Plasticizing screw cooling mechanism, control method thereof and plastic forming machine

Abstract

The invention discloses a plasticizing screw rod cooling mechanism, a control method thereof and a plastic molding machine, the plasticizing screw rod cooling mechanism comprises a plasticizing screw rod and a fixedly arranged cooling sleeve; a cooling liquid inlet channel and a cooling liquid return channel which are independent from each other are arranged in the plasticizing screw rod; at least two cooling grooves are formed in the handle part of the plasticizing screw rod, one cooling groove is communicated with the cooling liquid inlet channel through a cooling liquid inlet hole, and the other cooling groove is communicated with the cooling liquid return channel through a cooling liquid return hole; the cooling sleeve is arranged outside the cooling groove in a sleeving mode and forms a sealed cavity with the cooling groove, and an inlet and an outlet corresponding to the cooling liquid inlet hole and the cooling liquid return hole respectively are formed in the cooling sleeve. According to the plasticizing screw rod cooling mechanism, the control method thereof and the plastic forming machine, the structure is compact, response is rapid, control is accurate, the plasticizing screw rod is directly cooled, and the undesirable phenomena such as yellowing and blackening caused by plastic decomposition due to overheat of the screw rod are effectively prevented.

Description

Technical Field

[0001] This invention relates to the technical field of plastic molding machinery, specifically a plasticizing screw cooling mechanism and its control method, as well as a plastic molding machine. Background Technology

[0002] In plastic processing, the plasticizing screw is a key component, which conveys, compresses, shears, and melts plastic granules through rotation. The heat required for plasticizing mainly comes from two sources: radiant heating from the heating coil surrounding the melting cylinder, and frictional heat generated by the shearing of the material during screw rotation. The shearing heat generated is difficult to precisely control due to factors such as screw surface finish, rotational speed, and screw thread structure.

[0003] In actual production, especially when processing heat-sensitive plastics or requiring high-speed plasticizing, the temperature of the plasticizing screw is prone to becoming too high. Excessive screw temperature will directly cause localized overheating of the molten plastic in contact with it, leading to plastic decomposition and carbonization. This manifests as defects such as yellow-black streaks and black spots on the product, seriously affecting product quality and yield.

[0004] Currently, common cooling methods mainly involve air cooling or water cooling of the melt cylinder. However, this indirect cooling method is slow to respond, inefficient, and cannot precisely control the temperature of the screw body, thus having limited effectiveness in solving the problem of localized overheating caused by screw shear heat.

[0005] Therefore, the aforementioned technical problems need to be solved. Summary of the Invention

[0006] To address the above-mentioned technical problems, this invention provides a plasticizing screw cooling mechanism and its control method, as well as a plastic molding machine. The mechanism is compact, responsive, and precisely controlled, directly cooling the plasticizing screw and effectively preventing adverse phenomena such as yellowing and blackening of the plastic due to overheating of the screw.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A plasticizing screw cooling mechanism includes a plasticizing screw and a fixedly mounted cooling jacket;

[0009] The plasticizing screw has independent coolant inlet and coolant return channels inside; the shank of the plasticizing screw has at least two cooling grooves, one of which is connected to the coolant inlet channel through a coolant inlet hole, and the other is connected to the coolant return channel through a coolant return hole.

[0010] The cooling jacket is fitted outside the cooling tank and forms a sealed cavity with it. The cooling jacket is provided with an inlet and an outlet corresponding to the coolant inlet and coolant return hole, respectively.

[0011] The plasticizing screw cooling mechanism directly cools the plasticizing screw through the coolant inlet and return channels inside the screw. It is responsive, precise, and effectively prevents the plastic from decomposing and turning yellow or black due to overheating of the screw.

[0012] A further optimized solution includes a cooling generator. The inlet and outlet of the cooling jacket are connected to the cooling generator via pipelines, forming a closed cooling loop that flows through the interior of the plasticizing screw. This closed cooling loop achieves rapid and efficient cooling of the plasticizing screw.

[0013] Further optimizations include a melting cylinder, a plasticizing motor that drives the plasticizing screw to rotate, and a heating coil that heats the melting cylinder.

[0014] A further optimization is that the front end of the plasticizing screw is provided with a detachable dispensing nozzle, and an end cap is provided between the dispensing nozzle and the front end face of the plasticizing screw. The end cap has a flow channel inside, which connects the front end of the coolant inlet channel with the front end of the coolant return channel. A sealing ring is provided at the joint between the end cap and the front end face of the plasticizing screw.

[0015] To form a circuit, the coolant inlet and return channels need to be connected via a deflector at the front end of the plasticizing screw. Therefore, a dispensing nozzle is threaded onto the front end of the screw, pressing an end cap with an internal flow channel against the screw end face. This flow channel connects the two internal channels. A sealing ring is installed between the end cap and the screw end face to ensure a tight seal.

[0016] In a further optimized design, a rotary sealing ring is provided between the cooling jacket and the plasticizing screw shank. A dynamic seal is formed between the cooling jacket and the cooling tank via the rotary sealing ring, thus maintaining a seal even when the plasticizing screw rotates and moves axially.

[0017] A further optimized solution includes a positioning guide sleeve, which is fixedly installed and passes through the cooling sleeve to restrict the cooling sleeve from rotating with the plasticizing screw, while allowing the cooling sleeve to move axially along the positioning guide sleeve. To prevent the cooling sleeve from rotating with the screw, a positioning guide sleeve is fixed to the machine base, which passes through both cooling sleeves and only allows the cooling sleeves to slide axially.

[0018] In a further optimized design, the ports of the coolant inlet channel and coolant return channel at the rear end of the plasticizing screw are sealed with plugs.

[0019] A control method for a plasticizing screw cooling mechanism, using any of the plasticizing screw cooling mechanisms described above, comprises the following steps:

[0020] 1) The temperature T1 of the melting cylinder is monitored by the first temperature sensor, and the temperature T2 of the molten rubber is monitored by the second temperature sensor;

[0021] 2) The control system calculates the temperature difference T0 = T2 - T1;

[0022] 3) Compare the temperature difference T0 with a preset threshold ΔT;

[0023] 4) When T0 > ΔT, the control system starts the cooling generator, causing the cooling medium to circulate in the closed cooling loop to cool the plasticizing screw;

[0024] 5) When T0≤ΔT, the control system controls the cooling generator to stop working.

[0025] The control method for the cooling mechanism of this plasticizing screw is based on temperature difference feedback control. Specifically, a first temperature sensor is installed on the melt barrel to measure the barrel temperature T1; a second temperature sensor is installed near the screw head, in the melt flow channel, such as at the head flange, to measure the actual temperature T2 of the molten material. The control system calculates the temperature difference T0 (T0 = T2 - T1) in real time. Theoretically, under ideal conditions, the material temperature should be close to the temperature set in the heating barrel. When the shear heat is too high, T2 will be significantly higher than T1. Therefore, the control system presets a reasonable temperature difference threshold ΔT. When T0 > ΔT is detected, it is determined that the plasticizing screw is overheated, and the cooling cycle is automatically started; when T0 drops to ≤ ΔT, cooling is stopped.

[0026] To further optimize the scheme, the preset threshold ΔT is set and adjusted according to the characteristics of the processed material.

[0027] A plastic molding machine includes any of the plasticizing screw cooling mechanisms described above.

[0028] Compared with the prior art, the plasticizing screw cooling mechanism and its control method of the present invention, as well as the plastic molding machine, have the following technical advantages:

[0029] 1. Direct and efficient cooling: The cooling medium circulates directly inside the screw, directly removing heat from the screw's metal body. The cooling path is short, the thermal resistance is low, and the response speed is fast, making the cooling efficiency far higher than external cooling of the barrel.

[0030] 2. Precise control: It adopts feedback control logic based on melt temperature difference (T2-T1), which can keenly sense the temperature rise caused by abnormal shear heat and immediately start precise cooling. This avoids the lag and inaccuracy of traditional time control or fuzzy temperature control, and prevents the material from overheating and decomposing at the source.

[0031] 3. Stable and reliable structure: The combination design of cooling jacket, rotary sealing ring and positioning guide sleeve cleverly solves the problem of dynamic sealing and pipeline connection during the rotation and reciprocating motion of plasticizing screw, ensuring the long-term stable operation of cooling system.

[0032] 4. Wide applicability: This mechanism and method can be widely used in various plastic molding equipment such as injection molding machines and extruders that require precise temperature control. It is especially suitable for processing heat-sensitive plastics or high-speed precision molding processes, and can effectively improve product quality and yield. Attached Figure Description

[0033] Figure 1 This is a front cross-sectional view of a specific embodiment of the plasticizing screw cooling mechanism of the present invention;

[0034] Figure 2 yes Figure 1 Enlarged cross-sectional schematic diagram of the screw structure of Zhongsu Chemical Co., Ltd.

[0035] Figure 3 yes Figure 1 Enlarged cross-sectional view of the middle end cap;

[0036] Figure 4 yes Figure 1 Enlarged cross-sectional view of the intermediate cooling jacket.

[0037] In the diagram: 1. Heating coil; 2. Nozzle; 3. Head flange; 4. Molten rubber; 5. Dispensing nozzle; 6. Plug ring; 7. Medium; 8. End cap; 9. Sealing ring; 10. Plasticizing screw; 11. Coolant inlet channel; 12. Coolant return channel; 13. Molten rubber cylinder; 14. Hopper; 15. Granular rubber; 16. Front plate of injection station; 17. Cooling jacket; 18. Cooling tank; 19. Coolant inlet; 20. Rotary sealing ring; 21. Coolant return hole; 22. Positioning guide sleeve; 23. Transmission device; 24. Plasticizing motor; 25 / 26. Plug; 27. Motor support; 28. Platform; 29. ​​Coolant inlet pipe; 30. Coolant return pipe; 31. Cooling generator; 32. Cooling medium; 33. First temperature sensor; 34 / 36. Signal line; 35. Control system; 37. Second temperature sensor; 38. Guide positioning hole. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to the embodiments shown in the accompanying drawings.

[0039] like Figures 1 to 4 As shown, a specific embodiment of the plasticizing screw cooling mechanism of the present invention is presented.

[0040] like Figure 1As shown, the main body of the plasticizing screw cooling mechanism is mounted on the injection molding machine's injection stand supported by platform 28. The melt cylinder 13 is fixed via the injection stand's front plate 16, and the plasticizing screw 10 is housed within it. The rear end of the plasticizing screw 10 is connected to the plasticizing motor 24 via a transmission device 23, and is driven to rotate by the motor. Simultaneously, the motor support 27 can drive the entire drive unit to move axially along platform 28, thus realizing the injection action. A hopper 14 is installed above the feed port of the melt cylinder 13, and contains granular plastic material 15. A head flange 3 and a nozzle 2 are sequentially mounted on the front end of the melt cylinder 13. A heating coil 1 is segmented and wrapped around the nozzle 2, head flange 3, and melt cylinder 13.

[0041] The core improvement of this invention lies in the plasticizing screw 10 and its cooling circuit. For example... Figure 2 As shown, the plasticizing screw 10 has two parallel deep holes machined axially inside, serving as a coolant inlet channel 11 and a coolant return channel 12, respectively. At its rear shank, two annular cooling grooves 18 are machined, with coolant inlet holes 19 and coolant return holes 21 drilled through them, connecting the cooling grooves to their corresponding internal channels. A cooling sleeve 17 is installed on the outside of each of the two cooling grooves 18, with holes on the cooling sleeve 17 aligned with holes on the cooling grooves 18. Rotary sealing rings 20 are installed at both ends of the cooling sleeves 17 to ensure a seal with the rotating screw shank. The cooling sleeves 17 are connected to a cooling generating device 31, such as a small refrigeration unit, mounted on the platform 28 via a coolant inlet pipe 29 and a coolant return pipe 30. This device stores cooling media 32 such as cooling water or oil.

[0042] like Figure 1 and Figure 4 As shown, to ensure that the cooling sleeve 17 does not rotate with the screw, a positioning guide sleeve 22 is fixed on the front plate 16 of the injection stage and passes through the guide positioning holes 38 of the two cooling sleeves 17. The cooling sleeve 17 can only slide axially on the guide sleeve. The two channel openings at the rear end of the plasticizing screw 10 are sealed with plugs 25 and 26.

[0043] like Figure 1 and Figure 2 As shown, a dispensing nozzle 5 is threaded onto the front end of the plasticizing screw 10. The dispensing nozzle 5 presses an end cap 8 against the end face of the screw. The end cap 8 has a U-shaped or arc-shaped flow channel machined on the side facing the screw. When the end cap 8 is pressed, this flow channel connects the outlet of the coolant inlet channel 11 with the inlet of the coolant return channel 12, forming a "U"-shaped loop. A sealing ring 9 is installed on the end cap 8 to ensure no leakage at the connection. A spacer 7 and a plug ring 6 are used for injection sealing.

[0044] like Figure 1As shown, a first temperature sensor 33, installed in the middle section of the melting cylinder 13, is used to detect the cylinder wall temperature T1; and a second temperature sensor 37, installed on the head flange 3 with its probe in contact with the molten rubber 4, is used to detect the actual melt temperature T2. The two sensors are connected to the control system 35 via signal lines 34 and 36, respectively.

[0045] This invention also provides a control method for a plasticizing screw cooling mechanism, which, using the aforementioned plasticizing screw cooling mechanism, comprises the following steps:

[0046] 1) The temperature T1 of the melting cylinder 13 is monitored by the first temperature sensor 33, and the temperature T2 of the molten rubber is monitored by the second temperature sensor 37;

[0047] 2) The control system calculates the temperature difference T0 = T2 - T1;

[0048] 3) Compare the temperature difference T0 with a preset threshold ΔT;

[0049] 4) When T0 > ΔT, the control system 35 starts the cooling generator 31, so that the cooling medium 32 circulates in the closed cooling loop to cool the plasticizing screw 10.

[0050] 5) When T0≤ΔT, the control system 35 controls the cooling generator 31 to stop working.

[0051] The control method for the plasticizing screw cooling mechanism is based on temperature difference feedback control. Specifically, a first temperature sensor is installed on the melt barrel to measure the barrel temperature T1; a second temperature sensor is installed near the screw head, in the melt flow channel, such as at the head flange, to measure the actual temperature T2 of the molten material. The control system calculates the temperature difference T0 (T0 = T2 - T1) in real time. Ideally, the material temperature should be close to the temperature set in the heating barrel. When the shear heat is too high, T2 will be significantly higher than T1. Therefore, the control system presets a reasonable temperature difference threshold ΔT. When T0 > ΔT, it is determined that the plasticizing screw is overheated, and the cooling cycle is automatically started; when T0 drops to ≤ ΔT, cooling is stopped. The preset threshold ΔT is set and adjusted according to the characteristics of the processed material.

[0052] The present invention also discloses a plastic molding machine, including the above-mentioned plasticizing screw cooling mechanism.

[0053] This invention enables proactive and precise intervention in the temperature of the plasticizing screw, ensuring that the melt temperature is always controlled within a suitable range, thus solving quality problems such as yellowing and black spots in the product caused by screw overheating.

[0054] In summary, as described in the specification and figures, this invention has been manufactured into actual samples and tested multiple times. The test results demonstrate that the invention achieves its intended purpose, and its practicality is beyond doubt. The embodiments described above are merely for illustrative purposes and are not intended to limit the scope of the invention. Any equivalent embodiments made by those with common knowledge in the relevant technical field, utilizing the technical content disclosed in this invention without departing from the scope of the technical features and similar features of this invention, based on partial modifications or alterations, are within the protection scope of this invention.

Claims

1. A plasticizing screw cooling mechanism, characterized in that: It includes a plasticizing screw (10), a melting cylinder (13), and a fixed cooling jacket (17); The plasticizing screw (10) is sleeved inside the melting cylinder (13). The plasticizing screw (10) has an independent coolant inlet channel (11) and coolant return channel (12). The shank of the plasticizing screw (10) is provided with at least two cooling grooves (18). One cooling groove (18) is connected to the coolant inlet channel (11) through the coolant inlet hole (19), and the other cooling groove (18) is connected to the coolant return channel (12) through the coolant return hole (21). The cooling sleeve (17) is fitted outside the cooling tank (18) and forms a sealed cavity with it. The cooling sleeve (17) is provided with an inlet and an outlet corresponding to the coolant inlet (19) and the coolant return hole (21), respectively. It also includes a cooling generator (31), the inlet and outlet of the cooling jacket (17) are connected to the cooling generator (31) through pipelines to form a closed cooling loop that flows through the interior of the plasticizing screw (10).

2. The plasticizing screw cooling mechanism according to claim 1, characterized in that, It also includes a plasticizing motor (24) that drives the plasticizing screw (10) to rotate and a heating coil (1) that heats the melt cylinder (13).

3. The plasticizing screw cooling mechanism according to claim 1, characterized in that, The front end of the plasticizing screw (10) is provided with a detachable dispensing nozzle (5). An end cap (8) is provided between the dispensing nozzle (5) and the front end face of the plasticizing screw (10). The end cap (8) is provided with a flow channel inside, which connects the front end of the coolant inlet channel (11) with the front end of the coolant return channel (12).

4. The plasticizing screw cooling mechanism according to claim 3, characterized in that, A sealing ring (9) is provided at the joint between the end cap (8) and the front end face of the plasticizing screw (10).

5. The plasticizing screw cooling mechanism according to claim 1, characterized in that, A rotary sealing ring (20) is provided between the cooling jacket (17) and the shank of the plasticizing screw (10).

6. The plasticizing screw cooling mechanism according to claim 1, characterized in that, It also includes a positioning guide sleeve (22), which is fixedly installed and passes through the cooling sleeve (17), restricting the cooling sleeve (17) from rotating with the plasticizing screw (10), and the cooling sleeve (17) can move axially along the positioning guide sleeve (22).

7. The plasticizing screw cooling mechanism according to claim 1, characterized in that, The ports of the coolant inlet channel (11) and coolant return channel (12) at the rear end of the plasticizing screw (10) are respectively sealed by plugs (25, 26).

8. A control method for a plasticizing screw cooling mechanism, characterized in that, The plasticizing screw cooling mechanism according to any one of claims 1 to 7 comprises the following steps: 1) The temperature T1 of the melting cylinder (13) is monitored by the first temperature sensor (33), and the temperature T2 of the molten rubber is monitored by the second temperature sensor (37); 2) The control system (35) calculates the temperature difference T0 = T2 - T1; 3) Compare the temperature difference T0 with a preset threshold ΔT; 4) When T0 > ΔT, the control system (35) starts the cooling generator (31) so that the cooling medium (32) circulates in the closed cooling loop to cool the plasticizing screw (10); 5) When T0≤ΔT, the control system (35) controls the cooling generator (31) to stop working.

9. The control method for the plasticizing screw cooling mechanism according to claim 8, characterized in that, The preset threshold ΔT is set and adjusted according to the characteristics of the processed material.

10. A plastic molding machine, characterized in that: Includes the plasticizing screw cooling mechanism as described in any one of claims 1 to 8.

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