With the continuous progress of automobile manufacturing technology, people have put forward more and more high requirements for reducing the energy consumption of automobiles, which provides a broad space for the popularization and application of plastic parts in the automotive industry. In recent years, the proportion of plastic parts in automobile production is increasing. The plastic has been basically achieved trim of the car, for the car to reduce weight and save cost and plays an important role in reducing fuel consumption.
Plastic parts need popularization, and improve the quality of technology, mold as an industrial parent is bound to go ahead. Taking a car door panel of an automobile as an example, the manufacturing process and the key points of injection mold design are described.
Usually the car has the front and rear two doors, according to the door cover can be classified into the foreskin and non foreskin, according to the door shape features, can be divided into trumpet network and no horn network door. The surface quality of products set of door wrapping requirement is low, but not the appearance of a set of panels wrapping high quality requirements, such as product surface does not allow weld lines, do not allow the top white, high strength and no burr etc..
Process analysis of door panel
Door panels as automotive interior decoration products, according to the size of the car, the size is different. Figure 1 shows a car left front door trim panel, maximum size of 835mm * 520mm * 90mm, with more complex shapes, surface texture, of which a total of 21 column screw products, products around the periphery distribution of 7 upside down, all internal stiffeners die size for small 0.8mm, end end 1.1mm. In order to prevent the product from edge flying, all the horn meshes are fixed on the fixed die with an angle of 8 degrees.
According to the above technical requirements, the actual production of the material selected PP-T20, shrinkage of 1.2%, average wall thickness of 2.5mm, using 1600t injection molding machine injection molding.
Mold flow analysis
According to the analysis of product structure and process of the above requirements, the mold design for the first mock exam point structure. Next, we adopt
MOLDFLOW of the injection molding process of the simulation analysis, according to the shape of the product and the injection molding process, mold using 3 point nozzle design, and equipped with the lapping side gate and the channel size is 14mm in diameter, with adjustable valve to control the feeding speed. The detailed location of the gate is shown in figure 2.
In the cooling system, cooling water (Figure 3) with straight and water tower design, waterway diameter is set to 14mm, tower 30mm, heat distribution near the mouth water, in order to enhance the mold cooling effect and adjust the mould temperature, thus greatly shorten the cooling time and the production cycle, improve production efficiency.
Through software simulation analysis, we get the following results:
1. from the final product melting line distribution map (Fig. 4), it can be seen that the junction temperature is higher and the junction is more obvious, so the exhaust capacity must be enhanced and the temperature is controlled.
2. due to the uneven cooling and solidification process of injection molded products, the shrinkage of products is inconsistent (Fig. 5), and the channel needs to be moved and corrected to control cooling.
In conclusion, the following conclusions are drawn:
1., the product front appears low temperature, but it is still within the allowable temperature range, and does not affect the quality of the product.
2. product bonding line is not obvious, but attention should be paid to the exhaust at the end of the filling.
Uneven solidification of the 3. products, resulting in inconsistent shrinkage, it is recommended to cool evenly.
Die design features and die structure
1. mold design concept and characteristics
(1) the size of the die set is reasonable, the dynamic fixed die is the whole, the material is P20, so as to reduce the cost of material saving.
(2) take full consideration of cooling, water as much as possible, and the diameter is large.
(3) the top of a safe, reasonable, auxiliary inclined guide rod is pushed out.
(4) the setting of the parting surface is reasonable, the processing and die matching are convenient, and the R angle parting face is machined into the deviation.
2. die structure design
The basic appearance structure of the die is shown in Figure 6, and the basic appearance structure of the mould includes: hot runner protection guide post, positioning ring, lock module, pry die pit, die foot, hanging ring screw and waterway.
The basic requirements of the die are as follows:
1) hot runner pin heat mouth 20mm high, play a protective role in the installation.
2) every two plates between the pry pit size is set to 45mm * 45mm, deep 8mm.
3) side mold mold foot set.
4) A, B in each of the 4 point lifting, try to set in position rings on both sides of the mold.
(2) die positioning system (four pecks structure) as shown in figure 7. Around a circle with the outer mold 10 degree taper, the whole mold positioning and anti mold swelling effect. In addition, wear resistant plate should be added according to actual needs. Four pecks length is 85 ~ 90mm, height 50mm, and at the bottom of the R5mm above, the top edges of C6, by finishing in mold company.
(3) the setting of the guide pin and the flow regulating valve are as shown in figure 8.
1) because the template is too thick, the guide column G and P are fixed with screws, and the length is 1.5 times more than the diameter.
2) flow control valve is used to control the pouring velocity and closed flow mechanism, to achieve uniform filling, melting products control line, testing the mold on the machine with six angle wrench rotation, easy to use.
3) both movable and fixed mould should be equipped with regulating valve.
(4) horn net insert, pressure plate and thimble setting.
1) the insert of the moving die horn net is used to play the role of deep rib and fixed mould horn net exhaust, and the net rib is formed by carving,
Internal water circulation reduces the coefficient of product deformation.
2) there are 10 evenly distributed pressure plates between A and B plates, and the materials are treated with 40Cr and heat treatment.
3) setting the die on the side of the die.
4) the cylinder is pushed out with a cylinder, and the diameter of the cylinder and the thimble are usually set into even sizes such as 6mm, 8mm and 10mm, so that the deep hole drilling can be chosen to process the corresponding cutters.
(5) inclined plate.
1) the angle of the oblique mandril should not exceed 15 degrees, in principle, it is greater than 12 degrees, and all the guide rods are added, so as to strengthen the auxiliary function. The diameter of the guide rod and the inclined rod are usually set to more than 16mm, otherwise it is easy to break.
2) the angle of the inclined roof is greater than the angle of the angle of 2 to 3 degrees of the angle of the inclined rod. When the crown is reset, it can protect the inclined roof and make up the machining angle error.
3) oblique roof material commonly used NAK80 or 2738, in principle, can not be the same material as the mold.
4) set the guide rod to proofread oblique pushed out state, inclined top seat and the guide rod cannot interfere, ensure that the distance is more than 5mm.
(6) support column, stroke switch and forced reset hole.
1) the support column should be as close as possible to the center of the mold, and the number as large as possible and the diameter bigger.
2) a total of 2 switches, diagonal settings.
3) the number of reset holes is 4, which is consistent with the top hole of the machine.
The working process of the mould
When the die is opened, the movable and fixed mould is divided, the casting system is pulled by the pull rod, and the moving die is moved along with the plastic part, and the die is opened
After a certain distance, the moving die stops moving, and the ejecting mechanism moves forward under the force of the forced reset force of the injection molding machine
When the die is pushed out, the mechanism is reset under the action of forced reduction.
Key points and difficulties in mould design and manufacture
1., the door panel production cycle is relatively short, but the mold frame procurement time is longer, which brings pressure to the design order, must have rich
Accumulate experience and advance purchasing.
2. this kind of mold is inclined at most, the mold ejection and reset are unbalanced, and the product capacity and the relative movement of the inclined roof, so it is necessary to increase
Add two return rods, and increase the ejector plate screw to prevent the deformation of the product, and the product side should also take the increase block and strengthen the slope
The measures of top grinding and matching are perfected.
Elimination of 3. melting line. After the die was tested, it was found that the weld line was obvious, and solved by improving the location of the gate and strengthening the exhaust.
4. because the horn net can not be discharged until the die is fixed, so the relationship between the assembly and machining of the horn net must be paid attention to.
5. the machining deviation of the inclined hole of the template is large, so the machining process must be improved to ensure the concentricity of the assembly.
Now the development of automobile industry both in the technical level and product quality are put forward higher requirements, but also to the
The mold industry has brought great challenges. We have accumulated experience in the manufacture of car door mold
The stable operation mode of design, processing, assembly and coordination between die and mould factories can be guaranteed in the mould manufacturing cycle
Physical mold problems is more targeted and professional, for these similar mold production has certain reference and the day after