As one of the main tools of injection molding processing of injection mold, its quality, precision, manufacturing cycle and production efficiency in the process of injection molding, the level of direct impact on the quality of injection products, production, cost and product replacement.
Therefore, injection mold plays an important role in the production of plastic products. In general, the characteristics of injection mold has the following aspects:
1. The design difficulty is big: the plastic belongs to the polymer material, the melt body belongs to the viscoelastic body, the melt flow process changes with the shear stress, the shearing speed, the large molecule produces the directional direction in the flow process. It is partially compressed after filling the mold cavity, and in the cooling curing process plastic shrinkage is very complex, mold cavity in all parts of the direction of the shrinkage rate is different, and different types, grades of resin shrinkage is also very different, in the design of injection mold should be fully noted.
2. High manufacturing cost: Injection molds are aimed at the shape of a specific plastic products, specifications design, so a variety of injection mold structure is very different, it can not be bought at random in the market, it is impossible to mass production.
3. Short production cycle: the competition of the current product is very different, therefore, each manufacturer is racing against the clock, for the early launch of the market and strive to do their best, which requires injection mold from the design, manufacturing to put into production to shorten the time.
4. High technical content: The shape of injection molded products are complex, the size, precision requirements are also very high, and many are the main components, this injection molding mold design and manufacturing has brought great difficulty, in order to be able to make the mold according to quality on time, must be put into the strong, must concentrate on the advanced technology in machinery manufacturing.
What are the specific functions of the molding process parameters of injection mold?
1. Injection pressure
Injection pressure is provided by the hydraulic system of injection mold forming system. Injection mold pressure exists in order to overcome resistance during melt flow, or, in turn, the resistance in the flow process needs to be offset by the pressure of the injection molding machine to ensure the smooth process of filling. During injection molding, the pressure of the nozzle of the injection molding machine is highest to overcome the flow resistance in the melt. Subsequently, the pressure along the flow length toward the front end of the melt is gradually reduced, if the injection mold cavity internal exhaust Good, then the melt front end pressure is the atmospheric pressure.
2. Injection time
The injection time mentioned here refers to the time required for the plastic melt to fill the injection mold cavity, excluding the auxiliary time of mould opening and closing. Reasonable injection time can help melt ideal filling, and it is very important to improve the surface quality of products and to reduce the dimensional tolerances.
3. Injection temperature
Injection temperature is an important factor affecting injection pressure. The injection temperature must be controlled within a certain range. The temperature is too low, the melt material is not good, it affects the quality of the molding parts, increases the process difficulty, the temperature is too high, the raw material is easy to decompose.
4. Holding pressure and time
In the process of holding the injection molding machine nozzle continuously to the injection mold cavity filling, to fill due to the shrinkage of the workpiece and vacated volume. If the cavity is filled with no pressure, the workpiece will shrink about 25%, especially because the shrinkage is too large to form contraction traces. Pressure is generally to fill the maximum pressure of about 85%, of course, according to the actual situation to determine.
5. Back pressure
Back pressure is the pressure to be overcome when the screw reverses the back storage material. The use of high back pressure is conducive to the dispersion of pigment and plastic melting, but at the same time extend the screw retraction time, reduce the length of plastic fiber, increase the pressure of injection molding machine, so back pressure should be lower, generally not more than 20% of injection pressure
In the process of injection molding, the main contents of NC machining process consist of the following steps:
1. Select the parts or processes that are suitable for machining the NC machine tool of injection mold.
2. Process analysis of injection mold parts.
3. Make the process line, including the process division, the processing sequence arrangement, the Datum choice, as well as the connection with the non NC machining process.
4. The design of NC machining process, mainly including the determination of the work step, selection of tools, positioning and installation of fixtures, the determination of the route, the determination of cutting dosage.
5. Adjust the NC machining procedure, such as increasing the compensation for knives and cutters.
6. Tolerance distribution.
7. CNC machine Tools on the part of the instructions of injection mold processing.