Production method for a cylinder head for an internal combustion engine

Abstract

A production method for a cylinder head (1) of an internal combustion engine. The production method includes the following steps: dividing the cylinder head (1) into a main body part (2) and an operation part (3), the main body part (2) having a flame plate constituting the top of each cylinder, and the operation part (3) having a housing of a valve control device; first manufacturing the separate main body part (2) of the cylinder head (1) in a mold (5) by a casting process; and then manufacturing the operation part (3) of the cylinder head (1) by additive manufacturing with layer-by-layer stacking starting from the previously manufactured main body part (2) of the cylinder head (1).

Description

[0001] Cross-reference to related fields

[0002] This application claims the priority of Italian Patent Application No. 102020000014458 filed on June 17, 2020, the entire disclosure of which is incorporated herein by reference. Technical field

[0003] The present invention relates to a production method for a cylinder head of an internal combustion engine. Background art

[0004] Internal combustion engines generally include an engine block having a plurality of cylinders, each cylinder being provided with a corresponding combustion chamber and a corresponding piston, the piston being mechanically connected to a crankshaft so as to transmit the force generated by combustion to the crankshaft. The engine block is provided with at least one cylinder head, which forms the top of the cylinder (i.e., the upper closure of the cylinder) and is designed to accommodate intake and exhaust valves and corresponding control devices (i.e., return springs and camshafts).

[0005] Cylinder heads are currently made of steel (when there is no need to reduce weight) or of lightweight aluminum alloy (in the case of high-performance engines requiring less weight).

[0006] Different techniques can be used to manufacture semi-finished cylinder heads made of lightweight aluminum alloy: traditional solutions (e.g., as described in patent applications WO2005084851A1, DE102009021471A1, US2008017346A1, and DE102014204859A1) are melting processes, such as casting processes using a gravity system or casting processes at low temperatures (which can be die casting or sand casting), but additive manufacturing is currently also recommended as a viable solution because it allows manufacturers to obtain particularly complex and lightweight internal geometries (i.e., having particularly thin wall thicknesses).

[0007] However, it has proven unsatisfactory to use additive manufacturing to manufacture semi-finished cylinder heads made of lightweight aluminum alloy due to the long manufacturing time (and thus high manufacturing costs) resulting from the large size of the cylinder head, and particularly due to the relatively low mechanical resistance of the cylinder head, which can cause cracking in the area near the flame plate.

[0008] Patent application WO2014165734A1 describes a production method for an internal combustion engine piston, which includes two parts that are joined to each other by a connecting member and one of which is manufactured by casting or forging while the other is manufactured by an additive manufacturing process. Summary of the invention

[0009] The object of the present invention is to provide a production method for a cylinder head for an internal combustion engine, which allows a manufacturer to produce a cylinder head that is lightweight and at the same time has sufficient resistance (especially in the area of the flame plate).

[0010] According to the present invention, there is provided a production method for a cylinder head for an internal combustion engine, the production method comprising the following steps:

[0011] Dividing the cylinder head into a main body part having a flame plate constituting the top of each cylinder and an operating part having a housing of a valve control device;

[0012] First, separately produce the main body part of the cylinder head in a mold by a casting process;

[0013] Then, produce the operating part of the cylinder head by additive manufacturing with layer-by-layer stacking starting from the previously produced main body part of the cylinder head.

[0014] The appended claims describe the preferred embodiments of the present invention and form part of this specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will now be described with reference to the drawings showing non-limiting embodiments of the present invention, wherein:

[0016] Figure 1 is a schematic perspective view of a cylinder head of an internal combustion engine according to the present invention;

[0017] Figure 2 is Figure 1 a schematic exploded perspective view of the cylinder head of

[0018] Figure 3 is for manufacturing Figure 1 a schematic view of a production unit for the cylinder head of DETAILED DESCRIPTION

[0019] In Figure 1 the reference numeral 1 as a whole denotes the cylinder head of the internal combustion engine.

[0020] The cylinder head 1 forms the top of the cylinder of the internal combustion engine (i.e., the upper closure of the cylinder) and thus has a flame plate constituting the top of each cylinder; in addition, the cylinder head 1 is designed to accommodate the intake valve and the exhaust valve and the corresponding control devices (i.e., the return spring and the camshaft), so there is a housing for the intake valve and the exhaust valve and a housing for the valve control device in the cylinder head 1.

[0021] According to Figure 2, in the initial step (i.e., during the design phase), the cylinder head 1 is divided into a main body portion 2 having a flame plate forming the top of each cylinder and an operating portion 3 having a housing for valve control devices. In the cylinder head 1, these two portions 2 and 3 are permanently and inseparably connected to each other, i.e., the two portions 2 and 3 cannot be separated without damaging and cutting the cylinder head 1.

[0022] In the main body portion 2 of the cylinder head 1, there is a region of the combustion chamber where, after machining, the final surface will face the region where combustion occurs; therefore, the required material should locally exhibit very high mechanical and stress resistance.

[0023] In the operating portion 3 of the cylinder head 1, there is a region of the camshaft where the component design typically includes cavities and circuits with specific shapes, which are necessary for lubrication and cooling circuits; therefore, in the operating portion 3 of the cylinder head 1, the necessary features are basically lightweight and geometric complexity.

[0024] In Figure 3 , the reference numeral 4 as a whole represents a production plant designed to produce the cylinder head 1.

[0025] The production plant 1 includes a casting station S1 provided with a casting table (i.e., a die-casting machine), and the casting table includes a mold 5 that can be opened and negatively reproduces the shape of the separate main body portion 2 of the cylinder head 1. In the casting station S1, the separate main body portion 2 of the cylinder head is manufactured by a casting process, such as gravity or low-pressure casting in the mold 5; that is, a supply device supplies a predetermined amount of molten metal into the mold 5, which forms the main body portion 2 of the cylinder head 1 by hardening in the mold 5. Subsequently, after the molten metal hardens, the mold 5 is opened to remove the main body portion 2 of the cylinder head 1 in a semi-finished state. After removing the main body portion 2 of the cylinder head 1 in a semi-finished state from the mold 5, the excess parts (i.e., the residues of the casting process, such as risers and burrs) are removed.

[0026] The production plant 1 includes a processing station S2 provided with an industrial furnace 9, where the main body portion 2 of the cylinder head 1 is subjected to thermal quenching and aging treatment (before starting the operation of manufacturing the operating portion 3 of the cylinder head 1 by additive manufacturing as described below).

[0027] The production plant 1 includes a machining and installation station S3, where the main body portion 2 of the cylinder head 1 in a semi-finished state is machined by a machine tool 6 (this machining is carried out after the heat treatment in the processing station S2); in particular, first, the lower surface 7 of the main body portion 2 (as Figure 2 shown) is leveled by machining with a mechanical deburring machine, so that the lower surface 7 can obtain a predetermined surface roughness, and then the upper surface 8 of the main body portion 2 (as Figure 2As shown, it is parallel and opposite to the lower surface 7) and is leveled by machining with a mechanical deburring machine, thereby allowing the upper surface 8 to obtain a predetermined surface roughness.

[0028] Before starting the operation part 3 of manufacturing the cylinder head 1 by additive manufacturing described below, the lower surface 7 of the main body part 2 is leveled by machining with a mechanical deburring machine (for example, by milling), thereby allowing the lower surface 7 to obtain a relatively small predetermined surface roughness.

[0029] According to a preferred embodiment, during the machining of the main body part 2, the machining and installation station S3 allows geometric references (for example, holes or threaded holes passing through the lower surface 7 of the main body part 2) to be obtained in the main body part 2.

[0030] After the machining (including forming geometric references) of the lower surface 7 of the main body part 2 is completed, the main body part 2 of the cylinder head 1 is coupled to the adjusted support plate 10, and this support plate constitutes a position reference for subsequent additive manufacturing; that is, the main body part 2 of the cylinder head 1 is placed and constrained in a predetermined position on the support plate 10. Obviously, the lower surface 7 of the main body part 2 is in direct contact with the support plate 10, so the lower surface 7 of the main body part 2 should preferably be flat (due to the previous machining), so as to make the coupling between the main body part 2 and the support plate 10 more stable. According to a feasible embodiment, the support plate 10 has impact bodies, which project vertically from the support plate 10 and are designed to engage with corresponding cavities (consistent or inconsistent with the previously formed geometric references) available in the main body part 2 of the cylinder head 1; in this way, a better and more stable coupling between the main body part 2 and the support plate 10 is ensured.

[0031] The geometric references obtained in the main body part 2 (especially passing through the lower surface 7 of the main body part 2) help and improve (make it more precise) the coupling between the main body part 2 and the support plate 10.

[0032] After the main body part 2 is fixed on the support plate 10 and before starting the operation part 3 of manufacturing the cylinder head 1 by additive manufacturing described below, the upper surface 8 of the main body part 2 is leveled by machining with a mechanical deburring machine (for example, by milling), thereby allowing the upper surface 8 to obtain a predetermined surface roughness, which can be relatively small or not too small, so as to improve the subsequent adhesion of the operation part 3 of the cylinder head 1. That is, generally speaking, the surface roughness of the upper surface 8 is greater than that of the lower surface 7, because the lower surface 7 should be firmly attached to the support plate 10, and the operation part 3 of the cylinder head 1 should be printed on the upper surface 8 by additive manufacturing.

[0033] In other words, between the machining of the lower surface 7 of the main body 2 and the machining of the upper surface 8 of the main body 2, the main body 2 is fixed to the support plate 10 by placing the lower surface 7 of the main body 2 on the support plate 10. According to a different embodiment, the machining of the lower surface 7 of the main body 2 and the machining of the upper surface 8 of the main body 2 are both carried out before the main body 2 is fixed to the support plate 10 by placing the lower surface 7 of the main body 2 on the support plate 10 (obviously, for the subsequent printing process by additive manufacturing, it is necessary to ensure proper flatness).

[0034] The production plant 1 includes a measurement station S4 provided with a three-dimensional scanner 11, which performs a three-dimensional scan of the main body 2 (which is fixed to the support plate 10) (before starting the operation section 3 of manufacturing the cylinder head 1 by additive manufacturing described below) to obtain the actual three-dimensional contour of the main body 2; that is, due to the three-dimensional scan, the actual dimensions and shape of the main body 2 can be the net construction tolerance reconstructed. The design of the operation section 3 is preferably adjusted (such as heating and / or deforming) according to the actual three-dimensional contour of the main body 2; obviously, the adjustment is limited and the adjustment amount is less than a few millimeters, but these adjustments have achieved an almost perfect coupling between the main body 2 of the cylinder head 1 and the operation section 3 of the cylinder head 1 anyway.

[0035] The production plant 1 includes a filling station S5, where the main body 2 (which is fixed to the support plate 10) is inserted into a cup-shaped container 12, which is open at the top and has a (substantially) parallelepiped shape; the support plate 10 preferably constitutes the base of the container 12 (defining the container 12 at the bottom), that is, the container 12 is obtained by coupling the support plate 10 to four vertical side walls. The dimensions of the container 12 are set to accommodate the main body 2 with a small clearance inside, that is, to try to minimize the blank volume remaining inside the container 12 after inserting the main body 2. Before and after starting the operation section 3 of manufacturing the cylinder head 1 by additive manufacturing described below, all the holes or cavities opened in the upper surface 8 of the main body 2 are filled with metal powder 13, which is the same as the metal powder 13 to be used for the subsequent additive manufacturing; the function of the container 12 is to laterally hold the metal powder 13 for filling all the holes or cavities opened in the upper surface 8 of the main body 2.

[0036] Basically, there is only a powder bed 13 (flush with the upper surface 8 of the main body 2) outside the filling station S5, on which layer-by-layer deposition can be carried out by additive manufacturing.

[0037] According to a feasible embodiment, the filling of the powder 13 in the filling station can be carried out in a controlled (modified) atmosphere, in which air is replaced by an inert gas (such as argon).

[0038] Manufacturing plant 1 includes an additive manufacturing station S6 with an additive manufacturing machine 14 that operates according to an additive manufacturing process called PBF (“powder bed fusion”), so it uses thermal energy to melt specific points in a previously deposited layer of metal powder 13; in particular, the thermal energy generated by a laser source melts the metal powder 13, which solidifies upon cooling and thereby fabricates each part of the operating portion 3. Thus, the fabrication of the operating portion 3 starts from the layer design and obtains the final shape through a process of repeating layer by layer. After the fusion of one layer (horizontally), the build platform that houses the support plate 10 is lowered, a recoater deposits a new layer of metal powder 13 and the procedure is repeated.

[0039] The body portion 2 of the cylinder head 1 (which is fixed to the support plate 10, housed in the container 12 and filled with powder 13) is inserted into the additive manufacturing machine 14, so as to fabricate the operating portion 3 of the cylinder head 1 through additive manufacturing by stacking metal powder 13 layer by layer starting from the previously fabricated body portion 2 of the cylinder head 1; that is, the operating portion 3 of the cylinder head 1 is constructed layer by layer directly on top of the body portion 2 (which has been previously made by casting). In this regard, it should be noted that the additive manufacturing called PBF cannot add a powder layer 13 onto voids, so all the holes and cavities opened in the upper surface 8 of the body portion 2 are temporarily filled with metal powder 13 beforehand: in this way, the body portion 2 (temporarily) has a solid and flat surface in which the operating portion 3 of the cylinder head 1 can be constructed layer by layer.

[0040] The container 12 may include filling elements that project from the support plate 10 or the side walls (i.e., project towards the interior of the container 12) and negatively reproduce the external shape of the body portion 2 of the cylinder head 1, thereby reducing the amount of powder 13 required to fill the container 12 (ideally, completely avoiding filling with metal powder 13 before starting the additive manufacturing process). These filling elements (which are mounted on the support plate 10 or the side walls of the container 12) may also be movable (move in a single direction or in different directions perpendicular to each other), so as to approach or move away from the body portion 2 of the cylinder head 1 arranged within the container 12; the function of the movement of the filling elements is both to allow the body portion 2 to be inserted into or removed from the container 12 (i.e., the filling elements move away to form the “manipulation space” required for the movement of the body portion 2), and also to be able to compensate for the construction tolerances of the body portion 2 (i.e., adapt to a body portion 2 that is slightly larger or smaller compared to the conventional dimensions).

[0041] It should be noted that the body portion 2 of the cylinder head 1 can be designed to avoid (or at least limit) the presence of holes or cavities opened in the upper surface 8, thus simplifying the subsequent construction of the operating portion 3.

[0042] In the preferred but non-limiting embodiment shown in the figures, an additive manufacturing process called PBF that requires the use of metal powder 13 is used; according to other embodiments, other additive manufacturing processes that do not require the use and provision of the technical powder 13 can also be used, such as an additive manufacturing process called BIM ("Binder Injection Molding"), an additive manufacturing process called MIM ("Metal Injection Molding"), or an additive manufacturing process called LC ("Laser Cladding"). Obviously, since the additive manufacturing process called PBF is no longer used, it is no longer necessary to provide the container 12 and the metal powder 13 (and thus it is no longer necessary to provide the filling station S5 and the cleaning station S7).

[0043] The production plant 1 includes a cleaning station S7 provided with a cleaning machine 15: after the manufacturing of the operation part 3 is completed, the cylinder head 1 is completed, removed from the container 12, removed from the support plate 10 and inserted into the cleaning machine 15 for cleaning, in particular to remove the powder 13 deposited for the printing of the operation part 3 and the powder 13 previously used to temporarily close all the holes or cavities opened in the upper surface 8 of the main body part 2. The cleaning machine 15 uses suction to remove the powder 13, but it can also perform the final cleaning of the cylinder head 1 by sandblasting, ultrasonic or chemical cleaning. Obviously, possible printing supports should be removed (manually or automatically) before cleaning (sandblasting) the cylinder head 1.

[0044] The production plant 1 may also include a processing station S8 provided with an industrial furnace 16, in which the cylinder head 1 (which now completely has parts 2 and 3) undergoes a stress-relieving annealing heat treatment.

[0045] After the (possible) processing station S8, the cylinder head 1 is ready for different quality controls and subsequent machining required to obtain the final product.

[0046] According to a feasible embodiment, before starting the manufacturing of the operation part 3 of the cylinder head 1 by additive manufacturing (and in particular immediately before the filling station, that is, before adding the powder 13 to the main body part 2), the upper surface 8 of the main body part 2 can be deoxidized, that is, a chemical treatment is carried out to remove all surface oxides from the upper surface 8 of the main body part 2. The purpose of this deoxidation of the upper surface 8 of the main body part 2 is to improve the adhesion of the initial layer of the operation part 3 to the upper surface 8 of the main body part 2.

[0047] According to a feasible embodiment, before starting the manufacturing of the operation part 3 of the cylinder head 1 by additive manufacturing (and in particular when the main body part 2 is already inside the additive manufacturing machine 14), the upper surface 8 of the main body part 2 can be heated, for example, using an infrared lamp; the purpose of this heating of the upper surface 8 of the main body part 2 is to improve the adhesion of the initial layer of the operation part 3 to the upper surface 8 of the main body part 2.

[0048] According to a feasible embodiment, the main body portion 2 of the cylinder head 1 is manufactured by gravity casting using a first metal alloy (usually an aluminum-based alloy, such as A354 or A356 alloy), and the operating portion 3 of the cylinder head 1 is manufactured by additive manufacturing using a second metal alloy (usually an aluminum-based alloy, such as A6061, AlSi9Cu3 or AlSi10Mg alloy), which is different from and compatible with the first metal alloy (i.e., can firmly adhere to the first metal alloy and has the same thermal expansion as the first metal alloy in use). In this way, each metal alloy can be optimized for the stresses it will undergo in use; in fact, the main body portion 2 of the cylinder head 1 undergoes greater mechanical and thermal stresses from the combustion occurring in the cylinder during use (the main body portion 2 of the cylinder head 1 forms the top of the cylinder due to its inclusion of a flame plate), while the operating portion 3 of the cylinder head 1 undergoes much smaller mechanical and thermal stresses in use.

[0049] According to a different embodiment, the portions 2 and 3 of the cylinder head 1 are made of the same metal alloy (usually an aluminum-based alloy).

[0050] The embodiments described herein can be combined with each other without thereby exceeding the scope of protection of the present invention.

[0051] The above production methods have different advantages.

[0052] First of all, the above production method allows the manufacturer to obtain a cylinder head 1 that is very lightweight and at the same time highly resistant. This is because the main body portion 2 of the cylinder head 1 is manufactured by a traditional casting process, which ensures a high level of resistance (in addition, the main body portion 2 of the cylinder head 1 does not particularly benefit from being manufactured by additive manufacturing, because due to its need to resist greater mechanical and thermal stresses, it requires thicker walls and less complex geometries), while the operating portion 3 of the cylinder head 1 is manufactured by additive manufacturing, which allows for very complex geometries and smaller thicknesses for maximum light weighting.

[0053] In addition, using the casting process to manufacture parts that are much smaller than normal (i.e., the separate main body portion 2 of the cylinder head 1, which is approximately slightly larger than half of the total volume of the cylinder head 1) results in much higher mechanical resistance in the main body portion 2 of the cylinder head; in fact, by reducing the amount of molten metal to be fed into the mold 5, the solidification time is reduced, thus increasing the final mechanical resistance.

[0054] In other words, the above production method better combines the advantages (i.e., strengths) of two production techniques (casting and additive manufacturing) and eliminates the deficiencies (i.e., weaknesses) of these two production techniques.

[0055] In fact, casting is an ideal production technology for manufacturing the main body portion 2 of the cylinder head 1, because it ensures high mechanical characteristic values even at high temperatures. On the other hand, additive manufacturing is an ideal production technology for manufacturing the operating portion 3 of the cylinder head 1, because it ensures complex and lightweight geometries compared to traditional designs and for casting wall portions for different cores with very limited thickness and difficult to obtain; in addition, in order to obtain these geometries during the casting process, complex and difficult-to-control operations called "die making" and "core assembly" are required, that is, operations of filling and removing sand molds by equipment, and these sand molds are then assembled to obtain the "negative shape" of the desired shape.

[0056] In addition, manufacturing the separate operating portion 3 of the cylinder head 1 by additive manufacturing (which is a slow production technology, and the larger the part to be manufactured, the slower the technology) takes longer to produce the cylinder head 1 compared to production by separate casting, but this time is not overly long.

[0057] The operating portion 3 made by additive manufacturing is preferably designed initially for the purpose of lightening and optimizing the printing process (so-called "designed for additive manufacturing"), thus reducing the printing time, reducing the overall weight of the product, and optimizing the production process. In fact, by designing the operating portion 3 based on additive manufacturing, it is possible to minimize from the start the support brackets of the molten powder that are missing in the composition required for the printing process (i.e., the materials discarded and removed during the product cleaning phase).

[0058] Finally, the above production method can be implemented simply and economically because it only uses commercial production and processing technologies.

[0059] List of reference numerals

[0060] 1 Cylinder head

[0061] 2 Main body portion

[0062] 3 Operating portion

[0063] 4 Production plant

[0064] 5 Die

[0065] 6 Machine tool

[0066] 7 Lower surface

[0067] 8 Upper surface

[0068] 9 Industrial furnace

[0069] 10 Support plate

[0070] 11 3D scanning

[0071] 12 Container

[0072] 13 Powder

[0073] 14 Additive manufacturing machine

[0074] 15 Cleaning machine

[0075] 16 Industrial furnace

[0076] S1 Foundry station

[0077] S2 Processing station

[0078] S3 Machining and installation station

[0079] S4 Measuring station

[0080] S5 Filling station

[0081] S6 Additive manufacturing station

[0082] S7 Cleaning station

[0083] S8 Processing station

Claims

1. A production method for a cylinder head (1) of an internal combustion engine, the production method comprising the following steps: Dividing the cylinder head (1) into a main body part (2) and an operating part (3), the main body part (2) having a flame plate constituting the top of each cylinder, and the operating part (3) having a housing for valve control means; Firstly, manufacturing the separate main body part (2) of the cylinder head (1) in a mold (5) by a casting process; Then, manufacturing the operating part (3) of the cylinder head (1) by additive manufacturing with layer-by-layer superposition starting from the previously manufactured main body part (2) of the cylinder head (1).

2. The production method according to claim 1, wherein: The operating part (3) of the cylinder head (1) is manufactured by an additive manufacturing process called PBF by layer-by-layer superposition of metal powder (13); Before starting to manufacture the operating part (3) of the cylinder head (1) by additive manufacturing, an additional step is provided of filling all the holes or cavities opened in the upper surface (8) of the main body part (2) by using the same metal powder (13) used in additive manufacturing.

3. The production method according to claim 2, which includes an additional step of removing the metal powder (13) remaining in the main body part (2) of the cylinder head (1) and the metal powder (13) deposited during subsequent printing processes after manufacturing the operating part (3) of the cylinder head (1) by additive manufacturing.

4. The production method according to claim 2, which includes an additional step of inserting the main body part (2) into a cup-shaped container (12) before starting to manufacture the operating part (3) of the cylinder head (1) by additive manufacturing, the cup-shaped container being open at the top and laterally accommodating the metal powder (13) for filling all the holes or cavities opened in the upper surface (8) of the main body part (2).

5. The production method according to claim 4, which includes an additional step of placing and bonding the main body part (2) onto a support plate (10) before starting to manufacture the operating part (3) of the cylinder head (1) by additive manufacturing, the support plate being a position reference for additive manufacturing and defining the container (12) at the bottom.

6. The production method according to claim 4, wherein, The container (12) includes at least one filling element that protrudes towards the inside of the container (12) and negatively reproduces the external shape of the main body part (2) of the cylinder head (1), thereby reducing the amount of the metal powder (13) required to fill the container (12).

7. The production method according to claim 6, wherein, The filling element is movable relative to the container (12) so as to approach or move away from the main body part (2) of the cylinder head (1) placed inside the container (12).

8. The production method according to claim 1, which includes an additional step of leveling the upper surface (8) of the main body part (2) by machining with a mechanical deburring machine before starting to manufacture the operating part (3) of the cylinder head (1) by additive manufacturing, so as to allow the upper surface (8) to obtain a predetermined surface roughness.

9. The production method according to claim 1, which includes an additional step of deoxidizing the upper surface (8) of the main body portion (2) before starting the operation of manufacturing the operation portion (3) of the cylinder head (1) by additive manufacturing.

10. The production method according to claim 1, which includes an additional step of heating the upper surface (8) of the main body portion (2) before starting the operation of manufacturing the operation portion (3) of the cylinder head (1) by additive manufacturing.

11. The production method according to claim 1, which includes the following additional steps before starting the operation of manufacturing the operation portion (3) of the cylinder head (1) by additive manufacturing: performing a 3D scan on the main body portion (2) to obtain the actual 3D contour of the main body portion (2); and adjusting the design of the operation portion (3) according to the actual 3D contour of the main body portion (2).

12. The production method according to claim 1, which includes an additional step of placing and bonding the main body portion (2) of the cylinder head (1) onto a support plate (10) before starting the operation of manufacturing the operation portion (3) of the cylinder head (1) by additive manufacturing, the support plate being a position reference for additive manufacturing.

13. The production method according to claim 12, wherein, The support plate (10) has impact bodies that project vertically from the support plate (10) and are designed to engage corresponding cavities present in the main body portion (2) of the cylinder head (1).

14. The production method according to claim 12, which includes an additional step of leveling the lower surface (7) of the main body portion (2) by machining with a mechanical deburring machine before placing and bonding the main body portion (2) of the cylinder head (1) onto the support plate (10), thereby allowing the lower surface (7) to obtain a predetermined surface roughness.

15. The production method according to claim 12, which includes an additional step of forming geometric references in the main body portion (2) of the cylinder head (1) for coupling the main body portion (2) to the support plate (10), the geometric references being in particular holes or threaded holes opened in the lower surface (7) of the main body portion (2).

16. The production method according to claim 1, which includes an additional step of subjecting the main body portion (2) of the cylinder head (1) to thermal quenching and aging treatment before starting the operation of manufacturing the operation portion (3) of the cylinder head (1) by additive manufacturing.

17. The production method according to claim 1, which includes an additional step of subjecting the cylinder head (1) to stress-relieving annealing heat treatment after manufacturing the operation portion (3) of the cylinder head (1) by additive manufacturing.

18. The production method according to claim 1, wherein the main body portion (2) of the cylinder head (1) is manufactured by casting using a first metal alloy, and the operation portion (3) of the cylinder head (1) is manufactured by additive manufacturing using a second metal alloy different from the first metal alloy.

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