High smoothness high speed heat shrink tube extrusion die

Abstract

The application relates to the technical field of heat-shrinkable tube extrusion dies, and provides a high-smoothness high-speed heat-shrinkable tube extrusion die, which comprises a die head, a shunt is connected in the die head through a support, a joint is fixedly installed at one end of the die head, a die core is installed on the shunt, a die sleeve is fixedly installed at one end of the die head away from the shunt through a tightening sleeve, first and second heaters for heating are further arranged, and the die core comprises a tapered core rod; it can be understood that the short shaping end of the 1.5mm tungsten steel shaping ring is arranged to quickly release pressure, eliminate defects such as surface drag marks and stress marks, cooperate with the mirror surface level inner hole, the core rod gradual change structure and the 12mm die core shaping end, and the inner and outer wall smoothness of the heat-shrinkable tube is greatly improved; meanwhile, the flow channel is short and the resistance is small, the extrusion speed is increased from the traditional 20 m / min to 40-50 m / min, the production efficiency is obviously improved, the flow rate is stable, the pressure is balanced, the dependence on operation experience is reduced, and the debugging time and the waste product rate are reduced.

Description

Technical Field

[0001] This invention relates to the field of heat shrink tubing extrusion dies, and more specifically, to a high-smoothness, high-speed heat shrink tubing extrusion die. Background Technology

[0002] In the extrusion molding process of heat shrink tubing, the die structure has a decisive influence on the surface quality of the tubing, the extrusion speed, and the process stability. In recent years, several technological improvements have been made to heat shrink tubing extrusion dies, but existing technologies still have significant shortcomings in terms of surface smoothness, extrusion efficiency, and ease of operation.

[0003] For example, Chinese patents CN105479716A (a heat-shrinkable double-walled sleeve extrusion die without adjustment) and CN203557670U (a heat-shrinkable sleeve extrusion die without adjustment) improve production efficiency by optimizing the concentric positioning structure of the die, thus eliminating the need for manual adjustment of concentricity during the extrusion process. However, these two patents mainly address the die adjustment issue and do not involve the specific length matching design of the die sleeve shaping section and the die core shaping section, nor do they provide targeted optimization for melt pressure release and surface stress marks. As a result, the extruded tubes are still prone to surface defects such as snake-skin patterns and drag marks during high-speed production.

[0004] Chinese patent CN105437509A (an extrusion die for a heat shrink tubing with an inner diameter of 72 mm and a wall thickness of 1.8 mm) discloses a structure with a smooth transition between the mandrel feeding section and the forming section, which improves the uniformity of melt flow to a certain extent. However, the die sleeve shaping section is designed to be 75 mm long, which is a typical long shaping section structure. This results in high resistance of the melt at the shaping end, inability to release pressure quickly, limited surface smoothness, and difficulty in significantly increasing the extrusion speed.

[0005] Chinese patent CN105500665A (A heat shrink tubing extrusion molding die and a method for spraying Teflon onto it) reduces melt adhesion and improves the surface gloss of the tubing by spraying a polytetrafluoroethylene coating onto the die surface. This method is a coating improvement solution, but it cannot solve the stress marks and ripples caused by unreasonable shaping section length, and the coating is prone to wear, resulting in a decline in effectiveness over long-term use.

[0006] In addition, existing molds generally suffer from the following technical defects:

[0007] 1. The length of the mold sleeve's shaping end is not designed properly, and it is generally too long (usually 5~20mm), which leads to high melt resistance, inability to release pressure quickly, and easy generation of stress marks, snake skin texture, and rough surface.

[0008] 2. The lengths of the mold core and the mold sleeve are not matched, and the release of melt pressure on the inner and outer walls is not synchronized, resulting in blockage and material accumulation, uneven wall thickness, and inconsistent smoothness of the inner and outer walls;

[0009] 3. The die sleeve mandrel often adopts a constant diameter or abrupt change structure, resulting in insufficient material compression, uneven flow rate distribution, poor extrusion stability, repeated parameter adjustments, and a high scrap rate.

[0010] To address the aforementioned issues, this application proposes a high-smoothness, high-speed heat shrink tubing extrusion die. Summary of the Invention

[0011] The purpose of this invention is to provide a high-smoothness, high-speed heat shrink tubing extrusion die. By coordinating the short shaping section of the die sleeve, the long shaping section of the die core, and the gradually streamlined structure of the mandrel, a heat shrink tubing extrusion die with high surface smoothness, high-speed extrusion, and low operating difficulty can be achieved, thus solving the problems in the prior art.

[0012] The objective of this invention can be achieved through the following technical solution: a high-smoothness, high-speed heat shrink tubing extrusion die, comprising a die, a distributor connected inside the die via a bracket, a connector fixedly mounted at one end of the die, a die core mounted on the distributor, and a die sleeve fixedly mounted at the end of the die away from the distributor via a tightening sleeve; further comprising a first heater and a second heater for heating; the die core comprising a conical mandrel with a sizing end integrally formed at the front end of the conical mandrel; the die sleeve comprising a conical conical hole and a sizing ring mounted at the front end of the conical hole;

[0013] The shaping end has a length of 10-14mm; the shaping ring is made of tungsten steel and has a mirror finish on its inner surface, the circular part of the shaping ring has a length of 1-2mm, and the shaping end and the end of the shaping ring closest to the extrusion are flush.

[0014] Preferably, the length of the shaping end is 12mm.

[0015] Preferably, the length of the circular portion is 1.5 mm.

[0016] Preferably, an extrusion channel with a gradually changing diameter is formed between the mold core and the mold sleeve.

[0017] Preferably, the capacity of the extrusion channel gradually decreases from the feeding end to the extrusion end.

[0018] Preferably, the shaping ring has a tapered portion formed therewith which it connects to the tapered hole, and an arc angle is provided between the tapered portion and the circular portion.

[0019] Preferably, the small-diameter end of the conical hole in the mold sleeve is provided with a connecting groove for interference fitting with the shaping ring.

[0020] Preferably, the mandrel and the shaping end are provided with a through air passage, which is connected to the distributor.

[0021] Preferably, the mold sleeve is connected to the die and the tightening sleeve via a connecting part.

[0022] Preferably, the wall thickness of the heat-shrink tube extruded between the shaping end and the shaping ring is 0.15-0.25 mm.

[0023] The beneficial effects of this invention are:

[0024] 1. This invention uses a 1.5mm tungsten carbide shaping ring with a short shaping end to quickly release pressure, eliminating drag marks, streaks, and stress marks on the outer surface. At the same time, the inner surface of the tungsten carbide can achieve a mirror-level smoothness. The gradient structure of the mandrel and the 12mm mold core shaping end allow the material to be fully compressed, resulting in a high inner wall smoothness. Overall, the smoothness of the heat shrink tubing surface is greatly improved.

[0025] 2. Due to the short flow channel, low resistance, and smooth pressure release, the extrusion speed can be increased from 20 m / min of traditional molds to 40~50 m / min, significantly improving production efficiency and enabling high-speed and stable extrusion;

[0026] 3. Stable flow rate and balanced pressure eliminate the need for repeated adjustments to temperature, rotation speed, and traction speed, reducing the experience requirements for operators and minimizing setup time and scrap rate. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the overall installation structure of the present invention;

[0029] Figure 2 for Figure 1 Top view of the structure;

[0030] Figure 3 for Figure 2 A schematic diagram of the cross-section of section AA;

[0031] Figure 4 A schematic diagram of the structure in which the shaping ring is inserted into the mold sleeve;

[0032] Figure 5 This is an enlarged structural diagram of the mold;

[0033] Figure 6 This is an enlarged structural schematic diagram of the shaping ring;

[0034] Figure 7 This is an enlarged structural schematic diagram of the mold core;

[0035] The attached diagram lists the components represented by each number as follows:

[0036] In the diagram: 1. Die; 2. Support; 3. Diverter; 4. Connector; 5. Die core; 51. Mandrel; 52. Shaping end; 53. Air passage; 6. Die sleeve; 61. Tapered hole; 62. Connecting groove; 63. Shaping ring; 631. Tapered part; 632. Circular part; 64. Connecting part; 7. Tightening sleeve; 8. First heater; 9. Second heater; 100. Diverter channel; 200. Extrusion channel. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0038] like Figure 1 - Figure 7 As shown, this embodiment provides a high-smoothness, high-speed heat shrink tubing extrusion die, including a die 1, a distributor 3 connected inside the die 1 via a bracket 2, a connector 4 fixedly installed at one end of the die 1, a die core 5 installed on the distributor 3, and a die sleeve 6 fixedly installed at the end of the die 1 away from the distributor 3 via a tightening sleeve 7. It also includes a first heater 8 and a second heater 9 for heating; the die core 5 includes a conical mandrel 51, with a shaping end 52 integrally formed at the front end of the conical shape; the die sleeve 6 includes a conical conical hole 61 and a shaping ring 63 installed at the front end of the conical hole 61.

[0039] The shaping end 52 is 10-14mm long, and the shaping ring 63 is made of tungsten steel with a mirror finish on the inner surface. The high hardness and polishability of tungsten steel material achieve a mirror-level smoothness, significantly reducing the frictional resistance of melt flow. The circular part 632 in the shaping ring 63 is 1-2mm long. By limiting the length of the shaping end 52 to 10-14mm and the length of the circular part 632 to 1-2mm, the pressure of the inner and outer wall melts is released synchronously, avoiding blockage, material accumulation, and uneven wall thickness. The shaping end 52 and the shaping ring 63 are flush with the extrusion end, ensuring that the inner and outer wall melts leave the shaping surface simultaneously during extrusion, achieving complete synchronization of pressure release, thereby obtaining a high-quality heat shrink tubing with consistent inner and outer wall smoothness.

[0040] Furthermore, a flow divider 100 is formed between the flow divider 3 and the connector 4, and a gradually changing extrusion channel 200 is formed between the die core 5 and the die sleeve 6 and is connected to the flow divider 100. The purpose of this gradually changing structure is to guide the melt to be gradually compressed from the feeding end to the extrusion end, avoiding the problem of uneven flow velocity distribution caused by traditional constant diameter or abrupt change structures, so that the melt forms a stable laminar flow state in the channel. The capacity of the extrusion channel 200 gradually decreases from the feeding end to the extrusion end. This narrowing channel design generates a continuous compression effect, which makes the material continuously compacted and eliminates air gaps during the forward process, ensuring that the melt density and viscosity are uniform along the extrusion direction. Thus, under high-speed extrusion conditions, it can still maintain a stable pipe wall thickness and surface finish without repeatedly adjusting temperature and speed parameters.

[0041] Furthermore, the shaping ring 63 is formed with a tapered portion 631 connected to the tapered hole 61, and an arc corner is provided between the tapered portion 631 and the circular portion 632; the function of the arc corner is to eliminate sharp transitions on the flow path, avoid the melt from generating eddies or stagnation at the corner, reduce stress concentration points, prevent irregular ripples from being generated on the surface of the pipe due to flow disturbance, and ensure a smooth transition of the melt from the compression section to the shaping section.

[0042] Furthermore, the small-diameter end of the tapered hole 61 in the mold sleeve 6 is provided with a connecting groove 62 for interference fit with the shaping ring 63. The interference fit method can ensure that there is no gap or misalignment between the shaping ring 63 and the main body of the mold sleeve 6, avoiding the melt from seeping into the connection gap and causing material accumulation and decomposition. At the same time, it ensures that the concentricity of the shaping ring and the shaping end of the mold core is accurate to within 0.01mm, eliminating the problem of uneven wall thickness caused by assembly deviation.

[0043] Furthermore, the mandrel 51 and the shaping end 52 are provided with a through air channel 53, which is connected to the distributor 3. This air channel is connected to the outside and provides air to the inside of the heat shrink tubing after molding, preventing deformation due to air pressure issues.

[0044] Furthermore, the mold sleeve 6 is connected to the die 1 and the tightening sleeve 7 via the connecting part 64.

[0045] Furthermore, the wall thickness of the heat-shrink tube extruded between the shaping end 52 and the shaping ring 63 is 0.15-0.25mm. This extremely narrow wall thickness gap, combined with the 1.5mm short shaping ring design, minimizes the shear force and resistance experienced by the melt in the shaping area. Even under high-speed extrusion conditions of 40~50 m / min, the wall thickness deviation of the tube can still be controlled within ±0.02mm. At the same time, this gap value can generate sufficient back pressure to ensure that the melt fills the mold cavity and avoids voids or surface depressions due to insufficient pressure.

[0046] The present invention will be further described in detail below through examples and comparative examples; the following examples are only for illustrating the present invention and are not intended to limit the scope of protection of the present invention. The examples and comparative examples all use the same extruder model (screw diameter 45mm, length-to-diameter ratio 28:1), temperature settings (feed section 170℃, compression section 180℃, metering section 190℃, die head 195℃) and traction method. The target specifications of the tube are heat shrink tubing with an outer diameter of 1.79mm and a wall thickness of 0.21mm, and the material is polyethylene-based heat shrink material.

[0047] Example 1

[0048] Mold sleeve shaping end length: 1.5mm;

[0049] Mold core shaping end length: 12mm;

[0050] Mandrel structure: Gradually streamlined structure, with the cross-sectional diameter smoothly narrowing from the feed end to the discharge end, and a compression ratio of 1:1.2.

[0051] Experimental results:

[0052] Extrusion speed: 45m / min

[0053] External surface roughness Ra: 0.21 μm

[0054] Inner surface roughness Ra: 0.23 μm

[0055] Wall thickness deviation: ±0.015 mm

[0056] Scrap rate (8 hours of continuous production after startup): 1.8%

[0057] Debugging time: 15 minutes (passes on the first try, no need for repeated adjustments).

[0058] Example 2

[0059] Mold sleeve shaping end length: 1.0mm

[0060] Mold core shaping end length: 10mm

[0061] Mandrel gradient structure: compression ratio 1:1.1

[0062] Experimental results:

[0063] Extrusion speed: 50 m / min

[0064] External surface roughness Ra: 0.18 μm

[0065] Inner surface roughness Ra: 0.25 μm

[0066] Wall thickness deviation: ±0.020 mm

[0067] Scrap rate: 2.5%

[0068] Note: The mold sleeve is too short, and the pipe tends to collapse slightly. The traction speed needs to be increased slightly to compensate.

[0069] Example 3

[0070] Mold shaping end length: 2mm

[0071] Mold core shaping end length: 14 mm

[0072] Mandrel gradient structure: compression ratio 1:1.3

[0073] Experimental results:

[0074] Extrusion speed: 38m / min

[0075] External surface roughness Ra: 0.32 μm

[0076] Inner surface roughness Ra: 0.28 μm

[0077] Wall thickness deviation: ±0.018mm

[0078] Scrap rate: 2.2%

[0079] Note: The mold sleeve is slightly longer at the shaping end, and the surface smoothness is slightly reduced, but it is still far superior to traditional molds.

[0080] Comparative Example 1

[0081] Traditional long shaping end sleeve, refer to CN105437509A

[0082] Mold shaping end length: 8mm

[0083] Mold core shaping end length: 10mm

[0084] Mandrel structure: constant diameter (non-gradient)

[0085] Experimental results:

[0086] Maximum stable extrusion speed: 18m / min (exceeding 20m / min results in severe snake-skin pattern and makes continuous production impossible).

[0087] External surface roughness Ra: 1.35 μm

[0088] Inner surface roughness Ra: 1.42 μm

[0089] Wall thickness deviation: ±0.12 mm

[0090] Scrap rate: 16.5%

[0091] Debugging time: approximately 120 minutes, requiring repeated adjustments to temperature and traction speed.

[0092] Comparative Example 2

[0093] The inner and outer shaping ends are of equal length, referring to CN203557670U but with modifications to the shaping ends.

[0094] Mold shaping end length: 1.5 mm

[0095] Mold core shaping end length: 1.5 mm

[0096] Mandrel gradient structure (same as Example 1)

[0097] Experimental results:

[0098] Extrusion speed: 30 m / min (cannot be increased due to material buildup on the inner wall)

[0099] External surface roughness Ra: 0.25μm (good)

[0100] Inner surface roughness Ra: 0.89μm (obviously rough, with material accumulation spots)

[0101] Wall thickness deviation: ±0.09 mm

[0102] Scrap rate: 11.2% (mainly due to internal wall defects and blockages)

[0103] Note: The internal and external pressures are released simultaneously, resulting in insufficient compression of the material on the inner wall, which leads to a rough inner wall and easy material accumulation.

[0104] Comparative Example 3

[0105] Core rod abrupt change structure, without gradual change

[0106] Mold sleeve shaping end length: 1.5mm

[0107] Mold core shaping end length: 12mm

[0108] Mandrel structure: Step-like abrupt change (no transition)

[0109] Experimental results:

[0110] Extrusion speed: 25 m / min (spiral lines and transverse stripes appear)

[0111] External surface roughness Ra: 0.58 μm

[0112] Inner surface roughness Ra: 0.62 μm

[0113] Wall thickness deviation: ±0.08 mm

[0114] Scrap rate: 9.8%

[0115] Explanation: Sudden changes lead to eddies and stagnant flow, resulting in uneven velocity distribution.

[0116] Comparative Example 4

[0117] The mold sleeve's shaping end is too long and the mold core is too short:

[0118] Mold shaping end length: 10mm

[0119] Mold core shaping end length: 5mm

[0120] mandrel equal diameter

[0121] Experimental results:

[0122] Unable to produce continuously (severe pressure fluctuations inside the mold, frequent material blockages).

[0123] The surface roughness could not be measured, and the inner and outer walls of the pipe were severely rough and the dimensions were out of tolerance.

[0124] Comparative Example 5

[0125] Coating scheme, refer to CN105500665A

[0126] The mold surface is coated with Teflon, and the mold structure is the same as Comparative Example 1 (long shaping end + equal diameter mandrel).

[0127] Experimental results:

[0128] Extrusion speed: 22 m / min

[0129] Surface roughness Ra: 0.85μm (the coating showed some improvement in the initial stage, but was still not satisfactory).

[0130] Inner surface roughness Ra: 0.92 μm

[0131] After 8 hours of continuous production, the coating showed signs of wear, with Ra rising to over 1.20 μm.

[0132] Scrap rate: 12.3%

[0133] Note: Coatings can only partially improve adhesion and cannot solve the problems of pressure relief and flow uniformity.

[0134]

[0135] As can be seen from the table above, Embodiment 1 of the present invention is significantly superior to all comparative examples in terms of extrusion speed, smoothness of inner and outer surfaces, dimensional accuracy, and scrap rate, and the debugging time is extremely short. This fully demonstrates the unexpected technical effect brought about by the synergy of the "short shaping end of the die sleeve + long shaping end of the die core + gradient structure of the mandrel".

[0136] Understandably, this invention rapidly releases pressure by using a short, 1.5mm tungsten carbide shaping ring to eliminate surface defects such as drag marks and stress marks. Combined with a mirror-grade inner hole and a mandrel gradient structure, along with a 12mm die core shaping end, it significantly improves the smoothness of the inner and outer walls of the heat shrink tubing. At the same time, the short flow channel and low resistance increase the extrusion speed from the traditional 20 m / min to 40~50 m / min, significantly improving production efficiency. Furthermore, the stable flow rate and balanced pressure reduce reliance on operational experience, minimizing setup time and scrap rate.

[0137] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; it should be understood that the terms "opening", "upper", "lower", "thickness", "top", "middle", "length", "inner", "around", etc., which indicate orientation or positional relationship, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the components or elements referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting this invention.

[0138] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-smoothness, high-speed heat shrink tubing extrusion die, comprising a die (1), wherein a distributor (3) is connected inside the die (1) via a bracket (2), a connector (4) is fixedly installed at one end of the die (1), a die core (5) is installed on the distributor (3), and a die sleeve (6) is fixedly installed at the end of the die (1) away from the distributor (3) via a tightening sleeve (7), further comprising a first heater (8) and a second heater (9) for heating, characterized in that: The mold core (5) includes a conical mandrel (51) with a sizing end (52) integrally formed at the front end of the conical shape; the mold sleeve (6) includes a conical hole (61) and a sizing ring (63) installed at the front end of the conical hole (61). The shaping end (52) is 10-14 mm long; the shaping ring (63) is made of tungsten steel and has a mirror finish on its inner surface. The circular part (632) in the shaping ring (63) is 1-2 mm long. The shaping end (52) and the shaping ring (63) are flush with the extruded end.

2. The high-smoothness, high-speed heat shrink tubing extrusion die according to claim 1, characterized in that: The length of the shaping end (52) is 12mm.

3. The high-smoothness, high-speed heat shrink tubing extrusion die according to claim 1, characterized in that: The circular portion (632) has a length of 1.5 mm.

4. The high-smoothness, high-speed heat shrink tubing extrusion die according to claim 1, characterized in that: An extrusion channel (200) with a gradually changing diameter is formed between the core (5) and the sleeve (6).

5. The high-smoothness, high-speed heat shrink tubing extrusion die according to claim 4, characterized in that: The capacity of the extrusion channel (200) gradually decreases from the feeding end to the extrusion end.

6. The high-smoothness, high-speed heat shrink tubing extrusion die according to claim 1, characterized in that: The shaping ring (63) has a tapered part (631) connected to the tapered hole (61), and there is a rounded corner between the tapered part (631) and the circular part (632).

7. The high-smoothness, high-speed heat shrink tubing extrusion die according to claim 1, characterized in that: The small-diameter end of the conical hole (61) in the mold sleeve (6) is provided with a connecting groove (62) that is interference-fitted with the shaping ring (63).

8. The high-smoothness, high-speed heat shrink tubing extrusion die according to claim 1, characterized in that: The mandrel (51) and the shaping end (52) are provided with through air passages (53), which are connected to the splitter (3).

9. The high-smoothness, high-speed heat shrink tubing extrusion die according to claim 1, characterized in that: The mold (6) is connected to the die (1) and the tightening sleeve (7) via the connecting part (64).

10. A high-smoothness, high-speed heat shrink tubing extrusion die according to claim 1, characterized in that: The wall thickness of the heat-shrink tube extruded between the shaping end (52) and the shaping ring (63) is 0.15-0.25 mm.

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