EP2076348A1

EP2076348A1 - Clamping method for workpieces used for the production of compressor or turbine wheels

Info

Publication number: EP2076348A1
Application number: EP07800669A
Authority: EP
Inventors: Günter Leitold
Original assignee: STARRAGHECKERT AG
Current assignee: STARRAGHECKERT AG
Priority date: 2006-10-02
Filing date: 2007-10-01
Publication date: 2009-07-08
Also published as: US20100166519A1; KR20090082206A; WO2008040136A1

Abstract

Disclosed is a milling method for machining a workpiece of a compressor or turbine wheel in a machine tool. In said method, the contour of flow-conducting sections of the compressor or turbine wheel is machined using a rotating milling tool on the workpiece that is accommodated in a workpiece support and is fastened relative thereto for the production process. In order to increase the possibilities to automate said method, the workpiece (8) is placed, by means of a positioning aid, in a certain position within the workpiece support in a positioning step, said position being used for a subsequent production process and being at least radially predetermined relative to a longitudinal axis (6) of the workpiece support, and the workpiece is fastened within the machine tool in an axial direction relative to the workpiece support in a clamping step that differs from the positioning step.

Description

Clamping process for workpieces for the production of compressor or

turbine wheels

The invention relates to a milling method for machining a workpiece of a compressor or turbine wheel in a machine tool, in which using a rotating milling tool on the workpiece contour machining takes place provided for flow line sections of the compressor or turbine wheel, wherein the workpiece is received in a workpiece carrier and relatively is fixed to this for the production.

So-called compressor wheels (impellers) or turbine wheels (blisk) are produced both by casting processes and by machining processes on machine tools. In this case, it is customary in particular for compressor wheels and turbine wheels with a simpler geometry, which are often used, for example, in the automotive sector, to be produced by economic casting methods. Except complicated, not or only with great effort pourable, geometries, the limits of manufacturability by casting are also achieved by the more and more use found non-pourable materials. It is therefore a trend towards increased use of manufacturing compressor and turbine wheels using machine tools.

In such conventional manufacturing processes, it is customary to produce the compressor or turbine wheel in two sub-processes. In the first sub-process, the outer contour and the part required for subsequent assembly in a compressor or in a turbine are manufactured. This sub-process is often performed on lathes. In the second sub-process, the pre-machined blank is placed on a milling machine to produce the geometries of the compressor or turbine wheels. For this purpose, clamping devices must be provided in the milling machine, which clamp the respective workpiece within the smallest tolerances and sufficiently stable for the machining. Furthermore, the tensioning devices must be designed so that it can be used simultaneously At least 5-axis milling process can come to a collision between the clamping device and the tool or machine. For this purpose, the clamping devices are usually designed so that the voltage of the workpiece is done on the already prefabricated mounting parts of the workpiece.

With the known machine tools, which are suitable for such a machining task, different (adapted depending on the workpiece type) methods are used. Most often, the half-finished blanks are either bolted directly to the machine on appropriately prepared devices or screwed outside the machine on a workpiece carrier (pallet) and then brought into the machines either directly into the processing room of the machine tool or in an automated magazine system. For this purpose, the workpiece usually has a through hole through which a threaded bolt of the pallet is performed. With a nut screwed onto the free end of the threaded bolt manually, the workpiece is then clamped in the axial direction against the pallet.

When using workpiece carriers, solutions are also known in which active clamping elements are provided on the workpiece carriers themselves, with which the workpieces are then clamped. In addition, solutions are known in which the workpieces are clamped on handling systems directly on a, usually hydraulically or pneumatically operated, clamping system in the processing room of the machine. These clamping systems are usually designed as jaw tensioners or as clamping rings for an external stress on the blank or as clamping mandrels for internal stresses in existing holes. The longitudinal axes of these bores always run in alignment with the axis of rotation of the finished compressor or turbine wheel.

All of these clamping methods require either a very high set-up effort and high device costs or cause very high system costs and high assembly costs when converting the system to new workpiece types.

As a consequence, this leads either to a high personnel expenditure for the Operation of the machines and plants or the plants and processes are only conditionally suitable for an economically feasible and to be operated automation of the manufacturing process. In particular, a conversion of the plant to new types of workpieces is usually only completely manually to accomplish and thus has high setup costs. The economics of such manufacturing processes is therefore not satisfactory.

The invention is therefore based on the object to improve the efficiency of the aforementioned manufacturing process.

This object is achieved in a method of the type mentioned in accordance with the invention that in a positioning step, the workpiece preferably outside the machine tool by means of a positioning aid or a positioning in a provided for a subsequent manufacturing process, with respect to a longitudinal axis of the workpiece carrier, or Workpiece, at least radially predetermined, position is positioned in the workpiece carrier, and the workpiece is fixed in a different from the positioning step clamping step within the machine tool relative to the workpiece carrier in the axial direction.

The object is also achieved by a compressor wheel or Turbinenradspannvorrichtung according to claim 15 and a use according to claim 16.

The invention thus provides for the workpieces to be arranged in at least two preparation or set-up steps in a workpiece carrier receptacle suitable for milling in a milling machine tool and to be fixed therein. In this case, in the temporally preceding positioning step, the workpiece in the workpiece carrier, at least in relation to the longitudinal axis or another reference or reference variable, is already aligned in a radially correct position (radially correct with respect to a predetermined longitudinal axis of the workpiece carrier). A fixation in the direction of the longitudinal axis of the workpiece carrier is not yet after completion of the positioning step and before the introduction of the assembled workpiece carrier in the machine tool in front. This independent process step "positioning step" should thus take place outside the machine tool, which advantageously reduces set-up times in the machine tool During this process, the machine tool can therefore continue to be in productive use for the machining of other workpieces Insertion of the workpiece in a certain rotational position in and with respect to the workpiece carrier, it is particularly suitable for automation, for example to be carried out by means of a handling device, such as a robot, without operator.The workpiece carrier in turn can then at a later At the same time, the insertion of the stocked workpiece carrier can preferably be effected by means of a handling device automated.

Only in the preferably subsequent clamping step, the workpieces are then fixed in the axial direction, wherein the clamping step is to take place in the machine tool. Also clamping direction can preferably be automated. This division into simple and successive partial process steps enables a higher degree of automation and in particular a reduction of unproductive non-productive times of the machine tools.

To carry out the clamping step, the workpiece carrier should thus preferably be brought to a position other than that radially prepositioned with respect to the longitudinal axis, but preferably otherwise loosely, than at the time of performing the positioning step, only here the clamping step being carried out. The clamping step following the positioning step can preferably be carried out at a different location than the positioning step, in particular in the machine tool itself. In connection with the invention, it is particularly preferred if for the clamping step in many milling machines anyway, existing, in connection with one piece Compressor or turbine wheels but not yet used, tailstock is used.

For this purpose, the workpiece carrier can first be inserted into a workpiece holder of the machine tool with the workpiece already aligned in the radial direction relative to the workpiece carrier. Subsequently, the tailstock is relatively moved to the workpiece in the axial direction and pressed a pressing element by means of the tailstock against the hitherto free end side of the workpiece. The workpiece is (only) thereby clamped in the machine tool between the tailstock and a contact surface of the workpiece carrier. The clamping force and frictional force generated in this case should be so great that the occurring axial and tangential machining forces can be absorbed by the frictional connection. The inventive method thus allows the supply of clamping elements - such as screws or nuts - and their assembly on the workpiece during the set-up process at least largely and preferably completely dispense. This also contributes to achieving an uncomplicated automation of the manufacturing process.

Tailstocks have been used above all in workpieces that have a great length in relation to their radial extension and therefore tend to buckling during machining. For compressor and

Turbine wheels, however, the ratios of the dimensions of these workpieces are usually exactly the opposite, that is. the components usually have a small axial length with respect to their radial extent. Another difference to previous applications is the fact that until now tailstocks have only supportive effect when holding the workpiece, in particular to

To reduce bending deflections of the workpieces. In connection with the

However, the invention should preferably tailstock as the only clamping or

Clamping element can be used with which a clamping force of the workpiece is produced on the workpiece carrier. Preferably, however, the tailstock as that

Be provided by the clamping element at least a majority of the

Clamping force is provided. At least for certain appropriate implementing Forms of the invention, the tailstock can also be used to generate the only forces that counteract the forces acting in the circumferential direction processing forces. Thus, according to the invention, a complete new use of tailstocks is proposed.

In connection with the invention, an embodiment of the positioning method step is particularly suitable, in which the positioning is achieved by means of a positive connection between the workpiece and the workpiece carrier. The positive connection should take place at least with respect to the longitudinal or rotational axis of the compressor or turbine wheel in the radial directions. In a preferred embodiment, for this purpose, at least one recess and a pin-like positioning means intended for engagement in the recess can be provided on the workpiece carrier and the respective workpiece. The recess may in this case be assigned to the workpiece on the basis of a simple manufacturability, and the positioning means suitable for this purpose in its geometric form may be assigned to the workpiece carrier. Of course, solutions with reverse assignment are also possible.

In a preferred embodiment, even alone by performing the positioning step, a backup of the workpiece against

Rotary movements in the circumferential direction of the workpiece can be achieved. An embodiment suitable for this purpose may provide a positioning means which is one of a

Circular shape has different cross-sectional shape. Of course, in these embodiments as well, a recess matching the positioning means in terms of size, geometric shape and manufacturing accuracy can be provided. In such embodiments according to the invention, at least a significant portion, preferably all, of the tangential and radial forces are removed by the positioning means via a positive connection with the workpiece.

The to achieve this effect hitherto often common active clamping elements for clamping the workpiece on the workpiece carrier are in connection with the

Invention not mandatory, whose function to achieve a clamping force can, at least primarily, especially by the machine tool side Tailstock is taken. The resulting also low device costs contribute to the particular economics of embodiments according to the invention.

In further embodiments, clamping mandrels can also be provided as positioning means, which bear against the wall surface of the recess in which the respective mandrel is located during an actuation.

Despite the complexity of the contours to be produced and even with a large number of workpieces differing in size and shape, the method according to the invention makes possible a so-called chaotic production. In such a variety of workpieces are manufactured on a machine tool in practically any order or short order resulting without retooling. To achieve the fastest possible change, several workpiece carriers can be stored in a workpiece magazine with workpieces already arranged thereon in a positioning step. Such a workpiece magazine can be assigned to one or more machine tools. Since, in connection with the invention, workpieces can be exchanged very quickly in comparison with the processing times usually required, only a small number of workpiece carriers per workpiece type are required. In a preferred embodiment, only two or a little more workpiece carriers are provided in a series production of compressor or turbine wheels for a machine tool or a workpiece magazine per workpiece type.

Further preferred embodiments of the invention will become apparent from the claims, the description and the drawings.

The invention will be explained in more detail with reference to embodiments shown purely schematically in the figures, in which:

Fig. 1 is a perspective view of a pallet for receiving a

Workpiece; FIG. 2 shows the pallet from FIG. 1 with a workpiece arranged thereon; FIG.

3 shows a machine tool which can be used in connection with the method according to the invention;

FIG. 4 shows a detailed view of FIG. 3, in which a workpiece attachment of the machine tool is in a receiving position; FIG.

Fig. 5 is an enlarged detail view of Fig. 4;

FIG. 6 shows the machine tool of FIG. 3, in which the workpiece holder and a tailstock are in a position intended for milling; FIG.

Fig. 7 is an enlarged detail view of Fig. 6;

8 shows a further enlarged detail illustration from FIG. 7.

In Fig. 1 a formed as a pallet 1 workpiece carrier is shown, as it can be used in connection with the present invention. This is a standard zero-span workpiece pallet, such as those offered by the companies Erowa AG, CH-6233 Büron, and System 3R AG, CH-9230 Flawil, under the names Erowa system ITS and Macro Magnum. Such pallets 1 are for high-precision yet automated arrangements in a machine tool 2, as shown for example in Fig. 3, is provided. Both the pallet 1 and the machine tool 2 each have an interface in order to be able to securely hold pallets 1 in the machine tool 2 in processing positions by means of a workpiece holder 3 of the machine tool 2. On a workpiece side of the pallet on the pallet a disc-shaped adjustment part 4 is fixed. The workpiece-specific fitting part 4 has for this purpose four holes 5, in which screws not shown are arranged and screwed into the pallet 1. Centrally or coaxially to a Längsr provided for feed movements and axis of rotation 6 is in the fitting part 4 to its free end in sections conically and in cross-section circular shaped receiving pin 7 is provided, which has the function of a positioning. The receiving pin 7 projects from a planar, or planar, abutment surface 4a of the fitting part 4 associated with the pallet 1, the longitudinal axis 6 of the receiving pin 7 being aligned perpendicular to the abutment surface 4a. The receiving pin 7 can be arranged in a not visible in the illustration of FIG. 1 recess of the contact surface or fixed, in particular screwed by a thread, be.

The pallet 1 has on its underside positioning and tensioning aids, such as, for example, not shown in detail clamping pin and an index pin, by which they can be clamped by a clamping device of a machine tool 2. The trained in per se known manner positioning and clamping tools are part of the interface, by means of which the clamping of the pallet is made in the machine tool and the pallet is secured against relative movement with respect to the workpiece holder.

The pallet 1 is provided for receiving already pre-machined workpieces 8. The pre-machining may in particular include a turning of a portion of a piece of bar stock. As a result of the turning operation, the workpiece may already have received an outer contour that corresponds to the outer contour of the component to be produced. Such a preprocessed workpiece 8 is shown arranged on a pallet 1 in FIG. 2.

The workpiece 8 has to be arranged on the pallet 1 on its side facing the workpiece carrier end face on an open recess, which may preferably be formed as a blind hole or as a through hole. A longitudinal axis the recess coincides with the later axis of rotation of the compressor or turbine wheel. The contour or geometric shape and size of the receiving pin is adapted to the bore or agrees that the workpiece 8 comes through an arrangement on the receiving pin 7 in abutment against the contact surface 4a and with respect to the longitudinal axis 6 of the receiving pin against radial Movements is secured.

FIGS. 3 to 7 show a machine tool 2 intended for milling workpieces, which is suitable for 5-axis simultaneous machining. The machine tool thus has at least five driven axles, which can be used all or in part by a control of the machine tool simultaneously. Here are two axes of movement on the workpiece holder 3 and three axes of motion on a tool carrier 9 divided. Such equipped with at least five driven axes (three translational and two axes of rotation) for generating feed movements machines are capable of the compressor and turbine wheels typically complicated geometric shapes, in particular sheet shapes to be able to manufacture. Such a machine tool, for example, offered by the applicant under the name STC 100 and used in conjunction with other clamping methods.

The tool carrier 9 of the machine tool 2 is provided for receiving a milling tool, wherein a rotational axis 10 of the milling tool is aligned in a neutral position of the tool carrier 9 orthogonal to a workpiece axis of the workpiece holder 3 (FIGS. 7 and 8).

The workpiece holder 3 is intended to receive one of the pallets 1 with a workpiece 8 arranged thereon, wherein the workpiece holder 3 detects the pallet via its interface. The workpiece holder 3 also has a known tailstock 10, which can be delivered to the workpiece. A universal stop element 12 of the tailstock 10 can also be brought by a pivoting movement into a position in which the stop element 12th aligned with the bore of the workpiece 8. By means of a hydraulically or pneumatically actuated cylinder, for example, or by a spindle drive, the conically shaped stop element 12 can then be inserted into the bore at the free end face 8a of the workpiece and brought into abutment against the hitherto free end face of the workpiece. The workpiece 8 is thus clamped between the adjustment part 4 and the stopper member 12 and thus fixed against axial movement. However, the clamping force should in this case be dimensioned so that the forces occurring during milling machining in the circumferential direction of the workpiece due to frictions are also included.

In the position shown in FIGS. 3 to 5, the workpiece holder 3 is in a receiving position, in which the pallet workpiece carrier can be received in a horizontal orientation together with a workpiece prepositioned thereon.

In a first variant of the method according to the invention, the pallet 1 with the fitting part 4 arranged thereon can already be located in the workpiece holder 3 of the machine tool and be clamped there. For receiving a workpiece 8, the pallet 1 is brought in the machine tool in the horizontal position shown in Fig. 3 and 5. In this position, the receiving pin 7 is aligned at least substantially vertically.

Now one of the already prepared by turning workpieces 8 can be arranged with its recess or bore on the receiving pin 7 and thus loosely prepositioned. This arrangement can be advantageously carried out by an automatic handling machine, which removes such a workpiece from a workpiece storage and touches the receiving pin 7. The conical shape of the receiving pin 7 makes it possible to compensate for possible positioning inaccuracies of the handling machine and always to achieve an exact positioning of the workpieces 8 on the pallet 1. Subsequently, the tailstock 10 can be moved toward the workpiece 8, the stop element 12 pivoted to the free end face 8a of the workpiece and inserted into the recess. Due to the positive connection with the receiving pin 7 (positioning) and a resulting by a sufficiently large clamping force frictional engagement the workpiece for milling operations is held securely and with high precision in the machine tool and is securely clamped therein. In this setting, the workpiece can be finished. After completion of the processing, the workpiece holder 3 is again transferred to the horizontal position of Fig. 3, and the finished compressor wheel are removed manually or by means of the handling machine.

The invention allows for a variety of variations, not all of which can be discussed. For example, in a preferred variant of the method according to the invention, provision can be made, for example, for the workpieces to be already inserted into a pallet 1 outside the machine tool, preferably automatically. The positioning step carried out in this case can essentially correspond to the positioning step carried out in the machine tool. The respective workpiece carrier can be arranged for this purpose at a set-up point, not shown, on which the workpiece carrier is equipped with a workpiece.

Subsequently, the respective pallet can be transferred to a not-shown workpiece magazine of the respective machine tool, for example by means of an automatic handling machine. Again, in particular due to acting as an insertion aid receiving pin 7 and not required at this time voltage or clamping of the workpiece in the axial direction - reliable and yet with little technical effort, an automated setup process can be achieved. The pallets can be brought to the processing position in the machine tool in a certain time determined by a parent control computer manufacturing, in which connection their workpieces are clamped with the tailstock in the axial direction against the pallet. In this embodiment, at least two pallets, each adapted to the workpiece type fitting parts should be provided for each tool type for meaningful automation and uninterrupted production per machine tool. The pallets 1 are stored in a pallet magazine and can be equipped there by a structurally simple designed handling machine with workpieces. In this case, the corresponding workpiece carrier is preferably positioned at a transfer point only shortly before the loading of the workpiece into the machine tool. This has the advantage that the system thus linked allows a true chaotic production even without complex host computer and / or production planning system.

LIST OF REFERENCE NUMBERS

Pallet 10 tailstock

Machine tool 12 stop element

Workpiece holder

Adjustment part a contact surface

drilling

longitudinal axis

recording pen

Workpiece a free end face

tool carrier

Claims

claims

A milling method for machining a workpiece of a compressor or turbine wheel in a machine tool, in which using a rotating milling tool on the workpiece contour machining takes place provided for flow line sections of the compressor or turbine wheel, wherein the workpiece is received in a workpiece carrier and relative to this is fixed for manufacturing, characterized in that in a positioning step, the workpiece (8) by means of a positioning in a provided for a subsequent manufacturing process, with respect to a longitudinal axis (6) of the workpiece carrier at least radially predetermined position in the workpiece carrier is positioned, and the workpiece is fixed relative to the workpiece carrier in an axial direction in a clamping step different from the positioning step within the machine tool.

2. Milling method according to claim 1, characterized in that the positioning step is performed outside the machine tool.

3. Milling method according to claim 1 or 2, characterized in that the clamping step follows the positioning step in time.

4. Milling method according to at least one of the preceding claims, characterized in that in the positioning step by means of a positive connection with the workpiece carrier positioning of the workpiece (8) is generated in the radial position.

5. Milling method according to at least one of the preceding claims, characterized in that for carrying out the positioning and clamping step in the recording of the workpiece (8) in the workpiece carrier in a for Milling processing suitable arrangement exclusively means are used, which were either already arranged before the supply of the workpiece on the workpiece carrier or on the machine tool (2) are installed.

6. milling method according to at least one of the preceding claims, characterized in that the workpiece carrier and the workpiece have a recess and a pin-like positioning aid for engaging in the recess, wherein the recess is arranged in alignment with respect to the axis of rotation of the compressor or turbine wheel.

7. milling method according to at least one of the preceding claims, characterized in that is arranged to carry out the clamping step of the workpiece carrier with the prepositioned workpiece at a different location than that point at which the positioning step is performed.

8. Milling method according to at least one of the preceding claims, characterized in that the workpiece carrier together with the workpiece for

Performing the clamping step is arranged in a milling machine tool.

9. milling method according to claim 8, characterized in that the workpiece (8) by means of a tailstock (10) in the machine tool (2) is tensioned.

10. Milling method according to claim 9, characterized in that with the tailstock (10) a clamping force is exerted, whose direction with the longitudinal axis (6) is at least substantially aligned or at least parallel to this.

11. Milling method according to at least one of the preceding claims, characterized in that the workpiece carrier provided on the workpiece side with an adapted to the respective workpiece type replaceable adapter part and machine tool side is designed to be compatible with a quick release system.

12. A method for manufacturing a plurality of compressor or turbine wheels, in particular different compressor or turbine wheels, in a milling machine tool, characterized in that each of the for the

Production of compressor or turbine wheels provided workpieces arranged according to at least one of claims 1 to 11 in a machine tool and is subsequently milled.

13. The method according to claim 12, characterized by a workpiece carrier buffer are placed in the assembled workpiece carrier.

14. The method according to claim 12 or 13, characterized in that the respective workpiece is removed together with the workpiece carrier from the machine tool, the workpiece is taken from the workpiece carrier and subsequently the workpiece carrier outside the machine tool is equipped with one of the other workpieces.

15. Verdichterrad- or Turbinenradspannvorrichtung for arranging a provided for manufacturing a Verdichterrad- or turbine wheel workpiece in a Fräswerkzeugmaschine having a workpiece carrier, which is in the Fräswerkzeugmaschine and executable and on which the workpiece is arranged in a suitable manner for milling machining characterized by a positioning means, with respect to a longitudinal axis (6) of the workpiece carrier for milling machining a radial alignment of the workpiece (8) can be generated and by a tailstock (10), for performing milling operations on the workpiece (8) in Plant is brought against the workpiece to exert on the workpiece an axial clamping force.

16. Use of a tailstock of a tool provided for milling machine tool for arranging the tailstock against an end face of a Workpiece, characterized in that the tailstock (10) is provided for clamping a compressor or turbine wheel during milling of flow-conducting elements of the compressor or turbine wheel in a machine tool.