IT202300003837A1 - MACHINE AND MOLDING PROCESS - Google Patents

Description

DESCRIPTION

Title: MACHINE AND MOLDING PROCESS

Technical field of the invention

The present invention relates to a molding machine and a related molding process.

State of the art

Thermoforming processes of a semi-finished product are known, which give a pre-established shape to the semi-finished product by means of a compressive action exerted on the semi-finished product against a suitably shaped mold, also subjecting the semi-finished product, when in the mold, to a thermal cycle comprising at least one heating or cooling phase of the semi-finished product. To carry out the thermal cycle, it is known to heat and/or cool the mold (at least partially),

Summary of the invention

In the above context of thermoforming processes, the Applicant has made the following considerations regarding the heating and cooling of the mould.

? It is possible to achieve the aforementioned thermal cycle by equipping the mold with suitable ducts through which a fluid at the desired temperature is passed to alternatively cool or heat the mold depending on the process phases. Such ducts can for example be made starting from grooves arranged on the external surface of the mold (i.e. the surface that typically remains visible when the mold is completely closed and/or in general a surface of the mold, or of respective half-molds, external to surfaces of conformations foreseen to give shape to a semi-finished product) which are closed by means of an additional cover, or be entirely incorporated into the walls of the mold, e.g. by drilling the walls.

It is also possible to heat the mold by means of one or more electrical resistances in the form of a cartridge, housed in suitable holes made in the mold, in order to obtain a wide direct contact between the electrical resistances and the mold. The electrical resistances can be combined with ducts for the passage of a cooling fluid as described above.

However, the Applicant has found that the construction of the aforementioned fluid ducts for thermal regulation, regardless of the technique adopted, involves a complication in the manufacture of the mould and/or in its thermoregulation, with a consequent increase in costs.

For example, the use of ducts for both heating and cooling necessarily involves the provision of two quantities of heat transfer fluid at different temperatures (with respective tanks and recirculation systems) or the need to heat and/or cool the same fluid during the process, with a consequent lengthening of the cycle time.

Furthermore, the Applicant noted that such a duct solution may not be efficiently implemented on pre-existing molds, as the final shape and/or thickness of the mold walls may be unsuitable and/or insufficient to accommodate ducts and/or grooves having the desired dimensions.

Furthermore, the Applicant has also found that the adoption of cartridge-type electrical resistors necessarily represents a complication in the manufacture and/or management of the mould, in economic and/or time terms, if only because it requires necessary mould processing.

The Applicant therefore faced the problem of modifying the temperature of a mould, by sequentially cooling and heating the mould (regardless of the order of the heating and cooling phases) for the purposes of a moulding process, in a rapid and/or efficient manner, for example in terms of time and/or costs and/or desired temperature uniformity (e.g. at the surface of the internal cavity of the mould), and/or in a structurally simple and/or reliable and/or versatile manner, e.g. with respect to possible process variations, and/or possible mould shapes.

According to the Applicant, the above problem is solved by a molding machine and a related molding process in accordance with the attached claims and/or having one or more of the following characteristics.

According to one aspect, the invention concerns a molding machine. The machine comprises:

- a mold comprising a shaping surface;

- an actuation system structured to compress a semi-finished product against said conformation surface;

- a plurality of heating elements distinct from each other and removably fixed to said mould on an external surface of said mould,

- a plurality of cooling elements distinct from each other and removably fixed to said mold on said external surface of said mold,

where each heating element comprises:

- a thermally conductive base body in thermal contact with said external mold surface;

- an electrically resistive track thermally coupled to said base body, where each cooling element is in thermal contact with said external surface of said mold, where each cooling element comprises a main body having an internal chamber having an inlet port and an outlet port for a cooling fluid,

and where said base bodies of said heating elements are distributed on said external surface of said mould spatially separated from each other and said main bodies of said cooling elements are distributed on said external surface of said mould spatially separated from each other.

According to another aspect, the invention concerns a molding process. The process comprises:

- prepare a mold including a conformation surface;

- providing a plurality of heating elements which are distinct from each other and removably fixed to said mould on an external surface of said mould, each heating element comprising:

- a thermally conductive base body in thermal contact with said external mold surface,

- an electrically resistive track thermally coupled to said base body, - providing a plurality of cooling elements that are distinct from each other and removably fixed to said mold in a distributed manner on said external surface, where each cooling element is in thermal contact with said external surface of said mold, where each cooling element comprises a main body equipped with an internal chamber having an inlet and an outlet for a refrigerant fluid, where said base bodies of said heating elements are distributed on said external surface of said mold spatially separated from each other and said main bodies of said cooling elements are distributed on said external surface of said mold spatially separated from each other;

- perform the following operations from i) to iii) in any temporal order:

(i) cooling said conformation surface by circulating said cooling fluid in said cooling elements;

ii) placing a semi-finished product in contact with said conformation surface;

iii) heating said conformation surface by causing an electric current to pass through said electrically resistive tracks;

- with said semi-finished product in contact with said shaping surface, compressing said semi-finished product against said shaping surface to shape said semi-finished product.

According to the Applicant, in the field of compression molding, the heating and cooling elements as described above allow to combine efficiency and speed of management of the mold temperature with structural simplicity and reduced costs.

In fact, on the one hand, these cooling and heating elements have proven to be particularly suitable for the creation of thermal cycles, obtaining the desired temperatures of the semi-finished product and rapid variations of the same in a carefully controlled manner (e.g. obtaining the desired thermal powers), and on the other hand, their structure, together with their fixing on the external surface (since they are distinct from the mould and applied to the mould) in a spatially separate manner, allow for simplification of their fixing and/or subsequent maintenance compared to the comparative solutions described above. For example, in this way it is possible to avoid the preparation of two distinct quantities of fluid at different temperatures (together with the respective storage and recirculation systems) or having to subject the same heat-transfer fluid to a thermal cycle. Furthermore, they are limited to, or even eliminated, specific interventions on each individual mould, such as the creation of holes to house the resistors and/or to create the aforementioned continuous ducts.

In this way, it is also possible to modify the sizing and/or the arrangement of the heating and/or cooling elements following a modification of the production cycle, maintaining the same mold. Furthermore, at the end of the mold's life cycle, it is possible to dismantle the heating and cooling elements for possible further use on another mold.

Furthermore, thanks to the fixing of the heating and cooling elements on the external surface of the mould, it is possible to adapt this solution to any type of mould, even pre-existing ones, with limited interventions on the mould (and therefore with consequent economic savings).

The Applicant notes that the typology of heating elements of the present invention has been selected from a large number of possible typologies of heating elements, taking into account numerous factors (e.g. specific thermal power obtainable, cost, size and versatility of the conformation and/or spatial deposition of the resistive track, weight, heating and cooling times, simplicity of installation, maintenance and use, etc.) and finding with the present solution the best compromise between these factors.

The term "electrically resistive" refers to a material/element capable of providing desired electrical resistance properties in response to an electrical voltage applied to the material/element itself. For example, electrical resistance values can vary from a few dozen Ohms per unit area, up to even 1 Ohm per unit area.

By ?substantially orthogonal? in relation to geometric elements (such as lines, planes, surfaces, etc.) it is meant that such elements form an angle in the range 90?+/-15?, preferably 90?+/-10?.

By ?substantially parallel? in relation to the above geometric elements it is meant that such elements form an angle in the range 0?+/-15?, preferably 0?+/-10?.

The present invention in one or more of the above aspects may exhibit one or more of the following preferred features.

Preferably each heating element comprises an electrically insulating layer adhered to said base body (entirely) on the opposite side to said external surface. Preferably said electrically resistive track is formed on said electrically insulating layer. This improves safety.

Preferably, said machine and/or said molding process are for non-rotational molding (in rotational molding the entire, closed mold is rotated in space during the molding process and the semi-finished product is not subjected to compression against the conformation surface).

Preferably, said heating elements are equal to each other. Preferably, said cooling elements, more preferably called main bodies, are equal to each other. The expression "equal" means that the elements all have the same structure, shape and dimensions (except for manufacturing tolerances). In this way, the production of the heating elements is simplified (e.g. they can be mass-produced), as well as of the mold.

Preferably said base body comprises a first and a second mutually opposite face, where said second face is facing said external surface. Preferably said second face is flat. In this way a desired heat exchange is obtained, without the need, as with cartridge electric resistors, to insert the resistors into special holes.

Preferably, said external surface comprises, for each second face, a corresponding flat region. In the case of an originally non-flat external surface, it is advantageous to obtain (e.g. by milling) said flat region on the external surface. In one embodiment, in correspondence with said flat region the external surface has a seat for housing said base body (e.g. also obtained by milling the external surface).

Preferably, said second face is contained in a recess of said housing seat (in other words, the base body is inserted into the seat without mechanical interference with the walls of the seat itself). In this way, the fixing of the heating element is reversible (i.e. dismantling the element does not damage either the mold or the heating element). Furthermore, the heating element is more easily accessible than cartridge-type electrical resistors. In this way, some problems that may arise with cartridge-type electrical resistors housed in holes are reduced, if not eliminated, such as the risk of damage to the mold during maintenance/replacement of the resistors, the risk of localized stresses in the resistors and/or in the mold due to different thermal expansion between the electrical resistor and the mold, which can cause damage to the resistors and/or the mold and/or localized worsening of the heat exchange.

Preferably a maximum dimension of said base body (more preferably of said second face) is inscribed in a circumference having a diameter greater than or equal to 3 cm, more preferably greater than or equal to 6 cm, and/or less than or equal to 15 cm, more preferably less than or equal to 12 cm. In this way, sufficient space is provided for the track while limiting the overall dimensions of the heating element. Furthermore, in the aforementioned case of a flat region obtained on the external surface to fix the heating element, the aforementioned extension values of the base body limit the variation of the local thickness of the mold body at the second face, improving the heating uniformity. Preferably a minimum distance between each base body and the respective closest base bodies is greater than or equal to one sixth, more preferably greater than or equal to one quarter, even more preferably greater than or equal to one third, of said diameter of the circumference in which the base body is inscribed.

The Applicant has realised that the heating elements included in the machine according to the present invention allow to obtain, even in the case of a small footprint and appropriate spacing between the base bodies (i.e. by adopting a discretisation of the heating action), both a desired heating speed and a desired heating uniformity at the conformation surface, thanks also to the high specific thermal power obtainable (by means of electrical voltage applied to the track).

Preferably said base body is plate-shaped, more preferably with constant thickness. In this way the thermal resistance of the base body is reduced and/or the thermal power is distributed effectively.

Preferably the thickness of the base body is greater than or equal to 1 mm, and/or less than or equal to 3 mm, more preferably less than or equal to 2 mm. In this way the thermal resistance is limited without penalizing the structural robustness.

Preferably the said base body is made of metal material. This facilitates heat exchange.

In one embodiment, the base body is made of ceramic material (and in this case the heating element is preferably without the electrically insulating layer).

Preferably, said base body comprises an opening (e.g. a hole) passing through a substantially central portion thereof, more preferably the base body has a (substantially) annular shape. In this way, the thermal power transferred to the mold at the center of the heating element is reduced (e.g. to reduce the occurrence of hot spots and/or to make the temperature uniform).

In one embodiment, said mold comprises, for each heating element, a relief integral with said external surface and which engages said through opening of the respective heating element. In this way, the positioning of the heating elements is facilitated, which can be fitted onto the respective reliefs.

Preferably, each relief has a plan shape that is counter-shaped to a plan shape of the through opening of the base body of the respective heating element. Preferably, each relief has a plan shape that is free of rotational symmetry about an axis that is (substantially) orthogonal to said external surface. In this way, the base body can be applied to the external surface in one and only one angular position with respect to the relief, further facilitating the application of the heating elements.

Preferably a maximum dimension of said through opening (more preferably a diameter of said hole) is greater than or equal to 1.5 cm, more preferably greater than or equal to 3 cm, and/or less than or equal to 8 cm, more preferably less than or equal to 6 cm. In this way, structural strength and width of the opening are balanced to achieve a desired reduction in the thermal power transferred to the external surface.

Preferably each heating element is based on a thick film heating technology, more preferably a thick film heater. Such technology has proven to be highly versatile and efficient. Preferably said track is printed (e.g. by screen printing, direct-write deposition, ink-jet printing, etc.) on said electrically insulating layer (which is preferably arranged adjacent to said first face of the base body). In this way the track is produced in an industrially simple manner.

Preferably said track is made of a polymer resistive paste (or ink), more preferably comprising an organic matrix and a metal oxide powder dispersed in said matrix. Such resistive pastes have proven to be particularly suitable for making heating elements capable of generating the desired specific thermal power (e.g. thermal power per unit of surface) to heat the mold conformation surface, at low cost, size and/or weight.

Preferably, said track (preferably a single one) substantially covers the entire said first face. This improves the uniformity of heating.

Preferably, said track is substantially two-dimensional. In this way, the dissipation of thermal power into the air at the lateral surfaces (along the thickness) of the track is limited, and/or the overheating and/or the thermal resistance of the track.

Preferably said track has a thickness (in a direction substantially orthogonal to said first face) greater than or equal to 10 ?m, more preferably greater than or equal to 15 ?m, and/or less than or equal to 30 ?m, more preferably less than or equal to 25 ?m. Preferably said track has a width (in a direction substantially parallel to the first face and substantially orthogonal to a main development line of the track) greater than or equal to 1.5 mm, more preferably greater than or equal to 2 mm, and/or less than or equal to 3.5 mm, more preferably less than or equal to 3 mm. In this way the substantially two-dimensional track is created.

Preferably each heating element comprises a first and a second connector arranged in electrical contact (direct or not, for example by means of one or more electrically conductive tracks interposed between the connectors and the electrically resistive track) with said track. In this way the resistive track is powered.

Preferably each heating element comprises a protective (and electrically insulating) layer arranged on said track (opposite the electrically insulating layer). This protects the track (e.g. from dust, water, chemicals, etc.) and/or improves the safety of the heating element.

Preferably, said heating and/or cooling elements are fixed removably and reversibly (i.e. non-destructively) to the external surface. This further simplifies the operations of fixing, maintenance and/or replacement of the elements.

Preferably the main body of the cooling elements is made of metal material (e.g. steel, aluminum, etc.). This encourages heat exchange between the cooling fluid and the mold.

Preferably said main body of each cooling element comprises a thermal contact area with said external surface. Preferably said thermal contact area is flat. In this way a desired heat exchange is obtained. Preferably said external surface comprises, for each thermal contact area, a corresponding flat region. In the case of an external surface that is originally not flat, it is advantageous to obtain (e.g. by milling) the flat region on the external surface.

Preferably, said thermal contact area (possibly developed on a plane if not planar) is inscribed in a circumference having a diameter less than or equal to 50 cm, more preferably less than or equal to 30 cm, even more preferably less than or equal to 20 cm (for example less than or equal to 10 cm or less than or equal to 5 cm).

In this way, by limiting the maximum dimensions of the contact area of the cooling elements, the arrangement of the cooling elements on the external surface is facilitated, even in the presence of an external surface with a complex shape. Furthermore, in the aforementioned case where a flat region is obtained, the aforementioned contact area values limit the variation of the local thickness of the mold walls in correspondence with this region, improving the cooling uniformity.

Preferably a minimum distance between each cooling element and the respective closest cooling elements is greater than or equal to 2.5 cm, more preferably greater than or equal to 6 cm, even more preferably greater than or equal to 10 cm, and/or less than or equal to 20 cm, more preferably less than or equal to 15 cm. In this way the overall number of cooling elements is limited.

The Applicant has in fact surprisingly found that, although the cooling action of each cooling element is spatially localized and the cooling elements are spaced apart from each other (in other words by adopting a discretization of the cooling action), it is possible to obtain, in correspondence with the conformation surface of the mold, a cooling efficiency and/or uniformity sufficient for the purposes of the molding process.

Preferably each cooling element is associated with one and only one respective heating element, more preferably it is arranged in correspondence with the respective heating element, even more preferably it is adjacent to (e.g. in contact with) the respective heating element. In this way the intervention on the mold is rationalized. Preferably said main body of each cooling element is arranged in correspondence with said through opening of the base body of the respective heating element (preferably engaging said through opening). In this way the overall footprint of the two elements is limited and a desired cooling is obtained. Furthermore, the cooling element in this substantially central position of the base body can contribute to limiting the generation of hot spots in the portion of the mold arranged substantially in correspondence with the center of the base body (a portion typically more subject to overheating since it is entirely surrounded by the base body).

Preferably each main body comprises a striking surface shaped to grip (e.g. because it exceeds the through opening) said base body of the respective heating element, in cooperation with said external surface. In this way the heating element is fixed in a constructionally simple way by exploiting the fixing of the cooling element.

Preferably, said striking surface at least partially engages an edge of said through opening of the base body of the respective heating element. In this way, the fixing is rational with the aforementioned reciprocal positioning between two elements.

In one embodiment, said machine comprises a joint layer of thermally conductive material (directly) interposed between said base body of each heating element and said external surface, and/or a further joint layer of thermally conductive material (directly) interposed between said main body of each cooling element and said external surface.

Preferably said joint layer and/or said further joint layer comprises, more preferably is entirely made of, an electrically conductive paste (e.g. loaded with particles of metallic chemical elements to facilitate electrical conduction), more preferably heat-set. The paste in the plastic state (i.e. not yet heat-set), by uniformly filling any surface cavities (e.g. microscopic) of the external surface of the mold and/or of the base body/main body due to the respective surface roughness, allows to improve the mutual contact between the mold and the heating/cooling elements, and consequently the heat exchange.

In one embodiment, said joint layer and/or said further joint layer comprises, more preferably is made entirely of, a graphite sheet. This simplifies installation.

Preferably, said machine comprises a recirculation circuit of said refrigerant fluid connected to said inlet and to said outlet of each main body. Preferably, said recirculation circuit connects the main bodies of the cooling elements in parallel with each other. In this way, the refrigerant fluid enters the cooling elements at substantially the same temperature, encouraging uniformity of cooling.

In one embodiment, said mold comprises a first and a second half-mold. Preferably, each first and second half-mold comprises a respective conformation surface. The union of the respective conformation surfaces typically creates the conformation surface of the mold. For example, the mold is a compression mold equipped with two halves that are counter-shaped and capable of moving toward each other. In one embodiment, said actuation system is structured to move said respective conformation surfaces of said first and second half-mold toward each other to compress said semi-finished product (placed between the respective conformation surfaces).

In one embodiment, compressing said semi-finished product comprises bringing said respective conformation surfaces of said first and second half-molds closer together.

In one embodiment one or both of said respective conformation surfaces are rigid.

In one embodiment, one of said respective conformation surfaces is flexible, more preferably not permeable by a working fluid (in order to exert a compressive force on the semi-finished product by means of the working fluid, applied under pressure and/or sucked in under vacuum, e.g. in the case of vacuum molding).

For example, said actuation system comprises a hermetic chamber structured to house said mold and is structured to increase the pressure of an operating fluid present in said hermetic chamber (e.g. in the case of an autoclave).

In one embodiment, compressing said semi-finished product comprises arranging said semi-finished product in contact with said conformation surface within an airtight chamber and increasing a pressure of a working fluid present in said airtight chamber.

In one embodiment, said first half-mold comprises an elastically deformable membrane that forms at least partially (more preferably substantially internally) said conformation surface of said first half-mold. Preferably, said (rigid) conformation surface of the second half-mold is (substantially) counter-shaped to a final shape to be given to said semi-finished product. Preferably, bringing said conformation surfaces closer together comprises elastically deforming said membrane, e.g. by pressurizing a working fluid, to arrange said membrane in an expansion configuration in which it is elastically expanded towards said second half-mold. In this way, the conformation is simple even in the presence of complex final shapes and/or including undercuts.

Preferably said semi-finished product comprises a material, more preferably selected from the group: thermosetting polymers, thermoplastic polymers, heat-activated adhesives, thermosetting matrix composite materials, thermoplastic matrix composite materials, non-woven fabrics, fabrics. Preferably said process comprises changing a physical state (e.g. from liquid to solid) of said material during said heating and/or said cooling.

Preferably said actuation system is structured to elastically deform said membrane.

In one embodiment, arranging said semi-finished product comprises arranging at least one composite material comprising a plurality of fibres (e.g. carbon, Kevlar, glass or natural fibres) impregnated by a thermosetting matrix. Preferably said composite material comprises, more preferably consists of, one or more sheets of carbon fibre impregnated in a resin matrix, for example epoxy. The conformation of carbon fibre sheets, for example for the production of protective helmets (e.g. for the motorcycle and/or car sector), has proved to be particularly advantageous by the use of the aforementioned heating and cooling elements (as described below).

Preferably cooling said shape surface comprises cooling at least said respective shape surface of said second half-mold. Preferably arranging said semi-finished product comprises laminating said semi-finished product on said respective shape surface of said second half-mold during said cooling. The aforementioned process characteristics are particularly synergic in the presence of the semi-finished product comprising said composite material, since laminating the composite material on the cold second half-mold avoids the risk that the resin begins to reticulate before the lamination has been completed. Heating is performed after the lamination has been completed, so that the entire matrix begins to reticulate at the same time.

Preferably compressing said semi-finished product is performed during said heating. In this way the conformation is effective.

Preferably said cooling said forming surface comprises bringing said forming surface to a temperature between 10?C and 90?C, more preferably between 20?C and 80?C (extremes inclusive). Such temperatures are sufficient to consider a mold cold, for example for safety purposes and/or for process requirements (e.g. temperatures not sufficient to trigger cross-linking of a matrix).

Preferably said heating said forming surface comprises bringing said forming surface to a temperature greater than or equal to 150°C, more preferably greater than or equal to 200°C, and/or less than or equal to 400°C. In this way a wide range of thermosetting matrices can be employed.

Brief description of the figures

- figure 1 shows a schematic plan view of a component of a machine according to the present invention;

- figure 2 shows a schematic perspective view of the component of figure 1;

- Figure 3 shows a schematic sectional view of a portion of a mold of a machine according to an embodiment of the present invention;

- Figures 4 and 5 schematically show two phases of a molding process according to an embodiment of the present invention.

Detailed description of some embodiments of the invention

The features and advantages of the present invention will be further clarified by the following detailed description of some embodiments, presented by way of example and not of limitation of the present invention, with reference to the attached figures (not to scale).

In the figures, the number 999 indicates a molding machine according to the present invention. By way of example (fig. 4 and 5), the machine 999 comprises a mold 99 comprising a first 90 and a second half-mold 91. By way of example, the mold 99 comprises an external surface 92.

For example (fig. 4 and 5) each half-mold 90, 91 comprises a respective shaping surface 50. In detail, for example the first half-mold 90 comprises an elastically deformable membrane 93, which internally creates the shaping surface of the first half-mold 90, and the shaping surface of the second half-mold is shaped counter-shape to the final shape to be given to the formed semi-finished product. For example the second half-mold 91 is in turn divided into two mutually divisible parts (shown identical and specular to each other, fig. 4 and 5) to allow/facilitate the extraction of the thermoformed product.

For example, the machine 999 also comprises an actuation system 94 (shown only schematically in fig. 4 and 5) structured to bring the respective conformation surfaces 50 of the first and second half-molds closer together. For example, the actuation system comprises a pair of actuators structured to close the mold (bringing the first and second half-molds closer together) and a system for circulating a working fluid to elastically deform (expand, compress) the membrane 93.

For example, the machine 999 also comprises a plurality of heating elements 1 which are distinct from each other and removably fixed to the mould 99 in a distributed manner on the external surface 92. In the figures, the heating elements 1 are distributed in an exemplary manner in a substantially homogeneous manner on the external surface of the mould in correspondence with the second half-mould 91 only (lower half-mould).

In other embodiments (not shown), the heating elements can be fixed on the external surface also in correspondence with the first half-mold, and/or different distributions of the heating elements can be provided, for example with areas with a higher density of heating elements to concentrate the thermal power.

In one embodiment (not shown) the mold comprises two or more (e.g. up to four or five) pluralities of heating elements, each plurality being according to the present invention, where the heating elements of each plurality are equal to each other and different (in shape and/or size) from the heating elements of the remaining pluralities. For example, two pluralities of heating elements having a circular plan shape but with different diameters may be provided, and a plurality of heating elements having a rectangular plan shape. The same may apply to the cooling elements described below.

For example, each heating element 1 comprises a plate-like base body 2 (shown in detail in fig. 1 and 2) with a constant thickness of approximately 1.5 mm.

For example, the basic bodies 2 are all spatially separated from each other (fig. 4).

For example, each base body comprises a first 4 and a second face 5 mutually opposite, both flat, the second face 5 facing the external surface 92 (fig. 3).

Advantageously, the external surface may comprise, for each second face, a corresponding flat region (e.g. obtained by milling in the case of an originally non-flat external surface). In one embodiment (not shown), in correspondence with the flat region, the external surface may also present a seat for housing the base body (e.g. also obtained by milling the external surface). Preferably, the second face is contained in a recess of the housing seat.

In an alternative embodiment, not shown, the base body may not be entirely flat but shaped to match the shape of a portion of the external surface 92 intended to accommodate the base body.

For example, each base body is made of thermally conductive metal material, e.g. steel, aluminium.

For example, each heating element has a substantial cylindrical symmetry around an axis of symmetry 109, where each base body has a substantially annular shape with a through opening 3 in correspondence with a substantially central portion of it (for example, the development of the resistive track, the position of the connectors and the plan shape of the through opening are exceptions to the cylindrical symmetry). For example, an external diameter D1 of each base body 2 is equal to approximately 9 cm and a maximum dimension D2 of each through opening 3 (for example, measured in correspondence with the rounded edges of the opening) is equal to approximately 4 cm.

For example, a minimum distance D3 between each base body and the respective closest base bodies is approximately 4 cm (greater than one third of the external diameter D1). For example, each heating element 1 comprises an electrically insulating layer 6 adhered to the base body 2, adjacent to the first face 4, on the opposite side of the external surface 92. Advantageously (not shown), the electrically insulating layer 6 can be printed, laminated, or applied as a coating on the respective base body. In figure 3, the electrically insulating layer 6 is not shown.

For example, each heating element 1 comprises an electrically resistive track 7 printed (e.g. by silkscreening) on the electrically insulating layer 6.

For example (not shown) track 7 is made of a polymer resistive paste, preferably comprising an organic matrix and a metal oxide powder dispersed in the matrix. For example, track 7 is made of a polymer resistive paste of the RS121xx series? marketed by The fresh resistive paste is first deposited on the electrically insulating layer and then subjected to a hardening process (e.g. polymerization) to form the resistive track.

Document US4639391 also describes a resistive paste suitable for making an effective resistive track for the purposes of the present solution. For example, the track 7 is single (i.e. structurally continuous) and substantially covers the entire first face 4.

For example, track 7 is substantially two-dimensional, with a thickness (in a direction substantially orthogonal to the first face 4) equal to approximately 18 pm, and a width (in a direction substantially parallel to the first face 4 and substantially orthogonal to a main development line of the track) equal to approximately 2.5 mm.

For example, each heating element 1 comprises a first 8 and a second connector (only one is shown in Fig. 3) arranged in electrical contact with the track 7. Optionally, each heating element may comprise one or more electrically conductive tracks interposed between the connectors and the electrically resistive track, in order to be able to power the resistive track. The conductive track may also be made by means of molding techniques on the electrically insulating layer 6 and typically comprises particles of a noble metal, for example silver, to facilitate electrical conduction.

For example, figures 1 and 2, each heating element 1 comprises a pair of electrically conductive tracks 70 (of limited length) which provide a pair of electrical contact areas for the two connectors.

In one embodiment, not shown, the connectors can directly contact the resistive track.

For example, each heating element 1 comprises a protective layer 10 (fig.

3) and also electrically insulating, exemplarily arranged on the track 7 on the opposite side to the electrically insulating layer 6.

Each heating element is a thick film heater.

For example, the machine 999 also comprises a plurality of cooling elements 11 that are distinct from each other and fixed removably and reversibly (e.g. by means of a screw 97) to the mould 99 in a distributed manner on the external surface 92 that are spatially separated from each other. The same considerations set out above for the heating elements also apply to the cooling elements with reference to shapes and surface distributions on the mould. For example, each cooling element comprises a main body 111, for example made of metal material (e.g. steel), equipped with an internal chamber 13 having an inlet 14 and an outlet 15 for a cooling fluid (not shown), for example water or oil.

For example, each main body 111 is in thermal contact with the external surface 92 and comprises a thermal contact area 18 with the external surface 92. For example, the thermal contact area 18 is flat with a maximum dimension of approximately 4 cm.

Advantageously, the external surface can include, for each thermal contact area, a corresponding flat region (e.g. obtained by milling in the case of an originally non-flat external surface).

In one embodiment (not shown) the thermal contact area may be shaped counter-to a surface shape of a respective portion of the external surface 92 intended for fixing the element (i.e. the thermal contact area is not entirely flat).

For example, each cooling element 11 is associated with one and only one respective heating element 1 and is arranged in correspondence with the respective heating element 1.

For example, each cooling element 11 engages the through opening 3 of the respective heating element 1 , with the thermal contact area of the cooling element arranged within the through opening 3 of the base body of the respective heating element. For example, the cooling element 11 comprises a contact surface 12 shaped to at least partially engage an edge of the through opening 3 of the base body 2 in cooperation with the external surface 92.

In one embodiment (not shown) the mold comprises, for each heating element, a relief integral (e.g. integral) with the external surface and which engages the through opening of the respective heating element. Preferably each relief has a plan shape counter-shaped to a plan shape of the through opening of the respective heating element, and devoid of rotational symmetry about an axis substantially orthogonal to the external surface. In this embodiment the cooling element is removably fixed to the external surface in correspondence with the relief of the respective heating element (e.g. above the relief), the cooling element having a plan size (at least partially) greater than the plan size of the relief to form the aforementioned abutment surface.

For example, each cooling element 11 has substantial cylindrical symmetry about the central axis 109.

For example, a minimum distance (not shown) between each cooling element and its closest cooling elements is approximately 15 cm.

Preferably the machine comprises a plurality of temperature probes (not shown) applied to the external surface of the mold, where each probe returns a respective signal representative of a local temperature of the external surface. In this way the temperature distribution of the external surface is sampled. Preferably a (specific) heat output generated by a given heating element (or by a given subset of heating elements) is regulated as a function of a signal returned respectively by one or more of the temperature probes arranged with a given spatial relationship to the given heating element. For example, each heating element can provide a specific heat output in the range 15-20 W/cm<2>.

By way of example (not shown) the machine comprises a bonding layer of thermally conductive material directly interposed between the base body of each heating element and the external surface of the mould, and a further bonding layer (not shown) of thermally conductive material directly interposed between each main body and the external surface. By way of example the bonding layer and the further bonding layer are entirely made of a thermoset electrically conductive paste (e.g. such as the type used to make the conductive tracks 70).

Exemplarily (not shown) the machine 999 comprises a refrigerant recirculation circuit connected to the inlet port 14 and the outlet port 15 of each main body 111, the recirculation circuit connecting the cooling elements in parallel with each other.

With reference to figures 4 and 5, they show exemplarily some phases of a moulding process according to a form of the present invention carried out using the 999 machine.

For example, the molding process comprises cooling the conformation surface 50 of the second half-mold 91 by circulating the coolant in the cooling elements. For example, the conformation surface is maintained at a temperature of approximately 20°C.

By keeping the conformation surface 50 cool, it is therefore envisaged to laminate on the conformation surface a semi-finished product 80, exemplarily comprising a composite material consisting of one or more carbon fibre sheets impregnated in an epoxy resin (not shown).

In other embodiments, the sheets may comprise, or be made of, glass fibres, Kevlar fibres, natural fibres.

Once the semi-finished product is rolled, it is then exemplarily envisaged to heat the conformation surface 50 of the second half-mold 91, to a temperature of approximately 160-180°C, sufficient to achieve the cross-linking of the epoxy resin.

During heating, it is exemplarily envisaged to arrange the membrane 93 (e.g. by means of the actuation system and with the use of a pressurized gas) in an expansion configuration to compress the semi-finished product 80 between the first and second half-molds, to conform the semi-finished product.

Once the cross-linking is completed, it is exemplarily foreseen to return the membrane to a rest configuration, open the mold, in particular separate the two halves of the second half-mold 91 to extract the finished product.

By finished product we mean both a product that has completed its production process and is ready to be placed on the market (e.g. possibly after a final packaging phase), and a product intended for one or more further processes. The present invention finds advantageous application in any molding process comprising at least one cooling or heating phase of the mold with the semi-finished product in the mold, in order to subject one or more of the materials of the semi-finished product to a transformation of physical state by the administration or removal of heat, such as for example in the case of thermoplastic polymeric compounds to be softened and/or solidified, thermosetting polymeric compounds to be cross-linked (by heat), heat-activated adhesives to be activated (by heat).

Claims (10)

1. A molding machine (999) comprising: - a mold (99) comprising a shaping surface (50); - an actuation system (94) structured to compress a semi-finished product (80) against said conformation surface (50); - a plurality of heating elements (1) distinct from each other and removably fixed to said mould (99) on an external surface (92) of said mould; - a plurality of cooling elements (11) distinct from each other and removably fixed to said mould (99) on said external surface (92) of said mould; where each heating element (1 ) comprises: - a thermally conductive base body (2) in thermal contact with said external surface (92) of the mold; - an electrically resistive track (7) thermally coupled to said base body (2), where each cooling element (11) is in thermal contact with said external surface (92) of said mold, where each cooling element (11) comprises a main body (111) equipped with an internal chamber (13) having an inlet port (14) and an outlet port (15) for a cooling fluid, and where said base bodies (2) of said heating elements (1) are distributed on said external surface (92) of said mould spatially separated from each other and said main bodies (111) of said cooling elements (11) are distributed on said external surface (92) of said mould spatially separated from each other. 2. Machine (999) according to claim 1, where said heating elements (1) are equal to each other and are fixed removably and reversibly on said external surface (92), where said base body (2) comprises a first (4) and a second face (5) mutually opposed, where said second face (5) is facing said external surface (92), where said second face (5) is flat, where said base body (2) is plate-like, with a thickness greater than or equal to 1 mm, and less than or equal to 3 mm, and where said track (7) substantially covers all of said first face (4). 3. Machine (999) according to any of the preceding claims, wherein a maximum dimension (D1) of said base body (2) is inscribed in a circumference having a diameter greater than or equal to 3 cm, and less than or equal to 15 cm, wherein a minimum distance (D3) between each base body (2) and the respective closest base bodies (2) is greater than or equal to one sixth of said diameter of the circumference in which the base body is inscribed, wherein said base body (2) comprises a through opening (3) in correspondence with a substantially central portion thereof, wherein a maximum dimension (D2) of said through opening (3) is greater than or equal to 1.5 cm, and less than or equal to 8 cm, and wherein said base body (2) has a substantially annular shape. 4. Machine (999) according to claim 3, comprising, for each heating element (1), a relief integral with said external surface (92) and which engages said through opening (3) of the respective heating element (1), where each relief has a plan shape counter-shaped to a plan shape of the through opening (3) of the respective heating element (1), and devoid of rotational symmetry around an axis substantially orthogonal to the external surface (92). 5. Machine (999) according to any of the preceding claims, wherein each heating element (1) comprises an electrically insulating layer (6) adhered to said base body (2) on the opposite side to said external surface (92), wherein said track (7) is printed on said electrically insulating layer (6), wherein said track (7) is made of a polymer resistive paste, comprising an organic matrix and a metal oxide powder dispersed in said matrix, wherein said track (7) is substantially two-dimensional, wherein said track (7) has a thickness greater than or equal to 10 ?m and less than or equal to 30 ?m, and has a width greater than or equal to 1.5 mm and less than or equal to 3.5 mm, and wherein each heating element (1) is based on a thick film heating technology. 6. Machine (999) according to any of the preceding claims, wherein said cooling elements (11) are removably and reversibly fixed on said external surface (92), wherein said main body (111) of each cooling element (11) comprises a thermal contact area (18) with said external surface (92), wherein said thermal contact area (18) is inscribed in a circumference having a diameter less than or equal to 50 cm, and wherein a minimum distance between each cooling element (11) and respective closest cooling elements (11) is greater than or equal to 2.5 cm and less than or equal to 20 cm. 7. Machine (999) according to any of the preceding claims, wherein each cooling element (11) is associated with one and only one respective heating element (1 ), wherein said main body (111 ) of each cooling element (11 ) is arranged in correspondence with a through opening (3) of the base body (2) of the respective heating element (1), wherein each main body (111) comprises a striking surface (12) shaped to engage said base body (2) of the respective heating element (1), in cooperation with said external surface (92), and wherein said striking surface (18) at least partially engages an edge of said through opening (3) of the base body (2) of the respective heating element (1). 8. Machine (999) according to any of the preceding claims, comprising a joint layer of thermally conductive material interposed between each base body (2) and said external surface (92) of said mould, and a further joint layer of thermally conductive material interposed between said main body (111) of each cooling element (11) and said external surface (92) of said mould, and wherein said joint layer comprises an electrically conductive paste, preferably thermoset, or a graphite sheet, 9. Molding process including: - providing a mold (99) comprising a shaping surface (50); - providing a plurality of heating elements (1) distinct from each other and removably fixed to said mold on an external surface (92) of said mold, where each heating element (1) comprises: - a thermally conductive base body (2) in thermal contact with said external surface (92) of the mould, - an electrically resistive track (7) thermally coupled to said base body (2), - providing a plurality of cooling elements (11) which are distinct from each other and removably fixed to said mould (99) in a distributed manner on said external surface (92), where each cooling element (11) is in thermal contact with said external surface (92) of said mould, where each cooling element (11) comprises a main body (111) equipped with an internal chamber (13) having an inlet (14) and an outlet (15) for a cooling fluid, where said base bodies (2) of said heating elements (1) are distributed on said external surface (92) of said mould spatially separated from each other and said main bodies (111) of said cooling elements (11) are distributed on said external surface (92) of said mould spatially separated from each other; - perform the following operations from i) to iii) in any temporal order: i) cooling said conformation surface (50) by circulating said cooling fluid in said cooling elements (11); ii) placing a semi-finished product (80) in contact with said conformation surface (50); iii) heating said conformation surface (50) by creating a passage of electric current in said electrically resistive tracks (7); - with said semi-finished product (80) in contact with said shaping surface (50), compressing said semi-finished product (80) against said shaping surface (50) to shape said semi-finished product (80). 10. The process of claim 9, wherein said mold comprises a first (90) and a second half-mold (91) each comprising a respective shaping surface (50), wherein compressing said semi-finished product (80) comprises elastically deforming a membrane (93) of said first half-mold (90) that at least partially forms said shaping surface (50) of said first half-mold (90) to arrange said membrane (93) in an expansion configuration in which it is elastically expanded towards said second half-mold (91), wherein arranging said semi-finished product (80) comprises arranging at least one composite material comprising a plurality of fibres impregnated by a thermosetting matrix, wherein arranging said semi-finished product (80) comprises laminating said semi-finished product (80) onto said shaping surface (50) of said second half-mold (91) during said cooling, and wherein compressing said semi-finished product (80) is performed during said heating.