Step punching die

Abstract

The present invention relates to the field of punching dies, and specifically to a step punching die, comprising: a die frame, a first fixed die, a first movable die, a second fixed die and a core rod assembly, wherein the first fixed die has a positioning hole vertically penetrating through itself and a first surface perpendicular to the axis of the positioning hole, the core rod assembly is used to insert into the inside of the round tube of the step, the first movable die has at least a second surface, a third surface and a fourth surface, the second surface is parallel to and fits the first surface of the first fixed die, the third surface intersects the second surface and the fourth surface, the fourth surface is perpendicular to the second surface and is tangent to the outer wall of the round tube, the second fixed die has at least a fifth surface and a sixth surface, the fifth surface fits the outer wall of the round tube away from the first movable die, and the sixth surface is parallel to the fourth surface. The embodiment of the present invention effectively constrains the structure of the step through the positioning hole, and supports the inner wall of the round tube through the core rod assembly, and then separates the attachments of the round tube and its outer wall from the three surfaces through three blades, thereby effectively avoiding deformation of the round tube.

Description

Technical Field

[0001] The invention relates to the field of punching and cutting dies, and in particular to a step punching and cutting die. Background Art

[0002] In the manufacturing process of aluminum alloy ladders, the rungs are usually made of extruded aluminum alloy profiles. Usually, only round tubes need to be retained at both ends of the rungs, and the attachments on the outer wall of the round tubes need to be removed.

[0003] The existing processing method can easily cause the round tube part of the ladder to deform when cutting the ladder steps, affecting the product quality. In addition, burrs may be generated on the inner wall of the round tube after cutting, requiring an additional deburring process, which reduces production efficiency. Summary of the invention

[0004] The object of the present invention is to provide a step blanking die to solve the problem that the existing processing method easily causes the step to be deformed when cutting the step.

[0005] In order to solve the above technical problems, the present invention specifically provides the following technical solutions:

[0006] A ladder-step punching die, comprising: a die frame; a first fixed die, having a flat plate shape and a positioning hole vertically penetrating the first fixed die, wherein the first fixed die at least has a first surface facing the inside of the die frame and perpendicular to the axis of the positioning hole; a core rod assembly, which is used to be inserted into the inside of a round tube of the ladder step to support the inner wall of the round tube; two first movable dies, which are symmetrically arranged on both sides of the symmetrical surface of the ladder step and are controlled by a first driving device, wherein the first movable die at least has a second surface, a third surface and a fourth surface, wherein the second surface is parallel to and fits the first surface of the first fixed die, the third surface intersects the second surface and the fourth surface, and the fourth surface is perpendicular to the second surface. The movable die is provided at the other side of the circular tube, wherein the second fixed die has at least a fifth surface and a sixth surface, the fifth surface is in contact with the outer wall of the circular tube away from the first movable die, and the sixth surface is parallel to the fourth surface; wherein the intersection of the second surface and the third surface forms a first blade, the first blade is used to intersect with the positioning hole to cut off the attachments on the outer wall of the circular tube, the intersection of the third surface and the fourth surface forms a second blade, the intersection of the fifth surface and the sixth surface forms a third blade, the second blade is used to intersect with the third blade to cut off the attachments on the outer wall of the circular tube.

[0007] Furthermore, it also includes two second movable molds, which are symmetrically arranged on both sides of the ladder symmetry plane, and the two second movable molds are respectively controlled by a second driving device, and each of the second movable molds has at least: a seventh surface, which is parallel to and fits the first surface; a ninth surface, which is parallel to the movement direction of the second movable mold and perpendicular to the seventh surface; an eighth surface, which intersects with the seventh surface and is perpendicular to the ninth surface; wherein the intersection of the seventh surface and the eighth surface forms a fourth blade, and the fourth blade is used to intersect with the positioning hole to cut off the attachments on the outer wall of the circular tube.

[0008] Furthermore, the ladder step includes a circular tube, a vertical plate and a horizontal plate, the vertical plate is parallel to the radial surface of the circular tube and connected to the outer wall of the circular tube, the horizontal plate is perpendicular to the radial surface of the circular tube and connected to the side of the vertical plate away from the circular tube, and both sides of the horizontal plate are also provided with convex strips extending toward both ends of the length direction of the horizontal plate; the positioning hole matches the cross section of the ladder step, and the positioning hole is used to insert one end of the ladder step, the first blade is used to cut the vertical plate along the first surface, the second blade and the third blade are staggered to cut the vertical plate along the tangent direction of the circular tube, and the fourth blade cooperates with the first surface to cut the horizontal plate and the remaining vertical plates along the first surface of the first fixed mold.

[0009] Furthermore, a groove perpendicular to the first surface of the first fixed mold is provided on the first surface, and the length direction of the groove is parallel to the movement direction of the second movable mold. Steps matching the groove are provided on both sides of the fourth blade, and the fourth blade moves along the groove, and the steps are used to avoid the convex strip.

[0010] Furthermore, the angle between the second surface and the third surface is a right angle, the angle between the third surface and the fourth surface is an acute angle, the angle between the fifth surface and the sixth surface is an acute angle, and the angle between the seventh surface and the eighth surface is an acute angle.

[0011] Furthermore, the first movable mold is provided with an avoidance opening, and the avoidance opening is located between the first movable mold and the first surface of the first fixed mold, and between the first movable mold and the second movable mold. The avoidance opening is used to allow the second movable mold to continue punching without resetting the first movable mold after extending out of the punching.

[0012] Furthermore, the core rod assembly includes: a movable core shaft, one end of which is provided with a radially outwardly extending annular flange, and the other end is connected to a third driving device, and can move along its own axial direction, the annular flange is inserted into the inside of the circular tube of the ladder step, and there is a small gap between the outer diameter of the annular flange and the inner diameter of the circular tube; a fluid sleeve, which is sleeved on the outer side of the movable core shaft, and the length of the fluid sleeve is shortened and radially expanded when axially compressed, so as to fit tightly against the inner wall of the circular tube; a movable sleeve, which is sleeved on the outer side of the movable core shaft, one end of which is in contact with the fluid sleeve, and the other end of which is connected to a fourth driving device, and can move along its own axial direction to push the fluid sleeve to compress; wherein, when the movable sleeve pushes the fluid sleeve to move toward the annular flange, the fluid sleeve is axially compressed.

[0013] Furthermore, the fluid sleeve can be drawn out of the interior of the circular tube in a state of being axially compressed, thereby scraping off burrs on the inner wall of the circular tube.

[0014] Furthermore, the fluid sleeve includes a plurality of magnetic beads, and the magnetic beads are adsorbed on the outer peripheral surface of the movable core shaft through magnetic force.

[0015] Furthermore, a notch is provided on the surface of the magnetic bead, and the intersection line of the notch and the outer wall of the magnetic bead forms a fifth blade, and the fifth blade is used to remove burrs on the inner wall of the circular tube.

[0016] Compared with the prior art, this application has the following beneficial effects:

[0017] A step blanking die is provided, which effectively constrains the step structure through positioning holes, supports the inner wall of a round tube through a core rod assembly, and then separates the attachments of the round tube and its outer wall from three sides through three blades, thereby effectively avoiding deformation of the round tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0019] Figure 1 This is the processing drawing of the ladder steps;

[0020] Figure 2 A three-dimensional diagram of an embodiment of the present invention;

[0021] Figure 3 It is an assembly diagram of an embodiment of the present invention;

[0022] Figure 4A side view of an embodiment of the present invention;

[0023] Figure 5 for Figure 4 Cross-sectional view in the AA direction;

[0024] Figure 6 for Figure 5 Stereoscopic image of

[0025] Figure 7 for Figure 5 A schematic diagram of another working condition of

[0026] Figure 8 for Figure 5 A schematic diagram of another working condition;

[0027] Fig. 9 for Figure 4 Cross-sectional view in the BB direction;

[0028] Fig.10 It is a front view of an embodiment of the present invention;

[0029] Fig.11 for Fig.10 The cross-sectional view in CC direction;

[0030] Fig.12 for Fig.10 Cross-sectional view in DD direction;

[0031] Fig.13 It is a schematic diagram of a local structure of a mandrel assembly inserted into a round tube according to an embodiment of the present invention;

[0032] Fig.14 for Fig.13 Cross-sectional view in the EE direction;

[0033] The numbers in the figure represent the following:

[0034] 1-Mold frame;

[0035] 2-ladder rung; 21-round tube; 22-vertical plate; 23-horizontal plate; 24-convex strip;

[0036] 3-first fixed mold; 31-positioning hole; 32-first surface; 33-groove;

[0037] 4- mandrel assembly; 41- movable mandrel; 411- annular flange; 42- fluid sleeve; 421- magnetic bead; 422- notch; 423- fifth blade; 43- movable sleeve;

[0038] 5-first movable mold; 51-second surface; 52-third surface; 53-fourth surface; 54-first blade; 55-second blade; 56-avoidance opening;

[0039] 6-second fixed die; 61-fifth side; 62-sixth side; 63-third blade;

[0040] 7-second movable mold; 71-seventh surface; 72-eighth surface; 73-ninth surface; 74-fourth blade; 75-step. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Combination Figure 1 The structure of the ladder step 2 is complex, including components such as a circular tube 21, a vertical plate 22 and a horizontal plate 23. The circular tube 21 is the main load-bearing component of the ladder step 2. The vertical plate 22 is parallel to the radial surface of the circular tube 21 and is connected to the outer wall of the circular tube 21. The horizontal plate 23 is perpendicular to the radial surface of the circular tube 21 and is connected to the side of the vertical plate 22 away from the circular tube 21. Both sides of the horizontal plate 23 are also provided with convex strips 24 extending toward both ends of the length direction of the horizontal plate 23. The convex strips 24 are used to engage with the corresponding grooves 33 on the ladder column.

[0043] The purpose of this embodiment is to provide a step 2 punching die, which can effectively support the inner wall of the round tube 21 and prevent deformation during the punching process, and at the same time remove burrs on the inner wall of the round tube 21.

[0044] Combination Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 , Step 2 punching die includes:

[0045] The mold frame 1 is used to support and fix various mold components to ensure processing accuracy.

[0046] The first fixed mold 3 has a flat plate shape and a positioning hole 31 vertically passing through it. The positioning hole 31 matches the cross section of the ladder step 2. One end of the ladder step 2 is inserted into the positioning hole 31. The first fixed mold 3 has at least a first surface 32, which faces the inside of the mold frame 1 and is perpendicular to the axis of the ladder step 2.

[0047] The core rod assembly 4 is inserted into the mold frame 1 from the end of the mold frame 1 away from the ladder 2 and inserted into the inside of the round tube 21 to support the inner wall of the round tube 21 from the inside, so as to maintain the shape of the round tube 21 when cutting the vertical plate 22 and the horizontal plate 23.

[0048] There are two first movable molds 5 , which are symmetrical to each other relative to the symmetry plane of the ladder step 2 , are an integral part, and are driven by a first driving device, are arranged on one side of the circular tube 21 , and the first movable mold 5 has at least a second surface 51 , a third surface 52 , and a fourth surface 53 on the side facing the ladder step 2 , wherein the second surface 51 of the first movable mold 5 is parallel to and fits the first surface 32 of the first fixed mold 3 , the fourth surface 53 of the first movable mold 5 is perpendicular to the second surface 51 and is tangent to the outer wall of the circular tube 21 , and the third surface 52 of the first movable mold 5 is perpendicular to the second surface 51 and the fourth surface 53 .

[0049] The second fixed mold 6 is arranged on the other side of the circular tube 21. The side of the second fixed mold 6 facing the ladder step 2 has at least a fifth surface 61 and a sixth surface 62, wherein the fifth surface 61 of the second fixed mold 6 matches and fits the outer wall of the circular tube 21 on the side away from the first movable mold 5, and the fifth surface 61 is semicircular and is used to support the external shape of the circular tube 21. The sixth surface 62 of the second fixed mold 6 is parallel to the fourth surface 53 of the first movable mold 5.

[0050] The intersection line of the second surface 51 and the third surface 52 of the first movable mold 5 forms a first blade 54. As the first movable mold 5 moves along a direction parallel to the symmetry plane of the ladder step 2, the first blade 54 intersects with the positioning hole 31, thereby cutting off the vertical plate 22 along the first surface 32 of the first fixed mold 3.

[0051] The intersection line of the third surface 52 and the fourth surface 53 of the first movable mold 5 forms a second blade 55, and the intersection line of the fifth surface 61 and the sixth surface 62 of the second fixed mold 6 forms a third blade 63. The second blade 55 and the third blade 63 intersect each other, thereby cutting the vertical plate 22 along the tangent line of the circular tube 21.

[0052] Finally, the first movable mold 5 , the first fixed mold 3 and the second fixed mold 6 work together to separate the vertical plate 22 exposed outside the positioning hole 31 from the circular tube 21 .

[0053] Furthermore, the mold for processing the ladder step 2 also includes:

[0054] There are two second movable molds 7, which are symmetrically and movably arranged on both sides of the symmetry plane of the ladder step 2, and are driven by two second driving devices respectively. The two second movable molds 7 are inserted into the mold frame 1 along the direction inclined to the symmetry plane of the ladder step 2, and the angle between the movement direction of the second movable mold 7 and the movement direction of the first movable mold 5 is an acute angle.

[0055] The end of the second movable mold 7 facing the ladder step 2 has at least a seventh surface 71 and an eighth surface 72, wherein the seventh surface 71 of the second movable mold 7 is parallel to and fits the first surface 32 of the first fixed mold 3, and a ninth surface 73 is formed parallel to the movement direction of the second movable mold 7 and perpendicular to the seventh surface 71 of the second movable mold 7, the eighth surface 72 of the second movable mold 7 is inclined to the seventh surface 71 of the second movable mold 7 and perpendicular to the ninth surface 73, and the angle between the eighth surface 72 and the first surface 32 is an acute angle.

[0056] The intersection line of the seventh surface 71 and the eighth surface 72 of the second movable mold 7 forms a fourth blade 74, and the fourth blade 74 intersects with the positioning hole 31, thereby cutting off the horizontal plate 23 and the remaining vertical plates 22 along the first surface 32 of the first fixed mold 3, so that the vertical plates 22 and the horizontal plates 23 exposed outside the positioning hole 31 are completely separated from the round tube 21.

[0057] Furthermore, since a small section of the convex strip 24 needs to be retained on both sides of the horizontal plate 23, a groove 33 perpendicular to the first surface 32 is formed on the first fixed mold 3, and the length direction of the groove 33 is parallel to the movement direction of the second movable mold 7. A step 75 matching the groove 33 is formed on the fourth blade 74. The fourth blade 74 moves along the groove 33 to retain the convex strips 24 on both sides of the horizontal plate 23 while cutting off the horizontal plate 23 and the vertical plate 22.

[0058] In addition, the first movable mold 5 is provided with an avoidance opening 56 for avoiding the fourth blade 74. The avoidance opening 56 is arranged between the first movable mold 5 and the first surface 32, and between the first movable mold 5 and the second movable mold 7. The function of the avoidance opening 56 is: after the first movable mold 5 is extended to cut off a part of the vertical plate 22, the first movable mold 5 does not need to be reset, and the second movable mold 7 continues to cut off the horizontal plate 23 and the remaining vertical plates 22 to complete the punching work, thereby saving punching time and improving punching efficiency.

[0059] Furthermore, during the process of inserting the core rod assembly 4 into the round tube 21 , it is necessary to prevent the core rod assembly 4 from applying an axial force to the step 2 , otherwise the step 2 may easily move axially, resulting in unqualified punching lengths of the vertical plate 22 and the horizontal plate 23 .

[0060] To solve this problem, combined with Fig.13 , Fig.14 , the mandrel assembly 4 comprises:

[0061] The movable core shaft 41 has magnetism at one end and is formed with an annular flange 411 extending radially outward. The annular flange 411 is inserted into the interior of the circular tube 21. There is a small gap between the outer wall of the annular flange 411 and the inner wall of the circular tube 21. The other end of the movable core shaft 41 is connected to the third driving device, so that the movable core shaft 41 can move along its own axial direction.

[0062] A plurality of magnetic beads 421 are adsorbed by magnetic force and tightly laid on the outer wall of the core rod assembly 4. The diameter of the magnetic beads 421 is larger than the gap between the annular flange 411 and the circular tube 21. The plurality of magnetic beads 421 form a fluid sleeve 42 that can be retracted and expanded. When the length of the fluid sleeve 42 is shortened, the diameter of the fluid sleeve 42 is increased.

[0063] The movable sleeve 43 has no magnetic force and is not affected by magnetic force. One end of the movable sleeve 43 is sleeved on the outside of the movable core shaft 41. The outer diameter of the movable sleeve 43 is equal to the outer diameter of the annular flange 411. The magnetic beads 421 are laid between the end face of the movable sleeve 43 and the end face of the annular flange 411. The other end of the movable sleeve 43 is connected to the fourth driving device, and the fourth driving device is fixedly connected to the movable core shaft 41, so that the movable sleeve 43 can move twice along its own axial direction.

[0064] When the third driving device is actuated to insert the core rod assembly 4 into the interior of the circular tube 21, the movable core shaft 41, the magnetic bead 421 and the movable sleeve 43 are inserted into the interior of the circular tube 21 together. At this time, the core rod assembly 4 has no contact with the inner wall of the circular tube 21, thereby preventing the core rod assembly 4 from applying an axial force to the ladder step 2, thereby preventing the axial position of the ladder step 2 from moving.

[0065] Then the fourth driving device is actuated to move the sleeve inward a short distance, pushing the fluid sleeve 42 formed by the magnetic beads 421 toward the annular flange 411, shortening the length of the fluid sleeve 42 and increasing the diameter of the fluid sleeve 42, thereby supporting the inner wall of the circular tube 21 from the inside to the outside.

[0066] In addition, a plurality of notches 422 are formed on the surface of the magnetic bead 421. The notches 422 do not hinder the magnetic bead 421 from supporting the round tube 21 from the inside to the outside. When the third driving device is actuated to pull the core rod assembly 4 out of the inside of the round tube 21, a fifth blade 423 is formed between the notch 422 and the surface of the magnetic bead 421. The fifth blade 423 can effectively scrape out burrs inside and on the end of the round tube 21, making it easier to use a rotary riveting machine to widen the end diameter of the round tube 21 in the next process, thereby omitting an additional deburring process and improving production efficiency.

[0067] The processing steps of the step 2 punching die are as follows:

[0068] Step 1: Positioning and Support: Combination Figure 5 , Fig. 9 , insert the ladder step 2 into the positioning hole 31 of the first fixed mold 3, and under the action of the third driving device, the core rod assembly 4, the movable core shaft 41, the magnetic bead 421 and the movable sleeve 43 are inserted into the interior of the round tube 21 together. At this time, the magnetic bead 421 sleeve has not expanded, and the core rod assembly 4 has no contact with the inner wall of the round tube 21, avoiding the application of axial force to the ladder step 2.

[0069] Step 2: Expansion support: The fourth driving device pushes the movable sleeve 43 to move inward, compressing the magnetic bead 421 sleeve to shorten its length and increase its diameter, so that it is closely attached to the inner wall of the circular tube 21 and provides radial support.

[0070] Step 3: Cutting the vertical plate 22: Combining Figure 7 Under the action of the first driving device, the first movable mold 5 moves in a direction parallel to the symmetry plane of the ladder step 2, and the first blade 54 cooperates with the first surface 32 of the first fixed mold 3 to cut off a part of the vertical plate 22.

[0071] Step 4: Cut the horizontal board 23 and the remaining vertical board 22: Combine Figure 8 , Fig.10 , Fig.11 , Fig.12 Under the action of the second driving device, the second movable mold 7 is inserted in a direction forming an acute angle with the direction of the first movable mold 5, and the fourth blade 74 cooperates with the first surface 32 of the first fixed mold 3 to cut off the horizontal plate 23 and the remaining vertical plate 22. At the same time, a vertical groove 33 is provided on the first surface 32 of the first fixed mold 3, and a step 75 matching the groove 33 is provided on the fourth blade 74. During the cutting process, the groove 33 and the step 75 cooperate to retain the convex strips 24 at both ends of the horizontal plate 23.

[0072] Step 6, removing burrs: After the processing is completed, the fourth driving device is not activated, and the third driving device causes the movable mandrel 41 to be pulled out of the inside of the round tube 21 , and the fifth blade 423 formed on the surface of the magnetic bead 421 scrapes off the burrs on the inner wall of the round tube 21 .

[0073] Step 7, processing is completed: the first drive device, the second drive device, and the fourth drive device are reset, the ladder step 2 is processed, the shape of the round tube 21 remains intact, the inner wall is smooth, and no additional deburring process is required.

[0074] The above embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention. The protection scope of the present invention is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present invention.

Claims

1. A ladder rung punching die, characterized in that: include: Formwork; A first fixed mold, having a flat plate shape and a positioning hole vertically passing through the first fixed mold, wherein the first fixed mold has at least a first surface facing the inside of the mold frame and perpendicular to the axis of the positioning hole; A mandrel assembly, used to be inserted into the round tube of the ladder step to support the inner wall of the round tube; There are two first movable molds, which are symmetrically arranged on both sides of the symmetrical surface of the ladder steps and controlled by a first driving device, wherein the first movable mold has at least a second surface, a third surface and a fourth surface, the second surface is parallel to and fits the first surface of the first fixed mold, the third surface intersects the second surface and the fourth surface, and the fourth surface is perpendicular to the second surface and tangent to the outer wall of the circular tube; A second fixed mold is arranged on the other side of the circular tube, wherein the second fixed mold has at least a fifth surface and a sixth surface, the fifth surface is in contact with the outer wall of the circular tube away from the first movable mold, and the sixth surface is parallel to the fourth surface; Among them, the intersection line of the second surface and the third surface forms a first blade, and the first blade is used to intersect with the positioning hole to cut off the attachments on the outer wall of the circular tube. The intersection line of the third surface and the fourth surface forms a second blade, and the intersection line of the fifth surface and the sixth surface forms a third blade, and the second blade is used to intersect with the third blade to cut off the attachments on the outer wall of the circular tube.

2. A step blanking die according to claim 1, characterized in that: It also includes two second movable molds, which are symmetrically arranged on both sides of the symmetrical surface of the ladder step, and the two second movable molds are respectively controlled by a second driving device, and each of the second movable molds has at least: A seventh surface, parallel to and in contact with the first surface; a ninth surface, parallel to the movement direction of the second movable mold and perpendicular to the seventh surface; an eighth surface, intersecting the seventh surface and perpendicular to the ninth surface; The intersection line of the seventh surface and the eighth surface forms a fourth blade, and the fourth blade is used to intersect with the positioning hole to cut off the attachments on the outer wall of the circular tube.

3. A step blanking die according to claim 2, characterized in that: The ladder steps include a circular tube, a vertical plate and a horizontal plate, wherein the vertical plate is parallel to the radial surface of the circular tube and connected to the outer wall of the circular tube, and the horizontal plate is perpendicular to the radial surface of the circular tube and connected to the side of the vertical plate away from the circular tube, and the two sides of the horizontal plate are also provided with convex strips extending toward the two ends of the length direction of the horizontal plate; The positioning hole matches the cross-section of the ladder step, and the positioning hole is used to insert one end of the ladder step. The first blade is used to cut the vertical plate along the first surface. The second blade and the third blade are staggered and used to cut the vertical plate along the tangent direction of the circular tube. The fourth blade cooperates with the first surface to cut the horizontal plate and the remaining vertical plates along the first surface of the first fixed mold.

4. A step blanking die according to claim 3, characterized in that: A groove perpendicular to the first surface of the first fixed mold is provided on the first surface, and the length direction of the groove is parallel to the movement direction of the second movable mold. Steps matching the groove are provided on both sides of the fourth blade. The fourth blade moves along the groove, and the steps are used to avoid the convex strip.

5. A step blanking die according to claim 4, characterized in that: The angle between the second surface and the third surface is a right angle, the angle between the third surface and the fourth surface is an acute angle, the angle between the fifth surface and the sixth surface is an acute angle, and the angle between the seventh surface and the eighth surface is an acute angle.

6. A step blanking die according to claim 2, characterized in that: The first movable mold is provided with an avoidance opening, and the avoidance opening is located between the first movable mold and the first surface of the first fixed mold, and between the first movable mold and the second movable mold. The avoidance opening is used to allow the second movable mold to continue punching without resetting the first movable mold after extending out of the punching.

7. A step blanking die according to any one of claims 1 to 6, characterized in that: The mandrel assembly comprises: A movable mandrel, one end of which is provided with a radially outwardly extending annular flange, and the other end of which is connected to a third driving device, and can move along its own axial direction, wherein the annular flange is inserted into the inside of the circular tube of the ladder step, and there is a small gap between the outer diameter of the annular flange and the inner diameter of the circular tube; A fluid sleeve is sleeved on the outer side of the movable core shaft, and when the fluid sleeve is subjected to axial pressure, the length of the fluid sleeve is shortened and the radial expansion is performed so as to be closely attached to the inner wall of the circular tube; A movable sleeve, which is sleeved on the outer side of the movable core shaft, has one end in contact with the fluid sleeve and the other end connected to a fourth driving device, and can move along its own axis to push the fluid sleeve to compress; When the movable sleeve pushes the fluid sleeve to move toward the annular flange, the fluid sleeve is axially compressed.

8. A step blanking die according to claim 7, characterized in that: The fluid sleeve can be drawn out of the interior of the round tube in an axially compressed state, thereby scraping off burrs on the inner wall of the round tube.

9. A step blanking die according to claim 8, characterized in that: The fluid sleeve includes a plurality of magnetic beads, and the magnetic beads are adsorbed on the outer peripheral surface of the movable core shaft through magnetic force.

10. A step blanking die according to claim 9, characterized in that: A notch is provided on the surface of the magnetic bead, and the intersection line of the notch and the outer wall of the magnetic bead forms a fifth blade, and the fifth blade is used to remove burrs on the inner wall of the circular tube.

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