Barrel & Hopper Cooling System (Elements) :

:Barrel Cooling :

1. Barrel cooling is needed to prevent overheating that may cause degradation.
2. For small extruders fans that blow air over or around the barrel are used.
3. Other cooling system used include .
4. Cooling channel inside the barrel wall.
5. Find on the barrel or on the heaters to speedup that transfer.
6. A watet-fog spray over barrel.
7. Continuous, controlled vaporization of liquid (water)
8. Copper tubing carrying cold water is sometimes used.

*Hopper Cooling Systems*
• Water-cooling is used to cool the hopper throat to prevent bridging and to protect the rubber parts present in the screw support assembly.

Breaker Plate & Screen Pack :

Breaker Plate - 1. This is performed metal disk, with a multitude of small diameter holes. 2. The breaker plate is placed in between the screw and the die assembly. 3. It's principal function is to provide support for the screen pack . 4. The breaker plate helps also to convert the spiral flow of the polymer melts leaving the screw into a linear, axial one. Screen Pack - 1. Screen Pack is usually a multilayered, nearly symmetrical sandwich of metallic wire screens. 2. It is placed between the screw and the breaker plate, using the latter for physical support. It's role is to eliminate the particulate contaminants. 3. The screen pack composition is always based on trade-offs, there is need to eliminate particulates using screens with high mesh, but at the same time this create flow restriction, it reduced the throughput, thus low mesh would be preferred. 4. Decision should be made as for as the maximum tolerable size of the particulate contaminan

Advantage and Disadvantages of Injection Blow Moulding Process

√ Advantages - { injection Blow Moulding } 1. Accurate shaping of the neck. 2. A High level of dimensional accuracy. 3. Mini weight tolerance. 4. The highest quality surface finish. 5. Production absolutely free from waste. 6. Crystal clear containers for pharmaceutical application. 7. Finished bottle without weld line and scrap. 8. Secondary /finishing operation can be avoided. 9. Multi-cavities can be operated. √ Disadvantages -{ injection Blow Moulding } 1. The preform design generally establish the core rod length & diameter. 2. The process is more expensive than extrusion blow moulding. 3. Compromise between preform wall thickness and blow up ratio. 4. The ratio of the maximum wall thickness to minimum wall thickness across a preform cross-section should be less than 1.5 to prevent weld lines. 5. Preform thickness greater than 6 mm is unstable during blowing since the thick section cannot be properly conditioned. 6. The technique is not suitable

Function of the torpedo -(Hand injection Machine)

√ The function of the torpedo is to help the material for proper melting and crate back pressure for help in mixing. Torpedo used Vartical Hand Injection Machine .

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