Marine vermicular iron cylinder cover forming process based on 3D printing

Abstract

The invention provides a molding process for a marine vermicular iron cylinder cover based on 3D printing, and belongs to the technical field of metal casting molding. Comprising the following steps that a three-dimensional model is drawn based on a cylinder cover blank three-dimensional model, a 3D printing sand mold three-dimensional model is drawn on the basis of the three-dimensional model, and all sand mold cores are integrated to be divided into an upper-layer mold core structure, a middle-layer mold core structure and a lower-layer mold core structure; printing each mold core according to the model segmented in the step 1) by using a 3D printer; a chilling block, a core bar and an auxiliary sand core are installed at the corresponding positions of the mold core; after installation, the three layers of mold cores are subjected to dip-coating, drying in the shade and drying; and after drying, assembling layer by layer according to a bottom-middle-top sequence, and pressing a weight for pouring to obtain the required cylinder cover casting. The cylinder cover of a complex structure is treated through three-layer parting, the 3D printing technology and various auxiliary technological means are combined, and the problems that according to an inner cavity water jacket of the vermicular graphite cast iron cylinder cover of the marine medium-speed diesel engine, bonded sand in a skin seam is difficult to clean, and a 3D printing sand core is fractured are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of metal casting and forming, and specifically relates to a forming process of a marine vermicular cast iron cylinder head based on 3D printing. Background Art

[0002] As one of the key parts of marine medium-speed diesel engines, the cylinder head has a complex internal structure and an extremely irregular shape, especially the shape of the water cavity. The wall thickness of the casting is uneven, and the air tightness and overall strength requirements are very high, making it very difficult to cast.

[0003] In general, with traditional processes, vermicular graphite cast iron cylinder heads are produced by opening cold core metal molds. The sand core structure is complex and numerous, usually about 20 sand cores and upper and lower models; the production cycle is long and the cost is high. If there is a local adjustment or change in the process, it is difficult to change the mold; because the sand core is divided into multiple parts, it is difficult to clean the sand stuck in the seam of the water jacket in the inner cavity of the cylinder head. Manual repair of sand molds and manual assembly of sand cores are difficult due to the large number of people, and the cylinder head is prone to defects such as sand inclusion and water leakage; the production process requires a large number of skilled workers and a high level of skill, and the molders are seriously aging and gradually sluggish, which seriously affects production capacity. Description of the current status and characteristics of the cylinder head produced by traditional processes: The traditional process of the vermicular graphite cast iron cylinder head for a medium-speed marine diesel engine is cited. For details of the sand core division process structure layout, see Figure 23-27 As shown, Fig.23 The figure shows the top view of the cylinder head inner cavity and the outer skin core on the side. Fig.24 The figure shows the bottom view of the cylinder head inner cavity and the side outer skin core. Fig.25 The figure shows that the gap between the upper and lower water jacket sand cores forms a seam that is difficult to clean. Fig.26 The figure shows the top view of the lower sand mold. Fig. 27 The top view of the cover core is shown, which includes 27 types of sand cores, 33 in total, and upper and lower outer mold sand molds, a total of 35 sand mold and sand core units. In the past, the use of 3D printed sand molds to produce marine medium-speed diesel engine cylinder heads failed due to the lack of the idea of ​​overall design and overall dipping, and the sand core integration was not high. The weak parts of the inner water jacket sand core broke. In recent years, with the gradual maturity of the application of 3D printed sand molds in casting, there is an urgent need for a new 3D printing process method with the characteristics of no skin seams in the inner water channel of the cylinder head, the sand core can be designed with core bones to avoid sand core breakage, high sand core integration, simple and efficient process production process, low cost, and stable quality. Therefore, improvements are proposed. Summary of the invention

[0004] Technical problem solved by the invention: The purpose of the invention is to provide a molding process based on 3D printing of marine vermicular cast iron cylinder heads. By processing the cylinder head with complex structure through three-layer parting, combined with 3D printing technology and various auxiliary process means, the problems of sand sticking to the seams of the inner water jacket of the marine medium-speed diesel engine vermicular cast iron cylinder head being difficult to clean and the 3D printed sand core being broken are solved, thereby achieving the purpose of simple and efficient production process of the marine medium-speed diesel engine vermicular cast iron cylinder head, short production cycle and stable casting quality.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A forming process of a marine vermicular cast iron cylinder head based on 3D printing, comprising the following steps:

[0007] Step 1): Based on the 3D model of the cylinder head blank, draw a 3D model, draw a 3D printing sand mold 3D model based on the 3D model, integrate all the sand mold cores, and divide them into three layers of core structure: upper, middle and lower;

[0008] Step 2): using a 3D printer to print each core according to the model segmented in step 1);

[0009] Step 3): Install the chill, core bone and auxiliary sand core at the corresponding position of the core;

[0010] Step 4): After installation, the three layers of core are dipped, dried in the shade, and baked;

[0011] Step 5): After drying, assemble layer by layer in the order of bottom, middle and top, press on the weight for pouring, and obtain the required cylinder head casting.

[0012] Further limiting the above scheme, the three core layers are: an upper core, a middle core and a lower core;

[0013] The upper core is a cylinder head casting shape including a cover plate core, a riser core, the entire overflow groove core, an upper half core of a cylinder head bolt hole, and a gas outlet rod core;

[0014] The middle-layer core integrates the upper and lower water jacket cores of the cylinder head inner cavity, the safety valve hole core, the starting valve core, all the side panel outer skin sand cores, and the intake and exhaust duct cores, and arranges the exhaust hole core, the core bone installation hole, and the core bone placement groove at the corresponding position of the inner cavity sand core, and at the same time makes an auxiliary sand core for filling the core bone placement groove.

[0015] The lower core comprises a cylinder head bottom core, a cylinder head bolt hole lower core, an injector hole core and an inner runner; and a dark chiller hole reserved for installing a cylindrical chiller is arranged in the injector hole core;

[0016] A toilet-type vortex pouring cup is also provided to prevent dirty molten iron from entering the mold cavity.

[0017] To further limit the above scheme, a circle of anti-fire escapement positioning stop and a circle of anti-fire escapement semicircular groove are set on the matching surfaces between the three layers of cores; core head positioning and observation windows are also set on the matching surfaces of the three layers of cores.

[0018] To further limit the above scheme, repair glue is applied to the back and sides of the working surface of the cylindrical cold iron for installation, and the assembly clearance of the cylindrical cold iron is 0.2mm~0.5mm; the installation clearances of the core bone mounting hole, the core bone placement groove and the ductile iron core bone, and the auxiliary sand core for filling the hole groove are all 0.2mm~0.3mm. During installation, the repair glue is evenly applied to the mating surface. After installation, the extruded glue is wiped off and the glue is applied fully to ensure that the repair glue fills the gap.

[0019] To further limit the above scheme, when the assembled upper core, middle core, lower core and pouring cup are dip-coated, a water-based paint with good leveling property and a Baume degree of 30 to 40 is used; and the paint is dried in the shade for 24 hours.

[0020] As a further limitation of the above scheme, all cores are dried in a surface drying kiln at a temperature of 150° C. to 200° C. for 40 to 60 minutes.

[0021] Further limitation of the above scheme is that when assembling the core after drying, first poke open and remove the 2mm thick diaphragm sand sheet on the top surface of the injection hole of the lower core, fill φ1~φ2 grinding steel shot into the dark cold iron hole and compact it, do not fill it up, and fill the reserved 25mm~30mms deep cavity with resin sand and do not brush alcohol-based paint;

[0022] Install the lower, middle and upper cores, pouring cups and weight stacks in sequence. After installation, poke open the 2mm thick diaphragm sand sheets of all vent holes and use compressed air to clean the loose sand remaining in the vent holes.

[0023] The advantages of the present invention compared with the prior art are:

[0024] 1. This solution uses 3-layer parting to process the cylinder head with complex structure, combined with 3D printing technology and various auxiliary process means, to solve the problems of difficulty in cleaning the sand sticking to the seam of the inner water jacket of the marine medium-speed diesel engine vermicular cast iron cylinder head and the breakage of the 3D printed sand core, greatly reducing the number of sand cores, integrating all the inner sand cores and side outer sand cores of the cylinder head into the middle core, and setting the core bone installation at the local thin neck weak part of the water jacket, which increases the structural strength of the casting sand core, almost avoids the positioning error of the sand core assembly and improves the casting accuracy; no mold is required to speed up the process debugging progress; the purpose of simple and efficient production process of marine medium-speed diesel engine vermicular cast iron cylinder head, short production cycle and stable casting quality is achieved;

[0025] 2. In this solution, the upper and lower water jacket cores are integrated into one, which can effectively avoid the formation of skin seams in the water jacket and reduce the difficulty of cleaning;

[0026] 3. In this scheme, a vent hole with a curved shape is set at the center of the sand core, which is conducive to the exhaust of the sand core; a concentric marked countersunk hole and a 2mm thick diaphragm are set on its end face to facilitate the dipping operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of a three-dimensional model of a cylinder head in the present invention;

[0028] Figure 2 The structure of the upper core of the present invention is shown in FIG. Figure 1 ;

[0029] Figure 3 The structure of the upper core of the present invention is shown in FIG. Figure 2 ;

[0030] Figure 4 The structure of the middle core of the present invention is shown in FIG. Figure 1 ;

[0031] Figure 5 The structure of the middle core of the present invention is shown in FIG. Figure 2 ;

[0032] Figure 6 It is a front view structural diagram of the middle layer core of the present invention;

[0033] Figure 7 For the present invention Figure 6 A magnified schematic diagram of the structure of the middle part II;

[0034] Figure 8 For the present invention Figure 7 AA structural diagram in FIG.

[0035] Fig. 9 For the present invention Figure 6 A magnified schematic diagram of the structure of the middle part III;

[0036] Fig.10 For the present invention Fig. 9 Schematic diagram of the BB structure;

[0037] Fig.11 It is a structural schematic diagram of the core bone installation groove of the present invention;

[0038] Fig.12 It is a side view structural diagram of the middle layer core of the present invention;

[0039] Fig.13 For the present invention Fig.12 Schematic diagram of CC structure;

[0040] Fig.14 For the present invention Fig.13 A magnified schematic diagram of the structure of part IV;

[0041] Fig.15 The structure of the lower core of the present invention is shown in FIG. Figure 1 ;

[0042] Fig.16 The structure of the lower core of the present invention is shown in FIG. Figure 2 ;

[0043] Fig.17 It is a cutaway structural diagram of the lower layer core of the present invention;

[0044] Fig.18 For the present invention Fig.17 A magnified schematic diagram of the structure of Part I;

[0045] Fig.19 A bottom view of the pouring cup of the present invention;

[0046] Fig. 20 A top view of the pouring cup of the present invention;

[0047] Fig.21 It is a three-dimensional structural diagram of the pouring cup in the present invention;

[0048] Fig. 22 This is an assembly diagram of the core in the present invention;

[0049] Fig.23 It is a top view of the inner cavity and the outer skin core of the cylinder head in the prior art;

[0050] Fig.24 It is a bottom view of the inner cavity and the outer skin core of the cylinder head in the prior art;

[0051] Fig.25 It is a diagram of the upper and lower water jacket sand cores in the prior art;

[0052] Fig.26 It is a top view of the lower mold sand mold in the prior art;

[0053] Fig. 27 It is a bottom view of the cover plate core in the prior art. DETAILED DESCRIPTION

[0054] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] See also Figure 1-27 , describe the embodiments of the present invention in detail.

[0056] The production method of the compacted graphite cast iron cylinder head provided in the embodiment of the present invention is based on 3D printing technology, adopts 3D printing sand mold sand core, and the molding method of the casting is flexible.

[0057] Specific embodiment: A molding process based on 3D printing of a marine vermicular cast iron cylinder head, comprising the following steps:

[0058] Step 1): Based on the 3D model of the cylinder head blank, draw a 3D model, draw a 3D printed sand mold 3D model based on the 3D model, integrate all the sand mold cores, and divide them into three layers of core structure: upper, middle and lower; Figure 1 shown.

[0059] The three core layers are: an upper core, a middle core and a lower core;

[0060] like Figure 2-3 As shown, the upper core is a cylinder head casting shape including a cover plate core, a riser core 1-1, an overflow groove core 1-2, an upper half core 1-3 of a cylinder head bolt hole, and a gas outlet rod core;

[0061] like Figure 4-5 As shown, the middle core integrates the upper and lower water jacket cores 2-1 of the cylinder head inner cavity, the safety valve hole core 2-2, the start valve core 2-3, all the side plate outer skin sand cores 2-4, the intake and exhaust channel cores 2-5, and sets the exhaust hole core 2-8, the core bone installation hole 2-6, and the core bone placement groove 2-7 at the corresponding position of the inner cavity sand core, and at the same time makes an auxiliary sand core for filling the core bone placement groove. Figure 6-14 Shown

[0062] like Figure 15-16 As shown, the lower core comprises a cylinder head bottom core 3-1, a cylinder head bolt hole lower half core 3-2, an injector hole core 3-3 and an inner runner; and a dark chill hole 3-3-1 reserved for installing a cylindrical chill is set in the injector hole core, as shown in FIG. Figure 17-18 As shown;

[0063] A toilet-type vortex pouring cup 4 is also provided to prevent dirty molten iron from entering the cavity. Figure 19-21 shown.

[0064] A circle of anti-fire escapement positioning stop 5 and a circle of anti-fire escapement semicircular groove 6 are arranged on the matching surfaces between the three layers of cores; a core head positioning and observation window is also arranged on the matching surfaces of the three layers of cores.

[0065] Apply repair glue to the back and sides of the working surface of the cylindrical cold iron for installation. The assembly clearance of the cylindrical cold iron is 0.2mm~0.5mm; the installation clearances of the core bone installation holes 2-6, the core bone placement grooves 2-7, the ductile iron core bone 7, and the auxiliary sand core 8 for filling the holes and grooves are all 0.2mm~0.3mm. During installation, evenly apply repair glue to the mating surfaces. After installation, wipe off the extruded glue and apply the glue fully to ensure that the repair glue fills the gaps.

[0066] The outer end surface of the exhaust hole is provided with an "exhaust mark countersunk hole" and a "2mm thick diaphragm" to prevent the paint from flowing into the inner wall of the exhaust hole during dip coating.

[0067] Step 2): using a 3D printer to print each core according to the model segmented in step 1);

[0068] Print the core, pouring cup and auxiliary sand core; after printing, remove the "8" sample, grind the fracture surface and test the tensile strength of the molding sand;

[0069] Step 3): Install the chill, core bone and auxiliary sand core at the corresponding position of the core;

[0070] ①Install the cylindrical chiller, evenly apply sand mold repair glue (Q glue) on the side of the cylindrical chiller and the back of the working surface, and press the chiller into the core to reserve the chiller blind hole;

[0071] ②Evenly apply sand mold repair glue (Q glue) on the sides of the φ8×70 ductile iron core and auxiliary core, and insert the core and auxiliary core into the designated position of the middle core along the installation hole in turn;

[0072] ③Evenly apply universal silicate glue (K5 glue) on the surface of the core bone installation groove of the middle core, install the core bone and auxiliary core in turn, and press them to ensure that the gap is completely filled. In order to increase the wettability of K5 glue and the final bonding strength, heat it in the surface drying kiln at a heating temperature of 120℃~150℃ and a drying time of 20min~30min.

[0073] Step 4): After installation, the three layers of core are dipped, dried in the shade, and baked;

[0074] When the assembled upper core, middle core, lower core and pouring cup are dip-coated, a water-based paint with good leveling property and a Baume degree of 30 to 40 is used; dry in the shade for 24 hours.

[0075] All cores are dried in a surface drying kiln at a temperature of 150°C to 200°C for 40-60 minutes.

[0076] Step 5): After drying, assemble layer by layer in the order of bottom, middle and top, press the weight iron for pouring, and obtain the required cylinder head casting, such as Fig. 22 shown.

[0077] When assembling the core after drying, first poke open and remove the 2mm thick diaphragm sand sheet on the top surface of the injection hole of the lower core, fill φ1~φ2 grinding steel shots into the dark cold iron hole and compact it. Do not fill it up and reserve a 25mm~30mms deep cavity to fill it with resin sand and do not brush alcohol-based paint;

[0078] Install the lower, middle and upper cores, pouring cups and weight stacks in sequence. After installation, poke open the 2mm thick diaphragm sand sheets of all exhaust holes and use compressed air to clean the 3D printing resin-free loose sand remaining in the exhaust holes.

[0079] The present invention processes the cylinder head with complex structure through three-layer parting, combines 3D printing technology and various auxiliary process means, solves the problems of difficulty in cleaning the sand sticking to the seam of the inner water jacket of the marine medium-speed diesel engine vermicular cast iron cylinder head and breakage of the 3D printed sand core, greatly reduces the number of sand cores, integrates all the inner sand cores and side outer sand cores of the cylinder head into the middle core, and sets core bones for installation at the local thin neck weak parts of the water jacket, thereby increasing the structural strength of the casting sand core, almost avoiding the positioning error of the sand core assembly, and improving the accuracy of the casting; no mold is required, which speeds up the process debugging progress; and the purpose of simple and efficient production process of the marine medium-speed diesel engine vermicular cast iron cylinder head, short production cycle and stable casting quality is achieved.

[0080] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0081] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A forming process based on 3D printing of marine vermicular cast iron cylinder head, characterized in that: The following steps are involved: Step 1): Based on the 3D model of the cylinder head blank, draw a 3D model, draw a 3D printing sand mold 3D model based on the 3D model, integrate all the sand mold cores, and divide them into three layers of core structure: upper, middle and lower; Step 2): using a 3D printer to print each core according to the model segmented in step 1); Step 3): Install the chill, core bone and auxiliary sand core at the corresponding position of the core; Step 4): After installation, the three layers of core are dipped, dried in the shade, and baked; Step 5): After drying, assemble layer by layer in the order of bottom, middle and top, press on the weight for pouring, and obtain the required cylinder head casting.

2. The forming process of a 3D printed marine vermicular cast iron cylinder head according to claim 1 is characterized in that: The three core layers are: an upper core, a middle core and a lower core; The upper core is in the shape of a cylinder head casting, including a cover plate core, a riser core (1-1), an entire overflow groove core (1-2), an upper half core of a cylinder head bolt hole (1-3), and a gas outlet rod core; The middle layer core integrates the upper and lower water jacket cores (2-1) of the inner cavity of the cylinder head, the safety valve hole core (2-2), the start valve core (2-3), all the side plate outer skin sand cores (2-4), and the intake and exhaust duct cores (2-5), and arranges the exhaust hole core (2-8), the core bone installation hole (2-6), and the core bone placement groove (2-7) at the corresponding position of the inner cavity sand core, and at the same time, manufactures an auxiliary sand core (8) for filling the core bone placement groove. The lower core comprises a cylinder head bottom core (3-1), a cylinder head bolt hole lower core (3-2), an injector hole core (3-3) and an inner runner; and a dark chill hole (3-3-1) reserved for installing a cylindrical chiller is arranged on the injector hole core; A toilet-type vortex pouring cup (4) is also provided to prevent dirty molten iron from entering the mold cavity.

3. The forming process of a 3D printed marine vermicular cast iron cylinder head according to claim 2 is characterized in that: A circle of anti-fire escape positioning stop (5) and a circle of anti-fire escape semicircular groove (6) are arranged on the matching surfaces between the three layers of cores; a core head positioning and observation window is also arranged on the matching surfaces of the three layers of cores.

4. The forming process of a 3D printed marine vermicular cast iron cylinder head according to claim 2 is characterized in that: The back and side surfaces of the cylindrical cold iron working surface are smeared with repair glue for installation. The assembly clearance of the cylindrical cold iron is 0.2mm-0.5mm. The installation clearances of the core bone installation hole (2-6), the core bone placement groove (2-7) and the ductile iron core bone (7), and the auxiliary sand core (8) for filling the hole groove are all 0.2mm-0.3mm. During installation, the matching surface is evenly smeared with repair glue. After installation, the squeezed glue is wiped clean and the glue is fully applied to ensure that the repair glue fills the gap.

5. The forming process of a 3D printed marine vermicular cast iron cylinder head according to claim 2 is characterized in that: When the assembled upper core, middle core, lower core and pouring cup are dip-coated, a water-based paint with good leveling property and a Baume degree of 30 to 40 is used; dry in the shade for 24 hours.

6. The forming process of a 3D printed marine vermicular cast iron cylinder head according to claim 2, characterized in that: All cores are dried in a surface drying kiln at a temperature of 150°C to 200°C for 40-60 minutes.

7. The forming process of a 3D printed marine vermicular cast iron cylinder head according to claim 2, characterized in that: When assembling the core after drying, first poke open and remove the 2mm thick diaphragm sand sheet on the top surface of the injection hole of the lower core, fill φ1~φ2 grinding steel shots into the dark cold iron hole and compact it. Do not fill it up and reserve a 25mm~30mms deep cavity to fill it with resin sand and do not brush alcohol-based paint; Install the core in the order of lower, middle and upper cores, pouring cups and weight stacks. After installation, poke open the 2mm thick diaphragm sand sheets of all vent holes and use compressed air to clean the loose sand remaining in the vent holes.

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