A method and device for determining optimal injection speed and injection molding equipment

Abstract

This invention discloses a method, apparatus, and injection molding equipment for determining the optimal injection speed. The method includes: acquiring parameters of the injection molding equipment and information on the injection molding material; calculating the positional change of the pusher in the injection barrel required for one molding cycle based on the parameters of the injection molding equipment and the information on the injection molding material; obtaining the theoretical filling time using mold flow analysis and calculating the theoretical injection speed based on the positional change; determining multiple injection speeds as test speeds based on the theoretical injection speed; performing an injection molding process using the injection molding equipment and injection molding material at each test speed to obtain the effective viscosity and shear rate corresponding to each test speed; establishing a coordinate system for effective viscosity and shear rate to form a mapping relationship between effective viscosity and shear rate; and determining the optimal injection speed based on the mapping relationship. Using the above technical solution, it can be ensured that the injection speed does not exceed the maximum allowable shear rate of the rubber compound.

Description

Technical Field

[0001] The invention relates to the technical field of plastic processing, and in particular to a method and device for determining an optimum injection speed and injection molding equipment. Background Art

[0002] Plastic products are indispensable in people's daily life. Plastic products are generally obtained through injection molding process, using injection device to inject molten plastic raw materials into plastic injection mold, and then cool and solidify. Among them, injection speed refers to the moving speed of the screw or plunger during injection of the injection device, and the unit is mm / s (millimeter / second).

[0003] The injection speed should be determined according to the different structures, shapes and sizes of the products, runner systems, plastic properties, and related rheological data. The injection speed will affect the shear rate, and too high a shear rate will produce a thermal effect, affecting the thermophysical properties and shear strength of the plastic.

[0004] Therefore, how to ensure that the injection speed does not exceed the maximum shear rate allowed by the rubber has become a technical problem that needs to be solved urgently. Summary of the invention

[0005] The invention provides a method and device for determining an optimum injection speed and injection molding equipment to ensure that the injection speed does not exceed the maximum shear rate allowed by the rubber material.

[0006] According to one aspect of the present invention, a method for determining an optimal injection speed is provided, which is applied to process parameter adjustment of an injection molding process; the method comprises:

[0007] Acquire parameters of injection molding equipment and information of injection molding raw materials; the injection molding equipment includes an injection device and a plastic injection mold; the injection device includes an injection barrel and a pusher, and the pusher includes a screw and / or a plunger;

[0008] Calculating the position change of the pusher in the injection barrel required for one-time molding according to the parameters of the injection molding equipment and the information of the injection molding raw material;

[0009] The theoretical filling time is obtained by mold flow analysis, and the theoretical injection speed is calculated according to the position change;

[0010] According to the theoretical injection speed, determining a minimum injection speed and a maximum injection speed, and a plurality of injection speeds between the minimum injection speed and the maximum injection speed as test speeds;

[0011] According to each of the test speeds, the injection molding equipment and the injection molding raw material are used to perform an injection molding process to obtain an effective viscosity and a shear rate corresponding to each of the test speeds;

[0012] Establishing a coordinate system of the effective viscosity and the shear rate, wherein the effective viscosity and the shear rate corresponding to the same test speed constitute a coordinate point, and a mapping relationship between the effective viscosity and the shear rate is formed;

[0013] According to the mapping relationship, the optimal injection speed of the injection molding equipment for performing the injection molding process using the injection molding material is determined.

[0014] Optionally, the parameters of the injection molding equipment include the inner wall diameter of the injection barrel; the information of the injection molding raw material includes the density of the injection molding raw material;

[0015] Calculating the position change of the pusher in the injection barrel required for one-time molding according to the parameters of the injection molding equipment and the information of the injection molding raw material, including:

[0016] According to the parameters of the injection molding equipment and the information of the injection molding raw material, the weight of the product molded once is obtained;

[0017] The metering position L1 is calculated according to the first formula, and the switching position L2 is calculated according to the second formula; wherein the first formula is L1=(W×4×1000) / [(π×D²)×ρ]+L0, and the second formula is L2=L1-(L1-L0)×k; W is the weight of the product molded once, D is the inner wall diameter of the injection barrel, ρ is the density of the injection molding material, L0 is the safety distance of the injection barrel, k is the injection coefficient of the injection barrel, and 0.9<k<1;

[0018] According to the third formula, the position change △L of the pusher in the injection barrel required for one molding is calculated; wherein the third formula is △L=(L1+L')-L2; L1 is the metering position, L2 is the switching position, and L' is the rear release position.

[0019] Optionally, calculating the theoretical injection speed according to the position change includes:

[0020] According to the fourth formula, the theoretical injection speed S0 is calculated; wherein the fourth formula is S0=△L / T0; △L is the position change of the pusher in the injection barrel required for one-time molding, and T0 is the theoretical filling time.

[0021] Optionally, determining, according to the mapping relationship, an optimal injection speed of the injection molding process performed by the injection molding equipment using the injection molding material includes:

[0022] Fitting the mapping relationship into a mapping curve;

[0023] When it is determined that the slope of the mapping curve is zero, the test speed corresponding to the minimum shear rate is the optimal injection speed.

[0024] Optionally, it also includes: obtaining a molding cycle of the injection molding process performed by the injection molding equipment using the injection molding raw material;

[0025] Determining the optimal injection speed of the injection molding process performed by the injection molding equipment using the injection molding material according to the mapping relationship includes:

[0026] Fitting the mapping relationship into a mapping curve;

[0027] Determining whether the molding cycle is greater than or equal to a cycle threshold;

[0028] If the molding cycle is greater than or equal to the cycle threshold, then when it is determined that the slope of the mapping curve is the second slope k2, the test speed corresponding to the minimum shear rate is the optimal injection speed;

[0029] If the molding cycle is less than the cycle threshold, then when it is determined that the slope of the mapping curve is the first slope k1, the test speed corresponding to the minimum shear rate is the optimal injection speed;

[0030] Among them, 0≤|k1|<|k2|.

[0031] Optionally, the parameters of the injection molding equipment include the flow length ratio of the plastic injection mold;

[0032] Determining the optimal injection speed of the injection molding process performed by the injection molding equipment using the injection molding material according to the mapping relationship includes:

[0033] Fitting the mapping relationship into a mapping curve;

[0034] Determining whether the flow length ratio is greater than or equal to a flow channel threshold;

[0035] If the flow length ratio is greater than or equal to the flow channel threshold, then when it is determined that the slope of the mapping curve is the third slope k3, the test speed corresponding to the minimum shear rate is the optimal injection speed;

[0036] If the flow length ratio is less than the flow channel threshold, then when it is determined that the slope of the mapping curve is the fourth slope k4, the test speed corresponding to the minimum shear rate is the optimal injection speed;

[0037] Among them, 0≤|k3|<|k4|.

[0038] Optionally, determining, according to the mapping relationship, an optimal injection speed of the injection molding process performed by the injection molding equipment using the injection molding material includes:

[0039] Fitting the mapping relationship into a mapping curve;

[0040] Determining whether an insert is provided in the plastic injection mold;

[0041] If an insert is provided in the plastic injection mold, when it is determined that the slope of the mapping curve is the sixth slope k6, the test speed corresponding to the minimum shear rate is the optimal injection speed;

[0042] If no insert is provided in the plastic injection mold, when it is determined that the slope of the mapping curve is the fifth slope k5, the test speed corresponding to the minimum shear rate is the optimal injection speed;

[0043] Among them, 0≤|k5|<|k6|.

[0044] Optionally, the method further includes: obtaining the barrel capacity of the injection barrel and the barrel injection volume required for one-time molding according to the parameters of the injection molding equipment and the information of the injection molding raw material;

[0045] Determining the optimal injection speed of the injection molding process performed by the injection molding equipment using the injection molding material according to the mapping relationship includes:

[0046] Fitting the mapping relationship into a mapping curve;

[0047] Determining whether a ratio of the barrel injection volume to the barrel holding volume is greater than or equal to an injection threshold;

[0048] If the ratio of the barrel injection volume to the barrel holding volume is greater than or equal to the injection threshold, it is determined that when the slope of the mapping curve is the seventh slope k7, the test speed corresponding to the minimum shear rate is the optimal injection speed;

[0049] If the ratio of the barrel injection volume to the barrel capacity is less than the injection threshold, it is determined that when the slope of the mapping curve is the eighth slope k8, the test speed corresponding to the minimum shear rate is the optimal injection speed;

[0050] Among them, 0≤|k7|<|k8|.

[0051] According to another aspect of the present invention, there is provided a device for determining an optimal injection speed, which is used in the method for determining an optimal injection speed described in any embodiment of the present invention;

[0052] The determining device comprises:

[0053] A first acquisition module is used to acquire parameters of an injection molding device and information of injection molding raw materials; the injection molding device includes an injection device and a plastic injection mold; the injection device includes an injection barrel and a pusher, and the pusher includes a screw and / or a plunger;

[0054] A first calculation module calculates the position change of the pusher in the injection barrel required for one-time molding according to the parameters of the injection molding equipment and the information of the injection molding raw material;

[0055] The second calculation module is used to obtain the theoretical filling time by means of mold flow analysis, and calculate the theoretical injection speed according to the position change;

[0056] A test speed determination module, used to determine a minimum injection speed and a maximum injection speed according to the theoretical injection speed, and a plurality of injection speeds between the minimum injection speed and the maximum injection speed as test speeds;

[0057] An injection molding measurement module is used to perform an injection molding process according to each of the test speeds using the injection molding equipment and the injection molding raw materials to obtain the effective viscosity and shear rate corresponding to each of the test speeds;

[0058] A mapping relationship building module, used to establish a coordinate system of the effective viscosity and the shear rate, wherein the effective viscosity and the shear rate corresponding to the same test speed constitute a coordinate point, and form a mapping relationship between the effective viscosity and the shear rate;

[0059] The optimal injection speed determination module is used to determine the optimal injection speed of the injection molding process performed by the injection molding equipment using the injection molding material according to the mapping relationship.

[0060] According to another aspect of the present invention, there is provided an injection molding device, comprising: an injection device, a plastic injection mold, a control device, and a device for determining the above-mentioned optimal injection speed;

[0061] The determining device is electrically connected to the control device;

[0062] The control device is used to monitor the parameters of the injection device; the determination device is used to execute the method for determining the optimal injection speed described in any embodiment of the present invention.

[0063] The technical solution of the present invention can obtain the theoretical injection speed by adopting the mold flow analysis method, and then determine multiple test speeds based on the theoretical injection speed. The test speed can be limited to a more reasonable range, which can improve the test efficiency and avoid the test speed being too large or too small, exceeding the parameter critical value of the equipment, affecting the test results, and damaging the equipment; by establishing a coordinate system of the effective viscosity and the shear rate, a mapping relationship between the effective viscosity and the shear rate is formed, and the balance point of the effective viscosity and the shear rate can be determined. The test speed corresponding to the balance point is the optimal injection speed. When injection is performed at the optimal injection speed, a larger injection flow rate and a smaller shear rate can be achieved, thereby improving production efficiency and product quality.

[0064] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0066] Figure 1 is a flow chart of a method for determining an optimal injection speed provided in Embodiment 1 of the present invention;

[0067] Figure 2 is a schematic diagram of a mapping curve of effective viscosity versus shear rate provided by an embodiment of the present invention;

[0068] Figure 3 is a flow chart of a method for determining an optimal injection speed provided in Embodiment 2 of the present invention;

[0069] Figure 4 is another schematic diagram of a mapping curve of the effective viscosity changing with the shear rate provided by an embodiment of the present invention;

[0070] Figure 5 is another schematic diagram of a mapping curve of the effective viscosity changing with the shear rate provided by an embodiment of the present invention;

[0071] Figure 6 is another schematic diagram of a mapping curve of the effective viscosity changing with the shear rate provided by an embodiment of the present invention;

[0072] Figure 7is another schematic diagram of a mapping curve of the effective viscosity changing with the shear rate provided by an embodiment of the present invention;

[0073] Figure 8 is a structural schematic diagram of a device for determining an optimal injection speed provided in Embodiment 3 of the present invention;

[0074] Fig. 9 It is a structural schematic diagram of an injection molding device provided in Example 4 of the present invention. DETAILED DESCRIPTION

[0075] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0076] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0077] Embodiment 1

[0078] Figure 1 This is a flow chart of a method for determining an optimal injection speed provided in the first embodiment of the present invention. This embodiment can be applied to adjusting the process parameters of the injection molding process before or during the injection molding process. The method can be executed by a device for determining an optimal injection speed. The device can be implemented in the form of hardware and / or software. The device can be configured in the injection molding equipment. Figure 1 As shown, the method includes:

[0079] S1001. Obtain parameters of injection molding equipment and information of injection molding raw materials; wherein the injection molding equipment includes an injection device and a plastic injection mold, the injection device includes an injection barrel and a pusher, and the pusher includes a screw and / or a plunger.

[0080] Among them, the injection barrel and pusher of the injection device are used to inject the injection material in a molten state, and the pusher can transport the injection material to the nozzle. In addition, the injection device can also include a nozzle, a heater, a hopper, a meter, etc. The plastic injection mold includes a pouring system and a product cavity. The pouring system may include a cold runner, a hot runner, a cold material hole, etc. The product cavity can cool and solidify the injection material to form the final molded product.

[0081] The parameters of the injection molding equipment include but are not limited to the inner wall diameter of the injection barrel, the barrel capacity of the injection barrel, the flow length ratio of the plastic injection mold, whether inserts are provided in the plastic injection mold, etc. The information of the injection molding raw materials includes but is not limited to the name, material properties, density, etc. of the injection molding raw materials.

[0082] For example, the equipment parameters may be obtained according to the equipment manual provided by the manufacturer of the injection molding equipment, and the information of the injection molding raw materials may be obtained according to the Technical Data Sheet (TDS) provided by the raw material supplier.

[0083] S1002. Calculate the position change of the pusher in the injection barrel required for one-time molding according to the parameters of the injection molding equipment and the information of the injection molding raw material.

[0084] For example, the amount of material required for one molding can be calculated based on the parameters of the plastic injection mold (such as the volume of each flow channel, the volume of the product cavity, the volume of the cold material hole, etc.) and the information of the injection molding raw materials (such as the density, thermal conductivity, specific heat capacity, etc. of the injection molding raw materials); and then, based on the amount of material required for one molding and the parameters of the injection device, the amount of change in the position of the pusher in the injection barrel required for one molding is calculated, that is, the barrel injection amount required for one molding. In an optional embodiment, the mold flow analysis method can be used to calculate the amount of change in the position of the pusher in the injection barrel required for one molding.

[0085] S1003. Using mold flow analysis, obtain theoretical filling time, and calculate theoretical injection speed based on position change.

[0086] For example, computer simulation technology can be used to analyze, optimize and predict the flow behavior of molten plastic during the injection molding process. For example, the entire process from the injection device entering the plastic injection mold to filling, cooling, solidification and demolding can be simulated. The mold flow analysis process can first establish a geometric model of the three-dimensional mold and plastic parts, input the material properties of the injection molding raw materials (such as density, thermal conductivity, specific heat capacity, etc.); then set the process parameters (such as injection pressure, injection temperature, mold temperature, cooling method, holding pressure, etc.), simulate the flow process of the plastic, analyze and optimize the process parameters; finally, the theoretical filling time can be obtained, that is, the time required for the molten plastic to fill the mold. This is the idealized filling time assuming that all conditions are ideal and there are no external interference or process problems. It can also be called the injection time.

[0087] In the primary injection, the position change amount may have only one change process, the theoretical filling time may have only one filling stage, and the theoretical injection speed = position change amount / theoretical filling time.

[0088] In multi-stage injection, the position change may include multiple change processes, the theoretical filling time may include multiple filling stages, and there are multiple theoretical injection speeds during the injection process, each theoretical injection speed = corresponding position change / corresponding theoretical filling time.

[0089] S1004. According to the theoretical injection speed, determine the minimum injection speed and the maximum injection speed, and multiple injection speeds between the minimum injection speed and the maximum injection speed as test speeds.

[0090] The theoretical injection speed is the idealized injection speed assuming that all conditions are ideal and there are no external interference or process problems.

[0091] For example, the theoretical injection speed can be used as the median, with an upper and lower floating of 30% as the maximum injection speed and the minimum injection speed, respectively, and the injection speed can be gradually increased or decreased by 5%, and multiple injection speeds can be obtained as multiple test speeds to test and obtain the effective viscosity and shear rate at different injection speeds. For one-stage injection, there is only one injection speed in the injection process, and only the size of one injection speed needs to be changed; for multi-stage injection, there are multiple injection stages in the injection process, and the injection speeds of different injection stages can be different. The injection speeds of each injection stage can be increased or decreased synchronously by 5% of each other.

[0092] S1005. According to each test speed, injection molding is performed using injection molding equipment and injection molding materials to obtain effective viscosity and shear rate corresponding to each test speed.

[0093] Exemplarily, the drying temperature and drying time of the injection molding raw materials can be set according to the TDS provided by the raw material supplier. The temperature of the injection barrel and the nozzle can also be determined according to the data provided by the raw material supplier (which can be set according to the median of the data provided by the raw material supplier). The injection molding equipment and injection molding raw materials are used to carry out the injection molding process at different test speeds. The peak pressure (maximum injection pressure) and injection time corresponding to each test speed are obtained and recorded respectively. Then, based on each test speed and the peak pressure and injection time corresponding to each test speed, the effective viscosity and shear rate corresponding to each test speed are calculated.

[0094] Among them, effective viscosity = peak pressure × injection time × screw reinforcement ratio; shear rate = 1 / injection time; in the formula, the unit of effective viscosity is Pascal second (Pa·S), the unit of peak pressure is Pascal (Pa), the unit of injection time is second (S), and the unit of shear rate is S per second. -1 For all-electric injection molding machines, the screw reinforcement ratio is 1; for hydraulic injection molding machines, the screw reinforcement ratio is 10.

[0095] When performing the injection molding process, the injection time can be set long enough (can be set to the maximum injection time) to ensure that the actual injection time is less than the set injection time, and the injection pressure can be set high enough (can be set to the maximum injection pressure) to ensure that the peak pressure is less than the set injection pressure. If the actual injection time is greater than the maximum set injection time, the minimum injection speed can be appropriately increased, and if the peak pressure is greater than the maximum set injection pressure, the maximum injection speed can be appropriately reduced.

[0096] S1006. Establish a coordinate system of effective viscosity and shear rate. The effective viscosity and shear rate corresponding to the same test speed constitute a coordinate point, forming a mapping relationship between the effective viscosity and the shear rate.

[0097] Exemplarily, a mapping table may be formed based on all coordinate points; or, a mapping curve may be formed by curve fitting based on all coordinate points.

[0098] S1007. Determine the optimal injection speed of the injection molding equipment for the injection molding process using the injection molding material according to the mapping relationship.

[0099] For example, according to the mapping relationship between the effective viscosity and the shear rate, the injection speed corresponding to the minimum shear rate when the effective viscosity tends to be stable can be selected as the optimal injection speed. The coordinate point corresponding to the optimal injection speed is the balance point of the effective viscosity and the shear rate. At this time, the effective viscosity is insensitive to the shear rate, and the effective viscosity is low and the shear rate is small. If the injection speed is increased on the basis of the optimal injection speed, the shear rate will increase. After the fluid viscosity decreases to a certain extent, the viscosity will no longer decrease. Increasing its flow rate will only increase the shear heat of the plastic, which is not conducive to the thermophysical properties and trimming strength of the plastic; if the injection speed is reduced on the basis of the optimal injection speed, the shear rate will be reduced, and the shear heat will also be reduced. The viscosity will increase and the flow rate will decrease, which is not conducive to rapid injection, affecting cooling and solidification, thereby affecting production efficiency and product quality.

[0100] Optionally, according to the parameters of the injection molding equipment and the information of the injection molding raw materials, the position change amount of the pusher in the injection barrel required for one-time molding is calculated, including: according to the parameters of the injection molding equipment and the information of the injection molding raw materials, the weight of the product molded once is obtained; according to the first formula, the metering position L1 is calculated, and according to the second formula, the switching position L2 is calculated; according to the third formula, the position change amount △L of the pusher in the injection barrel required for one-time molding is calculated. Among them, the metering position L1 is the position of the pusher in the injection barrel before the one-time molding, which is the sum of the material position required for the one-time molding and the safety distance; the switching position L2 is the position of the pusher in the injection barrel after the one-time molding.

[0101] Among them, the first formula is L1=(W×4×1000) / [(π×D²)×ρ]+L0, the second formula is L2=L1-(L1-L0)×k, and the third formula is △L=(L1+L')-L2; W (in g) is the weight of the product molded once; D is the inner wall diameter of the injection barrel (in mm); ρ is the density of the injection molding material (in g / cm 3 ); L0 is the safe distance of the injection barrel (in mm); k is the injection coefficient of the injection barrel, 0.9<k<1; L' is the rear retraction position (in mm).

[0102] The safety distance L0 refers to the minimum safety distance that needs to be maintained between the pusher and the injection barrel to avoid collision between the pusher and the injection barrel and damage to the equipment. In an optional embodiment, the safety distance of the injection barrel is L0=10mm.

[0103] The injection coefficient of the injection barrel, also known as the filling coefficient, k>0.9 can ensure that most areas of the plastic injection mold can be fully filled during the injection process. Since there is a pressure holding stage after injection, in order to obtain more accurate data and to avoid over-injection, k is less than 1. In an optional embodiment, k=0.95.

[0104] The back release position L' refers to the retracted position of the pusher before injection, which is conducive to adjusting the injection pressure, ensuring a smoother plastic flow, improving the surface finish and dimensional accuracy after molding, and preventing bubbles or uneven molding. In an optional embodiment, the back release position 0mm≤L'≤2mm, for example, the back release position L' can be 2mm.

[0105] Specifically, the metering position L1=W×C+L0, C=1000 / (A×ρ), A=(π×D²) / 4, where C is the position of the unit weight of the injection molding material in the injection barrel, in mm / g; A is the cross-sectional area of ​​the inner wall of the injection barrel, which is also the cross-sectional area of ​​the pusher (screw or plunger), in mm 2 . Measuring position L1 = W×C+L0=W×[1000 / (A×ρ)] +L0=W×{1000 / [(π×D² / 4)×ρ]} +L0= (W×4×1000) / [(π×D²)×ρ]+L0. Switching position L2 = L1-(W×C)×k=L1-(L1-L0)×k.

[0106] For example, polycarbonate (PC) material can be used as the injection molding raw material, with a density of ρ=1.2g / cm³, a product weight of W=3.27g after one mold, an inner wall diameter of the injection barrel of D=18mm, and a theoretical filling time T0=0.354S obtained by mold flow analysis.

[0107] Taking the first-stage injection as an example, the metering position L1=(W×4×1000) / [(π×D²)×ρ]+L0≈3.27×4×1000 / (1017.36×1.2)+L0≈10.71+10≈20.71mm; the switching position L2=L1-(L1-L0)×k≈20.71-(20.71-10)×0.95≈10.54; the position change of the pusher in the injection barrel required for one-time molding △L=(L1+L')-L2≈(20.71+2)-10.54)≈12.17mm; the theoretical injection speed S0=△L / T0≈12.17 / 0.354≈34.4mm / S.

[0108] In an optional embodiment, when performing injection molding at different test speeds, the metering position L1 and the switching position L1 can be set to be the same, and the holding pressure and the holding time can be set to zero, so that the injection speed can be more accurately regulated.

[0109] In yet another optional embodiment, the peak pressure and effective viscosity of the third mold at different test speeds may be obtained and recorded respectively to improve the accuracy of the peak pressure and effective viscosity.

[0110] For example, different injection times and / or peak pressures can be obtained at different test speeds, thereby obtaining different effective viscosities and / or shear rates. The effective viscosity and shear rate corresponding to the same test speed can form a coordinate point, and all coordinate points can form a mapping table, as shown in Table 1, or a mapping curve, as shown in Table 1. Figure 2 shown.

[0111] Table 1 Injection time, peak pressure, shear rate and effective viscosity at different test speeds

[0112]

[0113] refer to Figure 1 and Figure 2 When the test speed is 88.9 mm / S, the effective viscosity reaches the minimum value and tends to be stable. When the test speed and shear rate continue to increase, the effective viscosity will not continue to decrease. In this way, the test speed of 88.9 mm / S can be set as the optimal injection speed, which can not only achieve the minimum effective viscosity and maximum injection flow rate, but also achieve a smaller shear rate, reduce shear heat, reduce the influence of shear heat on the thermophysical properties and cutting edge strength of plastics, and improve production efficiency and product quality.

[0114] According to the embodiment of the present invention, a theoretical injection speed can be obtained by adopting a mold flow analysis method, and then a plurality of test speeds can be determined based on the theoretical injection speed. The test speed can be limited to a more reasonable range, thereby improving the test efficiency and avoiding the test speed being too large or too small, exceeding the critical parameter value of the equipment, affecting the test results, and damaging the equipment. In addition, by establishing a coordinate system of effective viscosity and shear rate, a mapping relationship between the effective viscosity and the shear rate is formed, and the balance point of the effective viscosity and the shear rate can be determined. The test speed corresponding to the balance point is the optimal injection speed. When injection is performed at the optimal injection speed, a larger injection flow rate and a smaller shear rate can be achieved, thereby improving production efficiency and product quality.

[0115] Embodiment 2

[0116] Figure 3 1 is a flow chart of a method for determining an optimal injection speed provided by the second embodiment of the present invention. Compared with the above embodiment, this embodiment specifically refines how to determine the optimal injection speed according to the mapping relationship. Figure 3 As shown, the method includes:

[0117] S2001. Obtain parameters of injection molding equipment and information of injection molding raw materials; wherein the injection molding equipment includes an injection device and a plastic injection mold, the injection device includes an injection barrel and a pusher, and the pusher includes a screw and / or a plunger.

[0118] S2002. Calculate the position change of the pusher in the injection barrel required for one-time molding based on the parameters of the injection molding equipment and the information of the injection molding raw material.

[0119] S2003. Using mold flow analysis, obtain the theoretical filling time, and calculate the theoretical injection speed based on the position change.

[0120] S2004. According to the theoretical injection speed, determine the minimum injection speed and the maximum injection speed, and multiple injection speeds between the minimum injection speed and the maximum injection speed as test speeds.

[0121] S2005. According to each test speed, injection molding equipment and injection molding materials are used to perform injection molding to obtain the effective viscosity and shear rate corresponding to each test speed.

[0122] S2006. Establish a coordinate system of effective viscosity and shear rate. The effective viscosity and shear rate corresponding to the same test speed constitute a coordinate point, forming a mapping relationship between the effective viscosity and the shear rate.

[0123] S2007. Fit the mapping relationship into a mapping curve.

[0124] S2008. When it is determined that the slope of the mapping curve is zero, the test speed corresponding to the minimum shear rate is the optimal injection speed.

[0125] For example, the coordinate points corresponding to different test speeds can be curve fitted. In an optional embodiment, the fitted curve can pass through all coordinate points. When the slope of the mapping curve is zero, it means that the effective viscosity tends to be stable. If the shear rate continues to increase, the effective viscosity will no longer decrease with the increase of the shear rate, but the shear heat will increase significantly. By determining that the test speed corresponding to the minimum shear rate when the slope of the mapping curve is zero is the optimal injection speed, such as Figure 2 As shown in point a in the figure, a larger plastic flow rate and a smaller shear heat can be taken into account at the same time, thereby improving production efficiency and product quality.

[0126] In the second embodiment of the present invention, the optimal injection speed can be determined according to the slope of the mapping curve, and when the slope of the mapping curve is determined to be zero, the test speed corresponding to the minimum shear rate is the optimal injection speed, and the balance point of the effective viscosity and the shear rate can be determined. The test speed corresponding to the balance point is the optimal injection speed. When injecting at the optimal injection speed, a larger injection flow rate and a smaller shear rate can be achieved, thereby improving production efficiency and product quality.

[0127] Optionally, the method for determining the optimal injection speed also includes: obtaining a molding cycle of an injection molding process performed by an injection molding device using an injection molding material. According to the mapping relationship, determining the optimal injection speed of an injection molding process performed by an injection molding device using an injection molding material includes: fitting the mapping relationship into a mapping curve; judging whether the molding cycle is greater than or equal to a cycle threshold; if the molding cycle is greater than or equal to the cycle threshold, determining that when the slope of the mapping curve is the second slope k2, the test speed corresponding to the minimum shear rate is the optimal injection speed; if the molding cycle is less than the cycle threshold, determining that when the slope of the mapping curve is the first slope k1, the test speed corresponding to the minimum shear rate is the optimal injection speed; wherein, 0≤|k1|<|k2|.

[0128] The molding cycle refers to the time required for one injection molding process, including the injection time of the injection device, the cooling time of the plastic injection mold, the demoulding time, etc. For example, the automation evaluation can be performed in combination with the complexity of the injection molding equipment and the injection molding raw materials.

[0129] The first slope k1 and the second slope k2 can be fixed values, which can be adjusted according to the preparation accuracy and product quality requirements, or the first slope k1 and the second slope k2 can also be functions of the maximum value of the absolute value of the slope |K| of the mapping curve, for example, |k1| can be 5% of the maximum value of the absolute value of the slope |K| of the mapping curve, and |k2| can be 10% of the maximum value of the absolute value of the slope |K| of the mapping curve, but is not limited to this.

[0130] For example, for injection molding materials with a long molding cycle, such as engineering plastics, including but not limited to polyamide (PA), polycarbonate (PC), polyformaldehyde (POM), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), etc., their own melt viscosity is relatively high, requiring a higher injection pressure and a slower injection speed. Therefore, when determining the balance point between the effective viscosity and the shear rate, one cannot blindly pursue the lowest effective viscosity and continuously increase the shear rate, injection speed and injection pressure. When the absolute value of the slope of the mapping curve is less than or equal to |k2|, it is considered that the effective viscosity is less sensitive to the shear rate, and the test speed corresponding to the minimum shear rate when the absolute value of the slope of the mapping curve is less than or equal to |k2| is selected as the optimal injection speed, such as Figure 4 As shown in point c in the figure, in this way, the injection speed and injection pressure can be reduced as much as possible while reducing the effective viscosity to ensure that the plastic can completely fill the mold and the peak pressure will not exceed the rated pressure of the injection molding equipment, thereby improving product quality and equipment stability.

[0131] For injection molding materials with a long molding cycle, if the shear rate continues to increase on the basis of point C, the resulting losses may be greater than the benefits of reducing the effective viscosity. For example, for optical products, too high an injection speed and shear rate will cause defects such as spray marks or material flowers.

[0132] For injection molding materials with a short molding cycle, such as thermoplastics, including but not limited to polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyester (PET), etc., their own melt viscosity is low, fluidity is good, and it is easier to fill the mold. The test speed corresponding to the minimum shear rate when the absolute value of the slope of the mapping curve is less than or equal to |k1| can be selected as the optimal injection speed, such as Figure 4 As shown in point b.

[0133] Optionally, the parameters of the injection molding equipment include the flow length ratio of the plastic injection mold. According to the mapping relationship, the optimal injection speed of the injection molding equipment using the injection molding material for the injection molding process is determined, including: fitting the mapping relationship into a mapping curve; judging whether the flow length ratio is greater than or equal to the flow channel threshold; if the flow length ratio is greater than or equal to the flow channel threshold, determining that when the slope of the mapping curve is the third slope k3, the test speed corresponding to the minimum shear rate is the optimal injection speed; if the flow length ratio is less than the flow channel threshold, determining that when the slope of the mapping curve is the fourth slope k4, the test speed corresponding to the minimum shear rate is the optimal injection speed; wherein, 0≤|k3|<|k4|.

[0134] The flow length ratio refers to the ratio of the flow distance (flow length) of the molten plastic from the injection port to the farthest part of the mold during the injection molding process to the maximum thickness from the injection port to the mold cavity. The flow length ratio reflects the ease with which the plastic flows. A higher flow length ratio means that the plastic needs to flow a longer distance to complete the mold filling, which usually means that the mold design is more complex.

[0135] The third slope k3 and the fourth slope k4 may be fixed values, which may be adjusted according to the preparation accuracy and product quality requirements, or the third slope k3 and the fourth slope k4 may also be functions of the maximum value of the absolute value of the slope |K| of the mapping curve, for example, |k3| may be 5% of the maximum value of the absolute value of the slope |K| of the mapping curve, and |k4| may be 10% of the maximum value of the absolute value of the slope |K| of the mapping curve, but it is not limited thereto. When the injection raw materials and / or molds are different, the mapping curves may be different, and the same slope function may obtain different slopes.

[0136] For example, for a mold with a relatively long flow length, the mold design is generally more complex, usually with more cavities, flow channel design, and smaller flow channels. The molten plastic needs to flow a longer distance to reach the farthest part of the mold, causing greater flow resistance. The molten plastic needs to have better fluidity, that is, lower viscosity. Therefore, when determining the balance point between the effective viscosity and the shear rate, it is necessary to reduce the effective viscosity as much as possible. The test speed corresponding to the minimum shear rate when the absolute value of the slope of the mapping curve is less than or equal to |k3| can be selected as the optimal injection speed, such as Figure 5 As shown in point d in the figure, when the absolute value of the slope of the mapping curve is less than or equal to |k3|, the effective viscosity is almost at the lowest, ensuring that the effective viscosity can reach the minimum value, the plastic can completely fill the mold, and the product quality is improved.

[0137] For molds with a relatively short flow length, the mold design is generally simpler, the plastic is easier to flow and fill the mold, and the viscosity requirement is relatively loose. The test speed corresponding to the minimum shear rate when the absolute value of the slope of the mapping curve is less than or equal to |k4| can be selected as the optimal injection speed, such as Figure 5 As shown in point e in the figure, the shear rate and injection speed can be appropriately reduced, thereby increasing the injection time and reducing the injection pressure, which is conducive to accurate injection and improving product quality.

[0138] Optionally, based on the mapping relationship, determining the optimal injection speed of the injection molding equipment for the injection molding process using the injection molding raw material, includes: fitting the mapping relationship into a mapping curve; judging whether an insert is provided in the plastic injection mold; if an insert is provided in the plastic injection mold, determining that when the slope of the mapping curve is the sixth slope k6, the test speed corresponding to the minimum shear rate is the optimal injection speed; if no insert is provided in the plastic injection mold, determining that when the slope of the mapping curve is the fifth slope k5, the test speed corresponding to the minimum shear rate is the optimal injection speed; wherein, 0≤|k5|<|k6|.

[0139] Among them, the fifth slope k5 and the sixth slope k6 can be fixed values, which can be adjusted according to the preparation accuracy and product quality requirements, or the fifth slope k5 and the sixth slope k6 can also be functions of the maximum value of the absolute value of the slope |K| of the mapping curve, for example, |k5| can be 3% of the maximum value of the absolute value of the slope |K| of the mapping curve, and |k6| can be 12% of the maximum value of the absolute value of the slope |K| of the mapping curve, but it is not limited to this.

[0140] For example, when an insert is provided in a plastic injection mold, the insert will be fixed in the mold cavity before injection. When determining the balance point between the effective viscosity and the shear rate, too low effective viscosity and too high fluidity should be avoided. The test speed corresponding to the minimum shear rate when the absolute value of the slope of the mapping curve is less than or equal to |k6| can be selected as the optimal injection speed, such as Figure 6 As shown in point g in the figure, this is to avoid insert displacement caused by excessively high injection speed.

[0141] When no insert is set in the plastic injection mold, when determining the balance point between effective viscosity and shear rate, the test speed corresponding to the minimum shear rate when the absolute value of the slope of the mapping curve is less than or equal to |k5| can be selected as the optimal injection speed, such as Figure 6 As shown by point f in the figure, the effective viscosity can be reduced, fluidity can be increased, and production efficiency can be improved.

[0142] Optionally, the method for determining the optimal injection speed also includes: obtaining the barrel capacity of the injection barrel and the barrel injection volume required for one-time molding according to the parameters of the injection molding equipment and the information of the injection molding raw material. According to the mapping relationship, determining the optimal injection speed of the injection molding process of the injection molding equipment using the injection molding raw material includes: fitting the mapping relationship into a mapping curve; judging whether the ratio of the barrel injection volume to the barrel capacity is greater than or equal to the injection threshold; if the ratio of the barrel injection volume to the barrel capacity is greater than or equal to the injection threshold, determining that when the slope of the mapping curve is the seventh slope k7, the test speed corresponding to the minimum shear rate is the optimal injection speed; if the ratio of the barrel injection volume to the barrel capacity is less than the injection threshold, determining that when the slope of the mapping curve is the eighth slope k8, the test speed corresponding to the minimum shear rate is the optimal injection speed; wherein, 0≤|k7|<|k8|.

[0143] Among them, the seventh slope k7 and the eighth slope k8 can be fixed values, which can be adjusted according to the preparation accuracy and product quality requirements, or the seventh slope k7 and the eighth slope k8 can also be functions of the maximum value of the absolute value of the slope |K| of the mapping curve.

[0144] For example, when the injection volume of the barrel is large, for example, when the injection volume of the barrel is greater than or equal to 20% of the barrel capacity, the screw has enough time to establish a stable injection pressure and output an accurate and consistent injection time. The injection time is controllable, and a faster injection speed and shear rate, as well as a lower effective viscosity, can be achieved. The test speed corresponding to the minimum shear rate when the absolute value of the slope of the mapping curve is less than or equal to |k7| can be selected as the optimal injection speed, such as Figure 7 As shown in point h.

[0145] When the barrel injection volume is small, for example, when the barrel injection volume is less than 20% of the barrel capacity, the screw does not have enough time to establish a stable injection pressure and output an accurate and consistent injection time. The injection time is difficult to control. At this time, a slower injection speed and shear rate are required, sacrificing a certain degree of effective viscosity. The test speed corresponding to the minimum shear rate when the absolute value of the slope of the mapping curve is less than or equal to |k8| can be selected as the optimal injection speed, such as Figure 7 As shown in point i, this can increase the controllability of injection time and improve product quality and consistency.

[0146] In other optional embodiments, when the barrel injection volume is small, the injection barrel with a smaller barrel capacity can be replaced to increase the controllability of the injection time.

[0147] Embodiment 3

[0148] Figure 8 Schematic diagram of the structure of a device for determining an optimal injection speed provided by the third embodiment of the present invention. Figure 8 As shown, the device comprises:

[0149] The first acquisition module 810 is used to acquire parameters of the injection molding equipment and information of the injection molding raw materials; the injection molding equipment includes an injection device and a plastic injection mold; the injection device includes an injection barrel and a pusher, and the pusher includes a screw and / or a plunger;

[0150] The first calculation module 820 calculates the position change of the pusher in the injection barrel required for one-time molding according to the parameters of the injection molding equipment and the information of the injection molding raw material;

[0151] The second calculation module 830 is used to obtain the theoretical filling time by using mold flow analysis, and calculate the theoretical injection speed according to the position change;

[0152] A test speed determination module 840 is used to determine a minimum injection speed and a maximum injection speed, and multiple injection speeds between the minimum injection speed and the maximum injection speed as test speeds according to the theoretical injection speed;

[0153] The injection molding measurement module 850 is used to perform the injection molding process according to each test speed, using the injection molding equipment and the injection molding raw materials, and obtain the effective viscosity and shear rate corresponding to each test speed;

[0154] A mapping relationship building module 860 is used to establish a coordinate system of effective viscosity and shear rate, corresponding to the effective viscosity and shear rate of the same test speed to form a coordinate point, forming a mapping relationship between the effective viscosity and the shear rate;

[0155] The optimal injection speed determination module 870 is used to determine the optimal injection speed of the injection molding process performed by the injection molding equipment using the injection molding material according to the mapping relationship.

[0156] Optionally, the parameters of the injection molding equipment include the inner wall diameter of the injection barrel; the information of the injection molding material includes the density of the injection molding material. The first calculation module 820 includes:

[0157] A weight acquisition unit, used to acquire the weight of a molded product according to the parameters of the injection molding equipment and the information of the injection molding raw materials;

[0158] The first position calculation unit is used to calculate the metering position L1 according to the first formula and calculate the switching position L2 according to the second formula; wherein the first formula is L1=(W×4×1000) / [(π×D²)×ρ]+L0, and the second formula is L2=L1-(L1-L0)×k; W is the weight of the product molded once, D is the inner wall diameter of the injection barrel, ρ is the density of the injection molding material, L0 is the safety distance of the injection barrel, k is the injection coefficient of the injection barrel, and 0.9<k<1;

[0159] The second position calculation unit is used to calculate the position change △L of the pusher in the injection barrel required for one molding according to the third formula; wherein the third formula is △L=(L1+L')-L2; L1 is the metering position, L2 is the switching position, and L' is the rear release position.

[0160] Optionally, the second calculation module 830 includes:

[0161] The theoretical injection speed calculation unit is used to calculate the theoretical injection speed S0 according to the fourth formula; wherein the fourth formula is S0=△L / T0; △L is the position change of the pusher in the injection barrel required for one-time molding, and T0 is the theoretical filling time.

[0162] Optionally, the optimal injection speed determination module 870 includes:

[0163] A curve fitting unit, used for fitting the mapping relationship into a mapping curve;

[0164] The optimal injection speed determination unit is used to determine that when the slope of the mapping curve is zero, the test speed corresponding to the minimum shear rate is the optimal injection speed.

[0165] Optionally, a molding cycle acquisition module is also included, which is used to acquire the molding cycle of the injection molding process performed by the injection molding equipment using the injection molding material. The optimal injection speed determination module 870 includes:

[0166] A curve fitting unit, used for fitting the mapping relationship into a mapping curve;

[0167] A molding cycle judgment unit is used to judge whether the molding cycle is greater than or equal to a cycle threshold, and when the molding cycle is greater than or equal to the cycle threshold, determine that the test speed corresponding to the minimum shear rate when the slope of the mapping curve is the second slope k2 is the optimal injection speed, and when the molding cycle is less than the cycle threshold, determine that the test speed corresponding to the minimum shear rate when the slope of the mapping curve is the first slope k1 is the optimal injection speed; wherein 0≤|k1|<|k2|.

[0168] Optionally, the parameters of the injection molding equipment include the flow length ratio of the plastic injection mold. The optimal injection speed determination module 870 includes:

[0169] A curve fitting unit, used for fitting the mapping relationship into a mapping curve;

[0170] A flow length ratio judgment unit is used to judge whether the flow length ratio is greater than or equal to the flow channel threshold, and when the flow length ratio is greater than or equal to the flow channel threshold, determine that the test speed corresponding to the minimum shear rate when the slope of the mapping curve is the third slope k3 is the optimal injection speed, and when the flow length ratio is less than the flow channel threshold, determine that the test speed corresponding to the minimum shear rate when the slope of the mapping curve is the fourth slope k4 is the optimal injection speed; wherein 0≤|k3|<|k4|.

[0171] Optionally, the optimal injection speed determination module 870 includes:

[0172] A curve fitting unit, used for fitting the mapping relationship into a mapping curve;

[0173] An insert judgment unit is used to judge whether an insert is provided in the plastic injection mold, and when an insert is provided in the plastic injection mold, determine that the test speed corresponding to the minimum shear rate when the slope of the mapping curve is the sixth slope k6 is the optimal injection speed, and when no insert is provided in the plastic injection mold, determine that the test speed corresponding to the minimum shear rate when the slope of the mapping curve is the fifth slope k5 is the optimal injection speed; wherein 0≤|k5|<|k6|.

[0174] Optionally, an injection volume determination module is also included, which is used to obtain the barrel capacity of the injection barrel and the barrel injection volume required for one-time molding according to the parameters of the injection molding equipment and the information of the injection molding raw material. The optimal injection speed determination module 870 includes:

[0175] A curve fitting unit, used for fitting the mapping relationship into a mapping curve;

[0176] The injection volume judgment unit is used to judge whether the ratio of the barrel injection volume to the barrel capacity is greater than or equal to the injection threshold, and when the ratio of the barrel injection volume to the barrel capacity is greater than or equal to the injection threshold, determine that the test speed corresponding to the minimum shear rate when the slope of the mapping curve is the seventh slope k7 is the optimal injection speed, and when the ratio of the barrel injection volume to the barrel capacity is less than the injection threshold, determine that the test speed corresponding to the minimum shear rate when the slope of the mapping curve is the eighth slope k8 is the optimal injection speed; wherein, 0≤|k7|<|k8|.

[0177] The device for determining the optimal injection speed provided in the third embodiment of the present invention is used to execute the method for determining the optimal injection speed provided in any embodiment of the present invention. It has the functional modules and beneficial effects of executing the method for determining the optimal injection speed provided in any embodiment of the present invention. For the contents not described in detail in the third embodiment of the device for determining the optimal injection speed, please refer to the description of the embodiment of the method for determining the optimal injection speed above, and will not be repeated here.

[0178] Embodiment 4

[0179] Fig. 9 Schematic diagram of the structure of an injection molding device provided by the fourth embodiment of the present invention. Fig. 9 As shown, the injection molding device includes: an optimal injection speed determination device 910, an injection device 920, a plastic injection mold 930, and a control device 940. The optimal injection speed determination device 910 is electrically connected to the control device 940.

[0180] The control device 940 is used to monitor the parameters of the injection device 920. In other optional embodiments, the control device 940 may be integrated into the optimal injection speed determination device 910.

[0181] Exemplarily, the injection device 920 can inject the molten injection material into the plastic injection mold 930, and the final molded product can be formed after cooling and solidification. The injection device 920 may include an injection barrel, a pusher, a pusher control unit, a nozzle, a heater, a heater control unit, a hopper, a meter, etc., and the control device 940 may be electrically connected to the pusher control unit, the heater control unit, etc. (not shown in the figure). The plastic injection mold 930 may include a runner, a product cavity, a mold controller, a demolding device, etc. (not shown in the figure).

[0182] The injection molding equipment provided in the fourth embodiment of the present invention includes the device for determining the optimal injection speed provided in any embodiment of the present invention, and can execute the method for determining the optimal injection speed provided in any embodiment of the present invention. The injection molding equipment has the functional modules and corresponding beneficial effects required to execute the method for determining the optimal injection speed provided in any embodiment of the present invention. For the contents not described in detail in the fourth embodiment of the injection molding equipment, refer to the description of the embodiment of the method for determining the optimal injection speed above, and will not be repeated here.

[0183] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0184] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for determining an optimal injection speed, characterized in that: Process parameter adjustments applied to injection molding processes; including: Acquire parameters of injection molding equipment and information of injection molding raw materials; the injection molding equipment includes an injection device and a plastic injection mold; the injection device includes an injection barrel and a pusher, and the pusher includes a screw and / or a plunger; Calculating the amount of position change of the pusher in the injection barrel required for one-time molding according to the parameters of the injection molding equipment and the information of the injection molding raw material; The theoretical filling time is obtained by mold flow analysis, and the theoretical injection speed is calculated according to the position change; According to the theoretical injection speed, determining a minimum injection speed and a maximum injection speed, and a plurality of injection speeds between the minimum injection speed and the maximum injection speed as test speeds; According to each of the test speeds, the injection molding equipment and the injection molding raw material are used to perform an injection molding process to obtain an effective viscosity and a shear rate corresponding to each of the test speeds; Establishing a coordinate system of the effective viscosity and the shear rate, wherein the effective viscosity and the shear rate corresponding to the same test speed constitute a coordinate point, and a mapping relationship between the effective viscosity and the shear rate is formed; According to the mapping relationship, the optimal injection speed of the injection molding equipment for performing the injection molding process using the injection molding material is determined.

2. The method for determining the optimal injection speed according to claim 1, characterized in that: The parameters of the injection molding equipment include the inner wall diameter of the injection barrel; the information of the injection molding raw material includes the density of the injection molding raw material; Calculating the position change of the pusher in the injection barrel required for one-time molding according to the parameters of the injection molding equipment and the information of the injection molding raw material, including: According to the parameters of the injection molding equipment and the information of the injection molding raw material, the weight of the product molded once is obtained; The metering position L1 is calculated according to the first formula, and the switching position L2 is calculated according to the second formula; wherein the first formula is L1=(W×4×1000) / [(π×D²)×ρ]+L0, and the second formula is L2=L1-(L1-L0)×k; W is the weight of the product molded once, D is the inner wall diameter of the injection barrel, ρ is the density of the injection molding material, L0 is the safety distance of the injection barrel, k is the injection coefficient of the injection barrel, and 0.9<k<1; According to the third formula, the position change △L of the pusher in the injection barrel required for one molding is calculated; wherein the third formula is △L=(L1+L')-L2; L1 is the metering position, L2 is the switching position, and L' is the rear release position.

3. The method for determining the optimal injection speed according to claim 1, characterized in that: According to the position change, the theoretical injection speed is calculated, including: According to the fourth formula, the theoretical injection speed S0 is calculated; wherein the fourth formula is S0=△L / T0; △L is the position change of the pusher in the injection barrel required for one-time molding, and T0 is the theoretical filling time.

4. The method for determining the optimal injection speed according to claim 1, characterized in that: Determining the optimal injection speed of the injection molding process performed by the injection molding equipment using the injection molding material according to the mapping relationship includes: Fitting the mapping relationship into a mapping curve; When it is determined that the slope of the mapping curve is zero, the test speed corresponding to the minimum shear rate is the optimal injection speed.

5. The method for determining the optimal injection speed according to claim 1, characterized in that: Also includes: Obtaining a molding cycle of the injection molding process performed by the injection molding equipment using the injection molding material; Determining the optimal injection speed of the injection molding process performed by the injection molding equipment using the injection molding material according to the mapping relationship includes: Fitting the mapping relationship into a mapping curve; Determining whether the molding cycle is greater than or equal to a cycle threshold; If the molding cycle is greater than or equal to the cycle threshold, then when it is determined that the slope of the mapping curve is the second slope k2, the test speed corresponding to the minimum shear rate is the optimal injection speed; If the molding cycle is less than the cycle threshold, then when it is determined that the slope of the mapping curve is the first slope k1, the test speed corresponding to the minimum shear rate is the optimal injection speed; Among them, 0≤|k1|<|k2|.

6. The method for determining the optimal injection speed according to claim 1, characterized in that: The parameters of the injection molding equipment include the flow length ratio of the plastic injection mold; Determining the optimal injection speed of the injection molding process performed by the injection molding equipment using the injection molding material according to the mapping relationship includes: Fitting the mapping relationship into a mapping curve; Determining whether the flow length ratio is greater than or equal to a flow channel threshold; If the flow length ratio is greater than or equal to the flow channel threshold, then when it is determined that the slope of the mapping curve is the third slope k3, the test speed corresponding to the minimum shear rate is the optimal injection speed; If the flow length ratio is less than the flow channel threshold, then when it is determined that the slope of the mapping curve is the fourth slope k4, the test speed corresponding to the minimum shear rate is the optimal injection speed; Among them, 0≤|k3|<|k4|.

7. The method for determining the optimal injection speed according to claim 1, characterized in that: Determining the optimal injection speed of the injection molding process performed by the injection molding equipment using the injection molding material according to the mapping relationship includes: Fitting the mapping relationship into a mapping curve; Determining whether an insert is provided in the plastic injection mold; If an insert is provided in the plastic injection mold, when it is determined that the slope of the mapping curve is the sixth slope k6, the test speed corresponding to the minimum shear rate is the optimal injection speed; If no insert is provided in the plastic injection mold, when it is determined that the slope of the mapping curve is the fifth slope k5, the test speed corresponding to the minimum shear rate is the optimal injection speed; Among them, 0≤|k5|<|k6|.

8. The method for determining the optimal injection speed according to claim 1, characterized in that: Also includes: According to the parameters of the injection molding equipment and the information of the injection molding raw material, the barrel capacity of the injection barrel and the barrel injection volume required for one molding are obtained; Determining the optimal injection speed of the injection molding process performed by the injection molding equipment using the injection molding material according to the mapping relationship includes: Fitting the mapping relationship into a mapping curve; Determining whether a ratio of the barrel injection volume to the barrel holding volume is greater than or equal to an injection threshold; If the ratio of the barrel injection volume to the barrel holding volume is greater than or equal to the injection threshold, it is determined that when the slope of the mapping curve is the seventh slope k7, the test speed corresponding to the minimum shear rate is the optimal injection speed; If the ratio of the barrel injection volume to the barrel capacity is less than the injection threshold, it is determined that when the slope of the mapping curve is the eighth slope k8, the test speed corresponding to the minimum shear rate is the optimal injection speed; Among them, 0≤|k7|<|k8|.

9. A device for determining an optimal injection speed, characterized in that: A method for determining an optimal injection speed according to any one of claims 1 to 8; The determining device comprises: A first acquisition module is used to acquire parameters of an injection molding device and information of injection molding raw materials; the injection molding device includes an injection device and a plastic injection mold; the injection device includes an injection barrel and a pusher, and the pusher includes a screw and / or a plunger; A first calculation module calculates the position change of the pusher in the injection barrel required for one-time molding according to the parameters of the injection molding equipment and the information of the injection molding raw material; The second calculation module is used to obtain the theoretical filling time by means of mold flow analysis, and calculate the theoretical injection speed according to the position change; A test speed determination module, used to determine a minimum injection speed and a maximum injection speed according to the theoretical injection speed, and a plurality of injection speeds between the minimum injection speed and the maximum injection speed as test speeds; An injection molding measurement module is used to perform an injection molding process according to each of the test speeds using the injection molding equipment and the injection molding raw materials to obtain the effective viscosity and shear rate corresponding to each of the test speeds; A mapping relationship building module, used to establish a coordinate system of the effective viscosity and the shear rate, wherein the effective viscosity and the shear rate corresponding to the same test speed constitute a coordinate point, and form a mapping relationship between the effective viscosity and the shear rate; The optimal injection speed determination module is used to determine the optimal injection speed of the injection molding process performed by the injection molding equipment using the injection molding material according to the mapping relationship.

10. An injection molding device, characterized in that: The invention comprises: an injection device, a plastic injection mold, a control device and a device for determining the optimal injection speed as described in claim 9; The determining device is electrically connected to the control device; The control device is used to monitor the parameters of the injection device; the determination device is used to execute the method for determining the optimal injection speed according to any one of claims 1-8.

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