The invention relates generally to forming and repair of workpieces in a manufacturing environment and, more specifically, to forming and repair of high precision metal parts.
Various types of metal structures, used in a range of commercial, industrial and consumer applications are made by deformation under an applied load. Certain such structures may be repaired in similar remanufacturing operations. For example, engine blades in aircraft engines are manufactured to high and stringent tolerances to ensure high quality performance of the engine. Engine blades may be deformed as a result of loading such as, thermal stress, external collision and so forth. Such deformation in the blades may include for example, bending and twisting in operations similar to forging or other plastic deformation processes.
As a result, various types of precision forming and repair techniques have been developed to make and repair these workpieces with a high level of accuracy. In some conventional practices, a workpiece blank is formed, and the blank is manually or semiautomatically bent or twisted. Such operations may be repeated both for original manufacture and to repair the workpiece. Such techniques are time consuming and require highly skilled workers to achieve the desired level of accuracy. Certain other methods employ pressing the workpiece in a warm die and holding it for a sufficiently long time to achieve the desired shape. Such techniques may result in having a spring back effect in the workpiece that limits the accuracy of the repair of the workpiece.
In certain other conventional repair and forming techniques, for example in sheet metal forming, electromagnetic pressure forming has been employed for repairing and forming a workpiece. Such processes generally rapidly accelerate a workpiece blank under the influence of a strong electromagnetic field. The utility of electromagnetic pressure forming for workpiece manufacture and repair is typically limited to high conductivity materials because the forming efficiency for the low conductivity metals is very low owing to the inability to accelerate such materials via the field. Certain other techniques use integration of low rate and high rate forming methods but such techniques require manufacturing of dies for each production cycle, as the dies must necessarily conform to the shape of the workpiece and therefore the same die cannot be used for different workpieces.
Therefore, it would be desirable to develop a technique that enables a workpiece to be formed and repaired in a more efficient manner. More specifically, it would be desirable to have an efficient forming and repair technique that permit precision workpiece forming and repair while having adaptability for a wider range of workpieces.
Briefly, in accordance with one aspect of the present invention a hybrid metal forming system includes a die cavity defined by a first die and a second die and a press adapted to apply a static pressure over the first die to deform a workpiece against the second die. The hybrid forming system also includes a dynamic loading system coupled to and positioned between, the press and the die cavity.
In accordance with another aspect of the present invention a method of forming a workpiece comprises moving a die to deform a workpiece under a static load and indirectly dynamically loading the die against the workpiece while maintaining the static load.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
As discussed in detail below, the embodiments of the present technique employ an integration of a static load and a dynamic load for precision forming and repair of a workpiece in a manufacturing environment. It should be noted here that the static load may include a slow time varying load as compared to the dynamic load. The integration of the static load and the dynamic load includes loading a material of the workpiece in a combined environment of elastic-plastic and hyperplastic regimes that will be discussed in detail hereinafter. In particular, the slow time varying load may serve effectively as a static load based upon the strain rate or deformation regime implied by the rate of change of the loading.
Referring now to
In addition, a press controller 32 is coupled to the press 12 and a dynamic unit controller 34 is coupled to the dynamic loading system 14 for controlling the operation of the press 12 and the dynamic loading system 14, respectively. Further, a power source 38 is provided for operation of each of the controllers as listed above. In practice, the different loading systems may employ different power supplies based upon the needs of the loading systems. In the illustrated embodiment, the power supply 38 for the dynamic loading system 34 comprises a high voltage capacitor bank. A displacement sensing and control system 40 is coupled to the forming coil 24 and the driver plate 26 to maintain a desired spacing between the first die 18 and the second die 20. Moreover, a heating unit 42 may be coupled to the die cavity 22 for heating at least one of the first die 18 and the second die 20. Alternatively, the heating unit 42 may be employed for heating the workpiece 16 to enhance a formability of the workpiece 16. Further, an operator workstation 44 may be coupled to the press controller 32, the dynamic unit controller 34 and the coordinated controller 36 to faciliate controlling the operation of the press controller 32, the dynamic unit controller 34 and the coordinated controller 36 respectively.
In operation, the workpiece 16 is placed in the die cavity 22 and a static pressure is applied to the first die 18 via the press 12 to deform the workpiece 16 against the second die 20. In one embodiment, the press 12 comprises a mechanical press. In another embodiment, the press 12 comprises a hydraulic press. Next, a dynamic load is applied to the die cavity 22 via the dynamic loading system 14. In this embodiment, the dynamic loading system 14 comprises an electromagnetic pressure unit, though various other systems to perform a similar function may be used. Examples of such systems include an air driven impact pressing system, an impact pressing system driven by a spring, a hydraulic impact pressing system, an explosive charge driven system, and so forth.
In general, the forming coil 24 is coupled to the first die 18 to facilitate an indirect loading of the workpiece 16 via the dynamic loading system 14. Typically, the forming coil 24 and the driver plate 26 are positioned to maintain an initial spacing between the forming coil 24 and the driver plate 26. The spacing between the forming coil 24 and the driver plate 26 may change after the dynamic load is applied to the die cavity 22 via the dynamic loading system 14. The spacing between the forming coil 24 and the driver plate 26 may be adjusted via the displacement sensing and control system 40 by sensing a position of the driver plate 26 and the forming coil 24 as will be described in detail below.
In the illustrated embodiment, the dynamic loading system 14 indirectly applies a dynamic load to the die cavity 22 against the workpiece 16 through the forming coil 24 and the driver plate 26. In this embodiment, the dynamic load is an electromagnetic pressure applied via the dynamic loading system 14. The dynamic loading system 14 discharges energy to generate a discharging current in the forming coil 24 and an induced current in the driver plate 26. The discharging current in the forming coil 24 and the induced current in the driver plate 26 repel each other. As a result, the driver plate 26, stress enhancer unit 28 and the first die 18 are accelerated towards the workpiece 16 to load the workpiece 16 dynamically. As will be appreciated by those skilled in the art a plurality of electromagnetic pulses may be applied to the die in a similar manner as described above to achieve a desired size and shape of the workpiece.
Further, on completion of a cycle of the repair or forming process as described above, variations in dimensions of the formed/repaired workpiece 16 are measured and these variations in dimensions are verified with respect to desired tolerances for the dimensions. If the variations in dimensions of the formed/repaired workpiece 16 are within the desired tolerances, the workpiece 16 may be removed from the removing unit 30. Alternatively, if the measured variations in dimensions are outside range of the desired tolerances, then the dynamic load may be reapplied to the workpiece 16 to achieve the desired dimensions of the workpiece 16.
The technique illustrated and described above employs an integration of the static load and the dynamic load for the workpiece forming and repair process. As can be seen above, the application of the dynamic load to the workpiece 16 is performed in an indirect manner via application of the dynamic load to the first die 18 and the second die 20 and subsequently transfer of this dynamic load to the workpiece 16. The indirect application of the dynamic load enables the first die 18 and the second die 20 to be used for forming and repair of workpieces 16 of different size and shapes without replacing the first die 18 and the second die 20 for each cycle. Further, because the dynamic loading unit 14 is isolated from the die cavity 22, the same dynamic loading unit 14 with the forming coil 24 and the driver plate 26 may be used for application of dynamic load to different parts by means of different dies.
Moreover, the heating unit 42 may be employed to heat the first die 18, the second die 20 and/or the workpiece 16 that enhances the formability of the workpiece 16. The heating unit 42 may be operable to apply a thermal environment to the first die 18, the second die, 20 and the workpiece 16 independently in isolation with the dynamic loading system 14. As a result, the dynamic loading system 14 may be operated at a room temperature and the first die 18, the second die 20 and the workpiece 16 may be operated in an elevated temperature environment. The heating of the first die 18, the second die 20 and the workpiece 16 may be done by placing the workpiece 16 and the first and second dies 18 and 20 in a heated furnace. Alternatively, an electrical heating unit may be coupled to the die cavity 22 that may be employed for heating the first and second dies 18 and 20.
In the illustrated embodiment, the operation of the press 12 is controlled via the press controller 32 that may control the operational parameters of the press 12, such as, the static load, time for loading the workpiece 16 via the press 12 and so forth. Further, the dynamic load unit 14 is coupled to the dynamic unit controller 34 to control the operation of the dynamic load unit 14. Such control may include controlling the spacing between the forming coil 24 and the driver plate 26, controlling the dynamic load applied via the dynamic load unit 14 and so forth. In addition, the coordination of operation of the press 12 and the dynamic load unit 14 may be controlled via the coordinated controller 36. For example, the coordinate controller 36 may control the cycle time of operation of the press 12 and the dynamic load unit 14 for the forming and repair process.
It should be noted that after completion of a cycle of application of the dynamic load, the driver plate 26 and the spacer 52 move in a downward direction that changes the spacing between the forming coil 24 and the driver plate 26. Subsequently, the load application structure 46 with the spring assembly 48 applies a load to the forming coil 24 towards the spacer 52 to adjust the spacing to the optimum distance before the application of next cycle of the dynamic load. In practice, the gap may be effectively regulated by means of the spacer 52, or a series of such spacers. Thus, the technique illustrated above may be employed to maintain the optimum distance between the forming coil 24 and the driver plate 26 for each cycle of dynamic load operation in the forming and repair process of the workpiece 16. It should be noted that guides (not shown) may be used to constrain movement of the driver plate and movable die in an axial direction. Moreover, where the spacer or spacers effectively control the gap between the dies, a displacement control system may not be required in the system.
The method described herein above may be employed for variety of operations in a manufacturing environment. For example, the technique may be used for an extrusion of a workpiece 16 as illustrated in
The extrusion technique as illustrated above may be employed for an equal channel angular extrusion of the workpiece 16 as illustrated in
As noted above, the present technique allows for integration of static and dynamic load for forming and repair of workpieces 16 in a manufacturing environment.
By way of example,
Referring generally to
Next, the position of the forming coil 24 and the driver plate 26 is verified before application of the dynamic load via the dynamic load unit 14 (step 88). If the spacing between the forming coil 24 and the driver plate 26 is at the optimum distance then the process 80 proceeds to step 90. However, if the spacing between the forming coil 24 and the driver plate 26 is different than the optimum distance then the spacing is adjusted via the displacement sensing and control system 40 as shown in step 92 before the process 80 proceeds to step 90. At step 90, the process 80 proceeds with application of dynamic load to the die cavity 22. The application of dynamic load includes indirectly loading the first die 18 against the workpiece 16 at a high strain rate. In this embodiment, applying the load at a high strain rate comprises loading the first die 18 at a strain rate greater than 1 sec−1. As a result, the workpiece 16 may be at least partially deformed in a hyperplastic regime.
It should be noted here, as used herein, the term “hyperplastic regime” includes a regime where the material of the workpiece 16 comprises an extended ductility in high velocity conditions. As will be appreciated by those skilled in the art the deformation of the workpiece 16 in the hyperplastic regime increases formability of the workpiece 16. Furthermore, the deformation under the high strain rate reduces spring back of the workpiece 16.
At step 94, the die cavity 22 is opened and the dimensions of the workpiece 16 are measured. Further, at decision step 96, the variations in the dimensions of the workpiece 16 are verified to be within desired tolerances. If the variations in dimensions of the workpiece 16 lie within the desired tolerances then the process 80 proceeds to step 98 where the formed workpiece 16 may be removed. If the variations in dimensions of the workpiece 16 lie outside the desired tolerances then the process 80 proceeds to step 84 where the die cavity 22 is opened and subsequently to step 100 where the static load is reapplied. Further, at step 102 the dynamic load may be reapplied for adjusting the dimensions of the workpiece 16.
The method of forming illustrated hereinabove may have certain additional steps to enhance the process of forming of the workpiece 16. For example, the process may have a mechanism for heating the die cavity 22 as shown in an exemplary process 104 illustrated in
The technique illustrated above employs an integration of static and dynamic loading for precision forming and repair of workpieces in a manufacturing environment. It should be noted that the static loading reduces the energy requirement for the dynamic loading thus making the forming and repair process more efficient. Further, the integration of the static and the dynamic loading enhances the formability of the workpiece. It should also be noted that, the indirect loading of the workpiece via the dynamic loading unit enables the dynamic loading unit to maintain an optimal configuration for workpieces with different conductivity. As a result, the indirect application of the dynamic load as discussed above may be advantageous for application of multiple shots of dynamic load for forming or repairing of the workpiece.
The various aspects of the forming and repair technique described above may be used in various manufacturing environments. For example, the technique may be used for manufacturing of engine blades for an aircraft engine that requires a high degree of precision. The method may also be used for repair applications for thin metal structures. As noted above, the method described here may be advantageous in precision forming and repair of workpieces while having adaptability for a wide range of workpieces.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
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Number | Date | Country | |
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20050284857 A1 | Dec 2005 | US |