Design and manufacture of injection mold for the i

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Design and manufacture of injection mold for the inner barrel of full-automatic washing machine

the inner barrel of full-automatic washing machine is the core part of full-automatic washing machine. According to the use requirements, the main design properties of this part are as follows:

(1) because the clothes are washed in the barrel, the inner surface of the barrel is a mirror, and there are no burrs of nylon socks

(2) clothes are washed and dehydrated in the barrel, which needs to rotate at high speed in the washing machine, so the wall thickness is required to be uniform

(3) in order to strengthen the strength of the barrel, the greater the load, the more serious the oil leakage, and 14 ribs are set around the barrel

(4) there are 286 round holes around for dehydration

(5) large diameter and depth, 416mm diameter and 385mm depth

according to the design performance requirements of the inner barrel of the full-automatic washing machine, we need to pay attention to the design and manufacturing of injection mold, the selection of mold material and heat treatment

1 structural design and molding process of inner barrel mold

as we all know, the structure of injection mold is determined by factors such as the form of injection machine and the complexity of parts. The particularity of the mold structure of the inner barrel of the product can include the following points:

(1) there are reinforcing ribs around the outer side of the inner barrel, which obviously cannot be forced to demould. And because the inner barrel is basically cylindrical, it is more suitable for the cavity to be composed of multiple sliders. It is usually composed of four sliding blocks, which divide the circumference of 360 degrees into 90 degrees (right angles), which is easy to manufacture. When the mold is formed, the molten plastic in the mold cavity produces strong pressure on the mold cavity. The four sliding blocks are required to be equipped with reliable positioning and locking mechanisms. Therefore, the mold uses four sliding blocks to locate the adjacent parting plane, and locks with the inclined planes left on the moving and fixed templates. This mechanism is widely used in molds, which is convenient and feasible, and is also convenient for processing and mold assembly in production

(2) the four sliding blocks of the cavity need to be pushed out at the same time. If each sliding block is driven by a power source, it is difficult to ensure the synchronization of the four power sources. Therefore, two symmetrical power sources are used. The sliders are connected by the transmission plate, which transmits power. In addition, a tee mechanism is added to the mold, so that the two oil cylinders that push the four sliders use the same oil circuit, with oil inlet and oil return at the same time. The synchronous reliability of the structure is ensured. In addition, the four slide blocks are guided by eight oblique guides during the pushing process, and bear part of the gravity, further improving the motion reliability of the mold

(3) the inner wall of the inner barrel is required to be high, which is a mirror, and there must be no burrs. Therefore, the forming pins with through holes around the forming barrel wall cannot be placed on the four sliding blocks, and the core needs to be pulled from the inside of the core. There are many kinds of core pulling mechanisms inside the core, but from the perspective of mechanical structure, they can be divided into the following two kinds:

① the single core of each hole is an independent system, but there are 286 holes around the inner barrel that need to be broken down. If this scheme is adopted, the structure will be cumbersome and the stability will be poor. And if there is a problem with the core pulling at the top of the core, all the core pulling from the root to the top must be removed before maintenance, which increases the difficulty of maintenance. Therefore, this structure cannot be adopted

② considering the whole, each row of holes is regarded as a group, so there are 22 groups on the circumference, and each group has 13 shaped rods (a total of 286 shaped rods). The same power source is used, which greatly improves the reliability of the structure and facilitates maintenance

the second structure is adopted in the design of the die. An oil cylinder is selected as the power source for core pulling, and the rectangular spring with good performance is used to reset the core pulling rod for forming around. In order to reduce the thickness of the die, the dovetail groove steering structure is adopted at the center

③ the wall thickness of the inner barrel must be uniform, so the centricity of the medium core (punch) and cavity (concave) in the mold is required to be very high. To ensure this requirement, a 5 ° conical surface is set between the core fixing plate and the core to match

④ the design of gating system has a great influence on the performance, appearance and forming difficulty of products. The shape of the inner barrel is basically circular. And there is a round hole at the bottom of the barrel. According to the assembly requirements of the inner barrel in the washing machine, a flange is installed under the round hole at the bottom of the barrel; A large wave wheel is installed above the round hole at the bottom of the barrel (i.e. the bottom of the barrel). In order not to affect the assembly between products, the gate is set in the middle of the round hole wall. To sum up, the main runner is provided with a 20 ° conical surface so that the condensate in the runner can be pulled out smoothly. The spoke gate is used on the parting surface. Because this kind of gate is suitable for products with a hole in the middle of such a round inner barrel. In this way, the feeding is uniform, the flow rate is roughly the same on the whole circumference, and the air is easy to be discharged smoothly

⑤ molding action process of the mold after injection molding, the hydraulic cylinder (ygc80x150-f) works, drives the core pulling block to retreat, and drives the core pulling column to retreat through the turning of the batten. Due to the action of the rectangular spring, the forming rods around (a total of 22 groups of 286) are retracted into the core

then the moving die retreats to separate the core from the product (because there are 14 ribs on the outside of the product). After that, the second oil cylinder (ygc63x100-f) works, pushing the four sliding blocks to slide along the inclined guide column. When it touches the travel switch, the second oil cylinder stops feeding oil and brings out the product. Finally, take out the product through the manipulator of the injection molding machine. After that, the two oil cylinders return oil to make the four sliding blocks return, the mold is closed and locked, and the oil cylinder at the moving mold (ygc80 material science is the basic science of strategic emerging industry x150-f) enters oil to drive the core pulling block 35 and core pulling column 24, causing the forming rods around to eject and puncture with the four sliding blocks. At this time, the mold enters the next cycle

2 manufacturing process of inner barrel mold

a total of 286 side core holes are processed by horizontal CNC machining center. There are three sizes of side holes, 12mm, 8mm and 7mm, which need to be matched with the side core pulling, and the processing accuracy is high. The processing sequence is: first use the center drill to determine the center position of the hole on the inclined surface of the core, then pre drill the bottom hole, then drill the bottom hole and ream the hole. In order to ensure that all the reamed holes are unified in size, a special plug gauge is made to check the hole size and roughness at any time

the inner core pulling assembly adopts the form of 22 concentric sector oblique spokes, which is composed of core, core pulling rod screw strip and core pulling rod fixing strip. The core pulling rod is reformed from the formed ejector rod to ensure all breakdown. When installing the core pulling rod screw strip and the core pulling rod fixing strip, the outer conical surface should match with the inner conical surface of the core, and the inner conical surface should match with the outer conical surface of the core pulling rod. At that time, two schemes were considered:

(1) after the core pulling rod assembly was prepared separately, the tooling was used to process the dynamic mating conical surface on the digital control machine tool, and then the fitter group was used to decorate and equip all 22 core pulling rod assemblies. After fixing the core pulling rod assembly with the tooling, the fixing holes of each core pulling rod are processed together with the core

classification and performance

(2) all core pulling rod components are treated as a closed conical ring. After machining the inner and outer conical surfaces with the car, process the fixed holes of each core pulling rod together with the core and core pulling rod after assembly, and then take out 22 core pulling rods in 24 equal sections by wire cutting. Based on the advantages and disadvantages of the above two schemes, the second scheme is adopted, which greatly reduces the processing difficulty of the core pulling rod assembly and maximizes the smooth realization of the dynamic fitting accuracy. The vertical lathe is used to process the conical ring instead of the tooling, and the NC also reduces the processing cost. Now the mold is in use, and the ejection action of the core pulling rod assembly is smooth and stable, and the moving mating surfaces are in good contact

processing of deep and narrow ribs of cavity inserts: using advanced numerical control EDM, the die splicing structure can be changed into an overall structure, so as to simplify the structure and reduce the number of workpieces produced by the die. In this pair of dies, there are many narrow ribs on the female die inserts. Machining narrow ribs with EDM has been fully applied in this pair of dies

in EDM, in order to avoid the size change caused by electrode loss, electrolytic copper, a special electrode material for EDM, is used. Thus, the machining accuracy is guaranteed. In order to polish the narrow ribs on the side and control the machining depth, the EDM machine tool is specially equipped with translation head and other accessories, and the method of down flushing oil is adopted to help remove chips. At the same time, in order to obtain smaller surface roughness and higher productivity, we should reasonably convert electrical standards, select rough and fine electrical standards according to the actual situation, and implement graded processing. After processing, the side roughness of narrow reinforcement ra=2 sixty-three μ m. It greatly shortens the subsequent fitter polishing hours

the mold should be considered uniformly and comprehensively in the processing process. First, determine the two sides of the entire mold base as the reference plane, and then use numerical control milling to process the main oblique locking surfaces and convex core fixing holes of the fixed mold part, and process the main dimensions of the convex core on the numerical control milling, while ensuring the position accuracy of the convex core center. The four sliding blocks should be welded into one and processed at the same time, which provides a strong guarantee for the assembly of the mold to ensure the accuracy between them

3 mold material selection and heat treatment

whether the selection of mold material is reasonable will greatly affect the service life and processing technology of the mold. According to the different requirements of the structure and performance of this pair of dies, reasonable arrangements have been made in material selection

The material of the four slide blocks in the cavity is 45 steel. Because the die size is large, the blank must be normalized after forging to eliminate internal stress and improve cutting performance. After rough machining, it is quenched and tempered to Hb to ensure a certain strength and stiffness

the product requires a mirror surface, so the core adopts a better material in today's mold industry: P20 electroslag remelting. After special process treatment, the material can meet the requirements of high finish of the mold and processing technology

P20 material is selected for the second insert in order to ensure the crisscross ribs on the processing insert and the forming surface of the product. In addition, as the core pulling rod, core pulling block, forming rod and other parts are in the back and forth movement before disassembly when the mold is working, they must be marked, which has large wear and load, so carbon tool steels T8A and T10A are used. At the same time, the inner conical surface of the core pulling rod screw strip and the core pulling rod fixing strip is dynamically matched with the core pulling rod and the core, which is easy to fail. Usually, the action is not smooth, easy to stagnate, and the matching surface is roughened. Therefore, carbon, nitrogen and boron ternary co infiltration is considered to improve the comprehensive properties of surface wear resistance, bite resistance, contact fatigue strength and so on. The depth of ternary co infiltration can reach 0.1mm. At the same time, the deformation of the parts treated by CO infiltration is very small and the dimensional stability is good. Therefore, the heat treatment process can be arranged after all parts are assembled and grinded

for the heat treatment process of the core pulling rod, in order to obtain a high hardness surface layer to improve the wear resistance and fatigue strength of the workpiece, a local surface quenching process is adopted to ensure that the surface is quenched to a certain depth during quenching

the information fed back after the actual use of the mold fully reflects the correctness and necessity of the heat treatment process. All moving mating parts are in good working condition, move smoothly, and the wear of the moving mating surface is very small. These have reduced the difficulty of repairing the workpiece of the mold to a certain extent, and also extended the service life of the mold

4 Conclusion

with the development of mold industry, the requirements for mold design and manufacturing are becoming higher and higher. CAD/CAM is widely used in mold industry. CAD/CAM technology plays its irreplaceable advantages in the design and manufacturing of inner barrel plastic mold. It can be seen from the following points:

(1) the inner barrel injection mold has a relatively complex structure. The application of CAD technology provides a scientific basis for mold design, avoids tedious calculation and drawing work, and can more accurately and reasonably optimize the mold structure. Our company uses three-dimensional design and manufacturing software such as CAXA me and Pro/E to complete products

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