CN114407307A

CN114407307A - Injection molding process for household appliance shell

Info

Publication number: CN114407307A
Application number: CN202111574861.7A
Authority: CN
Inventors: 刘士东; 韦龙权; 周国兰
Original assignee: Nanjing Tianlu Plastic Packaging Material Co ltd
Current assignee: Nanjing Tianlu Plastic Packaging Material Co ltd
Priority date: 2021-12-21
Filing date: 2021-12-21
Publication date: 2022-04-29

Abstract

The application relates to an injection molding process for a household appliance shell, which relates to the field of injection molding quality control technology and comprises the following steps: s1, preparing raw materials and debugging an injection molding machine; s2, heating a charging barrel of an injection molding machine to 215-270 ℃, heating a hot runner in an injection molding system to 240-255 ℃, heating a movable mold of an injection mold to 75-85 ℃, and heating a fixed mold of the injection mold to 55-65 ℃; s3, adding the raw materials into a charging barrel of an injection molding machine to enable the raw materials to be in a molten state; s4, adding the raw materials in a molten state into the processed hot runner, and injecting the raw materials into the heated injection mold through a nozzle; s5, maintaining the pressure; s6, cooling and forming; s7, opening the movable mold, and taking out a finished shell product in the injection mold through a material taking device; and S8, repairing burrs around the shell by using the trimming mechanism. This application has injection moulding product surface quality's effect.

Description

Injection molding process for household appliance shell

Technical Field

The application relates to the field of injection molding quality control technology, in particular to an injection molding process for a household appliance shell.

Background

The housing of the household electrical appliance is usually made of plastic, such as an air conditioner housing, a display screen housing and the like, and is directly molded by an injection molding process during processing.

Injection molding is a method for producing and molding industrial products, and thermoplastic plastics or thermosetting materials are made into plastic products with various shapes by an injection molding machine through a plastic molding die.

In view of the above-mentioned related technologies, the inventor believes that in the actual production process, the injection molded product may have redundant thin rubber blocks or rubber threads at the peripheral position of the product due to various factors, and these thin rubber blocks or rubber threads are collectively called as burrs, which may affect the surface quality of the product.

Disclosure of Invention

In order to improve the influence of burrs on the surface quality of an injection-molded product, the application provides an injection molding process for a household appliance shell.

The application provides an injection moulding technology for household appliance shell adopts following technical scheme:

an injection molding process for a housing of a household appliance, comprising the steps of: s1, preparing raw materials and debugging an injection molding machine; s2, heating a charging barrel of an injection molding machine to 215-270 ℃, heating a hot runner in an injection molding system to 240-255 ℃, heating a movable mold of an injection mold to 75-85 ℃, and heating a fixed mold of the injection mold to 55-65 ℃; s3, adding the raw materials into a charging barrel of an injection molding machine to enable the raw materials to be in a molten state; s4, adding the raw materials in a molten state into the processed hot runner, and injecting the raw materials into the heated injection mold through a nozzle; s5, maintaining the pressure; s6, cooling and forming; s7, opening the upper fixed die and the fixed die, and taking out a finished product of the shell in the injection mold through a material taking device; and S8, repairing burrs around the shell by using the trimming mechanism.

By adopting the technical scheme, the influence on the temperature of the raw materials is reduced after the hot runner is preheated, so that the raw materials flow in the hot runner in a molten state; the deburring mechanism directly cuts off the deckle edge of shell after the shell is taken out, does benefit to the surface quality and the precision that improve the shell.

Optionally, after trimming, taking down the shell for surface treatment, carrying out online photographing detection by using an industrial detection camera, boxing and warehousing the qualified products, and screening out unqualified products.

Through adopting above-mentioned technical scheme, increased the holistic quality of shell product.

Optionally, the unqualified product is crushed by a crusher or melted for reuse.

By adopting the technical scheme, the occupied space of unqualified shell products is saved, the resource waste is reduced, and the method is green and environment-friendly.

Optionally, extracting device is including installing base and the slide on the injection molding machine, the base is located one side that the movable mould deviates from the cover half, and articulates on the base has the pendulum rod, the one end of pendulum rod articulates there is first branch, and the other end articulates there is second branch, the one end that the pendulum rod was kept away from to first branch is articulated with the movable mould, the one end that the pendulum rod was kept away from to second branch articulates there is the slide, vertical direction sliding connection is followed on the slide, be equipped with on the slide and be used for following the material piece of getting of taking out the shell in the cover half.

By adopting the technical scheme, when the movable die is far away from the fixed die, the first supporting rod drives the swing rod to rotate, the second supporting rod drives the sliding plate to move downwards to a position between the fixed die and the movable die under the driving of the swing rod, the material taking part takes out the shell, when the movable die is close to the fixed die, the swing rod rotates, the shell moves upwards along with the sliding plate, the action is rapid and continuous, the structure is compact, and the energy consumption generated by the increase of power elements is saved.

Optionally, get the material piece and include flitch and vacuum chuck, the flitch passes through first spring coupling on the slide, vacuum chuck is equipped with a plurality of and all installs the one side that deviates from the slide at the flitch, the flitch parallels with the slide and the flitch lateral wall is equipped with the polished rod perpendicularly, the polished rod passes the slide and is connected with the iron sheet, the slide lateral wall is equipped with the electro-magnet with iron sheet relative distribution, works as when electro-magnet and iron sheet separate, first spring is in natural state.

Through adopting above-mentioned technical scheme, the electro-magnet circular telegram adsorbs the iron sheet, and the iron sheet drives the polished rod when removing and is close to the cover half for vacuum chuck and shell butt and hold the shell, the electro-magnet outage, the iron sheet moves back under the elastic thrust of first spring, thereby drives the shell and shifts out the cover half.

Optionally, deburring mechanism includes frame and servo jar, be equipped with the guide rail in the frame, guide rail bottom surface sliding connection has the frame, be equipped with the top that is used for driving the frame to remove in the frame and push away the cylinder, frame and slide relative distribution and frame sliding connection have the cutter, cutter shape and shell outline looks adaptation, servo jar is installed on the frame and servo jar's actuating lever links to each other with the cutter.

Through adopting above-mentioned technical scheme, the top pushes away cylinder drive frame and is close to the slide, and servo cylinder drive cutter advances and excises the deckle edge around the shell, because cutter shape and shell outline looks adaptation, once excises and targets in place convenient and fast.

Optionally, a cooling ring is arranged on one side, facing the sliding seat, of the machine frame, a guide ring is arranged in the cooling ring, the guide ring is fixed to the machine frame through a connecting rod, a cutting groove is formed between the cooling ring and the guide ring, the shape of the cutting groove is the same as the outer contour of the shell, the width of the cutting groove is larger than the wall thickness of the shell, a branch pipe used for conveying liquid nitrogen is embedded in the outer wall of the cooling ring, a plurality of guide sleeves are arranged on the cooling ring, each guide pillar is arranged in each guide sleeve in a penetrating mode and is connected with a cutter, each guide pillar is connected with a second spring in a sleeved mode, two ends of each second spring are connected with the guide sleeves and the cooling ring respectively, and a plurality of ejector rods which are abutted to the cooling ring are arranged on the sliding seat.

Through adopting above-mentioned technical scheme, servo jar drive cutter gos forward for the shell periphery inserts the second and leads to the inslot, and the refrigeration effect of liquid nitrogen makes the deckle edge quick freezing and embrittlement around the shell in the branch pipe, and servo jar continues to promote the cutter and gos forward, and the cutter extrudees the second spring and gos forward and amputate deckle edge, has reduced the remaining possibility of excision, does benefit to the surface quality who improves the excision.

Optionally, be equipped with the guide rail in the frame, frame sliding connection is on the guide rail, be equipped with the top that is used for the drive frame to remove in the frame and push away the cylinder, be equipped with a plurality of air faucets that communicate with the grooving on the cooling ring, each the air cock passes through the gas-supply pipe and establishes ties, gas-supply pipe and high pressurized air source intercommunication.

Through adopting above-mentioned technical scheme, in the high-pressure gas input gas transmission pipe for each air cock blowout air current blows off the deckle edge sweeps in the grooving.

Optionally, a shield for covering the branch pipes is fixed on the cooling ring through screws, and heat preservation cotton is arranged on the inner side of the shield.

By adopting the technical scheme, the protective cover prevents personnel from directly contacting with the branch pipe, so that the protective function is achieved; the heat insulation cotton reduces heat transfer and ensures the freezing effect of liquid nitrogen in the branch pipe.

Optionally, the inner wall of the cooling ring is provided with first sealing rings corresponding to the two end faces of the cooling ring, the guide ring is provided with second sealing rings corresponding to the two first sealing rings one to one, and when the second spring is in a natural state, the end part of the cutter is inserted between the corresponding first sealing ring and the corresponding second sealing ring.

Through adopting above-mentioned technical scheme, two pairs of first sealing washer and second sealing washer have reduced the grooving and have circulated with external air current, do benefit to and keep in certain temperature range in making the grooving, reinforcing refrigeration effect.

In summary, the present application includes at least one of the following beneficial technical effects:

1. the influence on the temperature of the raw materials is reduced after the hot runner is preheated, so that the raw materials flow in the hot runner in a molten state; after the shell is taken out, the trimming mechanism directly cuts the rough edges of the shell, so that the surface quality and the precision of the shell are improved;

2. the method has the advantages that the burrs around the shell are rapidly frozen and embrittled by utilizing the refrigeration effect of the liquid nitrogen, so that the possibility of cutting residues is reduced, and the cut surface quality is improved.

Drawings

Fig. 1 is a schematic overall structure diagram of an embodiment of the present application.

Fig. 2 is a schematic structural diagram for embodying a first strut and a second strut in an embodiment of the present application.

Fig. 3 is a schematic structural diagram for embodying the cutter according to the embodiment of the present application.

Fig. 4 is an enlarged view of a in fig. 3.

Fig. 5 is a schematic structural diagram for embodying the branch pipe in the embodiment of the present application.

Description of reference numerals: 1. a base; 11. a slide base; 111. a slide plate; 12. a swing rod; 121. a first support bar; 122. a second support bar; 21. a material plate; 211. a first spring; 22. a vacuum chuck; 23. a polish rod; 231. iron sheets; 24. an electromagnet; 31. a frame; 32. a servo cylinder; 33. a guide rail; 34. a machine frame; 35. a pushing cylinder; 36. a cutter; 41. a cooling ring; 42. a guide ring; 421. a connecting rod; 43. a branch pipe; 44. a guide post; 441. a second spring; 45. a guide sleeve; 46. a top rod; 47. an air tap; 48. a gas delivery pipe; 49. a shield; 491. heat preservation cotton; 51. a first seal ring; 52. a second seal ring; 6. an injection molding machine; 61. fixing a mold; 62. and (4) moving the mold.

Detailed Description

The present application is described in further detail below with reference to figures 1-5.

The embodiment of the application discloses an injection molding process for a household appliance shell. Referring to fig. 1, the injection molding process for the housing of the home appliance includes the steps of: s1, preparing raw materials, debugging an injection molding machine 6, forming plastic raw materials required by the injection molding of the electric appliance shell by crushing, mixing and stirring, then putting the stirred raw materials into an oven, and setting the preheating time and temperature.

S2, heating a charging barrel of the injection molding machine 6 to 215-270 ℃, heating a hot runner in an injection molding system to 240-255 ℃, heating a movable mold 62 of the injection mold to 75-85 ℃, and heating a fixed mold 61 of the injection mold to 55-65 ℃.

And S3, adding the preheated raw materials into a charging barrel of the injection molding machine 6 to enable the raw materials to be in a molten state.

And S4, adding the raw materials in the molten state into the treated hot runner, and injecting the raw materials into the heated injection mold through a nozzle.

And S5, maintaining the pressure.

And S6, cooling and forming.

And S7, opening the movable mold 62, and taking out the finished shell product in the injection mold through a material taking device.

S8, repairing burrs at the periphery of the shell by using a trimming mechanism, taking down the shell for surface treatment after trimming, putting the shells on a conveying line one by using a manipulator, carrying out online photographing detection by using an industrial detection camera in the conveying process, comparing a photographed product picture with a picture in a database, detecting whether the surfaces of the products are qualified or not, boxing and warehousing the qualified products, screening out unqualified products, and carrying out crushing treatment or melting treatment by using a crusher for reuse.

As shown in fig. 1 and 2, the material taking device comprises a base 1 and a sliding seat 11 which are installed on the injection molding machine 6, the sliding seat 11 is vertically located above the fixed mold 61, a sliding plate 111 which moves along the height direction of the sliding seat 11 is connected in the sliding seat 11 in a sliding mode, the base 1 is located on one side, away from the fixed mold 61, of the movable mold 62, a swing rod 12 is hinged to the base 1, one end of the swing rod 12 faces downwards and is hinged to a first supporting rod 121, one end, away from the swing rod 12, of the first supporting rod 121 is hinged to the side wall of the movable mold 62, the other end of the swing rod 12 faces upwards and is hinged to a second supporting rod 122, and one end, away from the swing rod 12, of the second supporting rod 122 is hinged to the side wall of the sliding plate 111.

As shown in fig. 3, the lower end of the sliding plate 111 is provided with a material taking part, the material taking part comprises a material plate 21, the material plate 21 is located on one side of the sliding plate 111 departing from the swing rod 12, the material plate 21 is fixed with the side wall of the sliding plate 111 through a first spring 211, one side of the material plate 21 facing the sliding plate 111 is vertically provided with a plurality of polished rods 23, each polished rod 23 penetrates through the sliding plate 111, one end of each polished rod 23 penetrating through the sliding plate 111 is commonly connected with an iron sheet 231, the side wall of the sliding plate 111 is provided with an electromagnet 24 corresponding to the iron sheet 231, the electromagnet 24 is separated from the iron sheet 231 when the electromagnet is powered off, and the first spring 211 is in a natural state.

After injection molding is completed, the movable mold 62 is opened to be away from the fixed mold 61, the movable mold 62 drives the swing rod 12 to rotate through the first support rod 121, the second support rod 122 drives the sliding plate 111 to move downwards under the driving of the swing rod 12 until the material plate 21 moves between the fixed mold 61 and the movable mold 62, the electromagnet 24 is electrified to generate magnetism, the iron sheet 231 is adsorbed on the electromagnet 24, the iron sheet 231 pushes the polished rod 23 to overcome the elastic force of the first spring 211 to be close to the fixed mold 61 in the moving process, so that the vacuum chuck 22 is abutted to the shell and attracts the shell, then the electromagnet 24 is demagnetized and powered off, the material plate 21 moves back under the elastic pulling force of the first spring 211, the outer box is moved out of the fixed mold 61, and unloading operation is completed. When the movable die 62 moves back and is closed, the swing rod 12 rotates reversely to drive the sliding plate 111 to move upwards, and the shell is moved to the upper part of the fixed die 61.

The trimming mechanism comprises a frame 31 installed on the injection molding machine 6, a horizontal guide rail 33 is erected on the frame 31, the bottom surface of the guide rail 33 is connected with a machine frame 34 in a sliding mode, the machine frame 34 and the sliding seat 11 are distributed oppositely, a pushing cylinder 35 is installed on the guide rail 33, a piston rod of the pushing cylinder 35 is connected with the machine frame 34, a cutter 36 moving along the horizontal direction is connected in the machine frame 34 in a sliding mode, the shape of the cutter 36 is matched with the outer contour of the shell, the cutting edge of the cutter 36 faces the sliding seat 11, a servo cylinder 32 is installed on the side wall of the machine frame 34, and a driving rod of the servo cylinder 32 penetrates into the machine frame 34 and is connected with the cutter 36.

Referring to fig. 3 and 4, a plurality of guide posts 44 are disposed on a side wall of the cutting knife 36, a cooling ring 41 is disposed on a side of the cutting knife 36 facing the sliding seat 11, a guide sleeve 45 for each guide post 44 to pass through is disposed on the cooling ring 41, a second spring 441 is sleeved on each guide post 44, one end of the second spring 441 is fixed to the guide sleeve 45, the other end of the second spring is fixed to the cooling ring 41, and a plurality of ejector rods 46 corresponding to the cooling ring 41 are disposed on the sliding seat 11. A guide ring 42 is arranged in the cooling ring 41, the guide ring 42 is fixed with the machine frame 34 through a connecting rod 421, a cutting groove is formed between the guide ring 42 and the cooling ring 41, the shape of the cutting groove is the same as the outer contour of the shell, and the width of the cutting groove is larger than the wall thickness of the shell. The inner wall of the cooling ring 41 is fixed with first sealing rings 51 corresponding to two end faces of the cooling ring 41 respectively, the outer peripheral wall of the guide ring 42 is fixed with second sealing rings 52 corresponding to the two first sealing rings 51 one by one, the second sealing rings 52 and the first sealing rings 51 are made of rubber materials and have elasticity, when the second spring 441 is in a natural state, the cutter head of the cutter 36 is inserted between the first sealing rings 51 and the second sealing rings 52 opposite to the cutter head, when the edge of the shell is inserted between the first sealing rings 51 and the second sealing rings 52 opposite to the shell, the ejector rod 46 is abutted to the cooling ring 41, a gap of about 2mm is formed between the inner wall of the first sealing rings 51 and the outer peripheral wall of the shell, the second sealing rings 52 are abutted to the inner wall of the shell, and the cutting edge of the cutter 36 is flush with the outer peripheral wall of the shell.

As shown in figures 4 and 5, the cooling ring 41 is embedded with branch pipes 43 distributed along the outer contour thereof, the branch pipes 43 are connected with a liquid nitrogen conveying part, the liquid nitrogen conveying part comprises a liquid storage barrel and a liquid nitrogen pump, the branch pipes 43 are connected with the liquid storage barrel through pipelines, the liquid nitrogen pump is connected in series on the pipelines, when in use, the liquid nitrogen pump conveys the liquid nitrogen in the liquid storage barrel into the branch pipes 43, and then the liquid nitrogen flows back into the liquid storage barrel through the branch pipes 43 to form liquid nitrogen circulation. A protective cover 49 for covering the branch pipe 43 is fixed on the cooling ring 41 through screws and used for preventing people from directly contacting with the branch pipe 43, and heat insulation cotton 491 is arranged on the inner side of the protective cover 49.

A plurality of air nozzles 47 are arranged on the cooling ring 41, the air nozzles 47 are communicated with the cutting grooves, the air nozzles 47 are sequentially connected in series through air pipes 48, one end of each air pipe 48 is closed, and the other end of each air pipe is communicated with a high-pressure air source.

The pushing cylinder 35 is started, the driving machine frame 34 moves forwards integrally, the side edge of the shell is inserted between the first sealing ring 51 and the second sealing ring 52 corresponding to the shell, until the ejector rod 46 is abutted against the cooling ring 41, the burrs at the periphery of the shell in the groove are frozen by the low temperature of liquid nitrogen, the brittleness of the burrs is increased, after the burrs are frozen for a period of time, the servo cylinder 32 drives the cutter 36 to move forwards, the cutter 36 continuously compresses the second spring 441 and is close to the shell in the moving process because the cooling ring 41 is abutted against the burrs, the cutter 36 reaches the position of the shell, and the burrs on the shell are cut off. After the cutting operation is finished, the servo cylinder 32 drives the cutter 36 to move back, the pushing cylinder 35 drives the machine frame 34 to move back, the shell is separated from the cutting groove, and an operator or a mechanical arm is used for taking down the shell. After the cutting operation is performed for a period of time, high-pressure air is introduced into the air delivery pipe 48, and high-pressure air flow is sprayed from each nozzle to blow burr scraps in the cutting groove out of the cutting groove.

The implementation principle of the embodiment of the application is as follows: after the electrical appliance shell is injection molded, the movable die 62 drives the sliding plate 111 to move downwards between the movable die 62 and the fixed die 61 in the moving and opening process for discharging, after discharging, the movable die 62 is closed, the sliding plate 111 drives the shell to move upwards, and at the moment, the shell is opposite to the cutting groove; the pushing cylinder 35 drives the machine frame 34 to move forward until the cooling ring 41 is abutted to the ejector rod 46, the side edge of the shell is inserted into the cutting groove for freezing, the servo cylinder 32 pushes the cutter 36 to move forward for burr cutting, the servo cylinder 32 drives the cutter 36 to move back after cutting, and the pushing cylinder 35 drives the machine frame 34 to reset integrally. Because the shell deckle edges are embrittled by freezing, the resistance of the cutting knife 36 during cutting is reduced on one hand, and the deckle edges are convenient to fall off and the residue is reduced on the other hand, so that the surface quality and the precision of the shell are improved.

The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.

Claims

1. An injection molding process for a housing of a household appliance, characterized by comprising the steps of: s1, preparing raw materials and debugging an injection molding machine (6); s2, heating a charging barrel of an injection molding machine (6) to 215-270 ℃, heating a hot runner in an injection molding system to 240-255 ℃, heating a movable mold (62) of an injection mold to 75-85 ℃, and heating a fixed mold (61) of the injection mold to 55-65 ℃; s3, adding the raw materials into a charging barrel of an injection molding machine (6) to enable the raw materials to be in a molten state; s4, adding the raw materials in a molten state into the processed hot runner, and injecting the raw materials into the heated injection mold through a nozzle; s5, maintaining the pressure; s6, cooling and forming; s7, opening the movable mold (62), and taking out the finished shell product in the injection mold through a material taking device; and S8, repairing burrs around the shell by using the trimming mechanism.

2. An injection moulding process for a casing of a household appliance according to claim 1, characterized in that: and after trimming is finished, taking down the shell for surface treatment, adopting an industrial detection camera for online photographing detection, boxing and warehousing the qualified products, and screening out unqualified products.

3. An injection moulding process for a casing of a household appliance according to claim 2, characterized in that: and (4) crushing the unqualified product by a crusher or recycling the unqualified product after melting.

4. An injection moulding process for a casing of a household appliance according to claim 1, characterized in that: extracting device is including installing base (1) and slide (11) on injection molding machine (6), base (1) is located movable mould (62) and deviates from one side of cover half (61), and articulated on base (1) have pendulum rod (12), the one end of pendulum rod (12) articulates there is first branch (121), and the other end articulates there is second branch (122), the one end of pendulum rod (12) is kept away from in first branch (121) is articulated with movable mould (62), the one end that pendulum rod (12) were kept away from in second branch (122) articulates there is slide (111), slide (111) are along vertical direction sliding connection on slide (11), be equipped with on slide (111) and be used for following cover half (61) in take out the material piece of getting of shell.

5. An injection moulding process for a casing of a household appliance according to claim 4, characterized in that: get material piece and include flitch (21) and vacuum chuck (22), flitch (21) are connected on slide (111) through first spring (211), vacuum chuck (22) are equipped with a plurality of and all install the flitch (21) and deviate from one side of slide (111), flitch (21) parallel and flitch (21) lateral wall is equipped with polished rod (23) perpendicularly with slide (111), polished rod (23) pass slide (111) and are connected with iron sheet (231), slide (111) lateral wall is equipped with electro-magnet (24) with iron sheet (231) relative distribution, works as when electro-magnet (24) are separated with iron sheet (231), first spring (211) are in natural state.

6. An injection moulding process for a casing of a household appliance according to claim 5, characterized in that: trimming mechanism includes frame (31) and servo cylinder (32), be equipped with guide rail (33) on frame (31), guide rail (33) bottom surface sliding connection has frame (34), be equipped with top push cylinder (35) that are used for drive frame (34) to remove on frame (31), frame (34) and slide (11) relative distribution and frame (34) sliding connection have cutter (36), cutter (36) shape and shell outline looks adaptation, servo cylinder (32) are installed on frame (34) and the actuating lever of servo cylinder (32) links to each other with cutter (36).

7. An injection moulding process for a casing of a household appliance according to claim 6, characterized in that: a cooling ring (41) is arranged on one side of the machine frame (34) facing the sliding seat (11), a guide ring (42) is arranged in the cooling ring (41), the guide ring (42) is fixed with the machine frame (34) through a connecting rod (421), a cutting groove is formed between the cooling ring (41) and the guide ring (42), the shape of the cutting groove is the same as the outer contour of the shell, the width of the cutting groove is larger than the wall thickness of the shell, a branch pipe (43) for conveying liquid nitrogen is embedded in the outer wall of the cooling ring (41), a plurality of guide sleeves (45) are arranged on the cooling ring (41), guide posts (44) are arranged in each guide sleeve (45) in a penetrating manner, each guide post (44) is connected with the cutter (36), a second spring (441) is sleeved on each guide post (44), two ends of the second spring (441) are respectively connected with the guide sleeve (45) and the cooling ring (41), and a plurality of ejector rods (46) which are abutted against the cooling ring (41) are arranged on the sliding seat (11).

8. An injection moulding process for a casing of a household appliance according to claim 7, characterized in that: a plurality of air nozzles (47) communicated with the cutting groove are arranged on the cooling ring (41), the air nozzles (47) are connected in series through air pipes (48), and the air pipes (48) are communicated with a high-pressure air source.

9. An injection moulding process for a casing of a household appliance according to claim 8, characterized in that: a protective cover (49) used for covering the branch pipe (43) is fixed on the cooling ring (41) through screws, and heat insulation cotton (491) is arranged on the inner side of the protective cover (49).

10. An injection moulding process for a casing of a household appliance according to claim 7, characterized in that: the inner wall of the cooling ring (41) is provided with first sealing rings (51) corresponding to the two end faces of the cooling ring respectively, the guide ring (42) is provided with second sealing rings (52) corresponding to the two first sealing rings (51) one by one, and when the second spring (441) is in a natural state, the end part of the cutter (36) is inserted between the corresponding first sealing rings (51) and the corresponding second sealing rings (52).