Skip to main content

Transfer Molding And Extrusion Plastic Molding Process Of Making Plastics

Transfer molding, also called extrusion or gate molding , is the process of  forming articles in a closed mold, where the fluid plastic material is conveyed into the mold cavity under pressure from outside of the mold. 

The material, often a preheated preform, is placed in a heated transfer pot. As soon as the material is sufficiently softened, the plunger forces the almost fluid plastic through the orifice (sprue) into the closed mold where final cure takes place. Pressures used are 50 to 100% higher than those used for compression molding ; thus better details and higher strengths are possible . 


Transfer Molding


Extrusion Molding : 

Extrusion means the continuous flow of material through a die. Extrusion molding is used mostly for production of sheet, tube bar and typical applications in thermoplastic materials. Granulated powder made of such materials as vinyl resins, cellulose derivatives, nylon, polyethylene and polypropylene make up the materials used in the process. 

Extrusion Molding


Plastic extrusion machine consists of hopper into which the powder or pellets are fed into a heated cylinder, the screw feeding mechanisms, a nozzle and the die assembly. The rotating screw carries the heated plastic forward and forces it through heated die orifice of the required shape. As it leaves the die, it is gradually cooled by carrying it through cooling media while resting on a conveyor, It is then wound into coils or cut to desired lengths. 

There are advantages to the extrusion process. The tooling is low- cost compared to Injection molding. Material thickness can be accurately controlled. In addition, production rates are high and intricate profiles can be produced. 

Labels:

Comments

Post a Comment

Popular posts from this blog

Advantages And Disadvantages Of Air Refrigeration System :

 Advantages Of  Air Refrigeration : 1. The refrigerant used namely air is cheap and easily available. 2. There is no danger of fire or toxic effects due to leakages. 3. The weight to ton of refrigeration ratio is less as compared to other systems. Disadvantages Of Air Refrigeration : 1. The quantity of  Refrigerant used per ton of refrigeration is high as compared to other systems. 2. The COP of the system is very low. Therefore running cost is high. 3. The danger of frosting at the expander valves is more as the air contains moisture content. 
Post a Comment
Read more

ELECTRICAL COMPARATORS AND ITS WORKING

Electrical Comparators are used as a means of  detecting and amplifying small movements of a work contacting elements. An electrical comparator consists essentially of  a pick-up head or transducer for converting a displacement into a corresponding change in current and a meter or recorder connected in the circuit to indicate the electrical change, calibrated to show in terms of displacement. Generally, an amplifier is needed to provide the requisite sensitivity and to match the characteristics of different parts of  the circuit. Electrical comparators can be classified according to the electrical principle used in the pick-up head. Most of the comparators use either a differential transformer, an inductance bridge, a strain gauge or a capacitor as a means of detecting movement of the gauging element. There are different types of  electrical comparators. One kind called an electrolimit gauge is used to check or measure the outside diameter of a  roll. The objec...
Post a Comment
Read more

SIMPLE CARBURETOR - CONSTRUCTION AND WORKING

CONSTRUCTION OF SIMPLE CARBURETOR :  The main Components of Simple Carburetor are : Float Chamber, float, nozzle, venturi, throttle valve, inlet valve, and metering jet . In the float chamber, a constant level of petrol is maintained by the float and a needle valve.  The float chamber is ventilated to atmosphere.  This is used to maintain atmospheric pressure inside the chamber. The float which is normally a metallic hollow cylinder rises and closes the inlet valve as the fuel level in the float chamber increases to certain level. The mixing chamber contains venturi, nozzle and throttle valve. The venturi tube is fitted with the inlet  manifold. This tube has a narrow opening called venturi. A nozzle is provided just below the centre of this venturi. The nozzle keeps the same level of petrol as that of the level in the float chamber. The mixing chamber has two butterfly valves.  One is to allow air into the mixing chamber known as choke valve. The other is to al...
Post a Comment
Read more