Injection molding clamp force

The injection molding clamp force is directly proportional to the projected area of the part, or to the empirical pressure or viscosity factor. Clamp force can be related to melt flow length and part thickness [3] by... 

Semibatch Reactors. Semibatch reactors are the most versatile of reactor types. Thermoplastic injection molds are semibatch reactors in which shaped plastic articles are produced from melts. In mol ding thermoplastics, large clamping forces of up to 5000 metric tons are needed to keep molds together, while highly viscous polymers are forced into their cavities. Heat transfer is critical. If the molds are too cold, polymers soHdify before filling is completed if they are too hot, the time required for cooling delays production. 

Mold temperature = 90°C maximum clamping force = 700 kN maximum injection pressure 225 MPa. 

Sample application of the radial flow method. In this sample application, we are to determine the maximum clamping force and injection pressure required to mold an ABS suitcase shell with a filling time, tf=2.5 s. For the calculation we will use the dimensions and geometry schematically depicted in Fig. 8.49, an injection temperature of 227°C (500 K), a mold temperature of 27°C (300 K) and the material properties given in Table 8.8. 

Rework Example 8.10 to find clamping forces that are more realistic. Use an injection temperature of 240°C and a mold temprature of 90°C. Are your results reasonable ... 

The preceding discussion has shown that a significant portion of the electrical energy In injection molding is used in the operation of the clamping system. The amount of clamping force is determined by the projected area of the parts and runners. The relationship is ... 

In creating a process window for the combination of material, machine and heater used in this study, the first consideration was the moldability, which was dictated by the maximum injection pressure and the maximum clamp force. No changes in melt and mold temperature, injection velocity, or gate size could remedy this situation. Thus, an injection molding machine with higher injection speeds, pressures and clamp force was required to mold thin-walled syndiotactic polystyrene. 

With the pressures in the mixing head at between 1,500 to 3,000 psi (10.3 to 20.6 MPa), the in-mold pressures are significantly lower than in many of the other molding processes. When comparing a typical RIM in-mold pressure of 50 to 150 psi (0.4 to 1.1 MPa) with the 5000 to 30,000 psi (34.5 to 206.7 MPa) required for thermoplastic injection molding (Chapter 4), it becomes apparent why RIM is particularly suitable for larger parts. Automotive bumpers are routinely produced on RIM presses with 100 to 150 tons of clamping force, while comparable injection molded parts require presses of 3500 tons or more. 

Flash Excessive injection pressure Excessive melt temperature Mold parting face faulty Insufiticient clamp force Foreign matter on mold parting face Flow restriction in one or more cavities of multicavity mold... 

From the perspective of a life cycle analysis (LCA), the RIM process presents two winning cards with respect to thermoplastic injection molding the use of liquids instead of thermoplastic granules and the necessity to use much less clamping force during the molding process. 

The size of injection molding machines is usually specified in terms of injection capacity and clamp force. These factors are not directly related. Other important variables are the L D (length to diameter) ratio, barrel size, plasticizing rate, injection rate, and injection pressure. Major components of injection molding machines include the injection unit, the clamp unit, and the machine base which contains the power and control units. 

The main component of an injection-molding machine are (1) the injection unit which melts the molding material and forces it into the mold (2) the clamping unit which opens the mold and closes it under pressure (3) the mold used and (4) the machine controls. 

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