Decoration Steel Parts Engineering Parts Steel Parts By MIM

For MIM parts production, the injection process in the machine is very criticle to the whole part quality and the operation fo the follow-up procedure.

Below we would like to introduce some information of injection moulding cycle time.

Mold closing time refers to the closing time of the mould before injection. If it is too long, the temperature of the die is too low and the residence time that the melt in the barrel is too long; if the closing time is too short, the temperature of the die is relatively high.

2. MIM cycle -- Injection Time: Injection time refers to the time from the beginning of injection to the time when the plastic melt fills the mould cavity (plunger or screw advance time). In production, the injection time of small plastic parts is generally 3 to 5 seconds, and that of large plastic parts can reach tens of seconds. The filling time is inversely proportional to the filling speed, shorter injection time, higher filling speed. Lower orientation and higher shear rate. The apparent viscosity of most plastics decreases, especially those sensitive to shear rate.

3. Pressure-holding time: it refers to the time when the cavity continues to exert pressure after filling (the time when the plunger or screw stays in the advancing position), generally 20-25 seconds, and the extra-thick plastic parts can reach 5-10 minutes. If the pressure holding time is too short, plastic parts are not compact, easy to produce dents, and plastic parts size is instable, etc. If it is too long, it will increase the stress of plastic parts, resulting in deformation, cracking, demoulding difficulties.

At the same time, it should be noted that three temperatures that need to be controlled in MIM process. They are barrel temperature, nozzle temperature and mould temperature. The material and nozzle temperature mainly affect the plasticization and flow of plastics, while the mould temperature affects the flow and cooling finalization of plastics.