EP2313218B1 - Method and apparatus for producing a circular cylindrical body comprising a workable mass and having internal helical recesses - Google Patents

Abstract

A method is for producing a circular cylindrical body (10) comprising a workable mass, having at least one helical internal cavity extending in the interior of the body. The body (10) is initially produced with a straight internal recess, for example by means of extrusion. Afterwards the body is cut to a defined length. The body (10) that has been cut to length is then subjected to a rolling process by means of a friction surface arrangement (23) while being supported over the entire length thereof on a support means (16). The rolling process takes place in multiple steps, wherein a rolling movement using a first axis of rotation (25) is performed in a first step, and a rolling movement using a second axis of rotation (26) that is different from the first axis of rotation is used in a second step. There is also an apparatus for performing the method.

Description

The invention relates to a method and an apparatus for producing a circular-cylindrical body consisting of plastic mass, in particular a sintered metal blank, which has at least one helical inner recess extending in the interior of the body, according to the preamble of patent claim 1 or claim 7.

Such bodies are needed in particular in the production of drilling tools or drilling tool inserts made of hard metal or ceramic materials. Due to the helical course of the at least one inner recess, which serves in the finished drilling tool for the supply of coolant or lubricant in the cutting area, the drilling tool can be equipped with helical flutes, which is often sought to provide favorable cutting and machining properties of advantage and therefore.

It has already been attempted at an early stage to produce such sintered metal or ceramic blanks in the extrusion process by pressing the mass consisting of sintered metal powder or ceramic powder and binder through a pressing die having a cross section corresponding to the desired blank cross section and at least one inner core in the form of a pin, when extruding the plasticized mass for the formation of the is used by the entire blank extending inner recess.

The mass issuing from the press nozzle is generally very sensitive to pressure, ie the emerging blank deforms extremely easily when an external force is applied. Since such deformations are no longer reversible and thus lead to at least partially unusable blanks, it has been attempted to further develop the extrusion process so that the blank has helically extending cooling channels already on exiting the extrusion die. According to a proposal (see eg EP-A-0 465 946 ) this is achieved by the fact that on the inner circumference of the extrusion nozzle helically extending guide rails are mounted, which impose a swirling motion on the exiting plastic mass. In the cross section of the pressing nozzle flexible threads are fixed with a cross-section of the inner recess corresponding cross-section, wherein the threads extend to the outlet of the nozzle mouthpiece. Due to the flexibility of the threads, these can follow the swirling movement or the swirling flow of the plastic mass and thus produce the at least one internal cooling channel in the blank.

According to a further proposal, the nozzle mouthpiece and / or a hub shaped like a propeller, to which the abovementioned flexible limbs are fastened, are set into rotary motion during the extrusion process, which in turn produces an outer smooth blank with inner helical channels or recesses can.

In the production of such tool blanks, it is important that the pitch angle of the at least one helical inner recess over the entire length of the blank is kept constant and within narrow tolerance limits. This is necessary because in the Tool blank are regularly ground flutes after the sintering process. This grinding is done with largely automated machines, so that an uncontrolled high rejection rate can result from inaccurate production of helical inner recesses. It should be noted that tools are used with solid carbide cutting parts, inter alia, because the high strength of the material, in particular the torsional stiffness, to be exploited. To ensure this, the inner recess must not reach too close to the flute zoom, which can not be effectively excluded inaccurate production of the helical inner recess.

In the approaches described above for producing the blank with innnecting helical recesses, it is therefore necessary to closely monitor the extrusion tool and / or the sintering devices for the extrusion screw or, if present, for the swirl-producing bodies in the extrusion process and to match the mass flow rate. As a result, relatively long retooling and setting times are required on the extrusion tool, with the result that conventional methods are used economically primarily for large series. For small series or for the production of drilling tools with larger nominal diameters result disproportionately high machine setting costs, whereby the efficiency of the manufacturing process is called into question.

From the EP-B1-1 230 046 For example, a method and an apparatus for producing a sintered metal blank with internal helical recesses are already known. According to this known method, initially a substantially circular-cylindrical body is produced, for example extruded, with at least one inner recess running in a straight line inside it. This body is cut to a desired length and then subjected to rolling over its entire length on a support by means of a friction surface arrangement, whose velocity changes linearly and steadily over the length of the body, whereby the body is twisted uniformly. This twisting is done using an axis of rotation that intersects the longitudinal axis of the body.

By means of from the EP-B1-1 230 046 known method sintered metal blanks can be produced in which the pitch angle of the at least one helical inner recess over the entire length of the blank is kept constant and within narrow tolerated limits. As a result, it can generally be ensured that the at least one inner recess does not come too close to the flute, which still has to be introduced.

In practice, there are increasingly greater demands on the constant maintenance of the pitch angle of the at least one helical inner recess over the entire length of the blank within tight tolerances.

The object of the invention is therefore to provide a method and an apparatus for producing a circular mass consisting of plastic mass body, which is or these higher requirements.

This object is achieved by a method having the features specified in claim 1. Advantageous developments are specified in the dependent claims 2 to 6. The claim 7 has an apparatus for producing a circular mass consisting of plastic body. The dependent claims 8 to 12 relate to advantageous embodiments and further developments of the device specified in claim 7.

The advantages of the invention are in particular that by means of the claimed method of plastic mass existing circular cylindrical body can be produced, at least one helical inner recess over the entire length of the body has a very constant, held within very narrow tolerated limits helix angle. This advantage is based on the fact that the individual longitudinal sections of the circular cylindrical body each travel the same way during the rolling process. In contrast, put in the from the EP-B1-1 230 046 known methods, the individual longitudinal sections of the circular cylindrical body different lengths back paths. In particular, the paths which cover longitudinal sections located close to the axis of rotation during the rolling process are comparatively small, while those longitudinal sections which are arranged away from the axis of rotation cover comparatively large paths during the rolling process. As a result, the pitch accuracy of the helical recesses in the longitudinal portions located near the rotation axis is lower than in the longitudinal portions of the circular cylindrical body remote from the rotation axis. These different pitch accuracies in the known method do not occur when using the method according to the invention.

Figur 1

eine Draufsicht einer Ausführungsform einer Vorrichtung zur Herstellung eines aus einer plastischen Masse bestehenden Sintermetall- Rohlings mit einer innenliegenden Ausnehmung nach dem Stand der Technik,

Figur 2

die Ansicht entsprechend II in FIG 1,

Figur 3

in einer der FIG 1 entsprechenden Ansicht die Vorrichtung nach der Verdrillung des extrudier- ten Rohlings,

Figur 4

eine Skizze zur Veranschaulichung der Änderung der Drehachse während der Wälzbewegung beim er- findungsgemäßen Verfahren und

Figur 5

eine Skizze zur Veranschaulichung einer Vor- richtung zur Durchführung des erfindungsgemäßen Verfahrens.

Further advantageous features of the invention will become apparent from the exemplification thereof with reference to the figures. It shows

FIG. 1

a top view of an embodiment of an apparatus for producing a plastic mass sintered metal blank having an inner recess according to the prior art,

FIG. 2

the view corresponding to II in FIG. 1 .

FIG. 3

in one of the FIG. 1 corresponding view of the device after the twisting of the extruded blank,

FIG. 4

a sketch to illustrate the change of the axis of rotation during the rolling motion in the inventive method and

FIG. 5

a sketch illustrating an apparatus for carrying out the method according to the invention.

In the FIGS. 1 to 3 is denoted by the reference numeral 10 to a predetermined length L * tailored, ie cut to length sintered metal blank, which consists for example of a hard metal powder with kneaded binding or adhesive. This sintered metal blank is produced for example by extrusion, in such a way that it has a straight and continuous, shown in the figures with dotted line inner recess 12 which extends parallel to the center axis 14 of the circular cylindrical blank 10.

The production of the sintered metal blank is preferably carried out in the extrusion process with the aid of an extrusion die with a suitable core. The blank 10 has a relatively soft consistency, so that the handling, such. As the transport, must be done very carefully to prevent irreversible deformation. Therefore, the blank is preferably performed immediately after exiting the extrusion die on an air cushion and directed to the pad 16 shown in the figures, which in the FIGS. 1 and 3 coincides with the presentation plane. The blank is due to the consistency of the extruded mass on its outside sticky, so that a good adhesion with the support surface 16 results.

To reshape the blank 10 such that the rectilinear inner recess according to FIG. 1 or 2 is formed into a helical recess, the following arrangement is made:

Parallel to the flat bearing surface 16 at a vertical distance AV, a circular segment disc 18 with a bottom-side friction surface 20 is arranged. The circular segment disc 18 is rotatable about an axis of rotation 22 which is perpendicular to the surface of the support 16 and on the friction surface. The vertical distance AV between the surfaces 16 and 20 is preferably adjustable, which is indicated by the double arrow V in FIG. 2 is indicated. This vertical distance AV corresponds to the diameter D of the blank 10.

As in FIG. 1 shown, the blank 10 is placed on the support 16 so that its longitudinal axis 14, the axis of rotation 22 of the circular segment disc 18 cuts. Subsequently, the circular segment disc is lowered controlled so that it touches the blank 10 along a line which is offset diametrically to the bottom-side contact line of the blank 10 with the support 16. This alignment is in the Figures 1 and 2 shown.

Now, the circular segment disc 18 is pivoted at an angular velocity ω. Due to the frictional contact between the surface 20 of the circular segment disc 18 and the blank 10 of the blank is taken by rolling on the surface of the support 16 at a speed that changes linearly and steadily along the axis of the blank 10. The rolling speed at the inner end of the blank 10 is VWI and the rolling speed at the outer end of the blank 10 is designated VWA. Thus, if the segment disc 18 passes through a certain Verschenkwinkel φ, results along the rod-shaped blank 10 is a linear distribution of the rolling track, with the result that the circular cylindrical blank 10 is twisted during the rolling motion, in such a way that a pitch angle of the twist and thus a pitch angle of the helical inner recess 12 results, directly proportional to the pivot angle φ is.

Preferably, the circular segment disc 18 is held in contact with the rod-shaped blank 10 with as little contact force as possible, specifically during the entire twisting operation, ie during the entire pivoting about the pivoting angle φ (see FIG. Fig. 3 ). Here it may be advantageous to work with pressure sensors which act on the not shown lifting and lowering device for the circular segment disc 18.

From the above description and the FIGS. 1 to 3 It can be seen that the individual longitudinal sections of the blank 10 cover different rolling distances or travel distances during the rolling process. Thus, longitudinal sections of the blank 10, which are arranged in the vicinity of the axis of rotation 22, during the rolling process have smaller rolling distances than longitudinal sections of the blank 10, which have a greater distance from the axis of rotation 22. This has the consequence that the pitch angle of the helical recess 12 (see FIG. 3 ) in longitudinal sections of the blank 10, which are arranged near the rotation axis 22, the respective desired value less accurately comply than the pitch angle of the helical recess in longitudinal sections of the blank, which are arranged further from the axis of rotation.

This disadvantage is avoided by using a method according to the present invention. In the present invention, in contrast to the reference to the FIGS. 1 to 3 described prior art during the rolling process, a change in the axis of rotation. This change in the axis of rotation takes place in particular such that all longitudinal sections of the blank during the rolling process each cover the same rolling distance. Preferably, the rolling process takes place in two successive steps, wherein in the first step, a rolling movement about a first axis of rotation and in the second step, a rolling movement about a second axis of rotation takes place.

A method according to the invention serves as well as that of EP-B1-1 230 046 known method for producing a circular cylindrical body consisting of plastic mass, in particular a sintered metal blank, which has at least one helical inner recess running in the interior of the body.

In a method according to the invention, the body is as well as in the EP-B1-1 230 046 known method initially prepared with a straight course of the inner recess, for example extruded. The extruded body is cut to a desired length. Subsequently, it is subjected to a rolling process with support over its entire length on a support with a friction surface arrangement, so that a twisting of the body takes place.

Unlike the one from the EP-B1-1 230 046 Known methods, the axis of rotation, the use of which the rolling motion takes place, changed during the rolling process.

Preferably, the rolling process takes place in two successive steps, wherein in the first step, a rolling movement about a first axis of rotation and in the second step, a rolling movement about a second axis of rotation, wherein the second axis of rotation is different from the first axis of rotation. In its entirety, the rolling process takes place in such a way that each longitudinal section of the circular-cylindrical body travels the same path during the rolling process. The Rolling direction is maintained in the successive steps.

According to a first embodiment of the method according to the invention, the positioning of the axes of rotation is such that during the first step, the axis of rotation intersects the center line of the circular cylindrical body in the region of an axial end surface of the circular cylindrical body and during the second step, the axis of rotation of the center line of the circular cylindrical body in the area the other axial end surface of the circular cylindrical body intersects.

According to a second preferred embodiment of the method according to the invention, the positioning of the axes of rotation is such that during the first step, the axis of rotation intersects the extended centerline of the circular cylindrical body at a predetermined distance from an axial end surface of the circular cylindrical body and during the second step the axis of rotation extends Center line of the circular cylindrical body at the same predetermined distance from the other axial end surface of the circular cylindrical body intersects.

Another embodiment of the invention is to change the axis of rotation about which the rolling movement occurs during the rolling movement several times or continuously.

The FIG. 4 shows a sketch to illustrate the change of the axis of rotation during the rolling process.

At the beginning of the rolling process, the circular cylindrical body 10 is in the position in which it is represented by the reference numeral 10.

Starting from this position, in a first step, a twisting of the body using the Rotation axis D1, which runs perpendicular to the plane of the drawing. During this first step, the body is moved through an angle in the FIG. 4 in the vicinity of the rotation axis D1 is denoted by "a". The rotation axis D1 intersects the center line M of the circular cylindrical body at a predetermined distance from an axial end portion of the circular cylindrical body. In this twisting, the velocity changes linearly and steadily over the length of the body. At the end of the first step, the body is in a position offset by the angle α. He is there with the reference numeral 10 'provided.

Subsequently, in a second step, the body is twisted using a rotation axis D2. This also runs perpendicular to the drawing plane. The rotation axis D2 intersects the center line M 'of the circular cylindrical body 10' at a predetermined distance from the other axial end surface of the circular cylindrical body. In this second step, the body is moved through an angle, which in the FIG. 4 in the vicinity of the rotation axis D2 is also denoted by "α". Even with this twisting, the speed changes linearly and steadily over the length of the body. At the end of the second step, the body is in a position offset by the angle α. He is there with the reference numeral 10 "provided.

The entire twisting process is tuned to the effect that the different longitudinal sections of the circular cylindrical body cover the same distance or twisting distance during the entire twisting process. This is in the FIG. 4 illustrated by the longitudinal sections A1 and A2 of the circular cylindrical body.

The longitudinal section A1 of the circular cylindrical body is in the first step to those in the FIG. 4 moved with s1 path. After completion of the first step this longitudinal section is located in the body 10 'and is designated there by A1'.

In the second step, the longitudinal section Al 'around the in the FIG. 4 moved with s1 'designated distance. After completion of the second step, this longitudinal section is located in the body 10 "and is designated there by A1". The total distance is therefore: $$\mathrm{W}\mathrm{1}\mathrm{=}\mathrm{s}\mathrm{1}\mathrm{+}\mathrm{s}\mathrm{1}\mathrm{\text{'}}\mathrm{,}$$

The longitudinal section A2 of the circular cylindrical body is in the first step to those in the FIG. 4 moved with s2 path. After completion of the first step, this longitudinal section is located in the body 10 'and is designated there by A2'. In the second step, the longitudinal section A2 'to those in the FIG. 4 moved with s2 'designated distance. After completion of the second step, this longitudinal section is located in the body 10 "and is designated there by A2". The total distance is therefore: $$\mathrm{W}2\mathrm{=}\mathrm{s}2\mathrm{+}\mathrm{s}\mathrm{2}\mathrm{\text{'}}\mathrm{,}$$

The following applies: $$\mathrm{W}\mathrm{1}\mathrm{=}\mathrm{W}\mathrm{Second}$$

Consequently, during a complete twisting operation, all longitudinal sections of the circular cylindrical body travel the same entire distance. This advantageously has the consequence that the angle of rise of the at least one helical inner recess extending in the interior of the body over the entire length of the circular-cylindrical body has an increased pitch accuracy in comparison with the known method. This reduces the resulting later grinding of flutes Rejects or reduces the requirement for working accuracy during twisting.

The FIG. 5 shows a sketch to illustrate a device for carrying out the method according to the invention. This device has a flat support surface 16. In the vertical distance AV to this a Wälzscheibe 23 is arranged. This has a pad surface side friction surface 24. The Wälzscheibe 23 is rotatable about an axis of rotation 25 which is perpendicular to the surface of the support surface 16. This rotation takes place at an angular velocity ω. The vertical distance AV between the support surface 16 and the Wälzscheibe 23 is adjustable, as indicated by the double arrow V. In the first step, the rolling movement takes place using the axis of rotation 25. In the subsequent second step, the rolling movement takes place using a second axis of rotation 26, which is also perpendicular to the surface of the support surface 16. This rotation also takes place at the angular velocity ω. The rolling direction in the second step coincides with the rolling direction in the first step.

Claims (12)

1. Method of producing a circularly cylindrical body (10), which consists of plastics material and which has at least one helical internal recess (12) extending in the interior of the body, wherein the body is initially produced with a rectilinear course of the internal recess and the body, which is cut to a specific length, is subsequently subjected to a rolling process, while being supported over its entire length on a support (16), by means of a friction surface arrangement (23), which similarly engages over the entire length of the body, with a friction surface (24) arranged parallel to the support, characterised in that the rolling process is carried out in several steps, wherein in a first step a rolling movement is carried out with use of a first axis (25) of rotation of the friction surface arrangement and in a second step a rolling movement is carried out with use of a second axis (26) of rotation, which is different from the first axis of rotation, of the friction surface arrangement, wherein the axes of rotation extend perpendicularly to the support or to the friction surface.
2. Method according to claim 1, characterised in that the axis of rotation of the friction surface arrangement about which the rolling movement is carried out is changed a number of times or continuously during the rolling movement.
3. Method according to claim 1 or 2, characterised in that each length section of the circularly cylindrical body covers the same path during the rolling process.
4. Method according to any one of the preceding claims, characterised in that the rolling direction is maintained in the several steps.
5. Method according to any one of the preceding claims, characterised in that during the first step the first axis of rotation of the friction surface arrangement intersects the centre line of the circularly cylindrical body in the region of one axial end surface of the circularly cylindrical body and during the second step the second axis of rotation of the friction surface arrangement intersects the centre line of the circularly cylindrical body in the region of the other axial end surface of the circularly cylindrical body.
6. Method according to any one of claims 1 to 4, characterised in that during the first step the first axis of rotation of the friction surface arrangement intersects the prolonged centre line of the circularly cylindrical body at a predetermined distance from one axial end surface of the circularly cylindrical body and during the second step the second axis of rotation of the friction surface arrangement intersects the prolonged centre line of the circularly cylindrical body at the predetermined distance from the other axial end surface of the circularly cylindrical body.
7. Device for performing a method according to any one of the preceding claims, with a support surface (16) for supporting the body (10) over the entire length thereof, a friction surface arrangement (23), which engages the body similarly over the entire length thereof, with a friction surface (24) arranged parallel to the support and a drive unit (27) by which the friction surface arrangement is subjected to a movement producing a rolling process at the body, characterised in that the friction surface arrangement (23) is rotatable about a first axis (25) of rotation and about a second axis (26) of rotation, wherein the axes of rotation extend perpendicularly to the support or to the friction surface arrangement.
8. Device according to claim 7, characterised in that it comprises a control unit (28) which supplies control signals to the drive unit (27).
9. Device according to claim 8, characterised in that the control unit (28) generates the control signals for the drive unit (27) in such a way that in a first step of the rolling process the friction surface arrangement is rotated about the first axis (25) of rotation and in a second step of the rolling process the friction surface arrangement is rotated about the second axis (26) of rotation.
10. Device according to claim 9, characterised in that the control unit (28) generates the control signals for the drive unit (27) in such a way that the rotation of the friction surface arrangement in the first step and the rotation of the friction surface arrangement in the second step take place at the same angular speed (ω).
11. Device according to claim 9 or 10, characterised in that the control unit (28) generates the control signals for the drive unit (27) in such a way that the rotation of the friction surface arrangement in the first step and the rotation of the friction surface arrangement in the second step take place through the same size angle.
12. Device according to any one of claims 9 to 11, characterised in that the control unit (28) generates the control signals for the drive unit (27) in such a way that the rolling direction is maintained in the first step and in the second step.

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