User talk:Only for study

GAS INJECTION TECHNOLOGY The gas injection technique (GIT) is a special injection molding method. After the actual injection molding operation a permanent cavity is created in the molding as a second step by means of an inert compressed gas (nitrogen). The plastic is pressed against the mold wall by maintaining the gas pressure during the solidification process, thus defining the external contour of the component.

Need for Gas – Assisted Injection Moulding: The production of thick-walled mouldings from thermoplastics in the conventional injection moulding processes causes difficulties. The sink marks that occur due to volume contraction of the plastic cannot be completely compensated by the subsequent inflow of melt. Processes such as low-pressure structural foam moulding, gas counter pressure pressure injection moulding, and co injection moulding were developed to avoid sink marks that occurred during the production of thick – walled moldings form thermoplastics During gas-assisted injection moulding, a gas is injected into the interior of the melt with the objective of counteracting volume contraction during cooling by means of the internal gas pressure inside the moulding. Gas Assisted Injection Moulding Processes: There are two different methods of gas generation known: A) Discontinuous Pressure Generation	B) Continuous Pressure Generation Continuous Pressure Generation The continuous pressure generation functions with gas compressors which bring up the nitrogen pressure to a determined pressure level that is, 30MPa at the injection point, the pressure is reduced by means of suitable valves. The process is characterized by pressure control. A basic advantage of the continuous pressure control is that even high gas pressures can be maintained for almost the complete cooling time. The gas injection at several injection points or for different injection moulding machines can be preformed easily by using only one pressure – generating system. materials Polypropylene Acrylonitrile – Butadiene - Styrene polymer (ABS) PolyEthylene (PE) PolyPropylene (PP) PolyStyrene (PS) Styrene - Acrylonitrile copolymer (SAN) PolyPhneyleneoxide (PPO) modified Polycarbonate(PC) PolyButylene Terephthalate (PBT) Blends of PolyCarbonate (PC) – PolyButylene Terephtalate (PBT) Thermoplastic PolyUrethane (TPU) Thermoplatic elastomer (TPE) Gas Assisted Injection

Injection through the machine nozzle Injection directly into the mould

Advantages No Sink marks No built in stresses Shorter cycle time Reduction in weight

--Only for study (talk) 03:54, 15 December 2019 (UTC)