Design and analysis of die for the hottest base pa

Design and analysis of mold for base parts

the base is a very simple part, but there are still many design skills to do it well

product feature analysis

this product is the "base" under the flat panel color TV display, and the material is PC. The shape is relatively simple, but for the injection mold, the molding method is extremely cumbersome. The demoulding of the four screw seats is severely limited because the shell is 5 ° tilted around

preliminary idea of mold structure

making "inclined top block" is the most direct idea, as shown in Figure 2

as the demoulding of the four screw seats is achieved by pushing the tube, it can be seen from Figure 2 that the inclined ejector block and the push tube interfere with each other. If a notch is made on the inclined ejector block to avoid pushing the tube, but because the inclined ejector block should move 9.2mm horizontally during demoulding, the punch outside the push tube will be opened

in addition, because the lower part of the product has a circle of r0.5 rounded corners around, there must be a concave shape of 0.5 on the inclined top block. When the inclined top block is jacked up, there must be an inward horizontal movement, but the concave shape is 0 Including many parts of subdivision product 5 used in detail, when filled with plastic, it will block the horizontal movement of the inclined roof block. Therefore, the scheme of using inclined jacking block is not feasible

the second idea is to make a "retracted slider"

as shown in Figure 4, if the two retracted sliders move towards the middle and give way to the four screw seats, the product can be demoulded normally, but this scheme will also face two problems. The first is that the oblique shovel block must be on the side of the fixed mold. If it is placed on the side of the moving mold, the cooling water path of the moving mold core cannot be arranged. The second is that the gap between the two retracted slider tracks will definitely "drill", so that the mold will not work normally. Therefore, we must find a way to arrange the sliding track of the retracted slider on the side of the fixed mold

parting

first, let's simply separate the upper and lower molds, as shown in Figure 5

figure 5

in order to achieve internal sliding, the plastic waste that humans put into the sea every year is 4.8 million tons to 12.7 million tons of block core shrinking mechanism, and the mold core can be divided into as shown in Figure 6

Figure 6

the part of the foundation is like this, and the ideal cooling water path and push tube ejector can still be arranged

the remaining piece is shown in Figure 7

figure 7

it can be divided into three pieces, which is the "basic type" of designing the retracted slider and oblique shovel block. Because of the product shape, there are "edges" on one side and no "edges" on the other side, so the slopes of the two sides of the oblique shovel block are different, one side is 4 °, the other side is 10 °, see Figure 8

figure 8

the design of the retracted slider and the oblique shovel block is the key to the design of this set of die, and the design of all other parts is subject to the design of the retracted slider and the oblique shovel block. Due to the reasons mentioned above, these three pieces are arranged on one side of the fixed mold, the middle one becomes the oblique shovel block, and the two pieces on both sides are made into the retracted slider. Finally, the three designs are shown in Figure 9

Figure 9

the state of mold opening is shown in Figure 10

figure 10

at this time, the slider can be separated from the product, as shown in Figure 11

figure 11

until the slider is completely removed from the product, and the product moves backward with the moving die core, the concave "T-groove" on the retracted slider and the convex "T-groove" on the inclined shovel block are always not separated during the movement, as shown in Figure 12

figure 12

considering that these three parts are in the center of the product, cooling is particularly important, so "pond" and "water separator" are set in the inclined shovel block, as shown in Figure 13

figure 13

the retracted sliding blocks on both sides are made of beryllium copper, which can improve the efficiency of heat conduction. The oblique shovel block is made of wear-resistant alloy steel with a hardness of hrc52 degrees

design of fixed mold kernel

according to the customer's requirements, this set of mold is the first mock examination with two holes. Considering that the gate and cross flow channel should be as short as possible, and considering that there is enough space for sliding blocks in the two groups, the center distance of the two holes is designed to be 130mm, as shown in Figure 14

figure 14

we have adopted such a design for the fixation of the fixed mold kernel and the fixed mold frame. Considering that there is a relative movement distance (45mm) between the retracted slider and the oblique shovel block, and the retracted slider is attached to the fixed mold kernel, which is fixed to the fixed mold frame, and the oblique shovel block is fixed to the fixed mold base plate, so every time the mold is opened, the fixed mold frame will be separated from the fixed mold base plate by 45mm. Therefore, the fixed mold nut must be fixed on the fixed mold frame, but the bottom of the fixed mold frame is connected, and the conventional screw fixation method does not work. We use the fixing method shown in the figure below to make a step on the opposite side of the fixed mold kernel, and tighten the screws from the step, as shown in Figure 16

Figure 15

Figure 16

such a fixation method can make the fixed mold kernel very stable and obtain the shortest mainstream at the same time

the sliding connection design between the fixed mold frame and the fixed mold base plate

adopts the structure of adding an additional guide post guide sleeve to the ordinary standard mold base, and the moving distance is controlled by four limit screws, as shown in Figure 17

figure 17

this structure is relatively simple, convenient to process, and also saves the cost of customizing special mold bases (generally, non-standard mold bases need to be increased by 30%)

design of the sliding track of the retracted slider

the design of the sliding track of the retracted slider adopts a card slot structure. From Figure 18, it can be seen that there is a gap on the mold frame for the installation of the "track", and the processed "track" can be easily inserted from the gap on the side, and then fixed with screws. The "track" is made of high-quality wear-resistant alloy steel with a hardness of hrc58 degrees

Figure 18

Design of sprue

in order to obtain the best injection effect, the gate sleeve as shown in Figure 19 is used

figure 19

it requires the injection molding machine to be additionally equipped with a special extended nozzle. A 3 ° taper is used at the fit between the sprue sleeve and the die core to avoid galling of the sprue sleeve and flash when the fixed die frame is separated from the fixed die plate

shunt channel and feed port

the gate system of this product adopts the conventional latent gate, as shown in Figure 20

Figure 20

plastic enters from a small piece attached to the product, and then it is cut off after the product comes out. This kind of injection molding effect is better

figure 21

cooling of the fixed mold

in order to improve the efficiency of injection molding production and control the uniform mold temperature, so as to reduce the internal stress of the product, the fixed mold part adopts sufficient cooling. Two "single cycles" are used for the cooling of the fixed mold kernel, as shown in Figure 22

figure 22

the two "oblique shovel blocks" are important cooling positions. Due to the structure of the punch part of the product, cooling cannot be done on the retracted slider, and 50% of the heat of the entire punch is taken away by the "pond" in the middle of the "oblique shovel blocks". Its waterway is from the fixed mold bottom plate, as shown in Figure 23. In order to avoid the sprue sleeve, we made a circle on the fixed template, because we should consider the convenience of the injection molding machine workers to connect the water pipe, so we can only do this, as shown in Figure 23

figure 23

the connector at the outlet of the water pipe on the second floor of the fixed mold is arranged on the opposite side of the operation panel of the injection molding machine, so it is convenient for the machine adjuster to connect the water pipe. The water pipe connector should be placed on the top and bottom of the mold as little as possible, and the water pipe connector placed on the top is easy to rust when it is assembled and disassembled. The water pipe connector placed below is inconvenient to assemble and disassemble, and the plastic water pipe will affect the product to fall down. Therefore, the layout shown in Figure 24 is more appropriate

after the final assembly of the fixed mold part, two conical fine positioners are set on the parting surface. It is accurately positioned with the moving die to ensure that the wall thickness of the injected product is uniform and not misaligned, as shown in Figure 25

figure 25

a key action of this set of dies is to separate the fixed die frame from the fixed die base plate. In order to fairly confirm the 45mm gap of the dimensional tolerance of plastic parts formed by materials with different shrinkage characteristics, force the "oblique shovel block" and the "internal shrinkage slider" to be separated by 45mm. The pulling force of this action is achieved by four "nylon pullers". When opening the mold, due to the function of "nylon pull nails", the moving template tightly pulls the moving mold frame until the six "limit screws" on the fixed mold frame are in place. At this time, the retracted slider has been retracted to the antibacterial plastic. The moving template is separated from the fixed mold frame by positioning the antibacterial and mildew proof masterbatch according to a certain proportion of 1. If the tension of the "nylon pull pin" fails, the action of the "inner shrink slider" will also fail, and the product will be scratched by the "inner shrink slider". The inner surface of the hole on the fixed mold frame that matches the "nylon fastener" is required to be smooth, so that the tension of the "nylon fastener" can be fully reflected, and the service life of the "nylon fastener" will be extended

design of the moving die

see Figure 26 for the overall appearance of the moving die

figure 26

see Figure 27 for the dynamic die

figure 27

the moving die core is close to the two inner sliders and the inclined shovel block in the closed state of the die, including the 3 ° inclined plane and bottom surface on both sides. If the gap is large, it will "drill" and make the inner slider unable to work normally

figure 28

we put it transparent. From figure 29, we can see that there are two "ponds" and push tube holes on each moving die

figure 29

see Figure 30 for the water cooling of the moving die

figure 30

ejection of products

it can be seen from figure 31 that the ejection of products is relatively simple, which is realized by four push tubes

figure 31

see Figure 32 for the outline of the whole mold

figure 32