The material of the grid mold should be ductile cast iron. Generally, the grade used is 500. The material with a small grade is softer, and the mold surface is easily damaged when brushing the mold, causing damage to the mold. Easily deformed during use. The blank needs to be annealed when it leaves the factory to reduce the internal stress. The blank should be uniform everywhere, and there should be no internal defects such as pores and trachoma. In order to prevent the mold from deforming during use, it should be placed under natural conditions for more than half a year to eliminate internal stress. Using new and unaged materials to make molds often results in slight deformation of the mold during use due to stress, making it difficult to form the cast plate or the grid does not meet the quality standards; the service life of the mold is also affected. It has a great impact, and some are scrapped after only half a year of use. Generally, the battery manufacturer provides the size and structure of the blank, which is produced by the foundry according to the drawing. In this way, mold manufacturing saves time and effort and facilitates processing. The grid mold is divided into moving mold and static mold. Generally, the static mold is installed and fixed on the plate casting machine, and the thimble is installed on the static mold; the moving mold is installed on the guide rod of the plate casting machine, and the exhaust channel is designed on the static mold. The cooling water channel of the gate should be designed on both the static mold and the moving mold. The mold blank is shown in Figure 1.
The length of the blank used by the ordinary plate casting machine is 420~480 mm, the width is 240~280 mm, and the thickness is 45~50 mm. Industrial casting machines have larger molds, and the blank size is selected according to the specific situation. The lack of material cast from the blank is used to install fixing bolts, water channels, etc., and cast the shape as shown in Figure 1, which can save processing costs.
The same blank is used for both the movable and static molds. On the top of Figure 1 is the mold opening surface of the movable and static molds, and the two molds are opposite. There are several principles for the manufacture of grid molds: the principle of middle mold opening, that is, the opening parts of the movable mold and the static mold are in the middle position in the thickness direction of the grid. It can be seen from the grid diagram that the size of the middle position of the grid is the largest, Demoulding from an intermediate position is reasonable. The grid is centered on the left and right, that is, the grid position should be in the middle of the template. The principle of uniform arrangement mainly requires that the left and right sides are basically balanced in weight, and the cast plate falls evenly when it falls after demoulding, so that the grid will not be deformed;
The key parts of the grid mold manufacturing are: the ribs of the movable mold and the static mold should be opposite to each other, and the ribs should not be wrong; the design of the exhaust duct is reasonable; the distribution and position of the ejector pins should be reasonable.
The exhaust channel is slotted on the front of the mold, and then inlaid with the same material, and the gas in the mold cavity when the grid is cast is discharged by the gap of the inlaid edge to facilitate molding. Generally, three exhaust strips should be designed for ordinary size molds. The width of each exhaust strip is 15~20 mm, and the length should cover the boundary of the process pole. After the template is flattened, first open the exhaust groove, insert the exhaust strip, fix the exhaust strip with bolts (fixed form after forming), then cut the surface flat and open the rib. The inside of the exhaust duct is connected by a vertical hole, which goes straight to the bottom of the mold, and then is connected to an air nozzle. The exhaust channel plays the role of exhausting when casting the sheet. When brushing the mold, the exhaust nozzle should be connected to the outside compressed air, so that the gas passes through the exhaust channel and is ejected from the mold, so that the mold will not be blocked when spraying. exhaust duct. The exhaust duct plays an important role in the flexible casting grid of the mold. If the gap of the exhaust duct is too large, the lead alloy will flow into the gap when casting the plate, casting similar small rib defects, which will affect the coating plate; If it is too small, the injection molding powder may block the gap, and the effect of exhausting will not be achieved, resulting in poor exhausting, the problem of broken ribs, and the grid cannot be formed. The material of the exhaust strip must be selected from the material of the same batch number as the main template so as to have the same properties. The exhaust strip is designed on the movable mold.
The ejector pin is a device that ejects the grid when the grid is demolded after being formed in the mold. The grid is pushed out of the mold cavity by the force of the thimble, and it falls off in a balanced manner. The thimble is designed on the static mold, generally three rows and 12 thimbles are designed. The thimble is designed at the junction of the frame of the grid and the rib, or the junction of the rib and the rib. The smaller the cross-section of the thimble, the better, generally between φ 2~φ 3 mm. The thimble is flush with or slightly higher than the bottom of the rib groove of the mold, so that the trace of the thimble on the cast grid is the same as or slightly lower than the grid plane. Higher than the grid plane will affect the coating and hang up the coated steel wire. Or affect the service life of the coated strip. When the mold is installed on the plate casting machine, the ejection sequence of the ejector pins should be adjusted. The order of the upper and lower ejector pins of the grids with different weights is different. The grids that are light (meaning that the thickness is less than 1.5 mm) should be ejected at the same time, and the grids that are heavier should be ejected at the same time. Top then bottom. The thimble is fixed on the thimble strip, the maximum position of the thimble strip is adjusted by the screw fixed on the static die, and the original position is maintained by the spring. During operation, the cylinder pushes the ejector bar to eject the grid, and after the cylinder is retracted, the spring keeps the ejector pin to the original position.
A cooling water pipe should be installed at the gate of the mold, which is located about 40 mm below the upper edge of the movable mold and the static mold. If the temperature is not lowered, the mold will be overheated, and the temperature cannot be controlled, resulting in production difficulties.
The manufacturing size of the main rib grooves of the mold is generally 0.1mm larger than the size of the grid pattern, which is the experience of manufacturing molds and can be used as a reference.
At the corners of the ribs and the grid frame, a small lead angle should be made to reduce the resistance of the lead liquid flow. In the past, the mold surfaces of the grid moving and static molds were polished with fine quartz sand into a pockmarked surface to facilitate exhaust, but now they are rarely polished, mainly to save mold processing time.
The structure distribution of the grid cavity is shown in Figure 2. The top is the lead gate, the depth is about 25 mm, and the angle with the grid plane is 45. ~50. . Below is the buffer zone, with a depth of about 20 mm and a thickness of l ~2 mm. Below is the lead channel, which is opposite to the rib or frame of the grid, and its size is slightly larger than that of the rib, and the general cross-section is rectangular. There is an exhaust surface on the periphery of the grid, and the exhaust surface is slightly lower than the mold surface, mainly because a part of the gas in the mold cavity will be discharged through the surrounding of the mold, which plays the role of auxiliary exhaust.
On the back of the grid, the position of installing the solar heat pipe should be designed. Generally, it should be designed in the lower half. The jack of the thermocouple should be designed well. The position of the hole is different, and the temperature difference is also large. Therefore, when formulating the process temperature, it should be formulated according to the actual situation. Generally, the manufacturer should stipulate that all thermocouples of the mold should be in the same position, so as to facilitate the standardization and unification of process documents.