The Clamping Unit

Key Questions What types of clamping unit designs are there  

What are the advantages and disadvantages of using these designs  

The Injection Molding Machine (Lesson 2) The Mold (Lesson 4) 

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The assembled cell was put between two metal collectors and pressed to the level of operating pressure for purposes of reduction of the contact resistance of assembly parts between power covers of the clamp unit. 

Injection molding involves two distinct processes. The first is melt generation, mixing, and pressurization and flow, which is carried out in the injection unit of the molding machine. The second is product shaping, which takes place in the mold cavity. Injection molders, therefore, have two distinct parts the injection unit and the mold/clamping unit. The function of the injection unit is to melt the polymer and inject it into the mold the function of the clamping unit is to hold the mold, open and close the mold, and eject the finished product. 

In addition to the accumulator head, a number of other machine advances have taken place in the past 20 years. These are in-mold prefinish, automated flash trimming, leak detection, and conveying to filling station. Also, dual accumulators allow up to four parisons to be extruded simultaneously and molded on the clamping unit. 

These functions must be performed automatically under conditions that ideally should result in a high quality and cost-effective part. Injection molding machines have two principal components to perform the cyclical steps in the injection molding process. These are the injection unit and the clamp unit (Figure 11.4). We now describe the operation of the various units of the injection molding machine... 

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. 

Several techniques can be used for the clamping unit (1) hydraulic clamps, in which the hydraulic cylinder operates on the movable parts of the mold to open and close it (2) toggle or mechanical clamps, in which the hydraulic cylinder operates through a toggle linkage to open and close the mold and (3) various types of hydraulic mechanical clamps that combine features of (1) and (2). 

An injection molding machine is used. The clamping unit is used as a press and preplasticizing is done in the injection unit. With this technique, much more precise feeding of the preplasticized mixture keeps the molding tolerances down. 

A further development of TM is to plasticize the mbber mixture in a screw-type extmder solidly attached to the press, heat it up and inject it into the transfer cylinder. Closing the clamping unit then fills the mold cavities as in normal TM, Fig. 44 [7]. 

The clamping unit and plasticating unit of a horizontal machine are located... 

The clamping unit is responsible for carrying out the tasks opening and closing tightly , as well as rapid and precise movement . 

The clamping unit consists of one fixed platen and one movable platen. One mold half each is installed on one of the platens. 

To perform the mold movements, the clamping unit needs a drive mechanism. Two fundamentally different systems are used as drives. There is thus a basic distinction between mechanical clamping xmits and hydraulic clamping units. 

The Plasticating and Injection Unit (Lesson 3) The Clamping Unit (Lesson 5)... 

The clamping unit is open. There is no molded part in the cavity of the mold. The ejectors are in the retracted position. The mold has been adjusted to the prescribed temperature. 

The clamping unit moves the two halves of the mold together. A clamping force is built up, thus locking the mold tightly. 

During the ejection operation the controls coordinate the sequence of movements performed by the clamping unit and ejector. The ejectors cannot be allowed to move too quickly because this might cause them to pierce the molding. The movement opening the mold in the parting plane should also start slowly to avoid damaging the molded article. 

The improvements made in clamping units provide a great variety of movement and action in the larger BM machines. Small machines still need certain improvements to ensure good flash removal with low deformation of the clamping units. The most important development has been the use of proportional valves in hydraulic systems. With this technology, a machine runs more smoothly and more exactly to permit a wide variety of action in the mold, as well as accurate control of the closing speed (Fig. 4-7). 

The clamping unit is attached to the base plate of the main body. The unit has a profile vAilch locates in the charge chute location sleeve (Fig. 7). TWo micro-switches are set into the mating face of the body and indicate the correct seating of the machine. The position of the clamp levers is indicated on the panel by the use of a 50 mm stroke linear potentiometer attached to the actuating cylinder rod. The unit has three fall safe features... 

Independant tests of the clamp unit were carried out to... 

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