Tool assembly for power molding press machine

Abstract

To provide a tool assembly for a powder molding press machine which can be automatically removed from a powder molding press machine.SOLUTION: A tool assembly includes a lower punch chuck and a core rod chuck. The tool assembly includes: a lower punch having a lower punch draw bar for holding the lower punch in the lower punch chuck in a machine; and a core rod having a core rod draw bar for holding the core rod in the core rod chuck. In the tool assembly, a coupling mechanism for enabling action connection between the lower punch and the core rod includes a male side coupling element disposed on an outer surface of the core rod; and a female side coupling element disposed on an inner surface of the lower punch draw bar. The male side coupling element is an elastic element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a tool assembly for a powder compaction press. [Background technology]

[0002] Powder compaction is a widely used technique for producing metal parts by compressing metal powder in a die under high pressure. The main equipment required for the powder compaction process is a machine and a tool set that is attached to the machine during production. In recent years, CNC-controlled machines have been developed to improve the automation of this process, thereby increasing production efficiency. Thus, there is an increasing demand for automated tool sets to further increase production efficiency. In addition, recently introduced machines make it possible to utilize automated tool sets.

[0003] The main challenges to fully automating powder molding are limited access to the processing area, especially the interior of the machine, and the environmental degradation caused by the powder. A conventional tool set includes at least three tools: an upper punch, a die, and a lower punch. In addition to these components, a core rod is one of the tools often used in powder molding to form holes in metal parts. In powder molding equipment, a core rod is always used when producing molded parts with holes from powder materials.

[0004] WO 2009 / 030699 discloses a die press assembly for pressing super-hard steel cutting inserts for cutting tools. Such inserts have a central hole for mounting the insert to the free end of the cutting tool. To form the central hole, a core pin must be provided and placed through the die. The press assembly includes an upper punch, a lower punch, and a die. In particular, the assembly includes a core pin for forming the central hole. Furthermore, for each element, a clamping element including a chuck and a holder is provided to clamp and hold the element in a predetermined position within the workstation. When exchanging a metal cutting insert of a given size for a metal cutting insert of another size, all chucks remain within the powder press workstation. In contrast, the die, lower punch, and core pin can be removed from the workstation along with their respective holders. For this reason, a locking device is used to remove the elements from the workstation. The lower punch, die, and core pin each have a hole for accommodating the locking device. In particular, WO 2009 / 030699 describes radial locking pins in radial holes through the die, the upper and lower punches, and the core pin, connecting these three elements together. This design requires an additional actuation mechanism to operate the locking device.

[0005] European Patent Application Publication No. 3,106,295 discloses a magnetic coupling for connecting a lower punch and a core rod. A first coupling element is attached to the core rod, and a second coupling element is disposed on the lower punch. Both coupling elements are equipped with permanent magnets, and the magnetic force generated between the permanent magnets enables the first and second coupling elements to be connected. In this manner, the core rod can be coupled to the lower punch. However, magnetic couplings require a complex structure and are susceptible to debris. Metal powder can easily be attracted to the permanent magnets applied to the coupling elements, thereby reducing the reliability of the coupling and even damaging the tool. Summary of the Invention [Problem to be solved by the invention]

[0006] It is an object of the present invention to provide a tool assembly for a powder compacting press that can be automatically removed from the powder compacting press. It is a further object of the present invention to provide a tool assembly for reliable coupling and decoupling of a core rod and a lower punch. In particular, the tool assembly is characterized by its ease of operation. [Means for solving the problem]

[0007] According to the invention, these objects are achieved by the features of the independent claims, with further advantageous embodiments emerging from the dependent claims and the description.

[0008] The present invention provides a tool assembly for a powder compacting press machine for forming an object from metal powder, the tool assembly including a lower punch chuck and a core rod chuck. The tool assembly includes a lower punch having a lower punch drawbar for holding the lower punch chuck to the machine, and a core rod having a core rod drawbar for holding the core rod in the core rod chuck. The tool assembly further includes a coupling mechanism for enabling connection between the lower punch and the core rod. The coupling mechanism includes a male coupling element disposed on an outer peripheral surface of the core rod and a female coupling element disposed on an inner peripheral surface of the lower punch drawbar. Furthermore, the male coupling element is a resilient element.

[0009] When the core rod is inserted axially into the lower punch drawbar and reaches a predetermined position, the male coupling element mechanically interacts with the female coupling element to connect the core rod to the lower punch drawbar and form an integrated assembly. In particular, the male coupling element automatically engages with the female coupling element without an additional actuation mechanism. Preferably, in the engaged state, the core rod is concentrically positioned within the lower punch drawbar, and the male coupling element faces the female coupling element in the radial direction of the lower punch drawbar and the core rod. The male coupling element can be directly or indirectly connected to the female element. Furthermore, the male coupling element can be disconnected from the female element, particularly by axially withdrawing the core rod from the lower punch drawbar. Such a coupling mechanism has the advantages of simple structure and ease of handling.

[0010] Automation of machining processes has been widely utilized to improve production efficiency in most machining processes, including milling, grinding, and EDM. However, automation has not yet been fully implemented in the field of powder compaction press technology. One reason for this is that existing tool sets are not at all suitable for automation. In the powder compaction press process, several components, including the lower punch, core rod, die, and upper punch, must be inserted into the machine under difficult conditions. The space inside the machine is limited, making it impossible to prevent contamination caused by the powder. Metal powders, especially those made of carbon steel, are hard materials, and powder particles distributed within the tool set can damage the tool set. Therefore, one major challenge is to design a tool set that can be automatically replaced, i.e., automatically inserted and removed from the machine, by an automation system or robot within the limited space inside the machine. Another challenge is to design a tool set that can withstand wear in harsh environments, such as the debris and abrasive metal powder contained in the ambient air.

[0011] In addition to the tool assembly, a die and an upper punch are required to press a metal part. Additionally, a die chuck is required to hold the die in the machine, and an upper punch chuck is required to hold the upper punch. The die is used to press the metal powder into a hard metal part of the desired shape. In most applications, once a part is completed, the upper punch, die, lower punch, and core rod must be removed from the machine. In particular, the core rod is a thin, elongated element that is surrounded by several components during insertion, significantly limiting spatial access to the core rod. One solution is to connect the core rod to the lower punch, allowing it to be inserted and removed from the lower punch in a single step. The lower punch is configured to be gripped by an automatic changer, allowing the core rod to be inserted and removed automatically along with the lower punch.

[0012] The production cycle of the powder compaction press process has at least three stages. In the first stage, a tool set including a lower punch with a core rod, a die, and an upper punch is installed in the machine. To enable automatic tool installation using an automatic tool changer, the lower punch and core rod are inserted into the machine as a single unit. This can be achieved by first connecting the core rod to the lower drawbar outside the machine. In the second stage, a specified amount of metal powder is filled into the die, and the upper and lower punches press the metal powder into the die. The core rod penetrates the die, forming a hole in the final part. After the powder compaction process is completed, the upper punch is first removed from the machine, thus releasing the compressive force acting on the powder material. Subsequently, the pressed part is ejected from the die, and the die and the lower punch with the core rod are unloaded. The unloading process can also be automated or robotic to reduce production time and achieve a high-yield automated process. When another core rod needs to be applied to produce the next part, the core rod can be separated from the lower punch and another core rod can be coupled to the lower punch. Preferably, the coupling and decoupling of the lower punch and core rod occurs outside the machine. Additionally, it is important to ensure the connection between the core rod and the lower punch while the lower punch is being loaded and unloaded from the machine.

[0013] In an advantageous variant, coupling occurs automatically when the core rod is inserted through an opening at the end of the lower punch drawbar into a lower punch having a lower punch drawbar attached thereto. The lower punch and the lower punch drawbar each have an axially extending through-hole, which is centrally located when the lower punch drawbar is attached to the lower punch. When the core rod is axially inserted into these holes, the male coupling element, being an elastic element, is first radially compressed against the inner wall of the lower punch drawbar. When the male coupling element reaches the position of the female coupling element, the preloaded male coupling element is released and expands radially against the inner surface of the lower punch drawbar. The female coupling element is configured so that the male coupling element is locked in this position and is substantially unable to move axially. The male coupling element is particularly capable of moving circumferentially in the engaged state. When the male coupling element and the female coupling element are engaged, a mechanical clamping force acts, particularly primarily radially. The coupling force is not electrically or magnetically generated, which has the advantage of a simple yet reliable design.

[0014] The male coupling element may be fixedly or removably attached to the core rod. Even if the core rod is removably attached to the core rod, it is preferable to design the core rod and male coupling element so that they operate as a unit. The male coupling element should be attached to the core rod before it is inserted into the lower punch to facilitate handling.

[0015] A recess is formed in the outer circumferential surface of the core rod for receiving the male coupling element, and in particular the recess is formed in a predetermined direction on the core rod. In particular, the recess is configured to movably capture the male coupling element within the recess. Preferably, the recess at least partially surrounds the outer circumferential surface of the core rod for securely receiving the male coupling element therein.

[0016] In one variant, the male coupling element is a ring-shaped elastic element. To achieve a simple design, the male coupling element is a spring clip, in particular an open ring-shaped element with two ends.

[0017] At least one groove is formed on the inner circumferential surface of the lower punch drawbar as a counterpart of the male coupling element, which groove has a defined axial height and simultaneously serves as a reference element for automatically positioning the male coupling element, particularly in the axial direction.

[0018] Before the core rod is inserted into the lower punch, a spring clip is attached to the core rod so that it fits into the recess. When the core rod with the spring clip is inserted through the lower part of the lower punch, or more precisely, through the lower part of the lower punch drawbar, the spring clip is compressed by the inner surface of the lower punch drawbar, causing the two ends of the spring clip to move toward each other and applying a preload to the spring clip. When the spring clip reaches the groove position, it expands radially, achieving engagement between the spring clip and the groove, thereby connecting the core rod to the lower punch drawbar.

[0019] When the spring clip engages the groove, the two form an interference or press fit. The coupling force generated by the coupling element must withstand the load, i.e., the total weight of the core rod and core rod drawbar.

[0020] In one variation, the spring clip has a circular, such as round, cross section.

[0021] In a preferred variant, the cross-sectional diameter of the spring clip is greater than the height of the groove, which has the advantage that it can be easily disconnected from the groove. Preferably, the cross-sectional diameter of the spring clip is at least half the height of the groove.

[0022] In some embodiments, the male coupling element is made of metal, the same material as the core rod, or a different material than the core rod. When both the spring clip and the core rod are made of metal, the effects of temperature and humidity changes on geometric shape deformation are similar, resulting in stable function.

[0023] The female coupling element is preferably located adjacent the lower end of the lower punch drawbar to minimize the insertion path of the core rod.

[0024] It is also contemplated that the core rod may have one or more male elements and the lower punch drawbar may have one or more female elements.

[0025] A more particular description of the principles briefly described above will now be made by reference to specific embodiments thereof which are illustrated in the drawings. These drawings depict exemplary embodiments of the present disclosure and are therefore not to be considered limiting of its scope. The principles of the present disclosure will be described in detail through the use of and explained in the accompanying drawings. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a perspective view showing a part of a powder molding press machine. [Figure 2] FIG. 1 is a perspective view showing a part of a powder molding press machine. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] FIG. 10 is a cross-sectional view of a lower punch and a core rod. [Figure 6] FIG. 10 is a cross-sectional view of a lower punch and a core rod. [Figure 7] FIG. [Figure 8] FIG. 10 is a cross-sectional view of the core rod, spring clip, and lower punch. [Figure 9] FIG. 10 is a cross-sectional view of the lower chuck and core rod. [Figure 10] FIG. 10 is a cross-sectional view of the lower chuck and core rod. DETAILED DESCRIPTION OF THE INVENTION

[0027] Referring to Figures 1 and 2, the powder molding press machine 1 includes a press adapter having a lower plate 103, an intermediate plate 102, and an upper plate 101. Two guide pillars 104 and 105 vertically penetrate the three plates. The upper and intermediate plates are vertically movable. Spaces are provided to accommodate different machine requirements. In Figure 1, a lower punch 20 and a core rod 10 are loaded into the machine and clamped to a lower punch chuck 23 and a core rod chuck 13, respectively. The core rod chuck is supported by a spacer 110, which is fixed to the top surface of the lower plate. The lower punch chuck 23 is fixed to the top surface of the intermediate plate. For easy handling, the upper and intermediate plates are lowered to reduce the distance between them before loading the lower punch with the core rod. Figure 2 illustrates the die loading process. After the upper plate and the intermediate plate are moved upward to a specified processing position, the die is loaded into the die chuck 33 and clamped.

[0028] The unloading process, not shown in the diagram, is performed in reverse. The die is released from the die chuck and can be removed from the machine by the automatic tool changer. The lower punch is then gripped by the automatic tool changer and removed from the machine. Because the core rod is connected to the lower punch, it can also be automatically removed from the machine.

[0029] Figures 3 and 4 show the details of the lower punch 20 with the lower punch drawbar 22 and the die 30 with the die drawbar 32, respectively. Before being inserted into the machine, the lower punch is connected to a lower punch pallet 21 with a reference element thereon and the lower punch drawbar 22 attached thereto. This is because the lower punch with the lower punch pallet and lower punch drawbar is inserted into the machine as a single unit. The lower punch has an axial through-hole, called a lower punch hole 26, for receiving the core rod. The lower punch pallet 21 and the lower punch drawbar each have axial holes for inserting the core rod. As shown in Figure 2, in the installed state, all axial holes are centered. The lower punch has two cylindrical sections with different diameters. The lower section 20b has a larger diameter than the upper section 20a. To enable automatic replacement of the lower punch, the outer peripheral surface of the lower punch, particularly the lower portion 20b of the lower punch, is formed with a lower punch gripping interface 25. An automatic tool changer can securely grip the lower punch at the lower punch gripping interface.

[0030] Before being mounted on the machine, the die 30 is connected to a die pallet 31 with a die drawbar 32 attached to the die pallet 31. This is because the die with the pallet and drawbar is inserted into the machine as a single unit. A through hole, called a die hole 34, for accommodating a punch and a core rod is formed in the axial center of the die. The die pallet and die drawbar also have axial holes for inserting the core rod. As shown in FIG. 4, in the mounted state, all axial holes are centrally located. To enable automatic die change, a first gripper interface 35 is formed on the outer periphery of the die. In the embodiment shown in FIGS. 3 and 4, the lower punch gripping interface and the die gripping interface have a railroad track-like shape, allowing two fingers of a gripper of an automatic tool changer to grip a part from two sides.

[0031] Figures 5 and 6 show a core rod inserted into the lower punch in a clamped and released state, respectively. A core rod pallet 11 with a core rod draw bar 12 can be attached to the lower end of the core rod. The core rod has an elongated core rod body 13. As shown in Figures 6 and 9, the first section 17a of the core rod has a larger diameter than the second section 17b of the core rod. As a result, a gap, indicated by reference symbol G in Figure 9, is formed between the inner surface of the first section 24a of the lower punch draw bar and the second section 17b of the core rod. This prevents debris from being pinched between the lower punch draw bar and the core rod, thereby avoiding damage to the tool assembly. The second section 24b of the lower punch draw bar, located at the lower part of the draw bar, has a sloped inner surface, which prevents damage to the upper portion of the core rod when the core rod is inserted into the draw bar. This is because the upper portion of the core rod does not come into contact with the sloped inner surface.

[0032] In the illustrated embodiment, the male coupling element is a resilient element, specifically a spring clip 14 having two ends 14a, 14b as shown in Figure 7. Figure 8 is a cross-sectional view along line AA'.

[0033] A groove 28 is formed in the inner surface of the lower punch draw bar. The cross section of the groove in a plane perpendicular to the radial direction may be circular or rectangular.

[0034] An axial force is required to allow the spring clip to couple or separate from the groove in the drawbar. The cross section of the spring clip is circular. In one variation, the height of the axial groove H in FIG. 9 is designed to be less than half the diameter of the cross section of the spring clip, and the curvature converts the axial force into a radial force, causing the spring clip to contract. This applies both when inserting the core rod with the spring clip into the lower punch drawbar and when removing it from the lower punch drawbar. In another variation, the height of the axial groove H in FIG. 9 is designed to be equal to the diameter of the cross section of the spring clip to achieve a reliable coupling.

[0035] Figures 9 and 10 are enlarged explanatory views of portions C and B in Figures 5 and 6, respectively. These show the detailed position of the spring clip on the core rod in axial cross-section. In addition, Figure 9 shows the core rod inserted into the lower punch before the spring clip 14 reaches the grooved position. A recess 16 for accommodating the spring clip is formed in the outer peripheral surface of the core rod. Specifically, the recess is formed around the periphery. The recess shown in Figure 9 has a C-shaped cross-section. However, the cross-sectional shape is not limited to the shape shown. Other cross-sectional shapes can be used as long as the spring clip can be safely accommodated therein and the function of the recess can be realized. The recess is designed to safely hold the spring clip therein and compress the spring clip radially inward when the spring clip engages with the lower punch drawbar. The position of the recess is predetermined to maintain a set axial position. The spring clip can be produced separately from the core rod but must be maintained within the recess when the core rod is inserted into the lower punch. During the entire insertion process and before the spring clip and groove engage, the spring clip floats within the recess of the core rod. The spring clip does not expand unless a force is applied to it, and it does not compress unless a force is applied to it.

[0036] The spring clip has a ring shape with two ends 14a, 14b as shown in Figure 7. The cross-sectional diameter of the spring clip is selected so that the spring clip is in an unexpanded state when received in the recess.

[0037] When the spring clip engages the groove, the outer surface 15 of the spring clip is at least partially pressed against the surface 29 of the groove. The spring clip is coupled to the groove by the axial and radial expansion of the spring clip within the groove. This coupling must resist the large forces generated by the large weight. The force of the spring clip must be greater than the force due to the weight of the core rod assembly and greater than the axial force on the core rod that may occur during the loading cycle, but much less than the clamping force of the core rod chuck. The weight of the lower punch does not need to be considered because the spring clip is not used to lift the lower punch.

[0038] In one embodiment shown in Figure 7, the spring clip has an inner diameter of 9 mm and a cross section of 0.8 mm. The pull-out force varies between approximately 25 N and 45 N, depending on whether the core rod is perfectly centered in the lower punch or pressed to the side. For core rods weighing less than 2 kg, a minimum pull-out force of 50 N is required. To achieve a robust system, the core rod must be designed to be lightweight. The diameter and material of the spring clip can vary depending on the application and the size and weight of the core rod. [Explanation of symbols]

[0039] 1. Powder molding press machine 10 Core Rod 12 Core Rod Drawbar 13 Core rod body 14 Spring Clip 15 Outer surface of spring clip 16 Core rod recess 17 Core rod outer surface 17a First section of core rod 17b Second section of core rod 20 Lower punch 21 Lower punch pallet 22 Lower punch drawbar 23 Lower punch chuck 24 Inner surface of lower punch drawbar 24a Lower punch drawbar first section 24b Second section of lower punch drawbar 25 Lower punch gripper section 26 Lower punch hole 27 Lower punch drawbar hole 28 Groove 29 Inner surface of groove 30 Die 31 Dye Palette 32 Dyed Rover 33 Die chuck 34 Die hole 35 First Gripper Interface 101 Upper Plate 102 Intermediate plate 103 Lower Plate 104,105 Guide pillar

Claims

1. A tool assembly for a powder molding press (1) comprising a lower punch chuck (23) and a core rod chuck (13), comprising: a lower punch (20) having a lower punch drawbar (22) for holding said lower punch in said lower punch chuck in said machine; and a core rod (10) having a core rod drawbar (12) for holding said core rod in said core rod chuck; A tool assembly comprising:

1. A tool assembly comprising: a coupling mechanism for enabling a connection between the lower punch and the core rod, the coupling mechanism comprising a male coupling element (14) arranged on an outer surface of the core rod and a female coupling element (28) arranged on an inner surface of the lower punch drawbar, the male coupling element being a resilient element.

2. 2. A tool assembly according to claim 1, wherein the male coupling element is a ring-shaped elastic element, in particular an open ring-shaped element having two ends.

3. The tool assembly of claim 1 or 2, wherein the male coupling element is a spring clip.

4. The tool assembly of claim 1 , wherein the male coupling element is disposed at least partially around an outer periphery of the core rod.

5. 2. The tool assembly of claim 1, wherein a recess (16) is formed in an outer peripheral surface of the core rod to accommodate the male coupling element, and in particular, the recess is configured such that the male coupling element is movably captured within the recess.

6. The tool assembly according to claim 1 , wherein the male coupling element has a circular cross-section, in particular the male coupling element is round in cross-section.

7. 2. The tool assembly of claim 1, wherein an inner circumferential surface of the lower punch drawbar defines at least one groove (28) that functions as the female coupling element, the groove having a defined axial height.

8. The tool assembly of claim 7 , wherein the cross-sectional diameter of the male coupling element is at least half the height of the groove or substantially equal to the height of the groove.

9. The tool assembly of claim 1 , wherein the male coupling element is made of metal.

10. The tool assembly of claim 1 , wherein the male coupling element is disposed proximate a lower end of the core rod.

11. The tool assembly of claim 1 , wherein the female coupling element is disposed at a lower end of the lower punch drawbar.

Images