FORGING/COINING METHOD

CROSS-REFERENCES TO RELATED APPLICATIONS [0001] Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH [0002] Not Applicable. BACKGROUND OF THE INVENTION

1. Field of the Invention

[0003] This invention relates to methods for coining or forging powdered metal parts, particularly cylindrical parts.

2. Description of the Related Art [0004] Powder metal processing involves transforming powdered metal in the compaction process into a sintered product at a given density. The compacting process utilizes presses with a variety of motions to distribute the powder into various sections of the die and when compacted has a relatively even density distribution throughout the part. These motions are essential in distributing the right amount of material within the part. Coining processes, that requalify the sintered dimensions and in some cases further densify the part, are presently done in unsophisticated presses. To alter material flow in these coining processes, complex tooling is required and in most cases is part specific. [0005] Metal forming has improved over the years with the introduction of CNC (Computer Numerical Controlled) hydraulic presses. These presses have a wide range of adjustability to increase the precision of the formed part and are able to make a wider range of complex geometries. No longer are manufacturers bound by the limitations of most mechanical presses. Example CNC presses are described in U.S. Patent Nos. 5,435,216, 4,721 ,028 and 4,116,122. However, secondary presses for coining and forging have not kept pace with these developments as it applies to powder metal processing. This is where the need for a CNC forging/coining press becomes essential.

[0006] Thus, there is still a need for improved methods for coining and forging powder metal parts.

SUMMARY OF THE INVENTION

[0007] The invention provides a method wherein a CNC forging/coining press is used to integrate processing steps. A part can be cold worked to increase the overall density while simultaneously burnishing the inner or outer profile. Pressing from the lower and upper rams simultaneously can be obtained in such a press.

Another feature is the ability to vary pressing rates. Small features require a slower rate to reach a desired density as compared to a larger feature on the same part. Now the two features could be programmed so that at the final density both portions would reach a uniform density at the same time. Also in forging, if an area becomes fully dense in the center of the cross section of the part, there will be little material movement below the central dense area and the lower portion of the part due to the top down direction of the forging process. Balancing the pressing rates can reduce this limitation. [0008] One feature of the new method is to balance the press motion requirements for powder metal processing. Material needs to be redistributed in almost all cases in pressing operations. The later operations, forging/coining, require the same movements as required in the compacting operation. Where they differ is the need to use portions of the tooling to aid other portions of the tooling such as ejecting cores. The timing of the closed-loop systems is critical to insure no tooling is damaged.

[0009] As stated above, current methods for forging and coining incorporate relatively simple, unsophisticated machines for producing powdered metal parts. The present invention is a press with programmable features that would allow a variety of motions to forge and/or coin complex powdered metal parts. Having a press with advanced capabilities gives manufacturers the ability to combine processes that are currently done in separate machinery, for example, burnishing. The press would also allow users to program varying pressing rates for flanged parts to maintain even material flow while cold or hot working the part. The advanced functions would also reduce the complexity of the tooling required by adding programmable rotary motions for processing products with helical features.

[0010] In the hot forging process, the invention allows users to program a variety of motions to reduce the time a tool member comes in contact with the hot

part increasing the core rod tool life. Tool members could also be used in combination to aid in ejection of forms that have a high ejection force, for example, large core rods. This would reduce the stress on bolts currently used to hold such tool members further increasing the life of the tooling. [0011] One advantage of the invention is to off-load the complexities in the tooling arrangements and add them as features to the machine. Off-loading the tooling complexities to the press has three distinct advantages: (1) changes in tooling operation can be made by adjusting the program, not by expensive tooling modifications, (2) the material flow can be modified in a number of ways for a given set of tools, and (3) the overall cost of the tooling is less since there is no need for costly specialized adapters. These factors can reduce the development time and cost associated when launching new products. [0012] Thus, the invention provides a method for coining or forging a part having a wall with an inside diameter. In one form, the part is a powder metal part. The method uses a press including a first rod, a first ram surrounding the first rod, a die plate having a die cavity, a second rod opposite the first rod, and a second ram surrounding the second rod wherein the first rod and the second rod are dimensioned to fit within the inside diameter of the part. In the method, the part is positioned within the die cavity, one of the first rod and the second rod is located as a core rod within the inside diameter of the part, and at least one of the first ram and the second ram is moved toward the other of the first ram and the second ram such that both the first ram and the second ram contact and coin or forge the wall of the part. The one of the first rod and the second rod acting as the core rod is then ejected from the inside diameter of the part by pushing the one of the first rod and the second rod acting as the core rod with the other of the first rod and the second rod.

[0013] In one version of the method, the first rod is a lower rod, the second rod is an upper rod, the first ram is a lower ram, and the second ram is an upper ram. The first ram and the second ram are dimensioned to fit within the die cavity, and the first ram and the second ram both move toward each other such that both the first ram and the second ram contact and coin or forge the wall of the part. [0014] In another version of the method, the first rod is a lower rod, the second

rod is an upper rod, the first ram is a stationary lower ram, and the second ram is an upper ram. The first ram and the second ram are dimensioned to fit within the die cavity, and the second ram moves toward the first ram such that both the first ram and the second ram contact and coin or forge the wall of the part. [0015] In yet another version of the method, the part has an outwardly extending flange on an end of the part. In this version of the method, the first rod is a lower rod, the second rod is an upper rod, the first ram is a stationary lower ram, and the second ram is an upper ram having an outside diameter substantially equal to an outside diameter of the flange. The first ram and the second ram are dimensioned to fit within the die cavity, and the second ram moves toward the first ram such that both the first ram and the second ram contact and coin or forge the wall of the part.

[0016] In still another version of the method, the part is a gear having an inside surface with helical teeth. In this version of the method, the first rod is the core rod, the first rod is rotatable, and the first rod has an outer surface with helical ribs dimensioned to be slidingly complementary to the helical teeth of the gear. In this version of the method, the first rod is oscillated within the gear before ejecting the first rod from the gear in order to rotary burnish the helical teeth of the gear. [0017] In yet another version of the method, the part is a gear having an inside surface with helical teeth. In this version of the method, the first rod is the core rod, the first rod is rotatable, and the first rod has an outer surface with helical ribs dimensioned to be slidingly complementary to the helical teeth of the gear. The second rod is an upper rotatable rod having an outer surface with helical ribs dimensioned to be slidingly complementary to the helical teeth of the gear. In this version of the method, the first rod is oscillated within the gear before ejecting the first rod from the gear with the second rod in order to rotary burnish the helical teeth of the gear.

[0018] In still another version of the method, the first ram and the second ram are dimensioned to fit within the die cavity, and the method further comprises oscillating the first ram and the second ram when the first ram and the second ram coin or forge the wall of the part to aid in material movement and to provide for burnishing of the outer surface of the part. Preferably, the oscillation is at a high

frequency

[0019] In yet another version of the method, the part is a gear having an inside surface with helical teeth, and the first rod is the core rod and the first rod is an upper rotatable rod having an outer surface with helical ribs dimensioned to be slidingly complementary to the helical teeth of the gear. In this version of the method, the first rod, the first ram and the die table are moved toward the second ram such that both the first ram and the second ram contact and coin or forge the wall of the part. The gear may include a second inside surface having a diameter less than a diameter of the inside surface with helical teeth of the gear, and accordingly the second rod is dimensioned for sliding fit within the second inside surface of the gear to rotary burnish the second inside surface of the gear. [0020] In still another version of the method, the part is a gear having an inside surface with helical teeth, and the second rod is the core rod and the second rod is a lower rotatable rod having an outer surface with helical ribs dimensioned to be slidingly complementary to the helical teeth of the gear. This version of the method includes the step of moving the first rod, the first ram and the die table toward the second ram such that both the first ram and the second ram contact and coin or forge the wall of the part. [0021] In yet another version of the method, the method provides for locating the part within the die cavity. In this version of the method, the first rod is an upper rod, the second rod is a lower rod, the first ram is an upper ram, and the second ram is a lower ram. This version of the method includes the steps of extending a lower end of the first rod beyond a lower end of the first ram, locating the lower end of the first rod within the inside diameter of the part, positioning the part within the die cavity by way of the first rod, locating the second rod as the core rod within the inside diameter of the part, and moving the first ram and the die table toward the second ram such that both the first ram and the second ram contact and coin or forge the wall of the part. The part may be a gear having an inside surface with helical teeth, and the second rod may be a lower rotatable rod having an outer surface with helical ribbing dimensioned to be slidingly complementary to the helical teeth of the gear to rotary burnish the helical teeth. Also, the first rod may have an outside diameter less than an outside diameter of

the second rod to avoid contact of the first rod with the helical teeth. [0022] In still another version of the method, the first rod is an upper rod, the second rod is a lower rod and the second rod has an outside diameter greater than an outside diameter of the first rod, the first ram is an upper ram, and the second ram is a lower ram. This version of the method includes the steps of locating the second rod as the core rod within the inside diameter of the part, and moving the first rod, the first ram and the die table toward the second ram such that both the first ram and the second ram contact and coin or forge the wall of the part The part may be a gear having an inside surface with helical teeth, and accordingly, the second rod is a rotatable rod having an outer surface with helical ribs dimensioned to be slidingly complementary to the helical teeth of the gear to rotary burnish the helical teeth. This version of the method may further include the step of moving the die plate downward to eject the coined or forged part. [0023] In yet another version of the method, the method includes the step of providing the press with means for varying pressing rates of the first ram and the second ram to maintain even material flow while cold or hot working the part. The means for varying pressing rates may include a processor in communication with a hydraulic system for controlling downward and upward movement of the first ram and the second ram. [0024] In still another version of the method, the method includes the step of providing the press with means for varying downward and upward movement rates of the first rod and the second rod to maintain even material flow while cold or hot working the part. The means for varying downward and upward movement rates may include a processor in communication with a hydraulic system for controlling downward and upward movement of the first rod and the second rod.

[0025] In another aspect, the invention provides a method for coining or forging a part. In one embodiment, the part is a powdered metal part. The method uses a press including a core rod, a ram surrounding the core rod, and a die plate having a die cavity wherein the core rod is dimensioned to fit within an inside diameter of the part. The part is positioned within the die cavity, and the core rod is located within the inside diameter of the part. The ram is moved such that the ram contacts and coins or forges the part, and the core rod is oscillated axialJy

back and forth within the part before removing the core rod from the part to burnish the inside diameter of the part.

[0026] In one version of this method, the part is a gear having an inside surface with helical teeth, the core rod is rotatable, and the core rod has an outer surface with helical ribs dimensioned to be slidingly complementary to the helical teeth of the gear to burnish the part. In another version of this method, the press includes a second core rod, the second core rod being rotatable and having an outer surface with helical ribs dimensioned to be slidingly complementary to the helical teeth of the gear. The second core rod is located within the inside diameter of the part and oscillated axially back and forth within the part before removing the second core rod from the part to burnish the inside diameter of the part. The second rod may have an outside diameter less than an outside diameter of the core rod. The press may include a second ram such that the ram and the second ram can move toward each other to coin or forge the part. [0027] In yet another version of this method, a lower end of the core rod is extended beyond a lower end of the ram, and located within the inside diameter of the part. The part is then positioned within the die cavity by way of the first rod. In still another version of this method, the press includes a second core rod, and the part includes a second inside surface having a diameter less than a diameter of the inside surface of the part, and the second core rod is dimensioned for sliding fit within the second inside surface of the part.

[0028] In yet another aspect, the invention provides a method for coining or forging a part. In one embodiment, the part is a powdered metal part. The method uses a press including a ram and a die plate having a die cavity. In the method, the part is positioned within the die cavity, and the ram is moved such that the ram contacts the part, and the ram is oscillated back and forth when the ram contacts the part to coin or forge the part.

[0029] In one version of this method, the press has a second ram. The second ram is moved such that the second ram contacts the part, and the second ram is oscillated back and forth when the second ram contacts the part to coin or forge the part. In one form, the ram and the second ram are dimensioned to fit within the die cavity. In another form, the part has an outwardly extending flange on an

end of the part, and the second ram has an outside diameter substantially equal to an outside diameter of the flange, and the second ram moves toward the ram such that both the ram and the second ram contact and coin or forge the part. In another version of this method, the press has a core rod dimensioned to fit within an inside diameter of the part, and the core rod is located within the inside diameter of the part before coining.

[0030] In still another aspect, the invention provides a method for coining or forging a part. In one embodiment, the part is a powdered metal part. The method uses a press including a ram, a die plate having a die cavity, and means for varying pressing rates of the ram. The part is positioned within the die cavity, and the ram is moved such that the ram contacts the part. The pressing rate of the ram is varied after the ram contacts the part to coin or forge the part. The means for varying pressing rates may be a processor in communication with a hydraulic system for controlling downward and upward movement of the ram. [0031] The press may include a core rod dimensioned to fit within an inside diameter of the part, and means for varying downward and upward movement rates of the core rod. The core rod is located within the inside diameter of the part before or after positioning the part within the die cavity, and downward and upward movement rates of the core rod are varied within the inside diameter of the part. The means for varying downward and upward movement rates may be the processor in communication with a hydraulic system for controlling downward and upward movement of the core rod.

[0032] In one version of this method, the press has a second core rod opposite the core rod and has a second ram surrounding the second core rod wherein the core rod surrounds the ram, and the core rod and the second rod are dimensioned to fit within the inside diameter of the part. The core rod and the second core rod are located within the inside diameter of the part, and the ram and the second ram are moved toward each other such that both the ram and the second ram contact and coin or forge the wall of the part. The ram and the second ram may be dimensioned to fit within the die cavity. The core rod and the second core rod may also be rotatable.

[0033] These and other features, aspects, and advantages of the present invention will become better understood upon consideration of the following detailed description, drawings, and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS [0034] Figures 1a to 1j are front cross sectional views on a vertical plane containing the axis of the lower rod, lower ram, upper rod, and upper ram of a press executing a sequence of steps for a first example embodiment of a method for coining or forging a part according to the invention.

[0035] Figures 2a to 2i are front cross sectional views on a vertical plane containing the axis of the lower rod, lower ram, upper rod, and upper ram of a press executing a sequence of steps for a second example embodiment of a method for coining or forging a part according to the invention.

[0036] Figures 3a to 3f are front cross sectional views on a vertical plane containing the axis of the lower rod, lower ram, upper rod, and upper ram of a press executing a sequence of steps for a third example embodiment of a method for coining or forging a part according to the invention.

[0037] Figures 4a to 4f are front cross sectional views on a vertical plane containing the axis of the lower rod, lower ram, upper rod, and upper ram of a press executing a sequence of steps for a fourth example embodiment of a method for coining or forging a part according to the invention.

[0038] Figure 5 shows a helical gear that may be forged using the method shown in Figures 3a to 3f.

[0039] Figure 6 shows a helical gear that may be forged using the method shown in Figures 4a to 4f. [0040] Figures 7a to 7d are front cross sectional views on a vertical plane containing the axis of the lower rod, lower ram, upper rod, and upper ram of a press executing a sequence of steps for a fifth example embodiment of a method for coining or forging a part according to the invention.

[0041] Like reference numerals will be used to refer to like parts from Figure to Figure in the following description of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

[0042] Referring first to Figures 1a to 1j, there are shown front cross sectional views on a vertical plane containing the axis of the lower rod, lower ram, upper rod, and upper ram of a press executing a sequence of steps for a first example embodiment of a method for coining or forging a part according to the invention.

The press, indicated generally at 10, includes an upper core rod 20, an upper ram 30, a die plate 40, a lower core rod 50, and a lower ram 60 all having a common axis A. [0043] The upper core rod 20 is mounted for rotational movement on the piston (not shown) of a cylinder (not shown). The piston and the cylinder are part of an upper core rod hydraulic system for controlling downward and upward movement of the upper core rod 20. The upper core rod hydraulic system is controlled by a processor which is in communication with the upper core rod hydraulic system. The processor is a microprocessor, computer, microcomputer or other circuit capable of handling inputs and outputs to control the upper core rod hydraulic system in accordance with a programmed routine. An example control system for a hydraulic cylinder can be found in U.S. Patent No. 4,721,028 which is incorporated herein by reference along with the other patents cited herein. [0044] The upper ram 30 is mounted on a piston (not shown) of a cylinder (not shown). The piston and the cylinder are part of an upper ram hydraulic system for controlling downward and upward movement of the upper ram 30. The upper ram hydraulic system is also controlled by the processor.

[0045] The die plate 40 is mounted on a piston (not shown) of a cylinder (not shown). The piston and the cylinder are part of a die plate hydraulic system for controlling downward and upward movement of the die plate 40. The die plate hydraulic system is also controlled by the processor. The die plate 40 has a cylindrical die cavity 42.

[0046] The lower core rod 50 is mounted on a support shaft 52 for rotational movement. The support shaft 52 is mounted on a lower rod support 54 which is mounted on the piston (not shown) of a cylinder (not shown). The piston and the cylinder are part of a lower core rod hydraulic system for controlling downward

and upward movement of the lower core rod 50. The lower core rod hydraulic system is controlled by the processor.

[0047] The lower ram 60 is mounted on a support 62 which is mounted to a piston (not shown) of a cylinder (not shown). The piston and the cylinder are part of an lower ram hydraulic system for controlling downward and upward movement of the lower ram 60. The lower ram hydraulic system is also controlled by the processor.

[0048] Thus, downward and upward movement of the upper core rod 20, the upper ram 30, the die plate 40, the lower core rod 50, and the lower ram 60 of the press 10 can be operated in accordance with a routine programmed in the processor. In this regard, a commercially available CNC hydraulic press may be suitably modified to operate in accordance with the method of the present invention. User initiated control inputs may be provided to processor to set the operating parameters of the hydraulic press. For example, the processor may permit the user to select the up and down stroke speed of each hydraulic cylinder, the position at which the stroke is reversed, or the tonnage at which the stroke will reverse. Other user controlled inputs may also be provided to processor depending on the particular features desired with the press. For instance, rotational movement of the upper core rod 20 and the lower core rod 50 can be controlled by the processor.

[0049] Still referring to Figures 1 a to 1 j, the sequence of steps for a first example embodiment of a method for coining or forging a part according to the invention is shown. In Figure 1a, a hollow cylindrical part 70 is loaded into die cavity 42 and lower core rod 50 is inserted in the hollow interior of the part 70. The upper ram 30 then moves into the die cavity 42 to close off the die plate 40 as shown in Figure 1b. The upper core rod 20 and the lower core rod 50 then come into contact as shown in Figures 1b and 1c. In Figures 1d to 1h, the upper ram 30 and the lower ram 60 move into equal amounts in opposite directions to compact the part 70 while the upper core rod 20 and the lower core rod 50 move down at a faster rate to start burnishing the inside surface 74 of the wall 72 of the part 70.

The upper ram 30 and the lower ram 60 keep moving in equal amounts to density the part 70.

[0050] While the densification process is taking place, the upper core rod 20 and the lower core rod 50 are making an upward and downward motion during the process until the part 70 reaches its finished dimension. This upward and downward motion of the upper core rod 20 and the lower core rod 50 serves to densify and burnish the inside surface of the part 70. When the part 70 is a gear having helical teeth on the inside surface of the gear, the outer surface of the upper core rod 20 may have helical ribs dimensioned to be slidingly complementary to the helical teeth of the gear. Also, the outer surface of the lower core rod 50 may have helical ribs dimensioned to be slidingly complementary to the helical teeth of the gear. Because the upper core rod 20 and the lower core rod 50 are mounted for rotational movement, the upper core rod 20 and the lower core rod 50 rotate and serve to burnish the helical teeth of the gear during upward and downward motion. The upper ram 30 and the lower ram 60 also have the capability of small upward and downward high frequency motion while compacting the part 70 to aid in material movement during forging and to provide for burnishing of the outer surface of the part 70. [0051] In Figure 1 i, the upper core rod 20 and the upper ram 30 move up to their home positions while the die plate 40 moves down to expose the finished part 70. After removal of the finished part 70, the press 10 is in the loading position shown in Figure 1 j so that another part 70 may be loaded into the die cavity 42 for processing.

[0052] Turning now to Figures 2a to 2i, there are shown front cross sectional views of the press 10 executing a sequence of steps for a second example embodiment of a method for coining or forging a part according to the invention. In Figure 2a, the cylindrical part 70 is placed near the die cavity 42. Looking at

Figure 2b, upper core rod 20a is moved down to line up the cylindrical part 70 with the die cavity 42. It can be seen that upper core rod 20a has a diameter smaller than lower core rod 50 and the inside diameter of the part 70. Next, as shown in Figure 2c, the upper core rod 20a is moved up and the upper ram 30 is moved down to capture the part 70. Then, as shown in Figure 2d, the upper core rod 20a and the upper ram 30 move down to place the part 70 into the die cavity 42.

[0053] Turning to Figure 2e, the lower core rod 50 is inserted in the part 70, and the upper core rod 20a, the upper ram 30, the die plate 40, and the lower ram 60 move downward. No material movement occurs in the part 70. Then, as shown in Figure 2f, the upper core rod 20a, the upper ram 30, the die plate 40, and the lower core rod 50 move downward to forge the part. In Figure 2g, the upper core rod 20a and the lower core rod 50 move downward to eject the lower core rod 50. Because the upper core rod 20a has a diameter smaller than lower core rod 50, the upper core rod 20a does not contact the part 70 when ejecting the lower core rod 50. This aids in ejection of the lower core rod 50. Then, as shown in Figure 2h, the upper core rod 20a and the upper ram 30 move up to top- dead-center, and the die plate 40 moves downward to eject the part 70. In Figure 2i, the die plate 40, the lower core rod 50 and the lower ram 60 move to their original positions such that location and loading of another part 70 can occur. Thus, the method of Figures 2a to 2i provides for location of parts in a die cavity. This method is particularly useful for locating out of round parts in a die cavity.

[0054] In Figures 3a to 3f, there are shown front cross sectional views of a press executing a sequence of steps for a third example embodiment of a method for coining or forging a part according to the invention. In particular, the press sequence of Figures 3a to 3f may be used to forge a helical gear 70a as shown in Figure 5. Looking at Figure 5, the gear 70a includes a cylindrical wall 72a having an inside surface 74a with helical teeth 75a and an outside surface 76a with helical teeth 77a.

[0055] Referring now to Figures 3a to 3f, in Figure 3a, the press 10 is in the loaded position with gear 70a in the die cavity 42. In Figure 3b, the lower core rod 50 is inserted in the gear 70a, and the upper core rod 20a, the upper ram 30, the die plate 40 and the lower ram 60 move downward with no material movement of the gear 70a. In Figure 3c, the upper core rod 20a, the upper ram 30, the die plate 40 and the lower core rod 50 move downward to forge the gear 70a. The lower core rod 50 may have an outer surface with helical ribs dimensioned to be slidingly complementary to the helical teeth 75a of the gear 70a in order to burnish the helical teeth 75a of the gear 70a. The lower core rod 50 is mounted for rotational movement so that the lower core rod 50 may rotate and burnish the

helical teeth 75a of the gear 70a during upward and downward motion. In Figure 3d, the upper core rod 20a and the lower core rod 50 move downward to eject the lower core rod 50. Because the upper core rod 20a has a diameter smaller than lower core rod 50, the upper core rod 20a does not contact the part 70a when ejecting the lower core rod 50. In Figure 3e, the upper core rod 20a and the upper ram 30 move up to top-dead-center and the die plate 40 moves downward to eject the gear 70a. Then as shown in Figure 3f, the die plate 40, the lower core rod 50 and the lower ram 60 move to their original positions such that loading of another gear 70a can occur. [0056] In Figures 4a to 4f, there are shown front cross sectional views of a press executing a sequence of steps for a fourth example embodiment of a method for coining or forging a part according to the invention. In particular, the press sequence of Figures 4a to 4f may be used to forge a helical gear 70b as shown in Figure 6. Looking at Figure 6, the gear 70b includes a cylindrical wall 72b having an inside surface 74b with helical teeth 75b and an outside surface

76b with helical teeth 77b. A lower end of the gear 70b has an inwardly directed flange 79 on the inside surface 74b. The flange 79 forms a smooth inside surface of reduced diameter on the end of the gear 70b. [0057] Referring now to Figures 4a to 4f, in Figure 4a, the press 10 is in the loaded position with gear 70b in the die cavity 42. In Figure 4b, the upper core rod 20, the upper ram 30, and the lower core rod 50a are moved down to insert the gear 70b into the die cavity 42. The upper core rod 20 may have an outer surface with helical ribs dimensioned to be slidingfy complementary to the helical teeth 75b of the gear 70b in order to burnish the helical teeth 75b of the gear 70b. The upper core rod 20 is mounted for rotational movement so that the upper core rod 20 may rotate and burnish the helical teeth 75b of the gear 70b during upward and downward motion. The lower core rod 50a has a smaller diameter than the upper core rod 20 and therefore, the lower core rod 50a can burnish the inside surface of the flange 79 on the end of the gear 70b. In Figure 4c, the upper core rod 20, the upper ram 30, the die plate 40 and the lower core rod 50a move downward to forge the gear 70b. In Figure 4d, the upper core rod 20 moves upward to eject the lower core rod 50a. Alternatively, the lower core rod 50a

could eject the upper core rod 20. In Figure 4e, the upper core rod 20 and the upper ram 30 move up to top-dead-center, and the die plate 40 and the lower core rod 50a move downward to eject the gear 70b. In Figure 4f, the die plate 40 and the lower core rod 50a move to their original positions such that loading of another gear 70b can occur.

[0058] Figures 7a to 7d are front cross sectional views of a press executing a sequence of steps for a fifth example embodiment of a method for coining or forging a part according to the invention. In particular, the press sequence of Figures 7a to 7f may be used to forge a part 70c including a cylindrical wall 72c having an outside surface 76c with an outwardly directed flange 81.

[0059] Referring now to Figures 7a to 7d, in Figure 7a, the press 10 is in the loaded position with part 70c in the die cavity 42c of the die plate 40c. The die plate 40c has a ledge 44c located below the top surface 46c of the die plate 40c. The outwardly directed flange 81 of the part 70c rests on the ledge 44c when the part 70c is loaded in the die plate 40c. In Figure 7b, the lower core rod 50 is inserted in the part 70c, and the upper core rod 20a, the upper ram 30, the die plate 40c and the lower ram 60 move downward with no material movement of the part 70c. It can be seen that upper core rod 20a has a diameter smaller than lower core rod 50. In Figure 7c, the upper core rod 20a, the upper ram 30, the die plate 40c and the lower core rod 50 move downward to forge the part 70c. The lower core rod 50 is dimensioned to be slidingly complementary to the inside surface of the gear 70c in order to burnish the inside surface of the gear 70c. In Figure 7d, the upper core rod 20a and the lower core rod 50 move downward to eject the lower core rod 50. The upper core rod 20a and the upper ram 30 may then move up to top-dead-center and the die plate 40c may move downward to eject the part 70c. Because the upper core rod 20a has a diameter smaller than lower core rod 50, the upper core rod 20a does not contact the part 70c when ejecting the lower core rod 50. Then, the die plate 40c, the lower core rod 50 and the lower ram 60 move to their original positions such that loading of another part 70c can occur as shown in Figure 7a.

[0060] Although the present invention has been described with reference to certain embodiments, one skilled in the art will appreciate that the present

invention can be practiced by other than the described embodiments, which have been presented for purposes of illustration and not of limitation. For example, while the invention has particular utility in coining and/or forging powder metal parts, the invention can also be applied to wrought metal parts. Therefore, the scope of the appended claims should not be limited to the description of the embodiments contained herein.

INDUSTRIAL APPLICABILITY

[0061] The invention relates to methods for coining or forging powdered metal parts.