DE102018212771A1 - Workpiece retainer - Google Patents

Abstract

Disclosed is workpiece holding device (100) for holding a workpiece (4) in a processing system, the workpiece (4) undergoing thermal expansion and / or contraction in the workpiece holding device (100), and wherein the workpiece holding device (100) has at least two holding devices, which are designed to lie against the workpiece (4) at at least one location and to hold the workpiece (4) at a predetermined position, at least one of the holding devices (23; 33; 43) and at least one movable element (26; 36; 46) or is itself designed as a movable element (26; 36; 46) which is biased towards the workpiece (4) such that the movement of the movable element (26; 36; 46) of thermal expansion and / or Contraction follows.

Description

The present invention relates to a workpiece holding device for holding a workpiece in a machining system in which the workpiece undergoes thermal expansion and / or contraction.

In order to thermally treat workpieces, for example to heat or quench them, the workpieces often have to be arranged safely, quickly and precisely in relation to the treatment system. For this purpose, conventional clamping devices can be used, such as so-called three- or four-jaw chucks, which have three or four clamping jaws, which are grouped circumferentially around the tool to be held, and in which the workpiece is clamped and held before the workpiece is treated.

A disadvantage of this device, however, is that the thermal expansion or contraction that the workpiece undergoes during the thermal treatment can result in the jaws no longer being in contact with the workpiece and thus not being able to hold it sufficiently, or an excessive force exerted by the Baking leads to deformation of the workpiece.

The object of the present invention is therefore to provide a workpiece holding device for a workpiece to be thermally treated, which ensures a secure and firm positioning of the workpiece even during thermal expansion and / or contraction of the workpiece and reliably prevents deformation of the workpiece.

This object is achieved by a workpiece holder according to claim 1.

A workpiece pick-up device for picking up a workpiece in a processing system is presented below, the workpiece undergoing thermal expansion and / or contraction in the workpiece pick-up device. Furthermore, the workpiece holding device has at least two holding devices which are designed to rest against the workpiece in at least one position and to hold the workpiece in a predetermined position. In order to nevertheless securely and precisely clamp the workpiece in the event of contraction / expansion of the thermally treated workpiece, at least one of the holding devices has a movable element or is itself designed as a movable element which is preloaded in the direction of the workpiece such that the movement of the movable element follows the thermal expansion and / or contraction of the workpiece.

It is particularly advantageous if, in the case of a workpiece to be treated essentially in a circular manner, the movable element is movable both radially and tangentially. As a result, not only can thermal expansions / contractions be recorded during the thermal processing of the workpiece, but also manufacturing tolerances, such as a certain ovality of the workpiece during clamping, can be compensated for. Such an adaptation is particularly advantageous for workpieces with a closed curve, such as elements of a slide or roller bearing, bearing rings, gears, bolts, sleeves, washers, etc. Usually, especially in the case of radial workpieces, the holding devices can be moved radially, for example by means of an electrical or hydraulic drive, and are moved in the direction of the workpiece before the thermal treatment until the latter is firmly held between the holding devices. In order to be able to compensate for manufacturing tolerances, one or more of the holding devices can also be mounted so as to be eccentrically displaceable. A further embodiment provides that holding devices which hold a workpiece radially can also follow the thermal expansion of the workpiece in the axial direction.

Accordingly, it is particularly advantageous if the movable element is designed as an eccentrically mounted element, since the eccentric mounting provides both radial and tangential mobility of the element.

According to a further advantageous exemplary embodiment, the movable element is preloaded by means of a mechanical preload element. Mechanical prestressing elements can be easily installed and do not require any additional control, which overall makes the workpiece holding device easy to operate and inexpensive.

The mechanical prestressing element can be at least one spring element which interacts with the movable element and prestresses the movable element in the direction of the workpiece. The spring element can be, for example, a wire spring, a plate spring, coil spring and / or leaf spring, but plastics such as an elastomer can also be used.

Furthermore, it is possible for the mechanical pretension to be designed as a friction device which only allows the movable element to move after a certain coefficient of friction has been exceeded. This can be based on the pressure that exerts an expanding / contracting workpiece during thermal processing on the movable element, movement of the movable element only after a certain threshold value has been exceeded.

Instead of a mechanical pretensioning device, the pretensioning of the movable element can also be carried out by means of a device which can be controlled by a control unit. The pre-tensioning can take place, for example, via a hydraulic, pneumatic and / or electrically operated element that follows the thermal expansion / contraction. For example, the movable element can be an oil or gas operated pressure damper.

With bias voltages controlled by a control unit, a particularly precise tracking of the contraction / expansion is already possible. In order to increase the accuracy and sensitivity of the tracking even more, the holding device or the movable element can be equipped with at least one force measuring device which interacts with the control device and is designed to apply a force with which the movable element bears against the workpiece measure up. Depending on this measured force, the control device can then control the movable element in order to exert a uniform force on the workpiece during the treatment. The force measuring device also enables adaptation to manufacturing inaccuracies when the workpiece is clamped in the workpiece holding device, so that even when the workpiece is clamped, a uniform pressure is achieved at the various holding devices.

Alternatively or additionally, the control unit can of course also control the movable element based on a previously calculated value table in order to be able to compensate for the calculated and expected expansions / contractions. The value table can be determined empirically and / or stored in a database that is accessible to the control unit. This means that the database can either be stored internally in the control unit itself or can be present in an external database.

In a preferred embodiment, the control unit can also additionally react to forces which act on the workpiece through the machining system and, depending on the forces measured or anticipatively, increase or decrease a preload in a targeted manner. For example, in anticipation of electrical, mechanical or magnetic forces, which act temporarily on the workpiece, the current preload can be increased or decreased in a controlled manner by a preload value. This temporary superimposition of the bias voltage regulated due to the thermal expansion with a controlled offset can preferably be switched on and off. Here, too, the movable element can be controlled on the basis of a table of values in order to be able to reliably absorb and / or compensate the calculated and expected forces on the workpiece. Furthermore, the control unit can be designed in such a way that it can be switched from a regulated operation, in which preload forces are set based on measured values of the load cell, to a controlled operation, in which preload forces are set based on a table of values, and accordingly from the control operation to Regular operation can be switched back. For example, during a thermal expansion it is possible to regulate the preload to a certain preload pressure as far as possible or entirely, and during a subsequent thermal contraction, such as rapid quenching, to increase the preload pressure to a fixed value.

The table of values or a setting of the movable element can depend on the values of the table of values, in particular on measured and / or calculated temperature changes that are to be expected in the workpiece during the machining process.

According to a further advantageous exemplary embodiment, at least one of the holding devices is designed as an eccentrically mounted clamping cylinder or holding jaw. The clamping cylinder and / or the receiving jaw can itself be designed as movable elements. Alternatively or additionally, however, it is also possible that they each have at least one further movable element. Furthermore, corrugations or coatings made of hard particles, for example, can advantageously be applied to this clamping jaw or the clamping cylinder, which facilitate contact with the workpiece and ensure a firm hold of the workpiece in the workpiece receiving device.

The holding devices and / or movable elements of the tool holding device can be controlled individually or together.

So that the holding devices and / or movable elements do not themselves experience excessive thermal expansion / contraction, they are advantageously made from a temperature-resistant material, such as ceramic, polymer ceramic, aluminum silicate, stone, fireclay or from special steel alloys.

• - Einlegen des Werkstücks in die Werkstückaufnahmevorrichtung;
• - Radiales Verfahren der Haltevorrichtung, bis jede Haltevorrichtung das Werkstück kontaktiert;
• - Feinjustieren in radialer und/oder tangentialer Richtung der Haltevorrichtung über die beweglichen Elemente, sodass jede Haltevorrichtung und/oder jedes bewegliche Element mit einemvorbestimmbaren, vorzugsweise gleich hohem Haltedruck an dem Werkstück anliegt;
• - Starten der thermischen Behandlung;
• - Aktives oder passives Nachjustieren des beweglichen Elements/der Haltevorrichtung während der thermischen Behandlung, sodass der vorbestimmte Haltedruck mit dem die Haltevorrichtung und/oder das bewegliche Element an dem Werkstück anliegt, während vorbestimmbaren Zeitabschnitten oder der gesamten thermischen Behandlung konstant bleibt.

Another aspect of the present invention relates to a method for the thermal treatment of a workpiece, which is accommodated in a workpiece receiving device as described above, the method comprising the following steps:

• - Inserting the workpiece in the workpiece holder;
• - Radial movement of the holding device until each holding device contacts the workpiece;
• - Fine adjustment in the radial and / or tangential direction of the holding device via the movable elements, so that each holding device and / or each movable element rests on the workpiece with a predetermined, preferably equally high, holding pressure;
• - starting the thermal treatment;
• - Active or passive readjustment of the movable element / the holding device during the thermal treatment, so that the predetermined holding pressure with which the holding device and / or the movable element is applied to the workpiece remains constant during predeterminable periods of time or the entire thermal treatment.

Deformations during the thermal treatment of the workpiece can thereby be avoided.

Further advantages and advantageous embodiments are specified in the description, the drawings and the claims. In particular, the combinations of the features specified in the description and in the drawings are purely exemplary, so that the features can also be present individually or in a different combination.

The invention is to be described in more detail below with reference to exemplary embodiments illustrated in the drawings. The exemplary embodiments and the combinations shown in the exemplary embodiments are purely exemplary and are not intended to define the scope of the invention. This is defined solely by the pending claims.

• 1: eine schematische Draufsicht und Schnittansicht eines ersten Ausführungsbeispiels;
• 2: eine schematische Draufsicht und Schnittansicht eines zweiten Ausführungsbeispiels; und
• 3: schematische Schnittansichten durch bevorzugte Ausführungsbeispiele einer Haltevorrichtung;

Show it:

• 1 : a schematic top view and sectional view of a first embodiment;
• 2 : a schematic top view and sectional view of a second embodiment; and
• 3 : schematic sectional views through preferred embodiments of a holding device;

In the following, identical or functionally equivalent elements are identified with the same reference symbols.

1 shows in partial figure a a plan view and in partial figure b a partial sectional view through a workpiece holder 100 , In the in 1 The embodiment shown is the workpiece holder 100 a rotating table 2 on which a bearing ring 4 stored and rotated during a thermal treatment. Around the bearing ring 4 The workpiece holder is to be securely attached to the rotary table 100 in the illustrated embodiment with three holding devices, 20 . 30 and 40 equipped, which are each designed differently. The different configurations show 20 . 30 and 40 Various exemplary embodiments of the holding devices for the sake of simplicity. Usually, however, the holding devices on the rotary table are identical. However, it is also possible for two of the holding devices to be adjustable only in the radial direction, while the third holding device is adjustable radially and tangentially. This enables manufacturing inaccuracies, in particular ovality of the workpiece, to be compensated for.

As from the drawings 1a and 1b emerges are the holding devices 20 . 30 . 40 on the rotary table 2 in each case by means of a slide which can be moved in the radial direction 21 . 31 . 41 attached, the sled 21 . 31 . 41 one edition each 22 . 32 . 42 on which the workpiece 4 is on the hook. The requirements are preferably 22 . 32 . 42 on the sledge 21 . 31 . 41 interchangeably arranged to optimally select the support for different workpieces. Furthermore, the holding elements 20 . 30 . 40 one clamping jaw or one clamping cylinder each 23 . 33 . 43 on that the workpiece 4 fix between themselves. Here, as with the holding device 20 shown the holding element 23 firmly on the sled 21 be arranged. However, it is also possible that, as with the holding devices 30 . 40 shown the holding elements 33 . 43 themselves are eccentrically mounted and thus provide radial and tangential displaceability so that they can be picked up when the workpiece is picked up 4 on the rotary table 2 to be able to compensate for any manufacturing inaccuracies.

In the design of the holding device 30 is the clamping cylinder 33 eccentric on the sled 31 via an eccentrically arranged bracket 34 attached so that the cylinder 33 around the bracket 34 can turn.

In the embodiment of the holding device 40 against it are tension cylinders 43-1 . 43-2 provided, which in turn on an eccentrically mounted plate 45 are arranged. The plate 45 is in turn rotatable on the bracket 44 attached, so that here too a radial and tangential movement and thus an adjustment of the jaws 43-1 ; 43-2 possible manufacturing inaccuracies.

As in particular the sectional view of 1b can also be seen on the clamping cylinder 23 . 33 . 43 a moving element 26 . 36 . 46 arranged so that the holding device or the movable element 26 . 36 . 46 following thermal expansion / contraction of the workpiece. This moving element 26 . 36 . 46 can for example by means of a mechanical biasing element, for example in the form of a spring or a friction device, the expansion / contraction of the workpiece 4 follow. Of course, the movable element 26 . 36 . 46 also via a control unit 50 can be controlled to mechanically, hydraulically or pneumatically follow the contraction / expansion of the workpiece. A pressure measuring device can be used, in particular, in the controlled version 28 . 38 or 48 be provided, the force with which the workpiece on the movable element 26 . 36 . 46 presses or directly on the clamping cylinder 23 . 33 . 43 acts to be measured. This pressure measuring device 28 . 38 . 48 can either, as in the cut of the 1b shown, directly with the movable element 26 . 36 . 46 interact, but it is also possible that the pressure measuring device, as in the supervision of 1 shown, directly with the clamping cylinder 23 . 33 . 43 interacts.

The pressure measuring device 28 . 38 . 48 can measure the measured force and thus also the expansion / contraction of the workpiece during thermal treatment to the control unit 50 transfer. The transmission can, as shown schematically, for example wirelessly to / from a receiver / transmitter 51 in the control unit. The control unit 50 in turn controls the contact force of the holding element and / or the movable element, for example via a radial movement of the slide 21 . 31 . 41 , or by moving the movable element radially or tangentially 26 . 36 . 46 , The control unit 50 itself can directly on the workpiece holder 100 be arranged, but it is also possible for the control unit 50 and also to arrange an evaluation unit of the pressure measurement at a remote location.

In addition to direct measurement using a pressure measuring device, it is also possible for the control unit 50 controls the movement of the movable element and / or the holding device based on table values which are based, for example, on empirically detected temperature changes.

It is also possible that there is a temperature change in the workpiece 4 is measured during the heat treatment, for example by infrared measurement, and then the holding devices are controlled according to the values stored in the storage device.

2 also shows a workpiece holder 100 that differ from the in 1 discussed workpiece holder 100 only differs in that the workpiece 4 not on its outer circumference 4-1 but on its inner circumference 4-2 from the holding devices 20 . 30 . 40 is held. A preferred embodiment provides that the holding devices 20 . 30 . 40 on the rotary table 2 can be arranged such that both an external voltage according to 1 as well as an internal tension according to 2 is possible.

Instead of a rotary table 2 it is of course also possible to equip tool holding devices for straight workpieces or workpieces with any geometry as described above.

For a particularly good circulation of the clamping cylinders 23 . 33 . 43 and / or the movable elements on the workpiece, the clamping cylinders or clamping jaws, such as in 3 shown, certain surface structures in the form of corrugations, see for example 3a and 3b , Have, which enables a particularly good holding of the workpiece on the clamping cylinders. It is also possible, as in 3c shown that a friction layer of hard particles is applied to the clamping cylinder, which also enables a particularly good mounting on the workpiece.

These surface structures can at the same time be designed as movable elements which follow an expansion / contraction during thermal treatment of the bearing ring.

It is also possible that the coating, such as in the 3c shown, piezo elements are introduced, which generate a current when pressurized, which in turn is processed as a measured variable by a control device and is then controlled accordingly by the holding device or the movable element.

Overall, the novel workpiece holding device can be used to adapt to a thermally induced expansion / contraction of the workpiece, whereby deformations of the workpiece into the workpiece holding device during clamping and during thermal treatment can be avoided.

LIST OF REFERENCE NUMBERS

1

Workpiece retainer

2

rotary table

4

workpiece

20, 30, 40

holder

21,31,41

carriage

22, 32, 42

Support for workpiece

23, 33, 43

clamping cylinder

24, 34, 44

Bearing tension cylinder

26, 36, 46

movable element

28, 38, 48

Pressure measuring device

45

eccentrically mounted plate

50

control unit

51

wireless receiver / transmitter

Claims (10)

Workpiece holding device (100) for holding a workpiece (4) in a machining system, the workpiece (4) experiencing thermal expansion and / or contraction in the workpiece holding device (100), and wherein the workpiece holding device (100) has at least two holding devices (23; 33 ; 43) which are designed to lie against the workpiece (4) at at least one location and to hold the workpiece (4) at a predetermined position, characterized in that at least one of the holding devices (23; 33; 43 ) has at least one movable element (26; 36; 46) or is itself designed as a movable element (26; 36; 46) which is pretensioned in the direction of the workpiece (4) such that the movement of the movable element (26; 36; 46) follows the thermal expansion and / or contraction. Workpiece holding device (100) after Claim 1 , wherein the at least one movable element (26; 36; 46) is movable both radially and tangentially. Workpiece holding device (100) after Claim 1 or 2 , wherein at least one holding device (23; 33; 43) is designed as the at least one movable element (26; 36; 46) in the form of an eccentrically mounted clamping cylinder. Workpiece receiving device (100) according to one of the preceding claims, wherein the pretensioning of the at least one movable element (26; 36; 46) takes place by means of a mechanical pretensioning element. Workpiece holding device (100) after Claim 4 , wherein the mechanical biasing element is at least one spring element and the movable element (26; 36; 46) cooperates with the spring element which biases the movable element (26; 36; 46) towards the workpiece (4); and / or wherein the mechanical pretensioning element is a friction device which only allows the movable element (26; 36; 46) to move after a certain coefficient of friction has been exceeded. Workpiece receiving device (100) according to one of the preceding claims, wherein the bias of the at least one movable element (26; 36; 46) is controllable by means of a control device (50), wherein preferably the control device (50) is designed to control the movement of the movable element (26; 36; 46) to control. Workpiece holding device (100) after Claim 6 At least one force measuring device (28; 38; 48) is provided on at least one of the holding devices (23; 33; 43) and / or a movable element (26; 36; 46), which cooperates with the control device (50) and for this purpose is designed to measure a force with which the holding device (23; 33; 43) and / or the movable element (26; 36; 46) is applied to the workpiece (4). Workpiece holding device (100) after Claim 6 or 7 wherein the controller (50) controls movement of the movable member (26; 36; 46) based on a measured or calculated temperature change. Workpiece receiving device (100) according to one of the preceding claims, wherein the movable element (26; 36; 46) is a receiving jaw and / or a clamping cylinder. A method for the thermal treatment of a workpiece (4) which is accommodated in a workpiece receiving device (100) according to one of the preceding claims, the method comprising the following steps: - inserting the workpiece (4) into the workpiece receiving device (100); - Radially moving the holding device (23; 33; 43) until each holding device (23; 33; 43) contacts the workpiece (4); - Fine adjustment in the radial and / or tangential direction of the holding devices (23; 33; 43) and / or the movable element (26; 36; 46) e, so that each holding device (23; 33; 43) and / or each movable element ( 26; 36; 46) with a predeterminable, preferably equally high holding pressure on the workpiece (4); - starting the thermal treatment; - Active or passive readjustment of the at least one movable element (26; 36; 46) and / or at least one holding device (23; 33; 43) during the thermal treatment, so that the predetermined holding pressure with which the holding device (23; 33; 43) and / or the movable element (26; 36; 46) bears against the workpiece (4) while predeterminable time periods or the entire thermal treatment remains constant.

Images