A cold extrusion die set and its forming method for a toothed structure single-sided collar

Abstract

This invention discloses a cold extrusion die assembly and its forming method for a toothed single-sided collar. The die assembly consists of a shearing die, a preliminary upsetting die, an inner hole stretching die, a flange pre-upsetting die, a flange forming die, a punching and blanking die, and a locking tooth forming die; it also includes clamps for feeding materials in conjunction with each die; the cold upsetting process is a six-station forming process, in which preliminary upsetting, inner hole stretching, pre-upsetting of the flange, forming of the flange, punching and blanking, and forming of the locking teeth are performed sequentially after shearing and blanking. This invention adopts a positive extrusion stretching process, which can better control the uniformity of the wall thickness of collar-type products without exceeding the material deformation limit; the process of punching and blanking first, followed by forming of the locking teeth, avoids the ejector pin being subjected to multiple forces such as punching and extrusion simultaneously, thus preventing breakage and improving the service life of the ejector pin; one of the processes improves the quality of the flange inner hole after punching and the forming of the locking teeth, and ensures the consistency and stability of the locking tooth structure dimensions.

Description

Technical Field

[0001] This invention belongs to the field of riveting technology, specifically to the riveting category (B21J) and fastener category (F16B) in metal machining, and relates to a cold extrusion die assembly and its forming method for a toothed single-sided collar. Background Technology

[0002] Riveted fasteners typically consist of rivets and collars. In the manufacturing of riveted fasteners, existing standard collars typically have relatively thick tube walls and no internal steps or special structures. Based on the principle of constant volume during cold extrusion deformation, standard collars are usually designed using reverse extrusion molding, making the processing technology and mold structure relatively simple. However, for thin-walled long tube structures, conventional collar forming methods cannot guarantee the uniformity of wall thickness. Furthermore, collars used for internal locking single-drum applications have internal steps and small tooth structures, which cannot be formed using conventional processes.

[0003] A type of internally locking single-drum rivet consists of a rivet and a collar. The rivet head has a movable locking ring, and the shank has a locking groove. During installation, under the action of the locking ring and the riveting gun, the collar is compressed to form a local bulge and internal deformation, creating a double-locking structure. This double-locking structure gives the internally locking single-drum rivet excellent shock resistance. After installation, a high-strength rivet core is locked inside the collar, thus providing excellent shear resistance. Furthermore, the internally locking single-drum rivet has no protrusions after installation, preventing interference and resulting in an aesthetically pleasing appearance. It is widely used in the automotive and urban rail markets. The internally locking single-drum collar is made of 08AL material, and the processing technology is: cold extrusion molding → heat treatment → surface treatment. The collar has a two-stage stepped hole, with the internal steps extending in the opposite direction to form a small tooth structure. During riveting, the small teeth are compressed, causing metal flow and forming a locking structure with the locking groove. The deformation area of ​​the collar tube deforms during riveting to form a blind rivet head. Manufacturing through cold extrusion molding effectively ensures the consistency of the collar's dimensions and the stability of the small teeth formation. Currently, due to the technical difficulty and manufacturing stability required, most internal locking single-drum rivets used in the domestic automotive and urban rail transit sectors are imported products. Summary of the Invention

[0004] This invention discloses a cold extrusion die assembly and its forming method for a toothed single-sided collar, addressing the shortcomings of existing manufacturing technologies. The purpose of this invention is to provide a cold extrusion die assembly and its forming method for manufacturing toothed single-sided collars with stable appearance, dimensions, good wall thickness uniformity, and high product consistency, achieving these advantages.

[0005] This invention is achieved through the following technical solution:

[0006] A cold extrusion die assembly for a toothed single-sided collar, wherein the die assembly is used in conjunction with a cold heading machine for cold heading, characterized in that: the die assembly consists of a shearing die, a primary heading die, an inner hole stretching die, a flange pre-heading die, a flange forming die, a punching and blanking die, and a locking tooth forming die, and also includes clamps for feeding materials in conjunction with each die.

[0007] Shearing dies, including shears and scissors, are used to cut workpieces into bars of a fixed length by shearing them.

[0008] The initial upsetting die includes a punch at one station, a main die at one station, and an ejector pin at one station. It is used to optimize the flatness of the end face of the sheared bar after forming.

[0009] The inner hole stretching die includes a two-station punch, a two-station main die, a two-station ejector pin, and a two-station push tube. It is used to simultaneously reduce the diameter of the tube and stretch the inner hole using a positive extrusion method, and complete the sleeve in one step.

[0010] The flange pre-upsetting die includes a three-station punch, a three-station punch, a three-station main die, a three-station ejector pin, and a three-station push tube, and is used for pre-upsetting tapered flange heads;

[0011] The flange forming mold includes a four-station punch, a four-station punch, a four-station main mold, a four-station ejector pin, and a four-station push tube, used to form a flange.

[0012] The punching and blanking die includes a five-station punch tube, a five-station main die, a five-station ejector pin, and a five-station push tube, and is used to complete the punching and blanking of the center hole of the workpiece.

[0013] The locking tooth forming mold includes a six-station punch tube, a six-station main mold, a six-station ejector pin, and a six-station push tube. The inner diameter of the six-station main mold is equal to the outer diameter of the forming sleeve. The front ring rod of the six-station ejector pin is equipped with a shaping part, the diameter of which is equal to the inner diameter of the flange. The diameter of the rear rod of the six-station ejector pin is equal to the inner diameter of the sleeve. The connecting part between the front and rear of the six-station ejector pin is equipped with a six-station ejector pin shoulder with an angle of 5°. The locking tooth forming mold is used to shape the sleeve and form the locking tooth at the inner end of the sleeve.

[0014] Furthermore, each die punch and / or punch is mounted on the main slide of the cold heading machine, which can reciprocate. The main die, ejector pin and / or push tube are mounted on the die base of the forming machine. The running mechanism and ejection mechanism are arranged above and behind the die base. The blanks are transferred between each station using clamps.

[0015] Preferably, both the shearing die and the shears are provided with through holes for the bar stock to pass through. The through hole at the rear end of the shearing die is a flared expansion structure with the outer end larger than the inner end. The gap W1 between the shears and the shearing die is 0.02D1mm, the inner diameter D2 of the shears is 1.01D1mm, the inner diameter D3 of the shearing die is 1.015D1mm, and the feed angle α1 of the flared expansion structure of the shearing die is 30°, where D1 is the diameter of the bar stock.

[0016] Preferably, the punch and ejector pin at one station are cylindrical ejector rod structures, the main mold at one station is provided with a through hole with a variable diameter forming step, the inner diameter of the main mold D4 = D1 + 0.1 mm, the forming radius R1 is 0.2D4 mm, and the ejector pin imprint hole depth W2 = 0.5 mm.

[0017] Preferably, the second-station punch and the second-station ejector pin are cylindrical ejector rod structures, the second-station push tube is a sleeve fitted on the second-station ejector pin, and the second-station main mold is provided with a variable diameter through hole; the inner diameter of the main mold D5a = D4 + 0.05 mm, the inner diameter of the main mold with reduced diameter D5b = D0d - 0.06 mm, the inner diameter of the ejector pin extension hole D5c = D0c + 0.1 mm, the diameter of the main mold after reduction D5e = D5b + 0.06 mm, the guide angle for reduction α2 = 60°, the transition angle after reduction α3 = 30°, the bandwidth of the main mold with reduced diameter H1 = 0.8 mm, the bandwidth of the ejector pin extension hole H2 = 0.5 mm, and the transition fillet before reduction R2 = 0.3 mm; wherein, D0d is the outer diameter of the sleeve, and D0c is the inner diameter of the sleeve.

[0018] Preferably, the three-station punch and the three-station ejector pin are cylindrical ejector rod structures, the three-station punch and the three-station main mold are provided with variable diameter through holes, and the three-station push tube is a sleeve fitted on the three-station ejector pin; the inner diameter of the main mold is D6a = D5b + 0.02mm, the inner diameter of the ejector pin is D6b = D5c - 0.04mm, and the pre-upsetting flange bevel angle α4 = 30°.

[0019] Preferably, the four-station punch and the four-station ejector pin are cylindrical ejector rod structures, the four-station punch and the four-station main mold are provided with through holes, the end face of the four-station punch is provided with a flange forming cavity, and the four-station push tube is a sleeve fitted on the four-station ejector pin; the diameter of the punch flange forming cavity is D8 = D0a + 1mm, the depth of the punch forming cavity is W3 = W0a - 0.6mm, the depth of the punch hole is W4 = 2.2mm, the distance from the push tube to the horizontal plane of the main mold is W5 = W0bmm, the inner diameter of the main mold is D7a = D6a + 0.02mm, and the diameter of the ejector pin is D7b = D6b - 0.04mm; where D0a is the outer diameter of the flange, W0a is the flange thickness, and W0b is the sleeve length.

[0020] Preferably, the five-station punch tube is provided with a variable diameter through hole, the five-station main mold is provided with a through hole, the five-station ejector pin is a variable diameter cylindrical ejector rod structure, and the five-station push tube is a sleeve fitted on the five-station ejector pin; the inner diameter of the main mold is D9a = D0d mm, the diameter of the punching ejector pin is D9b = D0b - 0.03 mm, the inner tooth diameter of the punch tube is D10 = D0b - 0.06 mm, and the working width of the punching ejector pin is H3 = 0.8 mm.

[0021] Preferably, the six-station punch tube is provided with a variable diameter through hole, the six-station main mold is provided with a through hole, the six-station ejector pin is a variable diameter cylindrical ejector rod structure, the variable diameter section forms a shoulder and a groove formed by the diameter reduction is provided in front of the shoulder, and the six-station push tube is a sleeve fitted on the six-station ejector pin; wherein, the front ring rod of the six-station ejector pin is provided with a variable diameter shaping part with a smooth transition along the axial surface of the rod; the inner diameter of the main mold D10a=D9amm, the maximum diameter of the ejector pin shaping part D10b=D0bmm, the diameter of the ejector pin rod D10c=D0cmm, and the ejector pin shoulder angle α5=5°.

[0022] The present invention also discloses a forming method for a cold extrusion die assembly using the above-mentioned toothed single-sided collar: the collar is cold-headed using wire rod, and the material is lubricated by phosphating and saponification treatment of the wire rod surface.

[0023] The cold heading process is a six-station forming process, which includes: after shearing and blanking, the following steps are performed in sequence: initial heading and shaping, inner hole stretching, pre-heading flange, forming flange, punching and blanking, and forming locking teeth.

[0024] The shearing and blanking process is completed by the shearing die and the shears together. The shearing length is set by the forming machine operation panel and the stop gauge. The straightened wire rod enters the inner hole of the shearing die under the operation of the feeding wheel. When it contacts the front stop gauge, the shears complete the shearing and blanking of the wire rod under the reciprocating motion of the cutting mechanism.

[0025] Initial upsetting and shaping are performed at one station. The cut bar stock is moved to another station via a clamp. When the punch at one station pushes the bar stock 4mm into the main mold at one station, the clamp releases. The main slide continues to push the punch forward and compress the bar stock into the mold cavity of the main mold at one station, causing deformation. When the main slide reaches the top dead center, the initial upsetting and shaping is completed, and the punch begins to retract with the main slide. At the same time, the rear ejector mechanism pushes the ejector pin forward to eject the workpiece from the main mold at one station. When the front end of the workpiece is ejected to the mold surface of the main mold at one station by 6mm, the clamp at two stations closes to hold the workpiece until the workpiece is completely ejected, thus completing the shaping process at one station and optimizing the end face quality of the sheared bar stock.

[0026] The inner hole stretching is formed by two stations. The clamps at the two stations move the workpiece from the first station to the second station. When the punch at the second station pushes the workpiece into the main mold of the second station by 4mm, the clamps release and the punch continues to push the workpiece forward, forcing it to be stretched. Under the constraints of the main mold, ejector pin, and push tube, the metal flows in the forward direction to form the inner hole. After stretching is completed, the punch moves backward with the main slide. The rear ejection mechanism pushes the push tube forward to eject the workpiece from the main mold. When the front end of the workpiece is ejected to the mold surface by 11mm, the clamps at the third station close and clamp the tube of the workpiece until the workpiece is completely ejected, completing the tube diameter reduction and stretching of the inner hole at the two stations.

[0027] The pre-upsetting flange is formed in three stations. The three-station clamp moves the workpiece from the two stations to the three stations. When the three-station punch pushes the workpiece into the main mold of the three stations by 5mm, the clamp releases. The punch continues to push the workpiece and compress it to deform. Under the combined action of the punch, punch bar, ejector pin, push tube and main mold, the metal flows according to the confined space to complete the pre-upsetting of the flange. The rear ejection mechanism pushes the push tube forward to eject the workpiece from the main mold. When the workpiece is ejected to 11mm from the main mold surface, the four-station clamp closes to clamp the tube part of the workpiece until the workpiece is completely ejected, completing the three-station tapered pre-upsetting flange forming.

[0028] The flange is formed in four stations. The four-station clamps transfer the workpiece from the three stations to the fourth station. When the fourth-station punch pushes the workpiece 5mm into the main mold of the fourth station, the clamps release. The punch continues to push and compress the workpiece, deforming it. Under the combined action of the punch, punch bar, ejector pin, and main mold, the metal flows according to the confined space, completing the flange forming. The punch then retracts. The rear ejection mechanism pushes the ejector tube to eject the workpiece from the main mold. When the workpiece is ejected to 10mm from the main mold surface, the five-station clamps close to clamp the workpiece tube until the workpiece is completely ejected, completing the four-station flange forming.

[0029] The punching and blanking process is carried out at the fifth station. The fifth station clamp transfers the workpiece from the fourth station to the fifth station. When the fifth station punch tube pushes the workpiece into the fifth station main mold by 3mm, the clamp releases. The fifth station punch tube continues to push the workpiece. Under the combined action of the punch tube, main mold, ejector pin, and push tube, the waste material is punched off, and the punch tube retracts. The rear ejection mechanism pushes the push tube to eject the workpiece. When the workpiece is ejected to 14mm from the main mold surface, the sixth station clamp closes to clamp the workpiece tube until the workpiece is completely ejected, completing the punching and blanking process.

[0030] The locking teeth are formed in a six-station process. The six-station clamp transfers the workpiece from the five-station clamp to the six-station clamp. When the six-station punch pushes the workpiece 3mm into the six-station main mold, the clamp releases, and the six-station punch continues to push the workpiece. Under the combined action of the six-station punch, the six-station main mold, the six-station ejector pin, and the six-station pusher tube, the shaping and locking tooth structure on the inner hole step is completed. The six-station punch tube then retracts. The rear ejection mechanism pushes the pusher tube to eject the workpiece until it is completely ejected, thus completing the sleeve shaping and locking tooth formation.

[0031] This invention employs a continuous cold extrusion forming method, completing the processes of shearing, initial upsetting, inner hole stretching, pre-upsetting flange, flange forming, and blanking and locking teeth forming through a forming die and rotating clamps, thus realizing continuous cold extrusion production of collars. Among these processes, the reverse locking teeth inside the collar are a key factor influencing the riveting quality and performance of the product, and also a critical point affecting the quality of the cold extrusion forming process. Furthermore, because the wall of the collar's deformation zone is relatively thin, the uniformity of the wall thickness greatly affects the riveting quality of the product.

[0032] This invention employs both positive extrusion stretching and strong shrinkage processes in the same workstation to form the collar tube structure, effectively controlling the uniformity of the collar product wall thickness without exceeding the material deformation limit. Through batch production testing, the stretching and strong shrinkage processes used in this invention have demonstrated stable processing performance and long die life.

[0033] This invention relies on the local structure of a through-hole ejector pin to simultaneously improve the quality of the flange inner hole after punching and to form locking teeth. Specifically, a sloping shoulder structure is designed at the head of the through-hole ejector pin, and a concave groove formed by a diameter reduction is set in front of the sloping shoulder. When the punch tube pushes the workpiece to contact and squeeze with the ejector pin, the workpiece is squeezed against the arc of the ejector pin head, completing the shaping of the flange inner hole. After continuing to push the workpiece to contact the sloping shoulder of the ejector pin, part of the metal in the workpiece is squeezed and flows into the groove. When the through-hole ejector pin withdraws, the metal in the groove flows in the opposite direction to form the locking tooth structure. This invention ensures the consistency and stability of the locking tooth structure dimensions while guaranteeing the forming quality, realizing continuous cold extrusion forming of this type of collar.

[0034] Advantages of this invention: This invention adopts a continuous cold extrusion forming method, relying on a six-station parts forming machine, and designs and selects cold heading discs of appropriate size. Through forming process methods and tooling design, it completes process steps such as shearing, initial upsetting, inner hole stretching, pre-upsetting flange, forming flange, punching and blanking, and forming locking teeth, thereby realizing the continuous cold extrusion production of toothed single-sided collars.

[0035] This invention employs a positive extrusion stretching process, which can effectively control the uniformity of wall thickness in collar-type products without exceeding the material deformation limit. A process of first punching and blanking, followed by forming the locking teeth, avoids the ejector pin being subjected to multiple forces such as punching and extrusion simultaneously, thus preventing breakage and extending the ejector pin's service life. A single process is designed to improve the quality of the flange inner hole after punching and to form the locking teeth, while ensuring the consistency and stability of the locking tooth structure dimensions. This enables continuous cold extrusion forming of toothed single-sided collars. Attached Figure Description

[0036] Figure 1This is a schematic diagram of the collar structure made according to the present invention; in the figure, a is the flange, b is the sleeve, c is the locking tooth, i.e., the small tooth, W0a is the flange thickness, W0b is the sleeve length, D0a is the flange outer diameter, D0b is the flange inner diameter, D0c is the sleeve inner diameter, and D0d is the sleeve outer diameter.

[0037] Figure 2 This is a schematic diagram of the cold heading process for collars; in the diagram, d is the sheared blank bar, e is the workpiece at station 1, f is the workpiece at station 2, g is the workpiece at station 3, h is the workpiece at station 4, i is the workpiece at station 5, j is the workpiece at station 6, and D1 is the blanking diameter.

[0038] Figure 3 This is a schematic diagram of a shearing die; in the diagram, A0 is the shear, B0 is the shearing die, D2 is the inner diameter of the shear, D3 is the inner diameter of the shearing die, W1 is the gap between the shear and the shearing die, and α1 is the cutting angle of the shearing die.

[0039] Figure 4 This is a schematic diagram of a cold heading forming station structure; in the diagram, A1 is a station punch, B1 is a station main mold, C1 is a station ejector pin, D4 is the inner diameter of the station main mold, R1 is the shaping fillet of the station main mold, and W2 is the depth of the ejector pin hole in the station.

[0040] Figure 5 This is a schematic diagram of a two-station cold heading process. Figure 6 yes Figure 5 A magnified view of the middle circle; in the figure, A2 is the punch of the second station, B2 is the main mold of the second station, C2a is the ejector pin of the secondary station, C2b is the push tube of the second station, D5a is the inner diameter of the main mold of the second station, D5b is the inner diameter of the main mold of the second station with reduced diameter, D5c is the inner diameter of the ejector pin of the second station with stretched diameter, D5e is the transition inner diameter of the main mold of the second station, α2 is the guide angle for reduced diameter, α3 is the transition angle after reduced diameter, H1 is the bandwidth of the main mold with reduced diameter, H2 is the bandwidth of the ejector pin of the second station with stretched diameter, and R2 is the transition fillet before reduced diameter.

[0041] Figure 7 This is a schematic diagram of a three-station cold heading forming structure; in the diagram, A3a is the three-station punch, A3b is the three-station die, B3 is the three-station main die, C3a is the three-station ejector pin, C3b is the three-station push tube, D6a is the inner diameter of the three-station main die, D6b is the inner diameter of the three-station ejector pin, and α4 is the angle of the die pre-heading flange.

[0042] Figure 8 This is a schematic diagram of a four-station cold heading forming structure. In the diagram, A4a is the four-station punch, A4b is the four-station punch, B4 is the four-station main mold, C4a is the four-station ejector pin, C4b is the four-station push tube, D8 is the diameter of the four-station punch cavity, W3 is the depth of the four-station punch cavity, W4 is the depth of the four-station punch hole, W5 is the distance from the push tube to the horizontal plane of the main mold, D7a is the inner diameter of the four-station main mold, and D7b is the diameter of the four-station ejector pin.

[0043] Figure 9 This is a schematic diagram of a five-station cold heading process. Figure 10 yes Figure 9 A magnified view of the middle circle; in the figure, A5 is the five-station punch tube, B5 is the five-station main mold, C5a is the five-station ejector pin, C5b is the five-station push tube, D9a is the inner diameter of the five-station main mold, D9b is the diameter of the five-station punching ejector pin, H3 is the working bandwidth of the punching ejector pin, and D10 is the diameter of the inner teeth of the five-station punch tube.

[0044] Figure 11 This is a schematic diagram of a six-station cold heading process. Figure 12 yes Figure 11 A magnified view of the middle circle; in the figure, A6 is the six-station punch tube, B6 is the six-station main mold, C6a is the six-station ejector pin, C6b is the six-station push tube, D10a is the inner diameter of the six-station main mold, D10b is the diameter of the six-station ejector pin shaping part, D10c is the diameter of the six-station ejector pin rod part, and α5 is the angle of the six-station ejector pin shoulder.

[0045] Figure 13 This is a schematic diagram of the outline of the four-point clamp E used for cold heading. Detailed Implementation

[0046] The present invention will be further described below with reference to specific embodiments. These specific embodiments are further explanations of the principles of the present invention and are not intended to limit the present invention in any way. Any technology that is the same as or similar to the present invention does not exceed the scope of protection of the present invention.

[0047] Refer to the attached diagram.

[0048] This invention utilizes ML08AL wire rod as raw material for a toothed single-sided collar. Cold heading is achieved on a six-station parts forming machine through automatic feeding, extrusion deformation, and clamping. The specific forming process includes shearing, initial heading, inner hole stretching, pre-heading flange, forming flange, punching and blanking, and forming locking teeth. The cold heading process is designed as a six-station forming, with each station's mold mainly consisting of a punch (also called a male mold), an ejector pin, and a main mold (also called a female mold). The punch is mounted on the main slide of the forming machine and can reciprocate. The main mold and ejector pin are mounted on the mold base of the forming machine, with a running mechanism and an ejection mechanism located above and behind the mold base. Clamping automatically transfers the blank between stations, continuously and automatically achieving cold heading of the internally locking single-drum collar.

[0049] The ML08AL cold heading wire rod used in the collar adopts a process of one spheroidizing annealing and two cold drawing to improve the uniformity of wire rod structure and dimensional consistency. The surface of the wire rod is treated with phosphating to improve the lubrication performance of the material surface, which is beneficial to the metal flow during cold heading.

[0050] The shearing and blanking are completed by the shearing die and the shears. The shearing length is set by the forming machine operation panel and the stop gauge. The straightened wire rod enters the inner hole of the shearing die under the operation of the feeding wheel. When it contacts the front stop gauge, the shears complete the shearing and blanking of the wire rod under the reciprocating motion of the cutting mechanism.

[0051] The forming process at one station: The cut bar stock is moved to the first station via the clamping device. When the punch at the first station pushes the bar stock into the main mold of the first station by about 4mm, the clamping device releases. The main slide continues to push the punch forward and compress the bar stock into the mold cavity of the main mold at the first station, causing deformation. When the main slide reaches the top dead center position, the initial upsetting is completed, and the punch begins to retract with the main slide. At the same time, the rear ejection mechanism pushes the ejector pin forward, ejecting the workpiece from the main mold of the first station. When the front end of the workpiece is ejected to about 6mm from the mold surface of the main mold at the first station (the rear half of the workpiece is still in the mold cavity to prevent it from falling out. The same applies below), the clamping device at the second station closes to hold the workpiece until it is completely ejected.

[0052] Two-station forming process: The two-station clamp moves the workpiece from the first station to the second station. When the second-station punch pushes the workpiece into the main mold of the second station by about 4mm, the clamp releases, and the punch continues to push the workpiece forward, forcing it to be stretched. Under the constraint of the main mold, ejector pin, and push tube, the metal flows forward to form an inner hole. After stretching is completed, the punch retracts with the main slide. The rear ejection mechanism pushes the push tube forward to eject the workpiece from the main mold. When the front end of the workpiece is ejected to about 11mm from the mold surface, the three-station clamp closes to clamp the tube part of the workpiece until the workpiece is completely ejected.

[0053] The three-station forming process: The three-station clamp moves the workpiece from the two-station position to the three-station position. When the three-station punch pushes the workpiece into the main mold of the three-station position by about 5mm, the clamp releases. The punch continues to push and compress the workpiece, deforming it. Under the combined action of the punch, punch bar, ejector pin, push tube, and main mold, the metal flows according to the confined space, completing the pre-upsetting of the flange. The rear ejection mechanism pushes the push tube forward to eject the workpiece from the main mold. When the workpiece is ejected to about 11mm from the main mold surface, the four-station clamp closes to clamp the tube part of the workpiece until the workpiece is completely ejected.

[0054] The four-station forming process: The four-station clamp transfers the workpiece from the three-station station to the four-station station. When the four-station punch pushes the workpiece into the main mold of the four-station station by about 5mm, the clamp releases. The punch continues to push and compress the workpiece, deforming it. Under the combined action of the punch, punch bar, ejector pin, and main mold, the metal flows according to the confined space, completing the flange forming. The punch then retracts. The rear ejection mechanism pushes the ejector tube to eject the workpiece from the main mold. When the workpiece is ejected to about 10mm from the main mold surface, the five-station clamp closes to clamp the tube part of the workpiece until the workpiece is completely ejected.

[0055] Five-station forming process: The five-station clamp transfers the workpiece from the four-station clamp to the fifth station. When the fifth-station punch pushes the workpiece into the fifth-station main mold by about 3mm, the clamp releases, and the punch continues to push the workpiece. Under the combined action of the punch, ejector pin, and main mold, scrap is punched off, and the punch retracts. The rear ejection mechanism pushes the ejector tube to eject the workpiece. When the workpiece is ejected to about 14mm from the main mold surface, the six-station clamp closes to clamp the workpiece tube until the workpiece is completely ejected.

[0056] Six-station forming process: The six-station clamp transfers the workpiece from the five-station station to the six-station station. When the six-station punch pushes the workpiece into the main mold of the six-station station by about 3mm, the clamp releases, and the punch continues to push the workpiece. Under the combined action of the punch, ejector pin, and main mold, the locking tooth structure on the inner hole step is formed, and the punch retracts. The rear ejection mechanism pushes the ejector tube to eject the workpiece until the workpiece is completely ejected. At this point, the cold heading forming of the inner locking single-drum collar is completed.

[0057] The gap between the shearing die and the shears in this invention is 0.02 times the diameter of the cold heading wire rod. The inner diameter of the shearing die is 1.015 times the diameter of the cold heading wire rod, and the inner diameter of the shears is 1.01 times the diameter of the cold heading wire rod.

[0058] The inner diameter of the main mold at station 1 is 0.1 mm larger than the diameter of the bar stock, and the rounded corners of the forming transition inside the mold cavity are 0.2 times the diameter of the material.

[0059] The two-station design allows for simultaneous workpiece stretching and diameter reduction. The inner diameter of the main mold cavity in the second station is 0.05mm larger than the workpiece diameter in the first station. The transition radius between the main mold cavity and the diameter reduction guide is half the inner diameter of the main mold cavity. The cone angle of the diameter reduction guide inside the mold is 60°, and the width of the diameter reduction ligament is 0.8mm. The stretching ligament width of the ejector pin head in the second station is 0.5mm. The main mold has four venting grooves to prevent mold expansion during cold heading.

[0060] The inner diameter of the main mold in stations three, four, and five is 0.02 mm larger than the diameter of the workpiece tube in the previous station.

[0061] The bevel angle of the pre-forging flange of the three-station punch is 30°.

[0062] The clamps at positions one, two, three, four, five, and six are four-point clamp structures used for clamping and fixing workpieces.

[0063] The main dies at stations one, two, three, four, five, and six, as well as the part of the punch at station three that contacts the workpiece, are all made of tungsten steel with a heat treatment hardness of approximately HRC63.

[0064] The three- and four-station punches are designed with a through-hole structure. The through-hole length is the length of the workpiece included in the punch, to prevent the punch from carrying material when forming the flange.

[0065] The six-position ejector pin can realize the functions of flange inner hole shaping and forming locking teeth. The ejector pin is made of ASP60 material and has a heat treatment hardness of about HRC68.

[0066] The process steps of the present invention will be described in detail below with reference to the accompanying drawings.

[0067] like Figure 1 As shown, the internal locking single-drum collar consists of a flange, locking teeth (small teeth), and a sleeve. The reverse small teeth inside the collar are a key factor affecting the riveting quality and performance of the product, and also a critical point affecting the quality of the cold extrusion molding process. Furthermore, because the wall of the collar's deformation zone is relatively thin, the uniformity of the wall thickness greatly affects the riveting quality of the product.

[0068] like Figure 2 As shown, the cold heading process of the inner locking single drum sleeve ring sequentially forms the following semi-finished and finished products: shearing and blanking (d), initial heading and shaping (e), inner hole stretching (f), pre-heading flange (g), forming flange (h), punching and blanking (i), and forming locking teeth (j).

[0069] like Figure 3 As shown, the shearing and blanking are jointly completed by shears A0 and shearing die B0. The shearing length is set through the forming machine operation panel and the stop gauge. The straightened wire rod enters the inner hole of the shearing die under the operation of the feeding wheel. When it contacts the front stop gauge, the shears complete the shearing and blanking of the wire rod under the reciprocating motion of the cutting mechanism. The gap between the shears and the shearing die is taken as approximately 0.02D1, the inner diameter of the shears D2 is taken as approximately 1.01D1, the inner diameter of the shearing die D3 is taken as approximately 1.015D1, and the die entry angle α1 = 30°. The bar stock can easily enter the die, resulting in a bar stock with a relatively flat cut surface.

[0070] like Figure 4 As shown, the initial upsetting is completed by a punch A1 at one station, a main mold B1 at one station, and an ejector pin C1 at one station. The cut bar stock is moved to the first station via a clamping device. When the punch at one station pushes the bar stock into the main mold at one station by about 4mm, the clamping device releases. The main slide continues to push the punch forward and compress the bar stock into the mold cavity of the main mold at one station, deforming it. When the main slide reaches the top dead center position, the initial upsetting is completed, and the punch begins to retract with the main slide. At the same time, the rear ejection mechanism pushes the ejector pin forward, ejecting the workpiece from the main mold at one station. When the front end of the workpiece is ejected to about 6mm from the mold surface of the main mold at one station (the rear half of the workpiece is still in the mold cavity to prevent it from falling out. The same applies below), the clamping device at two stations closes to hold the workpiece until it is completely ejected. The inner diameter of the main mold is D4 = D1 + 0.1, the shaping fillet radius R1 is 0.2D4, and the ejector pin hole depth W2 = 0.5mm. A suitable clearance is provided to facilitate the entry of the workpiece from the previous station into the main mold of the next station. The shaping process optimizes the quality of the sheared bar end face, ensuring balanced force contact with the mold in subsequent processes, resulting in uniform metal flow and improved workpiece accuracy.

[0071] like Figure 5 , Figure 6 As shown, the inner hole stretching is accomplished by the second-station punch A2, the second-station main mold B2, the secondary-station ejector pin C2a, and the second-station push tube C2b. The second-station clamp moves the workpiece from the first station to the second station. When the second-station punch pushes the workpiece into the second-station main mold by about 4mm, the clamp releases, and the punch continues to push the workpiece forward, forcing it to be stretched. Under the constraint of the main mold, ejector pin, and push tube, the metal flows forward, resulting in diameter reduction and stretching to form the inner hole. After reaching the front dead center, the punch retracts with the main slide. The rear ejection mechanism pushes the push tube forward to eject the workpiece from the main mold. When the front end of the workpiece is ejected to about 11mm from the mold surface, the third-station clamp closes to clamp the workpiece tube until the workpiece is completely ejected. The inner diameter of the main mold is D5a = D4 + 0.05, the inner diameter of the main mold after diameter reduction is D5b = D0d - 0.06, the inner diameter of the ejector pin stretching hole is D5c = D0c + 0.1, the diameter of the main mold after diameter reduction is D5e = D5b + 0.06, the diameter reduction guide angle is α2 = 60°, the transition angle after diameter reduction is α3 = 30°, the bandwidth of the main mold after diameter reduction is H1 = 0.8mm, the bandwidth of the ejector pin stretching hole is H2 = 0.5mm, and the transition fillet radius before diameter reduction is R2 = 0.3mm. The tube diameter reduction and inner hole stretching are performed simultaneously using a positive extrusion method, forming the sleeve in one step.

[0072] like Figure 7 As shown, the pre-upsetting flange is completed by a three-station punch A3a, a three-station punch A3b, a three-station main mold B3, a three-station ejector pin C3a, and a three-station push tube C3b. The three-station clamp moves the workpiece from the two stations to the three stations. When the three-station punch pushes the workpiece into the three-station main mold by about 5mm, the clamp releases, and the punch continues to push and deform the workpiece. Under the combined action of the punch, punch, ejector pin, push tube, and main mold, the metal flows according to the confined space, completing the pre-upsetting of the flange. The rear ejection mechanism pushes the push tube forward to eject the workpiece from the main mold. When the workpiece is ejected to about 11mm from the main mold surface, the four-station clamp closes to clamp the workpiece tube until the workpiece is completely ejected. The inner diameter of the main mold is D6a = D5b + 0.02, the inner diameter of the ejector pin is D6b = D5c - 0.04, and the angle α4 of the punch-upset flange is 30°. Using a tapered pre-forged flange facilitates metal flow during subsequent flange forming, thus improving the quality of the formed flange.

[0073] like Figure 8As shown, the formed flange is constructed using a four-station punch A4a, a four-station punch A4b, a four-station main mold B4, a four-station ejector pin C4a, and a four-station push tube C4b. The four-station clamp transfers the workpiece from the three-station position to the four-station position. When the four-station punch pushes the workpiece into the four-station main mold by approximately 5mm, the clamp releases. The punch continues to push and deform the workpiece. Under the combined action of the punch, punch, ejector pin, and main mold, the metal flows within the confined space, completing the flange formation. The punch then retracts. The rear ejection mechanism pushes the push tube to eject the workpiece from the main mold. When the workpiece is ejected to approximately 10mm from the main mold surface, the five-station clamp closes to hold the workpiece tube until the workpiece is completely ejected. The die cavity diameter is D8 = D0a + 1, the die cavity depth is W3 = W0a - 0.6, the punch hole depth is W4 = 2.2mm, the distance from the ejector tube to the main die horizontal plane is W5 = W0b, the main die inner diameter is D7a = D6a + 0.02, and the ejector pin diameter is D7b = D6b - 0.04. This appropriate distance allows the flange to form freely outside the main die, reducing the flange forming load. Simultaneously, the punch hole controls the connecting skin to be in the appropriate position and reduces its thickness, improving die life and the quality of subsequent punched connecting skin.

[0074] like Figure 9 , Figure 10 As shown, the punching and blanking process is completed by the five-station punch tube A5, the five-station main die B5, the five-station ejector pin C5a, and the five-station push tube C5b. The station clamps transfer the workpiece from the four-station station to the five-station station. When the five-station punch pushes the workpiece into the five-station main die about 3mm, the clamps release, and the punch continues to push the workpiece. Under the combined action of the punch, ejector pin, and main die, the workpiece blanking is completed, and the punch retracts. The rear ejection mechanism pushes the push tube to eject the workpiece. When the workpiece is ejected to about 14mm from the main die surface, the six-station clamps close to clamp the workpiece tube until the workpiece is completely ejected. The inner diameter of the main die is D9a = D0d, the diameter of the punching ejector pin is D9b = D0b - 0.03, the diameter of the inner teeth of the punch tube is D10 = D0b - 0.06, and the working bandwidth of the punching ejector pin is H3 = 0.8mm. The diameter of the inner teeth of the rod tube is smaller than the diameter of the punching waste to prevent the waste from sticking to the ejector pin and affecting the mold life.

[0075] like Figure 11 , Figure 12As shown, the forming locking teeth are completed by a six-station punch tube A6, a six-station main mold B6, a six-station ejector pin C6a, and a six-station push tube C6b. The station clamps transfer the workpiece from the five-station station to the six-station station. When the six-station punch pushes the workpiece into the six-station main mold by approximately 3mm, the clamps release, and the punch continues to push the workpiece. Under the combined action of the punch, ejector pin, and main mold, the locking tooth structure on the inner hole step is formed, and the punch retracts. The rear ejection mechanism pushes the push tube to eject the workpiece until it is completely ejected. This completes the cold heading forming of the inner locking single-drum collar. The main mold inner diameter D10a = D9a, the ejector pin forming diameter D10b = D0b, the ejector pin shank diameter D10c = D0c, and the ejector pin shoulder angle α5 = 5°. The ejector pin with a shaping arc improves the quality of the flange inner hole after punching. As the punch pushes the workpiece and squeezes against the ejector pin's oblique shoulder, some metal flows into the ejector pin groove. Subsequently, as the punch retracts and the push tube pushes the workpiece away from the main mold, the metal in the groove comes into contact with the transition arc between the ejector pin head and the groove, initially forming the locking teeth. The subsequent squeezing against the ejector pin's shaping arc achieves secondary shaping of the locking teeth, improving the forming quality of the locking teeth and realizing one-time blanking and forming of locking teeth.

[0076] like Figure 13 As shown, the four-point clamp E is used for the transfer of workpieces between different processes during the forming process, and it is a tension-closing clamp.

Claims

1. A cold extrusion die assembly for a toothed single-sided collar, wherein the die assembly is used in conjunction with a cold heading machine for cold heading, characterized in that: The mold assembly consists of a shearing mold, a primary upsetting mold, an inner hole stretching mold, a flange pre-upsetting mold, a flange forming mold, a punching and blanking mold, and a locking tooth forming mold. It also includes clamps that are used to feed materials in conjunction with each mold. Shearing dies, including shears and scissors, are used to cut workpieces into bars of a fixed length by shearing them. The initial upsetting die includes a punch at one station, a main die at one station, and an ejector pin at one station. It is used to optimize the flatness of the end face of the sheared bar after forming. The inner hole stretching die includes a two-station punch, a two-station main die, a two-station ejector pin, and a two-station push tube. It is used to simultaneously reduce the diameter of the tube and stretch the inner hole using a positive extrusion method, and complete the sleeve in one step. The flange pre-upsetting die includes a three-station punch, a three-station punch, a three-station main die, a three-station ejector pin, and a three-station push tube, and is used for pre-upsetting tapered flange heads; The flange forming mold includes a four-station punch, a four-station punch, a four-station main mold, a four-station ejector pin, and a four-station push tube, used to form a flange. The punching and blanking die includes a five-station punch tube, a five-station main die, a five-station ejector pin, and a five-station push tube, and is used to complete the punching and blanking of the center hole of the workpiece. The locking tooth forming mold includes a six-station punch tube, a six-station main mold, a six-station ejector pin, and a six-station push tube. The inner diameter of the six-station main mold is equal to the outer diameter of the forming sleeve. The front ring rod of the six-station ejector pin is equipped with a shaping part with a diameter equal to the inner diameter of the flange. The diameter of the rear rod of the six-station ejector pin is equal to the inner diameter of the sleeve. The front and rear connecting parts of the six-station ejector pin are equipped with ejector pin shoulders with an angle of 5°. The locking tooth forming mold is used to shape the sleeve and form the locking teeth at the inner end of the sleeve.

2. The cold extrusion die assembly for the toothed single-sided collar according to claim 1, characterized in that: Each die punch and / or punch is mounted on the main slide of the cold heading machine and can reciprocate. The main die, ejector pin and / or push tube are mounted on the die base of the forming machine. The running mechanism and ejection mechanism are arranged above and behind the die base. The blanks are transferred between each station using clamps.

3. The cold extrusion die assembly for the toothed single-sided collar according to claim 2, characterized in that: Both the shearing die and the shears have through holes at their centers for the bar stock to pass through. The through hole at the rear end of the shearing die has a flared diameter expansion structure with the outer end larger than the inner end. The gap W1 between the shears and the shearing die is 0.02D1mm, the inner diameter D2 of the shears is 1.01D1mm, the inner diameter D3 of the shearing die is 1.015D1mm, and the feed angle α1 of the flared diameter expansion structure of the shearing die is 30°, where D1 is the diameter of the bar stock.

4. The cold extrusion die assembly for the toothed single-sided collar according to claim 3, characterized in that: The punch and ejector pin at station 1 are cylindrical ejector rod structures. The main mold at station 1 is equipped with a through hole with a variable diameter forming step. The inner diameter of the main mold is D4=D1+0.1mm, the forming radius is R1=0.2D4mm, and the ejector pin hole depth is W2=0.5mm.

5. The cold extrusion die assembly for the toothed single-sided collar according to claim 3, characterized in that: The second-station punch and ejector pin are cylindrical ejector rod structures. The second-station push tube is a sleeve fitted onto the second-station ejector pin. The second-station main mold has a variable diameter through hole. The inner diameter of the main mold is D5a = D4 + 0.05 mm, the inner diameter of the main mold after diameter reduction is D5b = D0d - 0.06 mm, the inner diameter of the ejector pin extension hole is D5c = D0c + 0.1 mm, the diameter of the main mold after diameter reduction is D5e = D5b + 0.06 mm, the guide angle for diameter reduction is α2 = 60°, the transition angle after diameter reduction is α3 = 30°, the bandwidth of the main mold after diameter reduction is H1 = 0.8 mm, the bandwidth of the ejector pin extension hole is H2 = 0.5 mm, and the transition fillet before diameter reduction is R2 = 0.3 mm. Wherein, D0d is the outer diameter of the sleeve, and D0c is the inner diameter of the sleeve.

6. The cold extrusion die assembly for the toothed single-sided collar according to claim 5, characterized in that: The three-station punch and three-station ejector pin are cylindrical ejector rod structures. The three-station punch and three-station main mold are equipped with variable diameter through holes. The three-station push tube is a sleeve fitted on the three-station ejector pin. The inner diameter of the main mold is D6a=D5b+0.02mm, the inner diameter of the ejector pin is D6b=D5c-0.04mm, and the pre-upsetting flange bevel angle α4=30°.

7. The cold extrusion die assembly for the toothed single-sided collar according to claim 6, characterized in that: The four-station punch and four-station ejector pin are cylindrical ejector rod structures. The four-station punch and four-station main mold are provided with through holes. The end face of the four-station punch is provided with a flange forming cavity. The four-station push tube is a sleeve fitted on the four-station ejector pin. The diameter of the punch flange forming cavity is D8=D0a+1mm, the depth of the punch forming cavity is W3=W0a-0.6mm, the depth of the punch hole is W4=2.2mm, the distance from the push tube to the horizontal plane of the main mold is W5=W0bmm, the inner diameter of the main mold is D7a=D6a+0.02mm, and the diameter of the ejector pin is D7b=D6b-0.04mm. Wherein, D0a is the outer diameter of the flange, W0a is the flange thickness, and W0b is the sleeve length.

8. The cold extrusion die assembly for the toothed single-sided collar according to claim 7, characterized in that: The five-station punch tube is equipped with a variable diameter through hole, the five-station main mold is equipped with a through hole, the five-station ejector pin is a variable diameter cylindrical ejector rod structure, and the five-station push tube is a sleeve fitted on the five-station ejector pin; the inner diameter of the main mold is D9a=D0dmm, the diameter of the punch ejector pin is D9b=D0b-0.03mm, the inner tooth diameter of the punch tube is D10=D0b-0.06mm, and the working width of the punch ejector pin is H3=0.8mm.

9. The cold extrusion die assembly for the toothed single-sided collar according to claim 8, characterized in that: The six-station punch tube is equipped with a variable diameter through hole, the six-station main mold is equipped with a through hole, and the six-station ejector pin is a variable diameter cylindrical ejector rod structure. The variable diameter section forms a shoulder and a groove formed by the diameter reduction is set in front of the shoulder. The six-station push tube is a sleeve fitted on the six-station ejector pin. Among them, the front ring rod of the six-station ejector pin is equipped with a variable diameter shaping part with a smooth transition along the axial surface of the rod. The inner diameter of the main mold is D10a=D9amm, the maximum diameter of the ejector pin shaping part is D10b=D0bmm, the diameter of the ejector pin rod is D10c=D0cmm, and the ejector pin shoulder angle α5=5°.

10. A cold extrusion forming method for a toothed single-sided collar: characterized in that: The cold extrusion die assembly of the toothed single-sided collar as described in any one of claims 1 to 9 is used; the collar is cold-headed using wire rod, which undergoes one spheroidizing annealing and two cold drawing processes, and the surface of the wire rod is treated with phosphating to improve the lubrication performance of the material surface; The cold heading process is a six-station forming process, which includes: after shearing and blanking, the following steps are performed in sequence: initial heading and shaping, inner hole stretching, pre-heading flange, forming flange, punching and blanking, and forming locking teeth. The shearing and blanking process is completed by the shearing die and the shears together. The shearing length is set by the forming machine operation panel and the stop gauge. The straightened wire rod enters the inner hole of the shearing die under the operation of the feeding wheel. When it contacts the front stop gauge, the shears complete the shearing and blanking of the wire rod under the reciprocating motion of the cutting mechanism. Initial upsetting and shaping are performed at one station. The cut bar stock is moved to another station via a clamp. When the punch at one station pushes the bar stock 4mm into the main mold at one station, the clamp releases. The main slide continues to push the punch forward and compress the bar stock into the mold cavity of the main mold at one station, causing deformation. When the main slide reaches the top dead center, the initial upsetting and shaping is completed, and the punch begins to retract with the main slide. At the same time, the rear ejector mechanism pushes the ejector pin forward to eject the workpiece from the main mold at one station. When the front end of the workpiece is ejected to the mold surface of the main mold at one station by 6mm, the clamp at two stations closes to hold the workpiece until the workpiece is completely ejected, thus completing the shaping process at one station and optimizing the end face quality of the sheared bar stock. The inner hole stretching is formed by two stations. The clamps at the two stations move the workpiece from the first station to the second station. When the punch at the second station pushes the workpiece into the main mold of the second station by 4mm, the clamps release and the punch continues to push the workpiece forward, forcing it to be stretched. Under the constraints of the main mold, ejector pin, and push tube, the metal flows in the forward direction to form the inner hole. After stretching is completed, the punch moves backward with the main slide. The rear ejection mechanism pushes the push tube forward to eject the workpiece from the main mold. When the front end of the workpiece is ejected to the mold surface by 11mm, the clamps at the third station close and clamp the tube of the workpiece until the workpiece is completely ejected, completing the tube diameter reduction and stretching of the inner hole at the two stations. The pre-forged flange is formed in three stations. The clamps in the three stations move the workpiece from the two stations to the three stations. When the punch in the three stations pushes the workpiece into the main mold of the three stations by 5mm, the clamps are released. The punch continues to push the workpiece and squeeze it to deform. Under the combined action of the punch, punch bar, ejector pin, push tube and main mold, the metal flows according to the confined space to complete the pre-forging of the flange. The rear ejection mechanism pushes the push tube forward to eject the workpiece from the main mold. When the workpiece is ejected to 11mm from the main mold surface, the four-station clamp closes to clamp the workpiece tube until the workpiece is completely ejected, thus completing the three-station tapered pre-upsetting flange forming. The flange is formed in four stations. The four-station clamps transfer the workpiece from the three stations to the four stations. When the four-station punch pushes the workpiece into the main mold of the four stations by 5mm, the clamps release. The punch continues to push the workpiece and squeeze it to deform. Under the combined action of the punch, punch bar, ejector pin and main mold, the metal flows according to the confined space to complete the flange forming. The punch then retracts. The rear ejection mechanism pushes the ejector tube to eject the workpiece from the main mold. When the workpiece is ejected to the main mold surface by 10mm, the five-station clamps close to clamp the tube part of the workpiece until the workpiece is completely ejected, completing the four-station flange forming. The punching and blanking process is carried out at the fifth station. The fifth station clamp transfers the workpiece from the fourth station to the fifth station. When the fifth station punch tube pushes the workpiece into the fifth station main mold by 3mm, the clamp releases. The fifth station punch tube continues to push the workpiece. Under the combined action of the punch tube, main mold, ejector pin, and push tube, the waste material is punched off, and the punch tube retracts. The rear ejection mechanism pushes the push tube to eject the workpiece. When the workpiece is ejected to 14mm from the main mold surface, the sixth station clamp closes to clamp the workpiece tube until the workpiece is completely ejected, completing the punching and blanking process. The locking teeth are formed in a six-station process. The six-station clamp transfers the workpiece from the five-station clamp to the six-station clamp. When the six-station punch pushes the workpiece 3mm into the six-station main mold, the clamp releases, and the six-station punch continues to push the workpiece. Under the combined action of the six-station punch, the six-station main mold, the six-station ejector pin, and the six-station pusher tube, the locking teeth structure on the inner hole step is shaped and formed. The six-station punch tube then retracts. The rear ejection mechanism pushes the pusher tube to eject the workpiece until it is completely ejected, completing the sleeve shaping and locking teeth forming.

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