How do you reduce jetting in injection molding?

Avoiding jetting To avoid jetting, mould geometry and process conditions have to be altered to induce laminar flow within the cavity, filling from the gate end as an unfolding melt front rather than an uncontrolled jet of melt. Reducing overall injection speed will help.

What is back pressure in injection molding?

Back Pressure in an injection molding process is often defined as “the resistance of the screw to recover as the metering section pumps molten plastic through the non-return valve to the front of the screw.” The pressure that is built up in front of the screw forces the screw back to the desired set-point.

How do you reduce injection pressure?

Increase the melt temperature to reduce the viscosity. This reduces the injection pressure required to fill the mold.

What is jetting in injection moulding?

Description: Jetting refers to a situation where molten plastic fails to stick to the mold surface due to the speed of injection. Being fluid, the molten plastic solidifies in a state that shows the wavy folds of the jet stream on the surface of the injection molded part.

What is specific injection pressure?

Specific Pressure: Also known as injection or plastic pressure, this is the actual material pressure within the screw and barrel assembly generated by a resistance to the flow of plastic in front of the screw during injection.

What is holding pressure and back pressure?

Back pressure is different from the injection pressure, the pressure at which the mold fills. That is sometimes called the first stage of pressure. The holding pressure is maintained after the molten plastic fills the mold and is maintained until the gate freezes or a timer releases it.

What affects injection pressure?

Injection pressure is the force applied by the reciprocating screw to push molten plastic resin into a mold cavity, up to about 95% of capacity. It’s balanced against the clamping pressure of the machine, and is calculated based on the size and shape of the part, as well as the size of the gate opening.

Why do you apply pressure after injection?

Relevance to clinical practice: Applying pressure to the injection area is a simple and cost-effective method to reduce the pain associated with injection.