Molding method for producing a monolithic part having at least one cavity therein

Abstract

A molding method for producing a monolithic part, specifically a monolithic part made of C-SMC, having at least one cavity therein, includes the steps of: providing a press having a first half mold (1 a), a second half mold (1 b), and a movable side carriage defining a molding space (Vs) therebetween; and placing at least one core (3, 4) within the molding space (Vs). The core (3, 4) includes a membrane (3) defining a receiving space (Vc) molded to form the at least one cavity of the monolithic part, and at least one connector (4) engaging the membrane (3). The method also includes the steps of encasing the cores (3, 4) with a charge of the material (C) to be molded, fixing the cores (3, 4) inside one of the first and second mold halves (1 a) and (1 b), and filling the containment space (Vc) of the membrane (3) with a filling material (R). After closing the first and second mold halves (1 a) and (1 b), the method includes the steps of applying a molding pressure to subsequently empty the containment space (Vc) filled with the filling material (R), and after opening the first and second mold halves (1 a) and (1 b), removing the core from the molded monolithic part.

Description

[Technical Field]

[0001] The present invention relates to a molding method for manufacturing monolithic parts with at least one cavity inside, in particular monolithic parts made of C-SMC, and to a machine for molding hollow monolithic parts, widely used in the automotive sector, in particular for manufacturing parts from C-SMC (Carbon Sheet Moulding Compound). [Background technology]

[0002] Currently, C-SMC parts are manufactured using conventional compression molding techniques, in which a press is used to apply a force capable of shaping a C-SMC charge. This molding technique produces complex, single-layer, monolithic parts that are relatively inexpensive and highly rigid.

[0003] Additionally, techniques are known for machining parts made from CFRP (carbon fiber reinforced polymer) to produce very stiff and high-strength components. These properties are enhanced by the possibility of molding closed shapes that are useful for the production of body-in-white (BiW) structural components.

[0004] Unfortunately, conventional techniques for processing C-SMC parts and those used to manufacture CFRP parts have inherent shortcomings in terms of mechanical properties, cost and takt time of the finished part.

[0005] The molding technology used for C-SMC parts cannot handle parts with internal voids, while the technology used for CFRP parts is expensive and its productivity cannot meet market demands. Summary of the Invention

[0006] The technical object of the present invention is therefore to provide a molding method for producing a monolithic part with at least one cavity inside and a machine for molding hollow monolithic parts, in order to make it possible to overcome the above-mentioned drawbacks of the prior art.

[0007] The object of the present invention is therefore to provide a molding method which makes it possible to manufacture monolithic elements, in particular from C-SMC, which are hollow and have complex shapes.

[0008] Another object of the present invention is therefore to provide a molding method that makes it possible to manufacture hollow monolithic elements from C-SMC at lower costs than in the prior art.

[0009] The stated technical and specified objects are substantially achieved by a molding method and machine comprising the technical features set forth in one or more of the appended claims. The dependent claims correspond to possible embodiments of the invention.

[0010] More specifically, the technical object is achieved by a molding method for manufacturing a monolithic part with at least one cavity therein, in particular a monolithic part made of C-SMC, comprising the step of providing a press with a first half-mold and a second half-mold that define a molding space therebetween, one of the first half-mold and the second half-mold being movable by an oil circuit and the other of the first half-mold and the second half-mold being fixed.

[0011] In a possible embodiment, the press also comprises a side carriage movable to cooperate with the mold halves to define a molding space and to make it possible to mold hollow monolithic parts having undercuts.

[0012] The method of the present invention also includes the steps of placing at least one core within the molding space, the core including a membrane defining the containment space to be molded to form at least one cavity of the monolithic part, and at least one connector configured to engage the membrane and enable filling of the containment space, and enveloping the core with a charge of the material to be molded, specifically a charge of C-SMC, such that the core is at least partially immersed in the charge.

[0013] The method of the present invention also includes the steps of fixing a core inside one of the first and second half molds, specifically the fixed half mold, filling the accommodating space of the membrane with a filling material via a connector, and, after closing the half molds (and, if necessary, the carriage, if present), applying a molding pressure to the charge of material to form a monolithic part.

[0014] After the aforementioned steps, the method according to the invention also comprises the steps of emptying the receiving space filled with filling material and, after opening the half molds (and, if necessary, the carriage, if present), removing the core from the molded monolithic part.

[0015] More specifically, the technical object is also achieved by a machine configured to carry out the method according to the preceding for molding hollow monolithic parts, in particular C-SMC parts, the machine comprising a press with a first half-mold and a second half-mold defining a molding space therebetween, one of the first half-mold and the second half-mold being movable and the other of the first half-mold and the second half-mold being fixed. In a possible embodiment, the press also comprises a movable side carriage to allow molding hollow monolithic parts with undercuts.

[0016] The machine according to the invention also comprises at least one core, the core comprising a membrane arranged in the molding space and defining a receiving space molded to form at least one cavity of the monolithic part, the core also comprising at least one connector adapted to engage with the membrane and enable filling of the receiving space. The machine also comprises an oil circuit adapted to move the movable half mold, either the first half mold or the second half mold, and the side carriage as required, and a vacuum circuit adapted to generate a negative pressure effect in the molding space.

[0017] Further features and advantages of the present invention will become more apparent in the following exemplary, and therefore non-limiting, descriptions of embodiments of a molding method and machine for producing hollow monolithic parts, in particular C-SMC parts. [Brief explanation of the drawings]

[0018] The description will now be made with reference to the accompanying drawings, which are provided for illustrative purposes only, without limiting the scope of the invention. [Figure 1] 1 shows a schematic diagram of one embodiment of a machine for manufacturing hollow monolithic parts, specifically C-SMC parts. [Figure 2] FIG. 1 shows a schematic diagram of another embodiment of a machine for manufacturing hollow monolithic parts, specifically C-SMC parts. [Figure 3] 3 shows a schematic diagram of another embodiment of a machine according to the invention; [Figure 3A] A schematic diagram of a detail of FIG. 3 is shown. DETAILED DESCRIPTION OF THE INVENTION

[0019] With reference to the accompanying drawings, the letter M denotes a machine for molding hollow monolithic parts, in particular C-SMC parts.

[0020] The machine M comprises a press with a first half mould 1a and a second half mould 1b defining a moulding space Vs between them, in which a charge C of material to be moulded, in particular a charge of C-SMC, is placed to obtain a hollow monolithic part.

[0021] Preferably, one of the first and second half moulds 1a and 1b of the press is movable, while the other of the first and second half moulds 1a and 1b is fixed and receives a charge C of material to be moulded.

[0022] In the embodiment shown in the accompanying drawings, it is the second mould half 1b that moves towards and away from the first mould half 1a, which is fixed.

[0023] In another possible embodiment, it is the first mould half 1a that moves towards and away from the second mould half 1b, the second mould half 1b being fixed.

[0024] Alternatively, both mold halves 1a, 1b can move towards or away from each other.

[0025] According to a further aspect of the invention, the press also comprises a movable side carriage configured to enable molding of hollow monolithic parts with one or more undercuts, in which case the carriage also moves at the moment when the first and second mold halves 1 a, 1 b move, and cooperates with the mold halves 1 a, 1 b to define a molding space Vs during the subsequent step of molding the hollow monolithic part.

[0026] To form the cavity of the monolithic part, the machine M also comprises at least one core 3, 4, which in turn comprises a membrane 3 defining a receiving space Vc, which is arranged inside the molding space Vs and is molded to form the cavity.

[0027] The shape of the membrane 3 is therefore determined by the shape of the cavity of the resulting monolithic part.

[0028] In the embodiment shown, the membrane 3 has a substantially parallelepiped shape, the edges of which are rounded (filleted) in order to obtain a hollow monolithic part having a cavity with a rectangular cross section with rounded corners.

[0029] In other embodiments not shown, the membrane 3 may have any shape.

[0030] Preferably, the membrane 3 is made of a material that can be selected from one of the following: liquid silicone rubber, latex rubber, PTE / PE for rotational molding, low melting point polymer for rotational molding, low melting point polymer for thermoforming, thermoplastic polymer for blow molding, thermoplastic polymer for injection molding.

[0031] Advantageously, these materials make it possible to model the membrane 3 so that it adopts the desired shape in the cavity of the monolithic part.

[0032] Advantageously, these materials also allow the membrane 3 to withstand the high pressures and temperatures (preferably above 150°) that occur during the molding process, while at the same time allowing the membrane 3 to be easily removed from the hollow monolithic part at the end of the molding process.

[0033] In fact, during the molding process, the membrane 3 defining the cavity must not lose its shape (especially by compression) or collapse, since this would result in a part at the end of the molding process whose cavity is of an inappropriate size or shape, or no cavity at all if the membrane 3 has collapsed. In this regard, the containment space Vc defined by the membrane 3 is filled with a filling material R, for example oil or a granular material, as will be explained in more detail below.

[0034] For filling purposes, the cores 3, 4 also comprise a connector 4, preferably, but not exclusively, a threaded connector, which engages with the membrane 3. Preferably, the connector 4 is hollow and its exterior is at least partially covered by the membrane 3 (FIG. 3A), which prevents the filling material R from leaking out of the receiving space Vc and altering the composition of the material load C while the receiving space Vc is being filled.

[0035] In other words, the cores 3, 4 are made in the form of a contoured bag that can be filled with a filling material R through at least one connector 4 to resist the molding pressure to form a cavity inside the monolithic part.

[0036] As shown in the accompanying drawings, the machine M also comprises an oil circuit 2 arranged to power the movable mould halves 1 a, 1 b, and a vacuum circuit 5 preferably arranged in the fixed mould halves 1 a, 1 b and arranged to create a negative pressure effect in the mould space Vs and to facilitate the spreading of the material charge C during the moulding process. In another possible embodiment, the vacuum circuit 5 may be arranged in the movable mould half 1 a, 1 b. Alternatively, the vacuum circuit 5 may be arranged in both mould halves 1 a, 1 b.

[0037] Thus, the aforementioned press is prepared for carrying out the molding method for producing a monolithic part with at least one cavity therein, in particular a monolithic part made of C-SMC.

[0038] During this step, the press is prepared so that the mold halves 1a, 1b and, if present, the side carriages are spaced apart from one another to allow placement of such a core in the molding space Vs. A charge of material C, in particular a charge of C-SMC, is then wound onto the cores 3, 4 so that the cores are at least partially immersed in the charge C. More specifically, the charge of material C can be wound onto the membrane 3 so as to almost completely cover it or to only partially cover it.

[0039] As shown in the accompanying drawings, at least one connector 4 at least partially protrudes from the material charge C, so that the cores 3, 4 can be fixed inside one of the first and second half moulds 1a, 1b, in particular inside the half mould which is fixed.

[0040] In other words, in the step of encasing the cores 3, 4 with the charge C of material, the cores 3, 4 are covered by the charge C of material to be molded, and at least one connector 4 is at least partially free of the charge C, and the thus encased cores 3, 4 can be fixed inside the fixed half moulds 1a, 1b.

[0041] Once the cores 3, 4 are fixed in the fixed mould halves 1a, 1b, the receiving space Vc of the membrane 3 is filled with a predetermined amount of filling material R via the connector 4.

[0042] Referring to the embodiment shown in FIG. 1, the containment space Vc is filled with a granular material that can be selected from one of the following: sand, salt, glass microspheres, honeycomb pellets.

[0043] On the other hand, in the embodiment shown in Figures 2 and 3, the filling material R is oil from the oil circuit 2 of the press.

[0044] More specifically, in these embodiments, in the step of fixing the cores 3, 4 to the stationary mold halves 1 a, 1 b, at least one connector 4 is fixed to the mold halves 1 a, 1 b in the vicinity of the delivery portion 2 a of the oil circuit 2. In doing so, the receiving space Vc is placed in fluid communication with the delivery portion 2 a of the oil circuit 2 during the filling step, allowing a predetermined amount of oil to flow from the oil circuit 2 into the receiving space Vc. Thus, in this case, when the receiving space Vc needs to be filled, part of the oil from the oil circuit 2 of the press is made to flow into the receiving space Vc via the connector 4.

[0045] After the step of filling the containment space Vc of the membrane 3, the method includes a step of closing the two half molds 1a, 1b and, if present, the side carriages, so that the material charge C and the cores 3, 4 are placed between the first half mold 1a and the second half mold 1b, and are thus contained in the molding space Vs.

[0046] After the step of closing the mold halves 1a, 1b, the method further includes the step of increasing the temperature of the material charge C so that it can move within the molding space Vs, flow along the membranes 3 of the cores 3, 4, and spread evenly throughout the molding space Vs.

[0047] The flow percentage of the charge in the forming space Vs can be high (high flow) or low (low flow) up to 99%. This flow percentage varies depending on the mechanical and morphological properties required for the finished product (e.g., thickness, size, extraction axis).

[0048] In other words, once the temperature is raised, the material charge C can flow through the forming space Vs, covering the entire membrane 3 and spreading throughout the forming space Vs.

[0049] In the step of wrapping the membrane 3 with the material charge C, if the material charge C is wrapped around almost the entire membrane 3 (e.g., 99% of the surface of the membrane 3), the material charge C will flow less within the forming space than if the material charge C is wrapped around the membrane 3 so that it covers only a portion of the membrane 3.

[0050] In a preferred embodiment, the membrane 3 has a smooth polished surface outside the containment space Vc that facilitates the flow and spreading of the material load C and makes it possible to obtain a cavity whose surface is free from defects and irregularities.

[0051] Advantageously, the membrane 3 thus formed makes it possible to obtain parts with good dimensional tolerances and high mechanical strength, despite the presence of cavities.

[0052] After filling the receiving space Vc and closing the mold halves 1a, 1b (and side carriages, if present), the method includes applying a molding pressure to the charge of material C to form a monolithic part.

[0053] Preferably, the compaction pressure applied to the charge of material C is between 8 bar and 300 bar, and even more preferably the compaction pressure is 120 bar.

[0054] If the fill material R is oil from the oil circuit 2 of the press, a forming pressure is applied to the charge C of material by expanding the membrane 3 .

[0055] More specifically, after the mold halves 1a, 1b and, if necessary, the movable side carriage have been closed, an additional amount of oil is filled into the receiving space Vc of the membrane 3 via the delivery part 2a in order to expand the membrane 3. This expansion exerts a pushing force on the material charge C, which compresses it between the membrane 3 and the mold halves 1a, 1b. In this case, the material charge C is therefore shaped by the pressure exerted by the oil contained in the receiving space Vc, which pressure pushes the membrane 3 from the inside towards the outside of the membrane 3.

[0056] On the other hand, if the filler material R is a granular material, the step of applying the molding pressure is achieved by moving one of the first and second mold halves 1a and 1b toward the other, while keeping the membrane 3 fixed. In this case, the first mold half 1a is pressed against the second mold half 1b, exerting pressure on the material charge C located therebetween, without any active action on the membrane 3, which is neither compressed nor expanded. Thus, the movable mold halves 1a and 1b are pressed against the fixed mold halves 1a and 1b so that the material charge C is compressed against the membrane 3, but the membrane 3 does not lose its shape (especially due to compression) thanks to the presence of the filler material R pre-filled in the receiving space Vc. If the mold halves 1a and 1b are provided with side carriages, they move together with the mold halves 1a and 1b to compress the material charge C and form the undercut required for the hollow monolithic part.

[0057] In other words, the filling material R present in the accommodation space Vc of the membrane 3 is able to support the molding pressure exerted by the mold halves 1a, 1b (and side carriages, if present) on the material charge C, so that the membrane 3 does not collapse (especially by compression) or lose its shape and does not prevent the monolithic part from being made correctly.

[0058] In another possible embodiment, the mould halves 1a, 1b and the membrane 3 can be acted on simultaneously so that the mould pressure is applied to the material charge C simultaneously from the inside to the outside of the containing space Vc of the membrane 3 thanks to the filling material R, and from the outside to the inside thanks to the movement of the mould halves 1a, 1b towards each other.

[0059] In a preferred embodiment, the mould halves 1 a, 1 b are provided with compression chambers to ensure that the correct moulding pressure is applied to the material charge C. The compression chambers are configured to act as limit stops for the mould halves 1 a, 1 b during the closing movement without losing the moulding pressure applied to the entire material charge C.

[0060] More specifically, when membrane 3 is filled with granular material, molding of the C-SMC charge is achieved by molding pressure applied by mold halves 1a and 1b to material charge C. Mold halves 1a and 1b are provided with vertical compression chambers to create limit stops for the movement of mold halves 1a and 1b to maintain the proper molding pressure. When molding pressure is applied by mold halves 1a and 1b, a portion of the resin contained in the C-SMC charge is forced out of molding space Vs into the compression chambers. In this case, the resin acts as a limit stop for mold halves 1a and 1b, while at the same time preventing a loss of some of the molding pressure applied to material charge C.

[0061] Alternatively, if the molding pressure is applied by expanding the membrane 3, the mold halves 1a, 1b are provided with horizontal compression chambers.

[0062] Once molding pressure is applied to the charge of material C to form the hollow monolithic part, the method includes emptying the filler material R from the containment space Vc.

[0063] More specifically, in the embodiment shown in FIG. 1, in which the filling material R is granular, the receiving space Vc is evacuated via the same connector 4 used to fill the receiving space with the filling material R.

[0064] In the embodiment shown in Figure 2, where the filling material R used is a predetermined amount of oil from the oil circuit 2, the step of emptying the receiving space Vc is achieved by putting the receiving space in fluid communication with the return part 2b of the oil circuit 2 so as to allow the predetermined amount of oil to flow back from the receiving space Vc to the oil circuit 2. As shown in Figure 2, the delivery part 2a and the return part 2b are made inside the fixed mould halves 1a, 1b, so that when the cores 3, 4 are fixed inside the mould halves 1a, 1b, the respective connectors 4 can be in fluid communication with the parts 2a, 2b so as to allow oil to enter and leave the receiving space Vc.

[0065] In other words, in this embodiment, the accommodating space Vc is connected to the delivery portion 2a and the return portion 2b of the oil circuit 2 by the respective connectors 4 so as to create an open circuit through which oil flows into and out of the accommodating space Vc during the steps of filling and emptying the accommodating space Vc, respectively.

[0066] The embodiment shown in Figure 3 differs from the embodiment shown in Figure 2 in that the delivery part 2a and the return part 2b of the oil circuit 2 are one and the same. In other words, in this embodiment, the receiving space Vc is in fluid communication with the same parts 2a, 2b of the oil circuit 2 of the press, in order to create a closed circuit through which oil flows into the receiving space Vc during the filling step and flows out from it during the emptying step of the receiving space Vc.

[0067] After the step of emptying the filling material R from the receiving space Vc, the method includes the step of removing the cores 3, 4 from the molded monolithic part.

[0068] To facilitate this step after the step of emptying the receiving space Vc, the method includes a step of activating a vacuum circuit 5 formed in at least one of the first half mold 1a and the second half mold 1b and communicating with the molding space Vs, in order to generate a negative pressure effect for separating the membrane 3 from the inner surface of the molded monolithic part.

[0069] In this case, once the step of emptying the receiving space Vc is completed and before the half molds 1a, 1b and (if present) the side carriages move away from each other to open the press, the vacuum circuit 5 is activated, thereby separating the membrane 3 from the cavity wall.

[0070] In other words, before the mould halves 1a, 1b are opened, the vacuum circuit 5 creates a suction action that separates the membrane 3 from the inner wall of the hollow monolithic part.

[0071] Advantageously, this step allows the cores 3, 4 to be easily and conveniently removed from the cavities of the monolithic part, avoiding the risk that the membranes 3 of the cores 3, 4 remain trapped in the cavities and impair the properties of the part.

[0072] Following the steps of activating the vacuum circuit 5 and opening the mold halves 1 a, 1 b, the method comprises the step of effectively removing the cores 3, 4. This step comprises the sub-steps of releasing at least one connector 4 from the fixed mold halves 1 a, 1 b and ejecting the molded monolithic part together with the connector 4 from the press.

[0073] In the embodiment shown in the accompanying drawings, the connector 4 is a threaded connector which is screwed into the fixed mould halves 1a, 1b during the step of fixing the cores 3, 4 and which is released therefrom during the aforementioned releasing step.

[0074] Alternatively, the connector 4 is connected to the fixed mould halves 1a, 1b and therefore to the oil circuit by inserting the connector 4 into a suitably shaped socket formed in the fixed mould halves 1a, 1b.

[0075] When the molded monolithic part is ejected from the press, the connector 4 is detached from the part and the membrane 3 is at least partially extracted through the opening left by the connector 4 in the molded monolithic part.

[0076] While the membrane 3 is being extracted through the openings left in the molded monolithic part by the connectors 4, parts of the membrane 3 may remain in the cavity. In order to also remove these parts of the membrane 3 from the cavity, the step of removing the cores 3, 4 may comprise the substep of forming at least one opening in the monolithic part to allow the membrane 3 to be extracted in whole or in part.

[0077] Advantageously, the possibility of extracting the membrane 3 through the opening left by the connector 4 or through a specially formed opening avoids the need to mold the part in parts that have to be subsequently joined, but makes it possible to directly mold a monolithic part.

[0078] Once at least one opening has been formed in the hollow monolithic part, the step of removing the cores 3, 4 also includes the sub-step of increasing the temperature of the hollow monolithic part.

[0079] In this substep, the whole part is placed in an oven capable of raising the temperature of the part before extracting the membrane 3 through the opening. In this case, the membrane 3 is softened, so that it is easier to extract it from the part through the opening just formed or the opening left by the connector 4.

[0080] Next, the method includes finishing the area of ​​the molded monolithic part near the opening left by the at least one connector 4 .

[0081] As shown in Figure 3A, during the molding step, part of the material charge C is deposited around the tip of the core 3, 4 where the connector 4 engages with the membrane 3. In this case, when the step of applying molding pressure is finished, the resulting monolithic part has a kind of "flash" near the connector 4. This "flash" is removed when the connector 4 and membrane 3 are removed to give the monolithic part its original desired shape.

[0082] Preferably, during this step of the method, any flash formed on the hollow monolithic part adjacent to the compression chamber is also removed.

[0083] Preferably, the burrs are removed by milling and / or drilling.

[0084] The present invention achieves its stated objectives by eliminating the drawbacks of the prior art.

[0085] More specifically, the present invention provides a method for molding hollow monolithic parts, which allows the production of complex parts with very good mechanical properties.

[0086] This method also allows for the production of BiW components that can meet current market standards.

[0087] Furthermore, this method is also cheaper than prior art methods and makes it possible to obtain competitive production rates that meet market productivity requirements.

[0088] Advantageously, the membrane 3 makes it possible to easily and reliably create cavities of the desired shape in the monolithic part.

Claims

1. 1. A molding method for producing a monolithic part made of C-SMC, the monolithic part having at least one cavity therein, comprising: providing a press comprising a first half mould (1 a) and a second half mould (1 b), one of which is moved by an oil circuit (2) and the other of which is fixed, the first half mould (1 a) and the second half mould (1 b) defining a moulding space (Vs) therebetween, the press also comprising a movable side carriage cooperating with the first half mould (1 a) and the second half mould (1 b) to define the moulding space (Vs); placing at least one core (3, 4) in said molding space (Vs), said core (3, 4) comprising a membrane (3) delimiting a encapsulation space (Vc) molded to form said at least one cavity of said monolithic part, and at least one connector (4) configured to engage said membrane (3) and to allow said encapsulation space (Vc) to be filled with a filler material (R); - enveloping said cores (3, 4) with a charge (C) of C-SMC of the material (C) to be moulded so that said cores (3, 4) are at least partially immersed in said charge; Fixing said core (3, 4) inside one of said first mould half (1 a) and said second mould half (1 b); Filling the containing space (Vc) of the membrane (3) with the filling material (R) through the connector (4); - applying a molding pressure to the charge of material (C) to form the monolithic part after closing the first half mould (1 a) and the second half mould (1 b); After these steps, Emptying the containing space (Vc) filled with the filling material (R); and removing the cores (3, 4) from the monolithic part after opening the first half mould (1 a) and the second half mould (1 b), In the step of filling the accommodating space (Vc) of the membrane (3), the accommodating space (Vc) is fluidly connected to a delivery portion (2a) of the oil circuit (2) to enable a supply flow in which a predetermined amount of oil flows from the oil circuit (2) to the accommodating space (Vc), and / or in the step of emptying the accommodating space (Vc), the accommodating space is fluidly connected to a return portion (2b) of the oil circuit (2) to enable a return flow in which the predetermined amount of oil flows back from the accommodating space to the oil circuit (2).

2. 2. The method of claim 1, wherein the delivery portion (2a) and the return portion (2b) of the oil circuit (2) are one and the same portion.

3. 3. The method according to claim 1 or 2, wherein the step of applying a forming pressure comprises the sub-step of supplying an additional amount of oil to the accommodating space (Vc) of the membrane (3) to expand the membrane (3) so that it applies the forming pressure to the charge (C) of material.

4. 4. The method according to any one of claims 1 to 3, wherein between the step of encasing the core (3, 4) with the charge of material (C) and the step of applying the molding pressure there is a step of increasing the temperature of the charge of material (C).

5. 5. The method according to claim 1, wherein in the step of fixing the core (3, 4) to one of the first and second half molds (1 a) and (1 b), the at least one connector (4) engages with the fixed half mold, either the first half mold (1 a) or the second half mold (1 b), so as to enable a flow of the filling material (R) during the steps of filling the receiving space (Vc) of the membrane (3) with the filling material (R) and during the steps of emptying the receiving space (Vc) of the membrane (3).

6. After the step of emptying the receiving space (Vc) and the step of opening the first half mould (1a) and the second half mould (1b), Releasing said at least one connector (4) from the fixed mould halves (1a, 1b); and ejecting the formed monolithic part together with the at least one connector (4) from the press.

7. The step of removing the cores (3, 4) comprises: the sub-step of removing said at least one connector (4) from said molded monolithic part; The method according to any one of claims 1 to 6, comprising the sub-step of at least partially extracting the membrane (3) from an opening left on the molded monolithic part by the at least one connector (4).

8. 8. The method according to claim 7, wherein the step of removing the cores (3, 4) is followed by a step of finishing the area of ​​the molded monolithic part near the opening left by the at least one connector (4).

9. The step of removing the cores (3, 4) from the molded monolithic part comprises: - forming at least one opening in said monolithic part, said at least one opening being configured to allow the membranes (3, 4) to be extracted completely or partially; 9. A method according to any one of claims 1 to 8, comprising the sub-step of increasing the temperature of the moulded monolithic part in order to soften the membrane (3).

10. 10. The method according to any one of claims 1 to 9, wherein the step of opening the first and second mould halves (1 a) and (1 b) is preceded by a step of activating a vacuum circuit (5) formed in at least one of the first and second mould halves (1 a) and in communication with the moulding space (Vs) in order to generate a negative pressure effect for separating the membrane (3) from the inner surface of the moulded monolithic part.

11. A machine (M) for forming hollow monolithic parts made of C-SMC, adapted to carry out the method according to any one of claims 1 to 10, a press comprising a first half mould (1 a) and a second half mould (1 b), one of which is movable and the other of which is fixed, the first half mould (1 a) and the second half mould (1 b) defining a moulding space (Vs) therebetween, the press also comprising a movable side carriage cooperating with the first half mould (1 a) and the second half mould (1 b) to define the moulding space (Vs); at least one core (3, 4) arranged in said molding space (Vs), said core (3, 4) comprising a membrane (3) defining a containment space (Vc) molded to form at least one cavity of said monolithic part, and at least one connector (4) configured to engage said membrane (3) and to allow said containment space (Vc) to be filled; an oil circuit (2) configured to move a movable half of the first half (1 a) and the second half (1 b); a vacuum circuit (5) configured to create a negative pressure effect in said forming space (Vs).

12. 12. The machine (M) according to claim 11, wherein the oil circuit (2) comprises a delivery portion (2a) and a return portion (2b) arranged inside the fixed other of the first half mold (1a) and the second half mold (1b), the delivery portion (2a) and the return portion (2b) being in fluid communication with respective connectors (4) to allow oil to flow from the oil circuit (2) to the accommodating space (Vc) and from the accommodating space (Vc) to the oil circuit (2), respectively.

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