Stable transportation control method of extrusion-injection molding integrated device

Abstract

The invention discloses a stable transportation control method of an extrusion-injection molding integrated device, which comprises the following steps of: adjusting the pushing speed v2 of an injection molding plunger or an injection molding screw, recording the pushing time length delta t1 of the injection molding plunger or the injection molding screw, and the pressure maintaining and cooling time lengths delta thold and delta tcool of an injection molding assembly, and combining the sizes of an extrusion screw and an extrusion nozzle, so as to control the stable transportation of the extrusion-injection molding integrated device. And calculating the conditions met by the actual rotating speed of the extrusion screw, so that stable transportation of the melt can be realized. According to the invention, 'cutoff-accumulation 'oscillation of the melt can be effectively avoided, and stability and high efficiency of the melt transportation process are realized.

Description

Technical Field

[0001] The invention relates to the field of extrusion / injection integrated molding, and in particular to a stable transportation control method for an extrusion-injection integrated device. Background Art

[0002] With the rapid development of optoelectronic information, medical, and automotive industries, the demand for high-end complex structural products in the domestic and international markets is growing, placing higher demands on their precision and the performance and efficiency of manufacturing equipment. However, single injection and single extrusion equipment have many processing links, high energy consumption, and low efficiency. The cumulative errors in each independent link lead to reduced precision of complex microstructure products, affecting the performance and value of the products. Therefore, extrusion-injection molding integrated cross-process equipment has developed rapidly. The developed extrusion-injection molding integrated device is a typical representative of the manufacturing industry's transformation towards high efficiency, green, and intelligent. It has broad application prospects in composite materials and recyclable and bio-based materials. For example, fiber-reinforced plastics and multi-layer co-extruded materials require an integrated extrusion-injection molding process to achieve structural optimization, with the extrusion layer providing strength and the injection molding part achieving sealing or functional integration. For example, environmentally friendly materials have a narrow processing window, and traditional multi-step processes are prone to degradation. The integrated extrusion-injection molding technology shortens processing time, reduces the thermal history of the material, and improves performance stability.

[0003] Existing single injection molding and single extrusion devices can directly set the required conveying rate according to the size characteristics of the product. However, due to the conflict of process modes, the transportation of polymer melts in the extrusion-injection molding integrated device has always been unstable. Among them, the extrusion process relies on the continuous rotation of the screw to produce a stable melt flow, while the injection molding process requires periodic high-pressure and high-speed filling. The extrusion process and the injection molding process in the extrusion-injection molding integrated device run alternately. On the one hand, the pressure-flow matching of the melt between the extruder outlet and the injection molding unit inlet is unbalanced, resulting in the "interruption-accumulation" oscillation of the melt. On the other hand, considering that extrusion has the continuous characteristics and injection molding has the intermittent characteristics, the holding pressure and cooling time are long. With the combination of the two, the stable and efficient transportation of the melt in the extrusion-injection molding integrated device has become the core pain point of the industry. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention proposes a stable transportation control method for an extrusion-injection molding integrated device. The pushing speed of the injection molding component and the length of the intermittent injection molding cycle are used to evaluate and determine the extrusion transportation flow rate and transportation volume. Ultimately, the rotation speed of the continuous extrusion process can be determined, thereby achieving stability in the transportation process of the extrusion-injection molding integrated device.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A stable transport control method for an integrated extrusion-injection molding device, which controls the actual speed N of the extrusion screw ′The following conditions must be met to achieve stable transport of the melt:

[0007]

[0008] Among them, D2 represents the diameter of the injection plunger or the inner diameter of the injection screw, Δt1 represents the pushing time of the injection plunger or the injection screw, and Δt hold and Δt cool Respectively represent the holding time and cooling time of the injection molded component, L d Indicates the length of the internal flow channel of the extrusion nozzle, D1 indicates the major diameter of the extrusion screw, and L indicates the thread length of the extrusion screw. It represents the function of the thread angle of the extrusion screw changing with the axis direction λ of the extrusion screw, and h(λ) represents the function of the thread groove depth of the extrusion screw changing with the axis direction λ of the extrusion screw.

[0009] Furthermore, the h(λ) and are all constants.

[0010] Furthermore, the extrusion-injection molding integrated device includes a hopper, an extrusion assembly and an injection molding group;

[0011] The extrusion assembly includes an extrusion barrel, an extrusion motor, an extrusion screw and an extrusion nozzle;

[0012] The hopper is located at the top of the entire integrated device, and the outlet of the hopper is connected to the inlet of the extrusion barrel. The extrusion barrel is used to mix and heat the materials. The extrusion motor drives the extrusion screw to transport the material melt mixed and heated by the extrusion barrel to the extrusion nozzle;

[0013] The injection molding assembly includes an injection molding barrel, an injection molding motor, an injection molding plunger and an injection molding nozzle; wherein, the outlet of the extrusion nozzle is connected to the inlet of the injection molding barrel; the injection molding nozzle is connected to one end of the injection molding barrel, the injection molding plunger is connected to the other end of the injection molding barrel, and the injection molding plunger is driven by the injection molding motor.

[0014] Furthermore, the injection molding plunger is replaced by the injection molding screw.

[0015] The beneficial effects of the present invention are as follows:

[0016] (1) The stable transport control method of the extrusion-injection molding integrated device of the present invention adopts an extrusion nozzle to temporarily store the extruded melt, and then drives the extruded melt into the injection molding unit with the help of the negative pressure generated by the retreat of the injection molding component, which effectively avoids the "interruption-accumulation" oscillation of the melt, helps to reduce the time cost of the transport process of the extrusion-injection molding integrated device, and uses the injection molding melt filling amount to control the melt plasticization amount in the extrusion process, thereby solving the problem of mismatch between continuous extrusion and intermittent injection molding processes.

[0017] (2) The stable transport control method of the extrusion-injection molding integrated device of the present invention can obtain the actual speed of the extrusion screw 203 that needs to be regulated based on these parameters by only adjusting the pushing speed of the injection molding plunger and recording the pushing time of the injection molding component and the holding pressure and cooling time of the injection molding component, thereby controlling the stable transport of the melt. The control method is simple and convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is an integrated extrusion-injection molding device according to an embodiment of the present invention.

[0019] Figure 2 Schematic cross-sectional view of an integrated extrusion-injection molding device according to an embodiment of the present invention.

[0020] Figure 3 Schematic diagram of the key dimensions of the screw extrusion-plunger injection molding integrated device according to an embodiment of the present invention.

[0021] Figure 4 Schematic diagram of the key dimensions of the screw extrusion-screw injection molding integrated device according to an embodiment of the present invention.

[0022] Figure 5 Schematic diagram of the structure of the extrusion screw according to an embodiment of the present invention.

[0023] Figure 6 This is a process diagram of the stable transportation control method of the extrusion-injection molding integrated device according to an embodiment of the present invention.

[0024] Figure 7 Schematic diagram of negative pressure driven melt transfer according to an embodiment of the present invention.

[0025] In the figure: hopper 1, extrusion component 2, injection molding component 3, extrusion barrel 201, extrusion motor 202, extrusion screw 203, extrusion nozzle 204, injection molding barrel 301, injection molding motor 302, injection molding plunger or injection molding screw 303, injection molding nozzle 304. DETAILED DESCRIPTION

[0026] The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments, and the purpose and effects of the present invention will become more apparent. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] like Figure 1 and 2 As shown, the extrusion-injection molding integrated device in this embodiment includes a hopper 1, an extrusion component 2 and an injection molding component 3.

[0028] The extrusion assembly 2 includes an extrusion barrel 201, an extrusion motor 202, an extrusion screw 203, and an extrusion nozzle 204. The hopper 1 is located at the top of the integrated device, with its outlet connected to the inlet of the extrusion barrel 201. The extrusion barrel 201 is used to mix and heat the materials. The extrusion motor 202 drives the extrusion screw 203, conveying the heated material melt from the extrusion barrel 201 to the extrusion nozzle 204.

[0029] The injection molding assembly 3 of this embodiment includes an injection molding barrel 301, an injection molding motor 302, an injection molding plunger 303, and an injection molding nozzle 304. The outlet of the extrusion nozzle 204 is connected to the inlet of the injection molding barrel 301, and the extrusion nozzle 204 can temporarily store the extruded plasticized melt. The injection molding nozzle 304 is connected to one end of the injection molding barrel 301, and the injection molding plunger 303 is connected to the other end of the injection molding barrel 301. The injection molding plunger 303 is driven by the injection molding motor 302.

[0030] In fact, the injection plunger 303 may also be replaced by an injection screw.

[0031] The amount of melt transported by extrusion is controlled by controlling the rotation speed of the extrusion motor 202 , and the amount of melt transported by injection is controlled by controlling the driving speed of the injection motor 302 .

[0032] The working principle of the entire extrusion-injection molding integrated device is as follows: the hopper 1 transports the polymer pellets into the extrusion component 2, after which the materials are mixed and heated by the extrusion barrel 201, and then enter the injection molding component 3 through the extrusion nozzle 204 by the extrusion screw 203, and the injection molding plunger 303 pushes the polymer into the injection molding nozzle 304.

[0033] like Figures 3 to 5 As shown, the diameter of the injection plunger or the inner diameter of the injection screw is defined as D2, the major diameter of the extrusion screw 203 is defined as D1, the thread length of the extrusion screw 203 is defined as L, the rotation speed of the extrusion screw 203 is defined as N, the function of the variation of the thread groove depth with the axis direction λ of the extrusion screw 203 is defined as h(λ), and the function of the variation of the thread angle with the axis direction λ of the extrusion screw 203 is defined as The diameter of the internal flow channel of the extrusion nozzle 204 is d1, and the length of the internal flow channel of the extrusion nozzle 204 is L d .

[0034] In order to achieve stable transportation of the extrusion-injection molding integrated device of this embodiment, Figure 6 As shown, the following reasoning steps are adopted:

[0035] Step 1: Determine the plasticizing amount of the injection molding barrel.

[0036] Adjust the pushing speed v2 of the injection plunger or the injection screw, record the pushing time Δt1 of the injection plunger or the injection screw, and obtain the plasticized amount Q2 of the injection molding barrel 301. Specifically, the following formula is used for calculation:

[0037]

[0038] Step 2: Establish an extrusion-injection timing matching equation to ensure that the extrusion melt volume strictly matches the injection molding requirements. Through timing rigidity constraints, eliminate the melt accumulation or interruption caused by the mismatch between the continuous extrusion feeding and the injection molding intermittent requirements in the traditional solution. By conducting a holding pressure and cooling test on the injection molding component 3, record the holding pressure and cooling time Δt of the injection molding component 3. hold and Δt cool , obtain the intermittent period length Δt2 as the synchronization benchmark of the extrusion process, specifically calculated using the following formula:

[0039] Δt2=Δt1+Δt hold +Δt cool

[0040] Step 3: Establish the extrusion-injection melt supply and demand balance equation, and use the natural negative pressure formed in the injection molding cylinder 301 when the injection molding plunger 303 retreats, such as Figure 7 As shown, the melt stored in the extrusion nozzle 204 is automatically sucked in, and the extrusion delivery flow rate is determined according to the circular tube flow model. The specific expression is as follows:

[0041]

[0042] The diameter d1 and length L of the internal flow channel of the extrusion nozzle 204 are d The selection should consider the plasticizing amount Q2 of the injection molding barrel, which satisfies the following formula:

[0043]

[0044] Preferably, the groove depth h(λ) is constant along the extrusion screw axis direction λ, and the thread angle λ is a constant along the direction of the extrusion screw axis.

[0045] The allowed plasticizing and transporting time of the extrusion component 2 should be less than the injection molding intermittent cycle length Δt2. The critical extrusion transport volume Q1 can be evaluated based on the injection molding intermittent cycle length Δt2. The expression is as follows:

[0046]

[0047] During the transport process, the critical extrusion transport volume Q1 of the extrusion screw 203 at a time length of Δt2 is equal to the injection barrel transport volume Q2 of the injection plunger or injection screw at a time length of Δt1, and the following relationship exists:

[0048] Q1=Q2

[0049] Step 4: Establish a quantitative model for stable extrusion speed. Based on the critical extrusion delivery volume Q1, the speed N of the extrusion screw 203 for stable delivery of the extrusion-injection molding integrated device can be evaluated. The expression is as follows:

[0050]

[0051] During the application process, the actual speed N of the extrusion screw 203 ′ It should be greater than N to ensure the stability of the transport process of the extrusion-injection molding integrated device.

[0052] N ′ ≥N

[0053] The melt transported by the extrusion screw 203 is first stored inside the extrusion nozzle 204, and will be sucked into the injection molding barrel 301 after the injection plunger or injection screw retracts, so that the next cycle can be carried out, reducing the overlapping time of injection molding pressure holding and cooling with the extrusion process, saving time and cost.

[0054] The present invention is specifically described below by way of examples.

[0055] In this embodiment, the injection molding component is an injection molding plunger.

[0056] Step 1: Determine the plasticizing amount of the injection molding cylinder. Adjust the pushing speed of the injection molding plunger to 100 mm / s, record the pushing time of the injection molding plunger to 0.935 s, and the inner diameter of the injection molding plunger is 18 mm. Obtain the plasticizing amount Q2 of the injection molding cylinder 301 as:

[0057]

[0058] Step 2: Establish the extrusion-injection timing matching equation. Carry out pressure holding and cooling tests on the injection molded components and record the pressure holding time Δt of the injection molded components. hold is 1s and the cooling time Δt cool The intermittent period duration Δt2 is 4s, which is calculated using the following formula:

[0059] Δt2=Δt1+Δt hold +Δt cool =5.935s

[0060] Step 3: Establish the supply and demand balance equation of extrusion-injection melt, and determine the extrusion transport flow rate by deriving and expanding the continuity equation and momentum equation of the melt in the round tube Among them: the selected extrusion screw thread groove depth h(λ) is constant, which is 3mm, and the thread angle The angle of the extrusion screw is 17.4°, the major diameter D1 of the extrusion screw is 18 mm, the diameter d1 of the extrusion nozzle is 2 mm, the length L of the extrusion screw is 400 mm, and the length L of the extrusion nozzle is d is 150mm. The specific expression is as follows:

[0061]

[0062] The critical extrusion transport capacity Q1 is evaluated as:

[0063]

[0064] During the conveying process, the conveying volume Q1 of the extrusion screw at Δt2 and the conveying volume Q2 of the injection plunger at Δt1 are related as follows:

[0065] Q1=Q2

[0066] Step 4: Establish a quantitative model for stable extrusion speed. Based on the critical extrusion delivery volume Q1, the extrusion screw speed N for stable delivery of the screw extrusion-plunger injection molding integrated device can be estimated as:

[0067]

[0068] During the application process, the actual speed of the extrusion screw N ′ It should be greater than N to ensure the stability of the conveying process of the screw extrusion-plunger injection molding integrated device.

[0069] N ′ ≥11r / min

[0070] The melt transported by the extrusion screw is first stored inside the extrusion nozzle and is automatically sucked into the injection molding barrel by the negative pressure generated by the retreat of the injection plunger, so that the next cycle can be carried out, reducing the overlapping time of injection molding pressure holding and cooling with the extrusion process, avoiding the waiting time for the extrusion process after the injection molding is completed, and realizing stable and efficient transportation of the screw extrusion-plunger injection molding integrated device. Compared with the existing molding process, it can greatly save time and cost.

[0071] The stable transport control method of the extrusion-injection molding integrated device of the present invention adopts the pushing speed of the injection plunger and the length of the intermittent injection molding cycle to evaluate and determine the extrusion transport flow rate and transport volume, and finally determines the rotation speed of the continuous extrusion process, thereby achieving the stability of the transport process of the screw extrusion-plunger injection molding integrated device.

[0072] Those skilled in the art will understand that the foregoing descriptions are merely preferred embodiments of the invention and are not intended to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, those skilled in the art will still be able to modify the technical solutions described in the foregoing examples or substitute equivalents for some of the technical features therein. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the invention shall be included within the scope of protection of the invention.

Claims

1. A stable transport control method for an integrated extrusion-injection molding device, characterized in that: Control the actual speed of the extrusion screw N ′ The following conditions must be met to achieve stable transport of the melt: Among them, D2 represents the diameter of the injection plunger or the inner diameter of the injection screw, Δt1 represents the pushing time of the injection plunger or the injection screw, and Δt hold and Δt cool Respectively represent the holding time and cooling time of the injection molded component, L d Indicates the length of the internal flow channel of the extrusion nozzle, D1 indicates the major diameter of the extrusion screw, and L indicates the thread length of the extrusion screw. It represents the function of the thread angle of the extrusion screw changing with the axis direction λ of the extrusion screw, and h(λ) represents the function of the thread groove depth of the extrusion screw changing with the axis direction λ of the extrusion screw.

2. The stable transport control method of the extrusion-injection molding integrated device according to claim 1, characterized in that: The h(λ) and are all constants.

3. The stable transport control method of the extrusion-injection molding integrated device according to claim 1, characterized in that: The extrusion-injection molding integrated device includes a hopper, an extrusion assembly and an injection molding group; The extrusion assembly includes an extrusion barrel, an extrusion motor, an extrusion screw and an extrusion nozzle; The hopper is located at the top of the entire integrated device, and the outlet of the hopper is connected to the inlet of the extrusion barrel. The extrusion barrel is used to mix and heat the materials. The extrusion motor drives the extrusion screw to transport the material melt mixed and heated by the extrusion barrel to the extrusion nozzle; The injection molding assembly includes an injection molding barrel, an injection molding motor, an injection molding plunger and an injection molding nozzle; wherein, the outlet of the extrusion nozzle is connected to the inlet of the injection molding barrel; the injection molding nozzle is connected to one end of the injection molding barrel, the injection molding plunger is connected to the other end of the injection molding barrel, and the injection molding plunger is driven by the injection molding motor.

4. The stable transport control method of the extrusion-injection molding integrated device according to claim 1, characterized in that: The injection molding plunger is replaced by the injection molding screw.

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