Micro precision plunger screw

Abstract

The invention relates to a trace precision plunger screw rod which comprises a material pipe, a plunger cylinder coaxially fixed at the front end of the material pipe, a nozzle coaxially fixed at the front end of the plunger cylinder, a screw rod mounted in the material pipe along the axis and a plunger screw rod head fixed at the top end of the screw rod, the front end of the plunger screw head is provided with a plunger sealing part, the outer diameter of the plunger sealing part is matched with that of a plunger cylinder sealing channel, and the outer diameter of the plunger sealing part is smaller than that of the screw. The injection mold has the advantages of reduction of injection weight, precise injection, increase of injection pressure, reduction of material retention time, reduction of material carbonization and degradation phenomena, improvement of quality of injected materials and the like, and is suitable for injection molding of trace materials.

Description

Technical Field

[0001] The invention relates to the technical field of injection molding, and in particular to a micro-precision plunger screw. Background Art

[0002] Injection molding is an extremely important part of modern industry, that is, at a certain temperature, a completely molten plastic material is stirred by a screw, injected into a mold cavity with high pressure, and a molded product is obtained after cooling and solidification. With the increasing sophistication of contemporary industrial products, the miniaturization and refinement of injection molding are also increasing. At present, the improvement of miniaturization in the injection molding process is mainly reflected in the use of screws with smaller diameters. However, in order to ensure the effective aspect ratio of the screw, the diameter of the screw cannot be very thin, because the thinner the screw, the higher the possibility of being twisted off during operation. In actual applications, the inner diameter of the material tube is generally not less than 14mm. However, the screw under this parameter still cannot meet the needs of miniaturization well. In addition, it is difficult for existing screws to control the injection amount of molten plastic, that is, it cannot meet the needs of precision.

[0003] Therefore, there is an urgent need in the art for a screw that can simultaneously meet the requirements of miniaturization and precision. Summary of the invention

[0004] The purpose of the present invention is to provide a micro-precision plunger screw in order to overcome the defects of the prior art.

[0005] In order to achieve the purpose of the present invention, this application provides the following technical solutions.

[0006] In the first aspect, the present application provides that the plunger screw includes a material tube, a plunger cylinder coaxially fixed at the front end of the material tube, a nozzle coaxially fixed at the front end of the plunger cylinder, a screw installed inside the material tube along the axis, and a plunger screw head fixed at the top end of the screw, wherein a plunger sealing channel is provided at the axis of the plunger cylinder, and a plunger sealing portion whose outer diameter matches the plunger sealing channel is provided at the front end of the plunger screw head, and the outer diameter of the plunger sealing portion is smaller than the outer diameter of the screw. In the present invention, a plunger screw head group is provided at the front end of the screw, and a plunger structure is formed by the plunger screw head group and the plunger cylinder, so that the extrusion amount of the material can be controlled by controlling the stroke amount of the plunger screw head group, so as to achieve the purpose of precision injection molding. That is, the screw is used to melt, compress, and convey plastic, and the plunger screw head at the front end of the screw is used to realize the functions of fine sealing and precision injection, so as to achieve the function of precision micro-injection. In addition, since the plunger screw head assembly in the device is only responsible for squeezing the material forward (similar to the role of a piston), there is no possibility of it being twisted off, so a smaller diameter plunger screw head can be used to achieve the purpose of micro-injection.

[0007] In an implementation manner of the first aspect, the plunger screw head includes a connecting thread and a plunger sealing portion in sequence from the rear end to the front end, and the connecting thread is fixed to the front end of the screw.

[0008] In one embodiment of the first aspect, a weight-reducing portion is provided at the top of the plunger screw head, the head of the weight-reducing portion is conical, the rest of the weight-reducing portion is cylindrical, and the outer diameter of the weight-reducing portion is smaller than the outer diameter of the plunger sealing portion. As is well known, in the field of injection molding screws, the cross-sectional area of ​​the screw is inversely proportional to the injection pressure, and the cross-sectional area of ​​the screw is proportional to the injection weight. In the present application, there are two purposes for setting the weight-reducing portion. The first is to reduce the weight of the injection molding to achieve the purpose of lightweight, reduce the residence time of the material in the material pipe, and reduce the occurrence of carbonization; the purpose of setting the plunger sealing portion is first to fine sealant, and the second is to increase the injection pressure.

[0009] In one embodiment of the first aspect, the plunger screw includes a meson and a check ring, wherein the meson is fixed on the outside of the plunger screw head, the check ring is sleeved on the outside of the plunger screw head, and the outer diameter of the check ring matches the inner diameter of the material tube, and the check ring is located at the front end of the meson.

[0010] In one embodiment of the first aspect, a guide portion, a sealing portion and a guide groove portion are sequentially provided between the connecting thread of the plunger screw head and the plunger sealing portion, wherein the meson is fixed on the outside of the guide portion, the check ring is sleeved on the outside of the sealing portion, and the outer diameter of the meson and the outer diameter of the tail end of the guide groove portion are both smaller than the outer diameter of the check ring but larger than the inner diameter of the check ring.

[0011] In one embodiment of the first aspect, the plunger cylinder is hollow along the axial direction, and a glue passage is provided inside the plunger cylinder, the middle part of the glue passage is a plunger sealing channel, the front end inner wall of the glue passage is provided with a nozzle thread, and the nozzle is fixed to the front end of the glue passage by the nozzle thread, the inner diameter of the tail end of the glue passage is the same as the inner diameter of the material pipe, and abuts against the front end of the material pipe.

[0012] In one implementation of the first aspect, an axial length of the plunger sealing channel in the plunger cylinder is greater than an axial length of the plunger sealing portion.

[0013] In one embodiment of the first aspect, the nozzle is through-connected along its axial direction, and the inner diameter of the tail end of the nozzle is the same as the inner diameter of the plunger sealing channel, and the small hole at the front end of the nozzle is through-connected with the middle hole of the nozzle, and the inner diameter is smaller than the inner diameter of the middle hole of the nozzle.

[0014] In one implementation of the first aspect, a driving unit is connected to the tail end of the screw, and the driving unit is used to drive the screw as a whole to rotate and discharge materials and move forward and backward along the material pipe.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) A plunger structure is formed by a plunger screw head group and a plunger cylinder, so that the extrusion amount of the material can be controlled by controlling the stroke of the plunger screw head group to achieve the purpose of precision injection molding;

[0017] (2) A smaller diameter plunger screw head can be used to achieve the purpose of microinjection;

[0018] (3) Micro-precision plunger screw can reduce the weight of the injected plastic;

[0019] (4) It can increase the injection pressure of plastic;

[0020] (5) Reduce the residence time of plastic in the material pipe to reduce the occurrence of carbonization. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the overall assembly diagram of the micro-precision plunger screw in Example 1;

[0022] Figure 2 It is a schematic diagram of the structure of the material pipe in Example 1;

[0023] Figure 3 Schematic diagram of the structure of the screw in Example 1;

[0024] Figure 4 It is a structural schematic diagram of the plunger screw head in Example 1;

[0025] Figure 5 for Figure 4 Schematic diagram of the cross-sectional structure of AA;

[0026] Figure 6 This is a schematic diagram of the structure of the reverse loop stopped in Example 1;

[0027] Figure 7 This is a schematic diagram of the structure of the meson in Example 1;

[0028] Figure 8 It is a structural schematic diagram of the plunger cylinder in Example 1;

[0029] Fig. 9 It is a schematic diagram of the structure of the nozzle in Example 1;

[0030] Fig.10 It is an enlarged schematic diagram of the local state of the plunger screw head group during the injection process;

[0031] Fig.11 This is an enlarged schematic diagram of the local state of the plunger screw head group at the beginning of injection molding;

[0032] Fig.12 It is an enlarged schematic diagram of the local state of the plunger screw head assembly when the screw continues to push forward;

[0033] Fig.13 It is an enlarged schematic diagram of the local state of the plunger screw head group when the screw restarts to feed glue;

[0034] Fig.14 This is a schematic diagram of the structure of the micro-precision plunger screw of Example 2 when it is assembled at the top of the screw;

[0035] Fig.15 It is a schematic structural diagram of the plunger screw head in Example 2;

[0036] Fig.16 This is a schematic diagram of the local structure of the top end of the screw in Example 2;

[0037] Fig.17 This is a schematic diagram of the structure of the marbles when sealing with glue in Example 2;

[0038] Fig.18 It is a schematic diagram of the side cross-section structure of the fork-type check ring in Example 3;

[0039] Fig.19 This is a schematic diagram of the main structure of the fork-type check ring in Example 3;

[0040] Fig. 20 This is the overall assembly diagram of the micro-precision plunger screw in Example 4;

[0041] Fig.21 Schematic diagram of the structure of the nozzle in Example 4.

[0042] In the accompanying drawings, 1 is a nozzle, 11 is a connecting screw thread, 12 is a glue injection channel, 2 is a material pipe, 21 is a feed port, 22 is a material pipe end hole, 3 is a screw, 31 is a feeding section, 32 is a compression section, 33 is a metering section, 4 is a plunger screw head, 41 is a weight reduction section, 42 is a plunger sealing section, 43 is a guide groove section, 431 is a guide groove, 44 is a sealing section, 45 is a guide section, 46 is a connecting screw thread, 5 is a backflow prevention ring , 51 is the check portion, 52 is the fork-shaped portion, 6 is the meson, 7 is the plunger cylinder, 71 is the connecting channel, 72 is the plunger sealing channel, 73 is the mounting screw hole, 8 is the plunger unit, 81 is the weight reduction portion, 82 is the plunger sealing portion, 83 is the second feed channel, 84 is the mounting cavity, 9 is the connected check ring, 91 is the first feed channel, 92 is the accommodating cavity, 93 is the connecting thread, 94 is the external thread, and 10 is the marble. DETAILED DESCRIPTION

[0043] Unless otherwise defined, the technical or scientific terms used in this specification and claims shall have the ordinary meanings understood by persons having ordinary skills in the technical field to which the present invention belongs. All the values ​​from the lowest value to the highest value listed herein refer to all the values ​​obtained by incrementing one unit between the lowest value and the highest value when the difference between the lowest value and the highest value is more than two units.

[0044] The specific embodiments of the present invention will be described below. It should be noted that in the specific description of these embodiments, for the sake of concise description, it is impossible for this specification to describe all the features of the actual embodiments in detail. Without departing from the spirit and scope of the present invention, those skilled in the art may modify and replace the embodiments of the present invention, and the resulting embodiments are also within the scope of protection of the present invention.

[0045] Example

[0046] The embodiments of the present invention will be described in detail below. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

[0047] Example 1

[0048] A micro-precision plunger screw, the assembly diagram of which is as follows Figure 1 As shown, it includes a material tube 2, a screw 3, a plunger screw head 4, a check ring 5, a meson 6, a plunger cylinder 7, a nozzle 1, a driving device (not shown in the figure), etc., wherein the screw 3 is coaxially installed in the material tube 2, the plunger cylinder 7 is fixedly installed on the top of the material tube 2 by bolts, and the nozzle 1 is fixedly installed on the top of the plunger cylinder 7 by bolts. The plunger screw head 4 is coaxially fixedly installed on the top of the material tube 2, and its main part is inserted in the plunger cylinder 7. The meson 6 is fixedly installed on the outside of the plunger screw head 4, the check ring 5 is sleeved on the outside of the plunger screw head 4, and the outer diameter of the check ring 5 is ground with a small gap with the inner wall of the material tube 2. The driving device is installed at the tail end of the screw 3, and is used to drive the screw 3 to rotate as a whole, move forward or backward. The specific structure of each component is as follows.

[0049] The structure of the material pipe 2 is as follows Figure 2 As shown, its structure is not much different from the existing material pipe, including a material pipe hole 22 that penetrates along the axial direction for installing the screw 3, and a feed port 21 is opened on the rear end wall of the material pipe 2. A heating device can be installed on the outer wall of the material pipe 2 to melt the material. The structure of the screw 3 is as shown in FIG. Figure 3As shown, its shape is not much different from that of an ordinary screw, and it includes a metering section 33, a compression section 32 and a feeding section 31 from front to back. However, in this application, the outer diameter of the screw 3 is relatively thin, and the effective aspect ratio can be set to 14 to 22:1. The inner diameter of the material tube 2 used is 14 mm, which is used for micro injection molding. Of course, the diameter of the screw 3 is between 14 and 30 mm, which can basically achieve micro injection molding. The smaller the diameter, the smaller the injection amount.

[0050] The structure of the plunger screw head 4 is as follows Figure 4 As shown, it includes a weight reduction portion 41, a plunger sealing portion 42, a guide groove portion 43, a sealing portion 44, a guide portion 45 and a connecting screw 46 from the front end (i.e., the left end) to the rear end (i.e., the right end), wherein the connecting screw 46 is inserted into the front end center of the screw 3 and fixes the plunger screw head 4 and the screw 3 through the thread. Figure 7 The meson 6 shown is fixed to the outside of the guide portion 45, and the two are fixed by threaded connection. The structure of the guide groove portion 43 is as follows Figure 5 As mentioned above, four guide grooves 431 are provided on the periphery thereof for glue application. Figure 6 The non-return ring 5 shown is sleeved on the outside of the sealing part 44, and the axial length of the sealing part 44 is greater than the axial length of the non-return ring 5, that is, the relative position of the non-return ring 5 and the plunger screw head 4 is stopped at the front end face of the non-return ring 5 and the tail end face of the guide groove part 43, and the rear end face of the non-return ring 5 and the front end face of the meson 6. The plunger sealing part 42 is cylindrical, and its connection with the guide groove part 43 is a conical structure. The outer diameter of the plunger sealing part 42 is smaller than the diameter of the screw 3. The diameter of the plunger sealing part is most preferably 1D~12D, and the second preferred is 12.1D~22D. Of course, it can also be made into 22.1D~500D. As long as it is smaller than the diameter of the screw, the weight reduction and pressure increase function can be achieved. However, it should be noted that the ratio of the diameter of the plunger sealing part to the diameter of the screw is between 0.2 and 0.9, which is reasonable and scientific, and preferably 0.5~0.9. However, since this embodiment is used for micro-injection, a large diameter should not be selected. For example, in this application, it can be made into 6 to 12 mm, and in this embodiment, it is set to 8 mm. In order to further reduce the volume and weight of the plastic in the metering chamber and increase the injection pressure of the material, the weight-reducing part 41 adopts a cylindrical structure with a smaller diameter, and its head is conical. The connection between it and the plunger sealing part 42 also adopts a conical connection method. In this embodiment, the outer diameter of the weight-reducing part 41 is set to 6 mm.

[0051] The structure of the plunger cylinder 7 is as follows Figure 8As shown, its structure is similar to the flange in the ordinary screw assembly, and a circle of flange screw holes is provided on its outer circumference, and it is fixed to the front end of the material tube 2 by a number of bolts. A through channel is provided at the axis of the plunger cylinder 7, and from the front end to the rear end are the mounting screw hole 73, the plunger sealing channel 72 and the connecting channel 71. Among them, the inner diameter of the connecting channel 71 is the same as the inner diameter of the material tube 2, and they are interpenetrating without gaps. The inner diameter of the plunger sealing channel 72 and the outer diameter of the plunger sealing part 42 are precisely ground, but relative sliding can occur between the two. There is also a tapered surface between the plunger sealing channel 72 and the connecting channel 71, and its taper is the same as the taper at the connection between the plunger sealing part 42 and the guide groove part 43. The axial length of the plunger sealing channel 72 of the plunger cylinder is greater than the axial length of the plunger sealing part 42. The inner wall of the mounting screw hole 73 is provided with a nozzle thread, and the nozzle 1 is fixedly installed in the mounting channel 73.

[0052] The structure of the nozzle 1 is as follows Fig. 9 As shown, a material passage penetrating front to back is also provided at the axis, and the inner diameter of the rear end material passage is the same as the inner diameter of the plunger sealing passage 72, and the two penetrate each other without a gap.

[0053] The working principle of the micro-precision plunger screw described in this embodiment is as follows. Fig.10 ~Attached Fig.13 Conduct the demonstration process.

[0054] During injection, as the screw rotates, the molten material flows forward. At this time, the check ring 5 is located at the front end, that is, the front end of the check ring 5 abuts against the rear end of the guide groove 43, and the plunger sealing portion 42 is not inserted into the plunger sealing channel 72. Fig.10 As shown. The flow path of the material is: the gap between the screw 3 and the inner wall of the material tube 2 → the gap between the meson 6 and the inner wall of the material tube 2 → the gap between the inner wall of the check ring 5 and the outer wall of the sealing part 44 → the guide groove 431 → the channel of the plunger cylinder 7 → the channel of the nozzle 1. Because the mold is in contact with the nozzle, the cold glue port in the mold prevents the material from flowing out from the front end of the nozzle 1, and the material will gradually be stored in the channel of the nozzle 1. After the stored material fills the channels of the nozzle 1 and the plunger cylinder 7, when the material continues to be fed, the volume of the material in the metering chamber gradually increases, and a reverse thrust is generated, and the screw 3 and the plunger screw head 4 will gradually move backward.

[0055] When the injection molding starts, the outlet at the front end of the nozzle 1 is opened first, and then the screw 3 is pushed forward by the driving device. At this time, the screw 3, the entire plunger screw head 4 and the meson 6 will move forward. Since the check ring 5 is only sleeved on the outside of the sealing portion 44, that is, it is not fixed, the check ring 5 will not move forward at this time until the front end of the meson 6 on the plunger screw head 4 abuts against the rear end of the check ring 5. Fig.11As shown. In this way, the check ring 5 and the meson 6 cut off the flow channel of the molten material, that is, the new material cannot flow forward, and the material originally stored in the nozzle 1 and the plunger cylinder 7 cannot flow backward, which plays a sealing effect.

[0056] The driving device drives the screw 3 to continue to move forward. At this time, the screw 3, the plunger screw head 4, the check ring 5, and the meson 6 will move forward together until the plunger sealing portion 42 enters the plunger sealing channel 72. Fig.12 As shown. Since the tolerance between the plunger seal portion 42 and the plunger seal channel 72 is very small, a structure similar to a syringe and a piston is formed. When the screw 3 continues to move forward, the plunger seal portion 42 can push the material forward, thereby ejecting the material from the nozzle. Since the diameter of the plunger seal channel 72 is fixed, the injection volume of the material can be accurately controlled by controlling the forward length of the plunger seal portion 42 (i.e., the stroke of the screw 3).

[0057] When the injection molding is completed, the melt driving device starts to rotate, and the material is pushed from the discharge port to the metering chamber by the thrust generated by the screw edge angle. When the material is pushed to the tail end of the check ring, the material pushes the check ring forward until the front end of the check ring 5 abuts against the tail end of the guide groove portion 43, so that the flow channel of the molten material is reopened. Fig.13 As the volume of the material in the metering chamber does not increase and the material cannot flow out from the front hole of the nozzle, the material will generate a reverse thrust to push the plunger screw assembly to continue to move backward until the plunger sealing portion 42 is completely pulled out of the plunger sealing channel 72, and then it returns to the state as shown in FIG. Fig.10 In the state shown, the next injection molding can be continued.

[0058] Example 2

[0059] In this embodiment, the structure of the material pipe, plunger cylinder, screw and nozzle is the same as that of embodiment 1, and the plunger screw head adopts a marble plunger screw head, and its structure is as follows: Fig.14 and Fig.17 As shown, it mainly includes three parts, namely, a plunger unit 8, a conjoined check ring 9 and a marble 10, wherein the plunger unit 8 is as shown in FIG. Fig.15 As shown, the conjoined check ring 9 is as shown in Fig.16 As shown, the details are as follows:

[0060] The front end of the plunger unit 8 is provided with a weight reduction portion 81 and a plunger sealing portion 82 in sequence, and these two structures are also the same as those in Example 1, and the cooperation principle with the plunger cylinder is also the same. However, in this embodiment, a mounting cavity 84 is provided at the rear end of the plunger unit, and a plurality of second material transfer channels 83 that penetrate inside and outside are provided at the front end of the mounting cavity 84, and the inner wall of the mounting cavity 84 is provided with threads.

[0061] An accommodating chamber 92 is provided at the axis center of the front end of the conjoined check ring 9. The inner wall of the rear end of the accommodating chamber 92 is spherical, and the inner wall of the rear end is provided with a first material passing channel 91 that passes through the inside and outside. The inner diameter of the middle part of the accommodating chamber 92 is constant, and the opening diameter of the front end of the accommodating chamber 92 becomes larger. An external thread 94 is provided at the outer wall of the front end of the conjoined check ring 9, and the external thread 94 matches the internal thread of the inner wall of the installation cavity 84, so that the plunger unit 8 and the conjoined check ring 9 are connected by threads. A marble 10 is provided in the accommodating chamber 92, and the diameter of the marble 10 is the same as the diameter of the inner wall of the rear end of the accommodating chamber 92. A connecting thread 93 is provided at the rear end of the conjoined check ring 9, and is fixed to the front axis of the screw rod through the connecting thread 93.

[0062] The cooperation between the plunger unit 8 (especially the weight reduction part 81 and the plunger sealing part 82) and the plunger cylinder in this embodiment is consistent with that in embodiment 1 and will not be repeated here, but the form of glue injection and rear end sealing is completely different from that in embodiment 1, as follows.

[0063] The material is conveyed by the screw rod and enters the accommodating chamber 92 from the first feeding channel 91, and pushes the marble 10 to roll forward until the marble 10 reaches the front end of the accommodating chamber 92. The material enters the installation cavity 84, and then flows through the second feeding channel 83 and enters the plunger cylinder. This is the state of the entire material storage. Fig.14 shown.

[0064] When the driving device starts to push the screw forward, the material will generate a reverse thrust, the material passes through the second feeding channel 83, and pushes the marble 10 backward until it abuts against the inner wall of the rear end of the accommodating chamber 92. In this way, the marble 10 blocks all the first feeding channels 91, forming a sealed state. Fig.17 The subsequent injection molding process is the same as that of Example 1 and will not be described again.

[0065] Example 3

[0066] In this embodiment, a structure similar to that of embodiment 1 is adopted, except that: in this embodiment, the check ring is replaced with Fig.18 , Fig.19 The fork check ring shown in the figure includes a check portion 51 and a fork-shaped portion 52. When installed, the check portion 51 is sleeved on the outside of the sealing portion of the plunger screw head, and the fork-shaped portion 52 is inserted into the guide groove of the plunger screw head. Therefore, the rotation of the guide groove can drive the rotation of the fork check ring. That is, when the screw rotates, the plunger screw head is driven to rotate synchronously, and the entire fork check ring can also be driven to rotate synchronously.

[0067] The ordinary ring-type check ring (the check ring used in Example 1) is replaced with a fork-type check ring because the fork-type check ring rotates and stops synchronously with the screw each time, so the check ring is in the same position each time it retreats and contacts the meson, which can achieve better sealing repetition accuracy. The fork-type check ring rotates synchronously with the screw head without relative friction movement, so the fork-type check ring will not have mechanical wear with the screw head, so this embodiment makes improvements.

[0068] Example 4

[0069] In this embodiment, the plunger cylinder and the nozzle are combined into a whole, and the assembly diagram is shown in FIG. Fig. 20 As shown, the structure of the nozzle is as follows Fig.21 As shown. In this embodiment, a connecting screw thread 11 is provided on the outside of the tail end of the nozzle 1, and is directly fixed to the top of the material tube 2 through the connecting screw thread 11. A through glue injection channel 12 is provided at the axis of the nozzle 1. In this embodiment, the tail end of the glue injection channel 12 is mutually connected with the channel in the material tube 2, and the front end inner diameter of the glue injection channel 12 remains unchanged, and is ground with a small gap with the plunger sealing part in the plunger screw head 4, that is, the glue injection channel in the nozzle 1 and the plunger sealing part in the plunger screw head 4 form a glue sealing structure. The rest of the structure and operation principle in this embodiment are similar to those in embodiment 1, and will not be repeated here.

[0070] The above description of the embodiments is to facilitate those of ordinary skill in the art to understand and apply the present application. It is obvious that those familiar with the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without having to pay creative labor. Therefore, the present application is not limited to the embodiments herein, and improvements and modifications made by those skilled in the art based on the contents disclosed in the present application without departing from the scope and spirit of the present application are within the scope of the present application.

Claims

1. A micro-precision plunger screw, characterized in that: The plunger screw comprises a material tube, a plunger cylinder coaxially fixed at the front end of the material tube, a nozzle coaxially fixed at the front end of the plunger cylinder, a screw installed inside the material tube along the axis, and a plunger screw head fixed at the top end of the screw, wherein a plunger sealing channel is provided at the axis of the plunger cylinder, a plunger sealing portion with an outer diameter matching the plunger sealing channel is provided at the front end of the plunger screw head, and the outer diameter of the plunger sealing portion is smaller than the outer diameter of the screw.

2. The micro-precision plunger screw according to claim 1, characterized in that: The plunger screw head comprises a connecting thread and a plunger sealing portion in sequence from the rear end to the front end, and the connecting thread is fixed to the front end of the screw.

3. The micro-precision plunger screw according to claim 2, characterized in that: A weight-reducing portion is provided at the top end of the plunger screw head, the head of the weight-reducing portion is conical, the rest of the weight-reducing portion is cylindrical, and the outer diameter of the weight-reducing portion is smaller than the outer diameter of the plunger sealing portion.

4. The micro-precision plunger screw according to any one of claims 1 to 3, characterized in that: The plunger screw includes a meson and a check ring, wherein the meson is fixed on the outside of the plunger screw head guide part, the check ring is sleeved on the outside of the plunger screw head, and the outer diameter of the check ring matches the inner diameter of the material tube, and the check ring is located at the front end of the meson.

5. The micro-precision plunger screw according to claim 4, characterized in that: A guide portion, a sealing portion and a guide groove portion are sequentially arranged between the connecting thread of the plunger screw head and the plunger sealing portion, wherein the pion is fixed on the outside of the guide portion, and the check ring is sleeved on the outside of the sealing portion.

6. The micro-precision plunger screw according to any one of claims 1 to 5, characterized in that: The plunger cylinder is hollow along the axial direction, and a glue passage is provided inside the plunger cylinder, the middle part of the glue passage is a plunger sealing passage, a nozzle thread is provided on the front end inner wall of the glue passage, and the nozzle is fixed to the front end of the glue passage by the nozzle thread, and the inner diameter of the tail end of the glue passage is the same as the inner diameter of the material tube, and abuts against the front end of the material tube.

7. The micro-precision plunger screw according to claim 1, characterized in that: The axial length of the plunger sealing channel is greater than the axial length of the plunger sealing portion.

8. The micro-precision plunger screw according to claim 1, characterized in that: The nozzle is through-connected along its axial direction, and the inner diameter of the tail end of the nozzle is the same as the inner diameter of the plunger sealing channel.

9. The micro-precision plunger screw according to claim 1, characterized in that: The tail end of the screw is connected to a driving unit, and the driving unit is used to drive the screw as a whole to rotate and move forward and backward along the material pipe to eject the material.

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