highly viscous and to a certain extent elastic mass.

The nozzle mouth is basically divided into two areas, namely a nozzle mouth entry area DME and a pure nozzle mouth flow area DMS. In the DMS section, the nozzle mouth has a predetermined, essentially constant cross-section, so that, in a first approximation, a constant flow velocity can be assumed in this area. In the DME area, it is important to keep the effective flow cross-section essentially constant at least over the axial length of the DME area, but preferably over the entire axial length of the nozzle mouth DM. For this purpose, the diameter in the DME area is just increased by a dimension M in comparison to the section DMS, so that the ring area defined by the two diameters of the areas DMS and DME is approximately as large as the cross-sectional area of the shaft 30 and the radial sectional area of the hub body 34 including the liaison offices 52 , Appropriate design of the transitions between the inner surface areas in the DME and DMS area can cause excessive pressure fluctuations in the mass 12 be switched off when flowing through the nozzle mouth DM. The design of the nozzle mouth DM, especially in the transition area between the sections DME and DMS, prevents an excessive pressure drop, so that it is ensured that there is sufficient pressure in the section DMS to close the cross section.

In the 1 are some possible designs of the upstream and / or downstream edges 54 or 56 of the hub body 34 indicated. With dash-dotted lines is an alternative design of an edge 156 indicated on the downstream side. With such designs, the flow conditions can be influenced as desired.

With the axial flow against the hub body 34 and the pens 40 . 42 reaction forces are also generated in the axial direction by the shaft 30 must be included. For this purpose, the wave 30 not just radial, but also axially supported.

The known extrusion device described above works as follows:
The highly viscous mass 12 emerges from the annulus 22 over a short run-in distance over the axial distance AX into the run-in area of the nozzle mouthpiece DME in the axial direction and moves it out of the rods or wires 40 , the hub body 34 respectively. 134 respectively. 234 as well as the wave 30 existing cooling duct former due to the angle of attack PHI into a continuous rotary movement corresponding to the slope WS of the helix. The position of the helix in the nozzle mouth DM and the slope of the helix WS correspond exactly to the position and the slope of the helix of the cooling channel formed in the blank. Accordingly, when the nozzle mouth DM flows through, there is no plastic deformation of the mass passing through, but rather the formation of the internal, helical cooling channels in a primary molding process. The bars 40 . 42 are mainly used to train. The same applies to the stress on the shaft 30 which can thus be formed with a relatively small diameter.

In 2 are parts insofar as they are in shape and function with those in the 1 shown with the same reference numerals as in 1 , In the following only on the of 1 deviating structure and function of the in 2 shown embodiment according to the invention, since what has been said above applies to the remaining structure.

In the in 2 shown embodiment of the invention is a nozzle mouthpiece 140 exchangeable and rotatable via an unspecified, outwardly sealing slide bearing on the nozzle carrier part 16 supported. The nozzle mouthpiece 140 extends over the length of the nozzle mouth flow area DMS of the nozzle mouth DM and is thereby driven by a motor 141 continuously driven. With 300 is a bolt that is fixed and rotatable in the nozzle mandrel 18 is held, for example with the nozzle dome 18 is screwed or on the nozzle mandrel 18 soldered or welded on. With 340 is a fixed connecting element called, over which the two coiled pins 400 . 420 with the bolt 300 and thus with the nozzle mandrel 18 are connected.

The arrangement of non-rotating bolt 300 , Connecting element 340 and pens 40 . 42 remains rigid and imparts a force component running radially to the direction of flow to the inflowing mass. The connecting element 340 can have a turbine guide vane-like configuration for this purpose. The resulting tendency of the crowd 12 a helical flow movement becomes by the rotary movement with the speed n of the motor 141 driven nozzle mouthpiece 140 strengthened. The drive speed of the engine 141 is so on the flow velocity of the mass 12 voted that the crowd 12 overall executes a helical flow in which the direction of movement of the mass particles at the radial height of the pins 400, 420 the helical shape of the pins 400 . 420 equivalent. An action on the pins and thus the connecting part 340 , Bolt 300 and nozzle mandrel 18 that leads to a straight bending of the pins or break at the solder joint between the connecting element 340 and the pens 400 . 420 or the bolt 300 could be largely eliminated.

There is a bending of the pins 400 . 420 thus excluded, the pens 400 . 420 as with the extrusion head described above 1 exactly the slope that the channels should have in the finished extrusion green body. Any irregularities in the flow, for example due to batch-to-batch density variations in the mass 12 etc. detected and lead to a readjustment of the speed n of the nozzle mouthpiece 140 ,

The readjustment is carried out with the aid of a slope marking arranged downstream of the nozzle by means of a wheel that moves along 142 into the pressed extruded green compact, which the green compact at every point as a readable measure of the current slope of the channels 3 is impressed. An image capture 143 can detect this measure and the speed n in the sense of a constant slope of the channels 3 adjust accordingly by the engine 141 is controlled accordingly. As an alternative, it would also be to control one between the motor 141 and nozzle mouthpiece 140 switched transmission conceivable.

The nozzle mouth DM is designed with a smooth inner surface, even in the area of the nozzle mouthpiece inlet DME. The helical flow then forms solely on the basis of the shear stress induced by wall friction and depends on the viscosity of the mass, and is not forced from the outside by a fixed swirl device or rotating beads that stir in the mass. A relaxation movement of the mass after exiting the nozzle, which runs counter to the direction of the helical channels, can therefore be avoided, so that the channels introduced maintain their slope with a high degree of constancy. In the event that stronger rotational forces on the flowing mass 12 but could also be applied, a surface texture or smaller driver projections on the inneum catch of the nozzle mouthpiece 140 be provided.

In the embodiment shown, the rotating area of the nozzle extends 10 over the nozzle mouth flow area DMS of the nozzle mouth DM, with a diameter widening M in the nozzle mouth inlet area DME corresponding to the connecting element arranged there 340 and bolts 300 is provided. However, it would also be conceivable to use the nozzle 10 to be rotatable in the DME area. On the other hand, it is also possible to use only a certain section of the nozzle mouthpiece 140 to make it rotatable or one over the length of the pins 400 . 420 to turn the outgoing section.

The pitch of the helically pre-twisted pins 400 . 420 corresponds to the slope of the channels 3 of in 3 extruded blank shown 24 , The dimension of the slope WS must be determined taking into account the expected sintering shrinkage, as must the pitch circle diameter on which the channels 3 come to rest.

The spiral axis A ( 3 ) coincides with the axis 44 of the bolt 300 together so that - to exactly the cross section of the pins 400 . 420 following cross section of the channels 3 to effect - the pens 400 . 420 precisely aligned on the side surfaces 36 . 38 of the connecting element 340 must be attached, which is preferably done via a welded or soldered connection. As material for the pens 400 . 420 is a material with a large modulus of elasticity, such as. B. steel, hard metal or a ceramic material is used.

In the embodiment shown there are two pins 400 . 420 intended. However, it should be emphasized at this point that the invention is not restricted to such a number and arrangement of the pins. It is equally possible to use only one pin, or several pins with an even circumferential distribution or with an uneven circumferential distribution on the bolt 340 or to be attached to the nozzle mandrel, whereby the individual cross sections of the pins can also differ from one another. It is equally possible to arrange the pins on different circles.

A blank according to the invention is in 3 shown. The method according to the invention is particularly suitable for small blank diameters DR or large cooling channel cross sections Q _K in relation to the blank diameter DR. The at least one pin can have any cross-sectional shape, and in the case of blanks for tools with two, three or more relatively small-area webs, it is useful to have a cooling channel with an elliptical, trigonal or similar for each web provided. To provide cross-sectional contour, in the case of blanks for tools with a relatively wide web, on the other hand, a cooling duct with a kidney-shaped contour or several cooling ducts with a circular, elliptical or trigonal contour.

With the method according to the invention, blanks can be extruded whose diameter DR ( 3 ) corresponds essentially to the final diameter of the tool to be manufactured. Because of the smooth wall of the nozzle mouthpiece 140 the fully cylindrical blank obtained after extrusion and finished sintering only has to be polished and provided with flutes. However, no further material removal is necessary.

The 4 to 12 show enlarged views of various embodiments of drilling tools according to the invention with a nominal diameter of 4 mm made of a tungsten carbide-based hard metal.

4 shows an isometric enlarged view of a coiled drilling tool with a diameter of 4 mm according to an embodiment of the invention. The tool points to its through the flutes 1 two webs separated from each other 2 one main cutting edge each 4 on. The flutes 1 and bridges 2 run at a spiral angle of approx. 30 ° to a drill shaft designed as a solid cylinder 9 , on which the tool can be clamped in a tool holder or in a chuck. The internal cooling channels 3 extend through the entire tool and are twisted with the same spiral angle as the flutes 1 and bridges 2 , In the tool shown, the coolant is largely directly into the flute 1 introduced because the exit surface of the cooling channels 3 over both sections of the open space divided by a so-called four-surface grinding 13 extends so that a large part of the coolant directly into the flute 1 flows. In order to enable a circumferential support of the drill in the bore, the in 4 shown drill also one on the cutting corner of the main cutting edge 4 starting support phase 11 on. The outlet openings of the internal cooling channels leave a trigonal cooling channel cross-sectional contour 30I recognize that compared to a circular cooling channel contour with the same minimum wall distance to the flute 1 allows an increased coolant emission.

In 5 is shown a further embodiment of a drill according to the invention, which in the 4 shown drill corresponds to the modified cooling channel contour. The comparison of the cooling channel contour 30III out 5 with the cooling channel contour 302 out 4 immediately illustrates the potential of coolant throughput by increasing the cross-section of the cooling channels 3 can be achieved. To further improve the chip evacuation flow, it would also be conceivable to use the flutes 1 to be designed in such a way that they expand from the drill tip to the drill shank.

Apart from an increase in the total cross-sectional area of the cooling channels, a clever choice of the cross-sectional contour can also lead to throughput optimization, as in 6 . 7 and 8th cooling channel cross-sections shown as an example:
It is now referenced to 6 , which is an enlarged cross-sectional view of a double-edged, drill, nominal diameter 4mm, with two webs 2 and two flutes 1 can be seen. The webs are on the cutting side 2 each through a rake face 5 limited to not cutting side through a chip-free surface 6 , The outer circumference of the drill is the reference symbol 7 assigned.

Starting from a drill core with a diameter d _K spread the rake face 5 and chip clearance 6 the bridges 2 to a web width such that the nominal diameter D of the drill is reached.

The bridges 2 are approximately symmetrical to a web center line S, which is drawn in radially to the drill axis A. On the line of symmetry S are on the lower web 2 the center M of a circle K, which is completely within the cross-sectional area of the cooling channel bore there 3 located. The center point M ″ of the circle K there with the same diameter 2R ₀ is located on the upper web, offset somewhat to the rear from the rake face, completely within the cross-sectional area of the cooling channel bore there 3 ,

Several cooling channel contours surrounding the respective cooling channel are thereby created 30 . 31 . 32 compared with each other according to different embodiments of the invention: on the lower web there is an elliptical contour 30 for the cooling channel 3 drawn with a solid line, another contour 31 for the cooling channel 3 with dashed line. There is a contour on the upper web 32 for the cooling channel 3 drawn in with a dashed line.

The cooling channel contours 30 . 31 have a shape symmetrical to the line of symmetry, while the cooling channel 32 deviates only on the non-cutting side from the contour specified by the touching circle K. The radii of curvature R ₁ , R ₁ 'and R ₁ ''each lie on the curvature maxima, the contours 30 . 31 each have two curvature maxima of equal curvature, while on the contour 32 there is only a maximum curvature with radius R ₁ ''.

It can be seen that with the cooling channel cross-sectional geometry according to the invention, while maintaining the same distance from the core diameter d _K , the cooling channel bores with a circular diameter 2R ₀ , a substantial increase in passage area in the areas of the cooling channel facing the chip face or the chip free face can be achieved.

The passage area is only limited by the minimum wall thicknesses to be observed, for the sake of clarity only the minimum wall thickness d _SPE , d _SPA and d _SPA '' between the cooling channel, which is particularly important for the breaking strength of the drill 3 and rake face 5 for each of the cooling channel contours 30 . 31 . 32 is drawn.

The minimum wall thicknesses are in turn predetermined by the minimum strength that the drill is to achieve and thus also by the radii R ₁ , or R ₁ 'or R ₁ ''at the curvature maxima of the respective cooling channel contour 30 . 31 . 32 , This is reflected in that for the elliptical cooling channel contour 30 a smaller minimum wall thickness d _SPE than for the cooling channel contours 31 . 32 with curvature maxima offset to the outside (minimum wall thickness d _SPA ).

The cooling channel contours hold 30 . 31 the minimum wall thickness d _SPE or d _SPA between the cooling duct 3 and rake face 5 a, which is essentially the (not named) minimum wall thickness between the cooling channel 3 and chip clearance 5 equivalent. In contrast, the contour shows 32 exemplary on the rake face 5 facing side has a greater minimum wall thickness d _SPA '' than on the rake face 5 opposite side. Because on the one hand the center point M 'of the enclosed circle is offset from the cutting side, on the other hand the cooling channel contour 32 only on the chip free surface 6 facing side a maximum curvature (radius R ₁ ''). However, cooling channel cross sections would also be conceivable in which the maximum curvature lies on the side facing the rake face.

7 shows a cross section through a double-edged drill, with a cooling channel on the upper web 3 with cooling channel trine profile 30T an elliptical cooling channel profile 30E is compared on the lower footbridge.

8th also shows a cross section through a double-edged drill, with two further cooling channel profiles 30II . 30 III to be shown.

With d _SPX , d _SFX and d _AUX are the minimum wall thicknesses between the cooling duct 3 and rake face 5 , Cooling duct 3 and chip clearance 6 and between the cooling channel 3 and outer circumference 7 ' designated, with R _1X and R _2X each the smallest and the largest radius adjacent to the cooling channel contour, where X stands for E, T, I, II, III.

In the in the 6 to 7 Cross sections shown are enlarged images of a drill with a nominal diameter of 4 mm, the cooling channel profiles inscribing the same circle with radius R ₀ .

The cooling channels have the following parameters on:

• - enclosed circle with R ₀ = 0.4, cross-sectional area 0.50 mm ² ;
• - Elliptical cooling channel profile 30E with main axis 2a = 0.55 mm, minor axis 2 B = 0.4 mm, cross-sectional area 0.69 2 mm;
• - Almost elliptical cooling channel profile 30II with the narrowest radius R _1II = 0.3 mm, the widest radius R2II = 0.5 mm, cross-sectional area 0.67 mm ² ;
• - Almost elliptical cooling channel profile 30III with the narrowest radius R _1III = 0.2 mm, the widest radius R _2III 0.5 mm, cross-sectional area 0.66 mm ² ;
• - Trigonal cooling channel profile, narrowest radius R _1T = 0.1 mm, widest radius R _2T = 0.4 mm, cross-sectional area 0.65 mm2.

It can be seen that the cross-sectional area of the closed circle is significantly smaller than that of the other cooling channels, while the remaining cooling channels have almost the same cross-sectional areas.

Trials and simulations at the in 6 to 8th The drills shown also showed that a larger radius radius at the maximum curvature can reduce the notch stresses that occur on the cooling channel under pressure and torsional stress on the tool. The best values were for the elliptical profile 30E achieved, while with the trigonal profile dramatically higher voltage peaks had to be accepted.

The 9 to 13 show different embodiments of a single-lip drilling tool according to the invention.

This in 9 The one-piece drilling tool shown here has a helical flute designated 1 and a helical web designated 2 which extends from a drill tip 8th through a cutting part 119 through to a drill shaft 109 extend. The jetty 2 has a major cutting edge 4 on, which extends from the tool circumference to the tool axis, which is at the tool tip 8th with the spiral curve of the flute indicated by dashed lines 1 coincides. In the jetty 2 is a cooling channel 3 molded, its kidney-shaped cross-sectional contour with 30N is labeled and which coils with exactly the same pitch as flute 1 and footbridge 2 extends through the entire tool to operate at one end of the drill shank 109 Pressed coolant directly to the chip area at the tool tip 8th to lead. The kidney shape fulfills on the one hand the requirement to make good use of the land area, so that a high coolant supply can be guaranteed. On the other hand, the radii at the point of smallest curvature are not higher than they would be with two circular cooling channels with the same minimum edge distances, so that increased stress peaks can be avoided under load, while at the same time an increased coolant throughput is achieved, the coolant not only selectively but also over the entire flute wall extends. It is clear that the drilling tool shown is due to its spiral flute 1 can support over its entire circumference in the borehole, whereby a higher centering accuracy can be achieved than with a classic straight-fluted single-lip drilling tool.

The other figures relate to modifications of the in 9 shown tool.

So that points in 10 shown tool instead of a fixed cutting edge provided on the web a modified cutting part 119A with a seat WPS for one insert. A corresponding indexable insert is designated WP. The main cutting edge 4 and the drill tip 8th are provided on the indexable insert WP. The circumference is on the tool bar 2 guide rails 20 attached, with which the tool is supported in the bore. It is important to ensure that the cooling channel 3 , or its cross-sectional contour 30N must be arranged so that the required minimum wall thickness for the insert seat WPS and the seat of the guide rails 20 is observed.

In the 9 and 10 The tools shown are not weakened by connection points of individual elements due to their one-piece design. For reasons of cost and in order to meet the different requirements for drill tip and tool length, deep drilling tools are often made of several parts, whereby different materials are often used for the drill head and drill shank than for the rest of the cutting part. For example, an extremely hard hard metal is suitable for the drill head, while toughness is more important for the cutting part, which is why another hard metal is often used there.

The 11 you can also remove a tool that consists of several components. On a cutting part 219 a drill head BK is soldered, which has the insert seat WPS for receiving the indexable insert WP. The solder joint LS is indicated with a dashed line. The cutting part 219 is again in a single team 209 soldered. The cooling channel 3 with kidney-shaped cross-sectional contour 30N extends helically through the drill head BK and cutting part 219 through, being in the shaft 209 a straight cooling duct connector between the cutting part 219 on the one hand and machine-side coolant supply can be provided on the other.

Finally they show 12 and 13 still cross-sectional views of two single-lip drill according to the invention. It can be seen that the flute 1 accounts for about a quarter of the space available on the drill diameter, while the web 2 in about three quarters. The cooling channel 3 of in 12 shown tool has the kidney-shaped contour already mentioned above 30N on while that in 13 shown drilling tool two cooling channels 3 has, each free-form contours 301 . 302 have, which correspond approximately to a distorted ellipse. Two guide strips are shown on the circumference. The guide rails 20 are therefore longer than the associated insert and follow the tool bar helically. In this way, circumferential support is achieved in the bore, which extends circumferentially over a certain circumferential area.

Of course there are deviations from the embodiments shown possible without to leave the basic idea of the invention.

Claims (26)

Extrusion process for continuous Manufacture of fully cylindrical sintered blanks ( 24 ) with at least one internal, helical channel ( 3 ) predetermined cross-section, in which the blank ( 24 ) forming, plastic mass ( 12 ) from a die mouth (DM) of an extrusion die ( 10 ) is pressed out in the form of a tube which is essentially circular cylindrical, preferably smooth on the inside, wherein it is twisted along the axis of at least one helically twisted on a nozzle mandrel ( 18 ) pin held in place ( 400 . 420 ) flows, which protrudes at least in sections into the nozzle mouthpiece (DM), and the mass ( 12 ) enters the nozzle mouthpiece (DM) essentially without twist, characterized in that - the pin ( 400 . 420 ) does not rotate, - the plastic mass ( 12 ) in the nozzle mouth (DM) in one of the spiral shape of the pen ( 400 . 420 ) corresponding, swirled flow is displaced, and - the rotational movement of the plastic mass ( 12 ) by means of a rotationally driven section engaging on the outer circumference of the mass ( 140 ) of the nozzle mouth (DM) is supported in such a way that the pin ( 400 . 420 ) is essentially not subject to any bending deformation. Extrusion method according to claim 1, characterized in that the rotary driven section ( 160 ) of the nozzle mouth (DM) at least in sections above that of the pin ( 400 . 420 ) penetrated section. Extrusion method according to one of the preceding claims, characterized in that the at least one pin ( 400 . 420 ) the frictional force of the mass ( 12 ) reducing fluid is supplied, in particular a liquid or liquid-like substance, preferably the plasticizer of the mass or at least one component of the plasticizer. Fully cylindrical sintered blank ( 24 ), producible with the method according to one of the preceding claims, characterized by at least one helically molded channel ( 3 ), whose cross-sectional contour ( 30 ; 31 ; 32 ; 30E ; 30T ; 30I ; 30II ; 30III ; 30N; 301, 302 ) perpendicular to the longitudinal axis (A) of the blank ( 24 ) deviates from a circular contour (K), the blank ( 24 ) has a diameter (D) of less than 12 mm, in particular less than 8 mm, for example less than 4 mm. Fully cylindrical sintered blank ( 24 ), producible with the method according to one of the preceding claims, characterized by at least one helically molded channel ( 3 ), where the cross-sectional area of the channel (Q _K ) is 20:80 or better, in particular 30:70, for example 50:50, in a plane perpendicular to the cylinder axis in relation to the cross-sectional area of the remaining material (QM) Blanks with more than one channel in a ratio of 20:80 or better, in particular 30:70, for example 40:60. Sintered blank ( 24 ) with the features of claims 4 and 5. Sintered blank ( 24 ) according to one of claims 4 to 6, characterized by a deviation of the helix shape from the target helix, which is at most at a point with a blank length (L _R ) of 100 mm 10 ' is. Sintered blank ( 24 ) according to one of claims 4 to 7, characterized by a blank length (L _R ) of over 300 mm, in particular over 400 mm, for example over 500 mm. Sintered blank ( 24 ) according to one of claims 4 to 8, characterized by a diameter-length ratio greater than 1: 5, in particular 1:10. Sintered blank ( 24 ) according to one of claims 4 to 9, characterized by a spiral angle above 10 °. Sintered blank ( 24 ) according to one of claims 4 to 10, characterized in that the cross-sectional contour ( 30T ; 30II ; 30III ) of the channel ( 3 ) is delimited by two side sections extending from the inside out, which run in a straight line, at least in sections. Sintered blank ( 24 ) according to one of claims 4 to 11, characterized in that the cross-sectional contour ( 30 ; 31 ; 32 ) of the channel ( 3 ) touching an imaginary circle (K) with a center point (M) and having at least one, preferably two curvature maxima, the distance to the longitudinal axis (A) of the blank in the direction of a line between the center point (M) and the longitudinal axis (A) greater or equal the distance from the center (M) to the longitudinal axis (A). Sintered blank ( 24 ) according to claim 12, characterized in that the two curvature maxima of the cross-sectional contour ( 30 ; 31 ; 30E ; 30T ; 30I ; 30II ; 30III ; 30N ) of the channel ( 3 ) have the same radial coordinates. Sintered blank ( 24 ) according to one of claims 4 to 13, characterized in that the cross-sectional area (Q _K ) of the channel ( 3 ) is symmetrical to a radial line. Sintered blank ( 24 ) according to one of claims 11 to 14, characterized in that the radius (R ₁ , R ₁ ', R ₁ '', R _1X ) at the strongest curvature of the Cross-sectional contour ( 30 ; 31 ; 32 ; 30E ; 30I ; 30II ; 30III ; 30N ; 301 . 302 ) of the internal cooling duct ( 3 ) 0.35 to 0.9 times, in particular 0.5 to 0.85 times, preferably 0.6 to 0.85 times and particularly preferably 0.7 to 0.8 times, for example corresponds to 0.75 times the radius of the circle (R ₀ ). Sintered blank ( 24 ) according to one of claims 4 to 15, characterized by a kidney-shaped cross-sectional contour ( 30N ) of the channel ( 3 ). Sintered blank ( 24 ) according to one of claims 4 to 15, characterized by an elliptical cross-sectional contour ( 30 . 30I . 30E ) of the channel ( 3 ). Sintered blank ( 24 ) according to one of claims 4 to 15, characterized by a trigonal cross-sectional contour ( 30T ) of the channel ( 3 ). Rotary cutting tool, especially drill, made from a sintered blank ( 24 ) according to one of the preceding claims, with shaft ( 9 ; 109 ; 209 ) and cutting part ( 19 ; 119 ; 119A WP 219 , BK, WP) in which at least one spiral flute ( 1 ) is incorporated and in its web ( 2 ) at least one coiled internal cooling duct ( 3 ), which extends from the drill tip ( 8th ) to an opposite end of the shaft ( 9 ; 109 ; 209 ) extends. Cutting tool according to claim 19, characterized through a one-piece Design. Cutting tool according to claim 19 or 20, characterized through the design as a two- or multi-lip tool. Cutting tool according to claim 19 or 20, characterized through the design as a single-lip tool. Cutting tool according to one of Claims 19 to 22, characterized by minimum wall thicknesses (d _AUX , d _SPX , d _SFX ) between the internal cooling duct ( 3 ) and outer circumference of the drill ( 7 ), between the internal cooling duct ( 3 ) and rake face ( 5 ) and between the internal cooling duct ( 3 ) and chip-free surface ( 6 ), which are in a range between a lower limit and an upper limit, the lower limit being 0.08 × D for D <= 1 mm and 0.08 mm for D> 1 mm, in particular 0.08 × D for D <= 2.5mm and at 0.2mm for D> 2.5mm, preferably at 0.08 × D for D <= 3.75mm and at 0.3mm for D> 3.75mm, for example at 0.1 × D for D <= 3mm and 0.3mm for D> 3mm, and the upper limit being 0.35 × D for D <= 6mm and 0.4 × D-0.30mm for D> 6mm (Wmax, 1), especially at 0.333 × D for D <= 6mm and at 0.4 × D-0.40mm for D> 6mm (W _{max, 2} ), preferably at 0.316 × D for D <= 6mm and at 0.4 × D- 0.50mm for D> 6mm (W _{max, 3} ), particularly preferably at 0.3 × D for D <= 6mm and at 0.4 × D-0.60mm for D> 6mm (W _{max, 4} ), for example at 0.2 × D (W _{max, 5} ) or 0.15 × D for D <= 4mm and at 0.6mm for D> 4mm (W _{max, 6} ), Cylindrical component (BK; 219; 209 ) a multi-piece cutting tool according to one of claims 19, 21 or 22, for example a deep hole drill, in particular a cutting part ( 219 ), Cutter holder, drill head (BK) or drill shank, in which at least one spiral flute ( 1 ) is incorporated and in its web ( 2 ) at least one coiled cooling channel ( 3 ), which extends through the entire component, made from a sintered blank ( 24 ) according to one of the preceding claims. Component according to claim 24, characterized by the Design with more than one flute. Component according to claim 24, characterized by the Design with a flute.