injection molding process of a material

Abstract

Title: Injection Molding Method for a Material The invention relates to an injection molding method for a material, using an injection mold. The method comprises the following steps: - determining the first instant (t2bis) at which cooling of the mold is stopped, at least on the basis of a cooling rate (Vc), and on the basis of a predetermined opening temperature (T2) of the injection mold; - with the injection mold still closed, from the first instant (t2bis) until a second instant (t2) corresponding to the opening of the injection mold, reheating the injection mold, in particular using a temperature control unit, and the temperature (T2bis) of the injection mold measured at the first instant (t2bis) being strictly greater than the predetermined opening temperature (T2) of the injection mold. Figure for the abstract: Fig. 3

Description

Title of the invention: Injection molding process for a material

[0001] The field of the present invention relates to a method of injection molding of a material, in particular a polymer, and an injection molding system configured to implement such a molding method.

[0002] The injection molding process for a material, particularly a polymer, is a manufacturing technique used to produce molded products in large series. The process involves, in a manner known per se, the use of an injection molding machine to inject the material, particularly in a molten or viscous state, into an injection mold configured to receive the molten material. Once the injection mold is filled, holding pressure is maintained while the material cools and hardens into a product whose shape is determined by the shape of a cavity in the injection mold. Once the material reaches a desired temperature, the injection mold is opened and the resulting product is ejected from the injection mold.

[0003] However, there is in particular a need to optimize the manufacturing cycle time using the injection molding process, while optimizing a homogeneous and regular appearance of the product obtained by said process.

[0004] The invention thus relates to a method of injection molding of a material, in particular a polymer, using an injection mold, said method comprising the following steps:

[0005] - with the injection mold open, heat the injection mold, in particular using of a thermoregulation unit;

[0006] - close the injection mold when the injection mold temperature T reaches a predetermined closing temperature Tl;

[0007] - injecting the material, in particular the polymer, into said mold so as to fill at least partially said mold;

[0008] - apply a holding pressure to the material in the injection mold according to a predetermined profile;

[0009] - cool the injection mold at the predetermined cooling rate Vc, in particular with the help of the thermoregulation unit;

[0010] - determine the first instant t2bis at which the cooling of said mold is stopped, at least_based on said cooling rate Vc, and based on a predetermined opening temperature T2 of the injection mold;

[0011] - the injection mold being still closed, from the first instant t2bis until a second instant t2 corresponding to the opening of the injection mold, reheat the injection mold, notably using the thermoregulation unit, and

[0012] the temperature T2bis of the injection mold measured at the first instant t2bis being strictly greater than the predetermined opening temperature T2 of the injection mold.

[0013] Thanks to the fact that the first instant t2bis is precisely determined, and that the injection mold is heated while still closed, between the first and second instants t2bis and t2, the heating moment is shifted (or brought forward) by a time difference between t2bis and t2. Thus, the heating of the injection mold is optimized, taking into account a time lag induced by thermal inertia, for example, due to a temperature difference between the temperature of a heat transfer fluid and the temperature of the injection mold in direct contact with the material.

[0014] Furthermore, optimizing the heating of the injection mold to a predetermined temperature Tl results in a product with a homogeneous and regular appearance. Consequently, this reduces the scrap rate in production.

[0015] In addition, the fact that the temperature of the injection mold T is taken as a reference temperature allows for better measurement reliability than taking the temperature of the heat transfer fluid, especially water-based, as a reference temperature.

[0016] In summary, the invention makes it possible to precisely adjust the amount of heat supplied to the material and thus reduce the duration of a complete manufacturing cycle for a product obtained by the process, at least by the difference in time between the first and second instants t2bis and t2. This increases the production rate of the product, and therefore facilitates mass production. Optimizing the amount of heat supplied to the material also reduces energy consumption, and therefore reduces carbon dioxide emissions. Furthermore, the product is obtained with a homogeneous and regular appearance, thereby reducing the scrap rate in production.

[0017] According to one aspect of the invention, the method comprises the following step: -measuring the holding pressure by a pressure sensor.

[0018] According to one aspect of the invention, the temperature of the injection mold is continuously measured, in particular using at least one injection mold temperature sensor.

[0019] According to one aspect of the invention, the process comprises the following steps after the step of closing the injection mold:

[0020] - establish a relationship, in particular a correlation, between the predetermined temperature of closure Tl and at least an outlet temperature T 1.3 of the heat transfer fluid downstream of the injection mold.

[0021] According to one aspect of the invention, the process comprises the following steps after the step of closing the injection mold:

[0022] - establish a relationship, in particular a correlation, between the predetermined temperature of closure Tl and at least an inlet temperature Tl.2 of the heat transfer fluid upstream of the injection mold.

[0023] According to one aspect of the invention, the method comprises:

[0024] - measure the inlet temperature Tl.2 of the heat transfer fluid upstream of the mold injection.

[0025] According to one aspect of the invention, the method comprises:

[0026] - measure the outlet fluid temperature T 1.3 of the heat transfer fluid downstream of the injection mold.

[0027] According to one aspect of the invention, the method comprises the following step:

[0028] - open the injection mold when the temperature of the injection mold reaches the predetermined opening temperature T2.

[0029] According to one aspect of the invention, the process comprises the following steps after the step of opening the injection mold:

[0030] - establish a relationship, in particular a correlation, between the predetermined temperature opening temperature T2 and at least one outlet temperature T2.3 of the heat transfer fluid downstream of the injection mold.

[0031] According to one aspect of the invention, the process comprises the following steps after the step of opening the injection mold:

[0032] - establish a relationship, in particular a correlation, between the predetermined temperature opening temperature T2 and at least one inlet temperature T2.2 of the heat transfer fluid upstream of the injection mold.

[0033] According to one aspect of the invention, the method comprises:

[0034] - measure the inlet temperature T2.2 of the heat transfer fluid upstream of the mold injection.

[0035] According to one aspect of the invention, the method comprises:

[0036] - measure the outlet fluid temperature T2.3 of the heat transfer fluid downstream of the injection mold.

[0037] The term "upstream" refers to the side of a device, particularly an injection mold, through which the heat transfer fluid is admitted into the device, or to the position of the heat transfer fluid before reaching the "downstream" position. For example, the term "upstream" will be used to designate the relative position of the heat transfer fluid closest to a heat transfer fluid inlet or heat transfer fluid distribution channel.

[0038] According to one aspect of the invention, the process comprises the following step:

[0039] - cool the injection mold at a predetermined cooling rate Vc, after the next step is completed: • set the thermoregulation unit to a cooling setpoint temperature Te.

[0040] According to one aspect of the invention, with the injection mold still closed, from the first instant t2bis until a second instant t2 corresponding to the opening of the injection mold, the injection mold is reheated, in particular using the thermoregulation unit, and the temperature T2bis of the injection mold measured at the first instant t2bis is strictly greater than the predetermined opening temperature T2 of the injection mold, after the following step is completed: • set the thermoregulation unit to a heating setpoint temperature Th.

[0041] According to one aspect of the invention, the cooling setpoint temperature Te is less than or equal to the predetermined opening temperature T2.

[0042] According to one aspect of the invention, the heating setpoint temperature Th is greater than or equal to the predetermined closing temperature Tl.

[0043] According to one aspect of the invention, the method comprises the following step:

[0044] - eject the product from the injection mold after opening the injection mold.

[0045] According to one aspect of the invention, the method comprises the following step:

[0046] - heat the injection mold at a predetermined heating rate Vh.

[0047] According to one aspect of the invention, the temperature measurement(s) are taken continuously.

[0048] The invention also relates to an injection molding system for a material, in particular a polymer, said system comprising:

[0049] - at least one injection mold;

[0050] - at least one temperature sensor for the injection mold;

[0051] - a thermoregulation unit configured to cool or heat the mold injection; and

[0052] - a control unit configured to implement a molding process by injection as defined above.

[0053] According to one aspect of the invention, the system further comprises:

[0054] - at least one pressure sensor configured to measure a holding pressure of the material in the injection mold according to a predetermined profile.

[0055] According to one aspect of the invention, the injection mold includes at least one injection orifice through which the material can be injected into the injection mold.

[0056] According to one aspect of the invention, the injection mold comprises at least two parts. One of these parts of the injection mold comprises the injection orifice.

[0057] According to one aspect of the invention, the thermoregulation unit comprises at least one heat transfer fluid circuit, in particular water-based, in thermal contact with the injection mold.

[0058] According to one aspect of the invention, the system further comprises: - at least one heat transfer fluid temperature sensor arranged to measure the heat transfer fluid temperature in the heat transfer fluid circuit.

[0059] According to one aspect of the invention, the system comprises at least one water reservoir connected to the thermoregulation unit.

[0060] According to one aspect of the invention, the heat transfer fluid circuit comprises:

[0061] - one or more heat transfer fluid channels. For example, fluid channels Heat transfer fluids can include a cold heat transfer fluid and a hot heat transfer fluid.

[0062] According to one aspect of the invention, the heat transfer fluid circuit includes at least one, or even two, heat transfer fluid temperature sensors connected to a heat transfer fluid channel to measure the heat transfer fluid temperature in the heat transfer fluid channel.

[0063] According to one aspect of the invention, the heat transfer fluid circuit comprises:

[0064] - a heat transfer fluid temperature sensor located upstream of the mold injection, configured to measure the inlet temperature T 1.2, T2.2 of the heat transfer fluid.

[0065] According to one aspect of the invention, the heat transfer fluid circuit comprises:

[0066] - a heat transfer fluid temperature sensor located downstream of the injection mold, configured to measure the outlet fluid temperature Tl.3, T2.3 of the heat transfer fluid.

[0067] According to one aspect of the invention, the system includes at least one material temperature sensor configured to measure the temperature of the material in the injection mold.

[0068] According to one aspect of the invention, the injection molding system comprises a plastic injection machine (or an "IMM (injection molding machine)" according to English terminology) configured to be connected to the injection mold.

[0069] Advantageously, the cooling rate Vc can follow a predetermined profile that varies according to time.

[0070] Advantageously, the heating speed Vh can follow a predetermined profile that varies according to time.

[0071] The predetermined profile can be determined in advance or iteratively.

[0072] Other features, details and advantages of the invention will become clearer upon reading the following description on the one hand, and several illustrative and non-limiting examples of embodiments given with reference to the accompanying schematic drawings on the other hand, in which:

[0073] [Fig-1] Fig. 1 is a schematic representation of a molding system by injection according to a variant embodiment of the invention;

[0074] [Fig.2] Fig.2 is a block diagram illustrating an injection molding process according to a variant embodiment of the invention;

[0075] [Fig.3] Fig.3 is a schematic representation of the temperature evolution depending on the weather.

[0076] The features, variants, and different embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive. In particular, variants of the invention may be conceived comprising only a selection of features, described hereafter in isolation from the other described features, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art.

[0077] In the following description, generally speaking, identical elements or elements with identical functions bear the same reference numeral. For the sake of brevity, only the differences between the embodiments presented are described.

[0078] Figure 1 shows an injection molding system for a polymer 2. The system 2 comprises an injection mold 4 having an injection port 6 through which the polymer can be injected into the injection mold 4. The injection mold 4 has two parts 8. One of these parts 8 of the injection mold 4 has the injection port 6.

[0079] Said system 2 further comprises:

[0080] - a temperature sensor for the injection mold 10;

[0081] - a thermoregulation unit 12 configured to cool or heat the mold injection 4, a water reservoir 13 being connected to this thermoregulation unit 12;

[0082] - a pressure sensor 14 configured to measure a holding pressure of the polymer in injection mold 4 according to a predetermined profile;

[0083] - a heat transfer fluid circuit 20, water-based, in thermal contact with the Injection mold 4. The heat transfer fluid circuit 20 has two heat transfer fluid channels 22. The thermoregulation unit 12 includes the heat transfer fluid circuit 20.

[0084] These heat transfer fluid channels 24 comprise a cold heat transfer fluid and a hot heat transfer fluid. The system 2 includes two material temperature sensors 25 configured to measure the temperature of the polymer in the injection mold 4. These material temperature sensors 25 are located upstream and downstream of the injection mold 4.

[0085] The heat transfer fluid circuit 20 comprises:

[0086] - a heat transfer fluid temperature sensor 26 located upstream of the mold injection 4, configured to measure the inlet temperature T1.2, T2.2 of the heat transfer fluid; and

[0087] - a heat transfer fluid temperature sensor 28 located downstream of the mold injection 4, configured to measure the outlet fluid temperature T1.3, T2.3 of the heat transfer fluid.

[0088] Said system 2 further comprises:

[0089] - a plastic injection molding machine 30 (or an "IMM (injection molding machine)" (according to English terminology) configured to be connected to the injection mold 4; and

[0090] Finally, the system 2 includes a control unit 40 configured to implement an injection molding process 100.

[0091] As illustrated in Figures 2 and 3, the injection molding process of the polymer 100, using the injection mold 4, is shown.

[0092] Said process 100 comprises the following steps:

[0093] - with the injection mold 4 open, heat the injection mold 4 using the thermoregulation unit 12 (S 110), at a predetermined heating speed Vh;

[0094] - close the injection mold 4 (S 120) when the injection mold temperature T reaches the predetermined closing temperature Tl (S 121);

[0095] The process 100 comprises the following steps after the step of closing the injection mold (S 120):

[0096] - establish a correlation relationship between the predetermined closing temperature Tl and an inlet temperature T 1.2 of the heat transfer fluid upstream of the injection mold 4 (S 122);

[0097] - establish a correlation relationship between the predetermined closing temperature Tl and an outlet temperature T 1.3 of the heat transfer fluid downstream of the injection mold 4(S124);

[0098] The process 100 comprises the following steps after the step of closing the injection mold 4:

[0099] - inject the polymer into said mold 4 so as to fill said mold 4 (S 130);

[0100] - apply a holding pressure to the polymer in the injection mold 4 according to a predetermined profile (S 140).

[0101] Process 100 comprises the following steps:

[0102] - cool the injection mold 4 at the predetermined cooling rate Vc, to with the help of the thermoregulation unit (S150), after the next step is completed: • set the thermoregulation unit 12 to a cooling setpoint temperature Te (S 152); - determine the first instant t2bis at which the cooling of said mold (S 154) is stopped, on the basis of said cooling rate Vc, and on the basis of a predetermined opening temperature T2 of the injection mold (S 156);

[0103] - the injection mold 4 being still closed, from the first instant t2bis until a second instant t2 corresponding to the opening of the injection mold 4, reheat the injection mold 4 using the thermoregulation unit (S160), and the temperature T2bis of the injection mold 4 measured at the first instant t2bis being strictly greater than the predetermined opening temperature T2 of the injection mold 4, after the next step is completed: • set the thermoregulation unit 12 to a heating setpoint temperature Th (S 164); - open the injection mold 4 when the temperature of the injection mold 4 reaches the predetermined opening temperature T2 (S 170);

[0104] The process comprises the following steps after the step of opening the injection mold 4 (S 170):

[0105] - establish a correlation relationship between the predetermined opening temperature T2 and an inlet temperature T2.2 of the heat transfer fluid upstream of the injection mold 4 (S 172);

[0106] - establish a correlation relationship between the predetermined opening temperature T2 and an outlet temperature T2.3 of the heat transfer fluid downstream of the injection mold 4 (S174).

[0107] Finally, process 100 comprises the following step:

[0108] - eject the product from the injection mold 4 after opening the injection mold 4 (S 180).

[0109] As illustrated in [Fig.3], the cooling setpoint temperature Te is lower than the predetermined opening temperature T2.

[0110] The heating setpoint temperature Th is higher than the predetermined closing temperature TL

[0111] Thanks to the fact that the first instant t2bis is precisely determined, and that the injection mold 4 is heated while still closed, between the first and second instants t2bis and t2, the heating moment is shifted (or brought forward) by a time difference between t2bis and t2. Thus, the heating of the injection mold 4 is optimized, taking into account a time latency induced by thermal inertia. for example, due to a temperature difference between the temperature of a heat transfer fluid and the temperature of the injection mold T directly in contact with the polymer.

[0112] Furthermore, optimizing the heating of the injection mold 4 to a predetermined temperature Tl results in a product with a homogeneous and regular appearance. Consequently, this reduces the scrap rate in production.

[0113] In addition, the fact that the temperature of the injection mold T is taken as a reference temperature allows for better measurement reliability than taking the temperature of the water-based heat transfer fluid as a reference temperature.

[0114] In summary, the invention makes it possible to precisely adjust the amount of heat supplied to the polymer and thus reduce the duration of a complete manufacturing cycle for a product obtained by process 100, at least by the difference in time between the first and second instants t2bis and t2. This increases the production rate of the product, and therefore facilitates mass production. Optimizing the amount of heat supplied to the polymer also reduces energy consumption, and therefore reduces carbon dioxide emissions. Furthermore, the product is obtained with a homogeneous and regular appearance, thereby reducing the scrap rate in production.

[0115] In these illustrated examples, the temperature measurement(s) are taken continuously. For example, the temperature of the injection mold T is continuously measured using the injection mold temperature sensor 4.

[0116] As illustrated in [Fig.3], advantageously, the cooling rate Vc and the heating rate Vh can follow a predetermined profile that varies with time.

[0117] The predetermined profile, whether it be the holding pressure or the cooling speed Vc or heating speed Vh, can be determined in advance or iteratively.

Claims

Demands

1. A method for injection molding a material (100), in particular a polymer, using an injection mold (4), said method comprising the following steps: - with the injection mold (4) open, heat the injection mold (4), in particular using a temperature control unit (12) (S 110); - close the injection mold (4) (S 120) when the temperature of the injection mold (T) reaches a predetermined closing temperature (T1) (S 121); - inject the material, in particular the polymer, into said mold (4) so ​​as to at least partially fill said mold (4) (S 130); - apply a holding pressure to the material in the injection mold (4) according to a predetermined profile (S 140); - cool the injection mold (4) at a predetermined cooling rate (Vc), in particular using the thermoregulation unit (12) (S150);- determine the first instant (t2bis) at which the cooling of said mold (4) is stopped, at least on the basis of said cooling rate (Vc), and on the basis of a predetermined opening temperature (T2) of the injection mold (4) (S 156); - the injection mold (4) being still closed, from the first instant (t2bis) until a second instant (t2) corresponding to the opening of the injection mold (4), reheat the injection mold (4), in particular with the help of the thermoregulation unit (12) (S160), and the temperature (T2bis) of the injection mold (4) measured at the first instant (t2bis) being strictly greater than the predetermined opening temperature (T2) of the injection mold (4).;

2. Method (100) according to claim 1, comprising the following steps: - cool the injection mold (4) at the predetermined cooling rate (Vc) (S 150), after the following step is completed: • set the thermoregulation unit (12) to a cooling setpoint temperature (Te) (S 152).

3. Method (100) according to claim 2, wherein the cooling setpoint temperature (Te) is less than or equal to the predetermined opening temperature (T2).

4. A method (100) according to any one of the preceding claims, comprising the following step: - opening the injection mold (4) when the temperature of the injection mold reaches the predetermined opening temperature (T2) (S 170).

5. A method (100) according to any one of the preceding claims, comprising the following steps: with the injection mold (4) still closed, from the first instant (t2bis) until a second instant (t2) corresponding to the opening of the injection mold (4), reheat the injection mold (4), in particular with the help of the thermoregulation unit (12) (S 160), and the temperature (T2bis) of the injection mold (4) measured at the first instant (t2bis) being strictly greater than the predetermined opening temperature (T2) of the injection mold (4), after the following step is completed: • set the thermoregulation unit (12) to a heating setpoint temperature (Th) (S 164).

6. Method (100) according to the preceding claim, wherein the heating setpoint temperature (Th) is greater than or equal to the predetermined closing temperature (Tl).

7. Method (100) according to any one of the preceding claims, wherein the cooling rate (Vc) follows a predetermined profile that varies with time.

8. Injection molding system for a material (2), in particular a polymer, said system (2) comprising: - at least one injection mold (4); - at least one temperature sensor for the injection mold (10); - a thermoregulation unit (12) configured to cool or heat the injection mold (4); and - a control unit (40) configured to implement an injection molding process (100) according to any one of the preceding claims.

9. System (2) according to claim 8, comprising a plastic injection molding machine (30) (or an "IMM" (injection molding)

10. machine) » according to English terminology) configured to be connected to the injection mold (4). System (2) according to claim 8 or 9, wherein the thermoregulation unit (12) comprises at least one heat transfer fluid circuit (20), in particular water-based, in thermal contact with the injection mold (4).

Images