When assembling the stamping mold, it is necessary to ensure a certain gap between the concave and convex molds, and the gap needs to be even, so as to extend the service life of the mold and ensure the quality of the stamping parts.
1. Direct measurement, use measuring tools to directly measure the gap between the concave and convex molds. Due to the complex structure between the concave and convex molds, the measuring tool can only be used on stamping molds with a single-side gap of more than 0.02mm. If the gap is too small, it will be difficult to Measurement.
2. According to the reference measurement of the gasket, insert a paper or metal sheet of uniform thickness into the gap between the concave and convex mold mating parts. Use the thickness of the gasket as a reference standard to ensure that the fitting gap of the concave and convex molds is even.
3. Measurement by light transmission method, using light to illuminate the fitting gap between the concave and convex molds, and judging whether the gap between the concave and convex molds is uniform by the size of the light gap.
4. Apply a layer of paint on the punch with a thickness equal to the matching gap between the concave and convex molds, and then insert the concave mold. This method is simple and practical, and is more suitable for stamping molds that cannot be tested and adjusted with gaskets.
5. Copper plating method: Plate a layer of copper on the working end of the punch, with a thickness equal to the matching gap between the concave and convex molds, and then insert the concave mold. This method is similar to the coating method. During the use of the stamping die, the copper layer can automatically fall off.
Sometimes you will encounter the problem of mold chewing when processing stamping molds. In fact, this is a very common mold processing failure problem.
During the processing of stamping molds, a certain gap should be maintained between the convex and concave mold cutting edges and should not collide. There are several reasons for the collision of the cutting edges. In terms of design and equipment, the punch may be fixed improperly, for example, if the punch is fixed using a chiseling method, the punch may become loose. If a low melting point alloy is used for solidification, the punch may also become loose. If the punching force is large and the root of the punch is not hardened, or the punch is subject to excessive lateral force, the punch may become loose.
Die chewing situations in stamping mold processing can be divided into these types. The convex and concave molds or guide parts are not installed vertically. The assembly of upper and lower templates, fixed plates, convex and concave molds and other parts are not parallel to each other. The punching gap is uneven. The fixation of the punch does not meet the design requirements. Repeated punching or stack punching means punching one blank twice or stacking several blanks together for punching. The waste materials or blanking parts left on the mold are not cleaned in time. The mold parts are greatly worn. For example, the wear of the guide parts causes the fitting gap to be too large and is not repaired in time. There is looseness in the mold repair assembly. In order to prevent die chewing, a die with a guide device should be used as much as possible, which is especially important for die with a small blanking gap. The way the punch is fixed should be carefully considered, and the mold manufacturing should be strong and reliable. It is necessary to strictly follow the operating procedures of the punch machine, clean the working surface of the mold in time, and avoid repeated punching and overlapping punching. This is especially important for composite punching dies. It is necessary to strengthen the maintenance and management of molds to ensure that the molds are in good condition. At the same time, we produce injection molding, which is a very important way in the processing of plastic products. Most of the plastic products on the market today are made by injection molding. So in the injection molding process, the factors that affect the injection molding process are What?
1. Equipment accuracy
The links that affect injection molding processing have a great relationship with the equipment. Generally speaking, the overall level of the injection molding machine will lead to corresponding changes in the quality of the products produced.
2. Mold error
Molds also play a very important role in injection molding production. The quality of the mold affects the quality of the injection molded products.
You may encounter problems of this kind and that during the mold injection molding process. What are the possible defects?
Defects that may be encountered during the mold injection molding process are as follows:
1. Characteristics of defects in injection molded parts: The injection molding process is incomplete because the mold cavity is not filled with plastic or the injection molding process lacks certain details.
2. Possible reasons for the problem: (1) Insufficient injection speed. (2). Plastic material shortage (3). The screw does not leave screw padding at the end of the stroke. (4).Changes in running time. (5). The temperature of the injection cylinder is too low. (6).Insufficient injection pressure. (7). The nozzle part is sealed. (8). The heater outside the nozzle or injection cylinder cannot operate. (9).The injection molding time is too short. (10). Plastic is attached to the throat wall of the hopper. (11). The capacity of the injection molding machine is too small (ie, injection weight or plasticizing capacity). (12). The mold temperature is too low. (13). The mold anti-rust oil was not cleaned. (14). The anti-return ring is damaged and the molten material flows back.
3. Solution: (1). Increase the injection speed. (2). Check the amount of plastic in the hopper. (3). Check whether the injection stroke is set correctly and change it if necessary. (4). Check whether the check valve is worn or cracked. (5). Check whether the operation is stable. (6). Increase the melt temperature. (7). Increase back pressure. (8). Increase injection speed. (9). Check the nozzle hole for foreign matter or unplasticized plastic. (10). Check the outer layer of all heaters and use an ammeter to check whether the energy output is correct. (11). Increase the screw forward time. (12). Increase the cooling capacity of the hopper throat area, or reduce the temperature of the rear area of the injection cylinder. (13). Use a larger injection molding machine. (14). Increase the mold temperature appropriately. (15). Clean the anti-rust agent in the mold. (16). Check or replace the back-off ring.
Differences in size of injection molded parts: 1. Characteristics of defects in injection molded parts: The change in weight and size during the injection molding process exceeds the production capacity of the mold, injection molding machine, and plastic combination. 2. Possible reasons for the problem: (1). The plastic input into the injection cylinder is uneven. (2). The temperature or fluctuation range of the injection cylinder is too large. (3). The capacity of the injection molding machine is too small. (4). The injection pressure is unstable. (5). The screw reset is unstable. (6). Changes in operating time and inconsistent solution viscosity. (7). The injection speed (flow control) is unstable. (8). Plastic types that are not suitable for the mold are used. (9). Consider the impact of mold temperature, injection pressure, speed, time and holding pressure on the product.
What are the effects of injection molding?
The first one to bear the brunt is plastic materials. The complexity of plastic material properties often determines the complexity of the injection molding process. Under normal circumstances, the complexity of materials is not the result we want. The performance of plastic materials varies greatly due to different varieties, different brands, different processors who produce injection molded parts, and even different batches. Therefore, adjustments must be made based on the properties of the material. Different performance parameters may lead to completely different molding results. This is also a different situation that everyone likes to see.
Second is the injection temperature. This is a very important one. The melt flows into the cooled mold cavity and loses heat due to thermal conduction. A certain amount of heat loss occurs. At the same time, heat is generated due to shearing. This heat may be more or less than the heat lost by thermal conduction, mainly depending on the conditions of the injection molded part. This also causes some heat to be lost. The viscosity of the melt becomes lower as the temperature increases. In this way, the higher the injection temperature, the lower the viscosity of the melt, and the smaller the required filling pressure. At the same time, the injection temperature is also limited by thermal degradation temperature and decomposition temperature. This restriction causes temperature changes.
The third is the mold temperature of the injection molded part. Is the mold temperature as high as possible or as low as possible? The lower the mold temperature of injection molded parts, the faster the heat is lost due to heat conduction, the lower the temperature of the melt, and the worse the fluidity. The temperature also affects the speed of fluidity. This phenomenon is particularly evident when lower injection rates are used. If you don’t believe it, don’t bother doing a test if conditions permit.
Injection time. The length of time has a certain impact on the injection molding industry. The impact of injection time on the injection molding process is reflected in three aspects: 1. Shortening the injection time will increase the shear strain rate in the melt, so the injection pressure required to fill the cavity must also increase. 2. Shorten the injection time and increase the shear strain rate in the melt. Due to the shear thinning characteristics of the plastic melt, the viscosity of the melt decreases, and the injection pressure required to fill the cavity must also decrease. This is exactly the opposite of the first point.
3. Shorten the injection time, increase the shear strain rate in the melt, and increase the shear heat. At the same time, less heat is lost due to heat conduction. Therefore, the temperature of the melt is higher and the viscosity is lower. The injection pressure required to fill the cavity is Also lower it. The combined effect of the above three conditions makes the curve of the injection pressure required to fill the cavity appear “U” shaped. That is, there is an injection time when the required injection pressure is small. This is the impact of injection molding time on the injection molding process.
The influence of injection molding process conditions on products is as mentioned above. Injection molding processing has certain special significance for plastic materials, injection temperature, mold temperature, and injection time. The plastic material determines the complexity of injection molding. Injection temperature causes high or low viscosity. The temperature of the mold causes differences in fluidity. The injection pressure is also different depending on the injection time.
